IRIX Base Documentation 2002 November/SGI IRIX Base Documentation 2002 November.iso/usr/share/catman/u_man/cat1/perlguts.z/perlguts

Text File | 2002-10-03 | 151.2 KB | 4,489 lines

PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



NNNNAAAAMMMMEEEE
     perlguts - Perl's Internal Functions

DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
     This document attempts to describe some of the internal functions of the
     Perl executable.  It is far from complete and probably contains many
     errors.  Please refer any questions or comments to the author below.

VVVVaaaarrrriiiiaaaabbbblllleeeessss
     DDDDaaaattttaaaattttyyyyppppeeeessss

     Perl has three typedefs that handle Perl's three main data types:

         SV  Scalar Value
         AV  Array Value
         HV  Hash Value

     Each typedef has specific routines that manipulate the various data
     types.

     WWWWhhhhaaaatttt iiiissss aaaannnn """"IIIIVVVV""""????

     Perl uses a special typedef IV which is a simple integer type that is
     guaranteed to be large enough to hold a pointer (as well as an integer).

     Perl also uses two special typedefs, I32 and I16, which will always be at
     least 32-bits and 16-bits long, respectively.

     WWWWoooorrrrkkkkiiiinnnngggg wwwwiiiitttthhhh SSSSVVVVssss

     An SV can be created and loaded with one command.  There are four types
     of values that can be loaded: an integer value (IV), a double (NV), a
     string, (PV), and another scalar (SV).

     The six routines are:

         SV*  newSViv(IV);
         SV*  newSVnv(double);
         SV*  newSVpv(char*, int);
         SV*  newSVpvn(char*, int);
         SV*  newSVpvf(const char*, ...);
         SV*  newSVsv(SV*);

     To change the value of an *already-existing* SV, there are seven
     routines:










                                                                        PPPPaaaaggggeeee 1111






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



         void  sv_setiv(SV*, IV);
         void  sv_setuv(SV*, UV);
         void  sv_setnv(SV*, double);
         void  sv_setpv(SV*, char*);
         void  sv_setpvn(SV*, char*, int)
         void  sv_setpvf(SV*, const char*, ...);
         void  sv_setpvfn(SV*, const char*, STRLEN, va_list *, SV **, I32, bool);
         void  sv_setsv(SV*, SV*);

     Notice that you can choose to specify the length of the string to be
     assigned by using sv_setpvn, newSVpvn, or newSVpv, or you may allow Perl
     to calculate the length by using sv_setpv or by specifying 0 as the
     second argument to newSVpv.  Be warned, though, that Perl will determine
     the string's length by using strlen, which depends on the string
     terminating with a NUL character.

     The arguments of sv_setpvf are processed like sprintf, and the formatted
     output becomes the value.

     sv_setpvfn is an analogue of vsprintf, but it allows you to specify
     either a pointer to a variable argument list or the address and length of
     an array of SVs.  The last argument points to a boolean; on return, if
     that boolean is true, then locale-specific information has been used to
     format the string, and the string's contents are therefore untrustworty
     (see the _p_e_r_l_s_e_c manpage).  This pointer may be NULL if that information
     is not important.  Note that this function requires you to specify the
     length of the format.

     The sv_set*() functions are not generic enough to operate on values that
     have "magic".  See the section on _M_a_g_i_c _V_i_r_t_u_a_l _T_a_b_l_e_s later in this
     document.

     All SVs that contain strings should be terminated with a NUL character.
     If it is not NUL-terminated there is a risk of core dumps and corruptions
     from code which passes the string to C functions or system calls which
     expect a NUL-terminated string.  Perl's own functions typically add a
     trailing NUL for this reason.  Nevertheless, you should be very careful
     when you pass a string stored in an SV to a C function or system call.

     To access the actual value that an SV points to, you can use the macros:

         SvIV(SV*)
         SvNV(SV*)
         SvPV(SV*, STRLEN len)

     which will automatically coerce the actual scalar type into an IV,
     double, or string.

     In the SvPV macro, the length of the string returned is placed into the
     variable len (this is a macro, so you do _n_o_t use &len).  If you do not
     care what the length of the data is, use the global variable PL_na.
     Remember, however, that Perl allows arbitrary strings of data that may



                                                                        PPPPaaaaggggeeee 2222






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     both contain NULs and might not be terminated by a NUL.

     If you want to know if the scalar value is TRUE, you can use:

         SvTRUE(SV*)

     Although Perl will automatically grow strings for you, if you need to
     force Perl to allocate more memory for your SV, you can use the macro

         SvGROW(SV*, STRLEN newlen)

     which will determine if more memory needs to be allocated.  If so, it
     will call the function sv_grow.  Note that SvGROW can only increase, not
     decrease, the allocated memory of an SV and that it does not
     automatically add a byte for the a trailing NUL (perl's own string
     functions typically do SvGROW(sv, len + 1)).

     If you have an SV and want to know what kind of data Perl thinks is
     stored in it, you can use the following macros to check the type of SV
     you have.

         SvIOK(SV*)
         SvNOK(SV*)
         SvPOK(SV*)

     You can get and set the current length of the string stored in an SV with
     the following macros:

         SvCUR(SV*)
         SvCUR_set(SV*, I32 val)

     You can also get a pointer to the end of the string stored in the SV with
     the macro:

         SvEND(SV*)

     But note that these last three macros are valid only if SvPOK() is true.

     If you want to append something to the end of string stored in an SV*,
     you can use the following functions:

         void  sv_catpv(SV*, char*);
         void  sv_catpvn(SV*, char*, int);
         void  sv_catpvf(SV*, const char*, ...);
         void  sv_catpvfn(SV*, const char*, STRLEN, va_list *, SV **, I32, bool);
         void  sv_catsv(SV*, SV*);

     The first function calculates the length of the string to be appended by
     using strlen.  In the second, you specify the length of the string
     yourself.  The third function processes its arguments like sprintf and
     appends the formatted output.  The fourth function works like vsprintf.
     You can specify the address and length of an array of SVs instead of the



                                                                        PPPPaaaaggggeeee 3333






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     va_list argument. The fifth function extends the string stored in the
     first SV with the string stored in the second SV.  It also forces the
     second SV to be interpreted as a string.

     The sv_cat*() functions are not generic enough to operate on values that
     have "magic".  See the section on _M_a_g_i_c _V_i_r_t_u_a_l _T_a_b_l_e_s later in this
     document.

     If you know the name of a scalar variable, you can get a pointer to its
     SV by using the following:

         SV*  perl_get_sv("package::varname", FALSE);

     This returns NULL if the variable does not exist.

     If you want to know if this variable (or any other SV) is actually
     defined, you can call:

         SvOK(SV*)

     The scalar undef value is stored in an SV instance called PL_sv_undef.
     Its address can be used whenever an SV* is needed.

     There are also the two values PL_sv_yes and PL_sv_no, which contain
     Boolean TRUE and FALSE values, respectively.  Like PL_sv_undef, their
     addresses can be used whenever an SV* is needed.

     Do not be fooled into thinking that (SV *) 0 is the same as &PL_sv_undef.
     Take this code:

         SV* sv = (SV*) 0;
         if (I-am-to-return-a-real-value) {
                 sv = sv_2mortal(newSViv(42));
         }
         sv_setsv(ST(0), sv);

     This code tries to return a new SV (which contains the value 42) if it
     should return a real value, or undef otherwise.  Instead it has returned
     a NULL pointer which, somewhere down the line, will cause a segmentation
     violation, bus error, or just weird results.  Change the zero to
     &PL_sv_undef in the first line and all will be well.

     To free an SV that you've created, call SvREFCNT_dec(SV*).  Normally this
     call is not necessary (see the section on _R_e_f_e_r_e_n_c_e _C_o_u_n_t_s _a_n_d
     _M_o_r_t_a_l_i_t_y).

     WWWWhhhhaaaatttt''''ssss RRRReeeeaaaallllllllyyyy SSSSttttoooorrrreeeedddd iiiinnnn aaaannnn SSSSVVVV????

     Recall that the usual method of determining the type of scalar you have
     is to use Sv*OK macros.  Because a scalar can be both a number and a
     string, usually these macros will always return TRUE and calling the Sv*V
     macros will do the appropriate conversion of string to integer/double or



                                                                        PPPPaaaaggggeeee 4444






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     integer/double to string.

     If you _r_e_a_l_l_y need to know if you have an integer, double, or string
     pointer in an SV, you can use the following three macros instead:

         SvIOKp(SV*)
         SvNOKp(SV*)
         SvPOKp(SV*)

     These will tell you if you truly have an integer, double, or string
     pointer stored in your SV.  The "p" stands for private.

     In general, though, it's best to use the Sv*V macros.

     WWWWoooorrrrkkkkiiiinnnngggg wwwwiiiitttthhhh AAAAVVVVssss

     There are two ways to create and load an AV.  The first method creates an
     empty AV:

         AV*  newAV();

     The second method both creates the AV and initially populates it with
     SVs:

         AV*  av_make(I32 num, SV **ptr);

     The second argument points to an array containing num SV*'s.  Once the AV
     has been created, the SVs can be destroyed, if so desired.

     Once the AV has been created, the following operations are possible on
     AVs:

         void  av_push(AV*, SV*);
         SV*   av_pop(AV*);
         SV*   av_shift(AV*);
         void  av_unshift(AV*, I32 num);

     These should be familiar operations, with the exception of av_unshift.
     This routine adds num elements at the front of the array with the undef
     value.  You must then use av_store (described below) to assign values to
     these new elements.

     Here are some other functions:

         I32   av_len(AV*);
         SV**  av_fetch(AV*, I32 key, I32 lval);
         SV**  av_store(AV*, I32 key, SV* val);

     The av_len function returns the highest index value in array (just like
     $#array in Perl).  If the array is empty, -1 is returned.  The av_fetch
     function returns the value at index key, but if lval is non-zero, then
     av_fetch will store an undef value at that index.  The av_store function



                                                                        PPPPaaaaggggeeee 5555






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     stores the value val at index key, and does not increment the reference
     count of val.  Thus the caller is responsible for taking care of that,
     and if av_store returns NULL, the caller will have to decrement the
     reference count to avoid a memory leak.  Note that av_fetch and av_store
     both return SV**'s, not SV*'s as their return value.

         void  av_clear(AV*);
         void  av_undef(AV*);
         void  av_extend(AV*, I32 key);

     The av_clear function deletes all the elements in the AV* array, but does
     not actually delete the array itself.  The av_undef function will delete
     all the elements in the array plus the array itself.  The av_extend
     function extends the array so that it contains key elements.  If key is
     less than the current length of the array, then nothing is done.

     If you know the name of an array variable, you can get a pointer to its
     AV by using the following:

         AV*  perl_get_av("package::varname", FALSE);

     This returns NULL if the variable does not exist.

     See the section on _U_n_d_e_r_s_t_a_n_d_i_n_g _t_h_e _M_a_g_i_c _o_f _T_i_e_d _H_a_s_h_e_s _a_n_d _A_r_r_a_y_s for
     more information on how to use the array access functions on tied arrays.

     WWWWoooorrrrkkkkiiiinnnngggg wwwwiiiitttthhhh HHHHVVVVssss

     To create an HV, you use the following routine:

         HV*  newHV();

     Once the HV has been created, the following operations are possible on
     HVs:

         SV**  hv_store(HV*, char* key, U32 klen, SV* val, U32 hash);
         SV**  hv_fetch(HV*, char* key, U32 klen, I32 lval);

     The klen parameter is the length of the key being passed in (Note that
     you cannot pass 0 in as a value of klen to tell Perl to measure the
     length of the key).  The val argument contains the SV pointer to the
     scalar being stored, and hash is the precomputed hash value (zero if you
     want hv_store to calculate it for you).  The lval parameter indicates
     whether this fetch is actually a part of a store operation, in which case
     a new undefined value will be added to the HV with the supplied key and
     hv_fetch will return as if the value had already existed.

     Remember that hv_store and hv_fetch return SV**'s and not just SV*.  To
     access the scalar value, you must first dereference the return value.
     However, you should check to make sure that the return value is not NULL
     before dereferencing it.




                                                                        PPPPaaaaggggeeee 6666






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     These two functions check if a hash table entry exists, and deletes it.

         bool  hv_exists(HV*, char* key, U32 klen);
         SV*   hv_delete(HV*, char* key, U32 klen, I32 flags);

     If flags does not include the G_DISCARD flag then hv_delete will create
     and return a mortal copy of the deleted value.

     And more miscellaneous functions:

         void   hv_clear(HV*);
         void   hv_undef(HV*);

     Like their AV counterparts, hv_clear deletes all the entries in the hash
     table but does not actually delete the hash table.  The hv_undef deletes
     both the entries and the hash table itself.

     Perl keeps the actual data in linked list of structures with a typedef of
     HE.  These contain the actual key and value pointers (plus extra
     administrative overhead).  The key is a string pointer; the value is an
     SV*.  However, once you have an HE*, to get the actual key and value, use
     the routines specified below.

         I32    hv_iterinit(HV*);
                 /* Prepares starting point to traverse hash table */
         HE*    hv_iternext(HV*);
                 /* Get the next entry, and return a pointer to a
                    structure that has both the key and value */
         char*  hv_iterkey(HE* entry, I32* retlen);
                 /* Get the key from an HE structure and also return
                    the length of the key string */
         SV*    hv_iterval(HV*, HE* entry);
                 /* Return a SV pointer to the value of the HE
                    structure */
         SV*    hv_iternextsv(HV*, char** key, I32* retlen);
                 /* This convenience routine combines hv_iternext,
                    hv_iterkey, and hv_iterval.  The key and retlen
                    arguments are return values for the key and its
                    length.  The value is returned in the SV* argument */

     If you know the name of a hash variable, you can get a pointer to its HV
     by using the following:

         HV*  perl_get_hv("package::varname", FALSE);

     This returns NULL if the variable does not exist.

     The hash algorithm is defined in the PERL_HASH(hash, key, klen) macro:







                                                                        PPPPaaaaggggeeee 7777






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



         i = klen;
         hash = 0;
         s = key;
         while (i--)
             hash = hash * 33 + *s++;

     See the section on _U_n_d_e_r_s_t_a_n_d_i_n_g _t_h_e _M_a_g_i_c _o_f _T_i_e_d _H_a_s_h_e_s _a_n_d _A_r_r_a_y_s for
     more information on how to use the hash access functions on tied hashes.

     HHHHaaaasssshhhh AAAAPPPPIIII EEEExxxxtttteeeennnnssssiiiioooonnnnssss

     Beginning with version 5.004, the following functions are also supported:

         HE*     hv_fetch_ent  (HV* tb, SV* key, I32 lval, U32 hash);
         HE*     hv_store_ent  (HV* tb, SV* key, SV* val, U32 hash);

         bool    hv_exists_ent (HV* tb, SV* key, U32 hash);
         SV*     hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash);

         SV*     hv_iterkeysv  (HE* entry);

     Note that these functions take SV* keys, which simplifies writing of
     extension code that deals with hash structures.  These functions also
     allow passing of SV* keys to tie functions without forcing you to
     stringify the keys (unlike the previous set of functions).

     They also return and accept whole hash entries (HE*), making their use
     more efficient (since the hash number for a particular string doesn't
     have to be recomputed every time).  See the section on _A_P_I _L_I_S_T_I_N_G later
     in this document for detailed descriptions.

     The following macros must always be used to access the contents of hash
     entries.  Note that the arguments to these macros must be simple
     variables, since they may get evaluated more than once.  See the section
     on _A_P_I _L_I_S_T_I_N_G later in this document for detailed descriptions of these
     macros.

         HePV(HE* he, STRLEN len)
         HeVAL(HE* he)
         HeHASH(HE* he)
         HeSVKEY(HE* he)
         HeSVKEY_force(HE* he)
         HeSVKEY_set(HE* he, SV* sv)

     These two lower level macros are defined, but must only be used when
     dealing with keys that are not SV*s:

         HeKEY(HE* he)
         HeKLEN(HE* he)

     Note that both hv_store and hv_store_ent do not increment the reference
     count of the stored val, which is the caller's responsibility.  If these



                                                                        PPPPaaaaggggeeee 8888






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     functions return a NULL value, the caller will usually have to decrement
     the reference count of val to avoid a memory leak.

     RRRReeeeffffeeeerrrreeeennnncccceeeessss

     References are a special type of scalar that point to other data types
     (including references).

     To create a reference, use either of the following functions:

         SV* newRV_inc((SV*) thing);
         SV* newRV_noinc((SV*) thing);

     The thing argument can be any of an SV*, AV*, or HV*.  The functions are
     identical except that newRV_inc increments the reference count of the
     thing, while newRV_noinc does not.  For historical reasons, newRV is a
     synonym for newRV_inc.

     Once you have a reference, you can use the following macro to dereference
     the reference:

         SvRV(SV*)

     then call the appropriate routines, casting the returned SV* to either an
     AV* or HV*, if required.

     To determine if an SV is a reference, you can use the following macro:

         SvROK(SV*)

     To discover what type of value the reference refers to, use the following
     macro and then check the return value.

         SvTYPE(SvRV(SV*))

     The most useful types that will be returned are:

         SVt_IV    Scalar
         SVt_NV    Scalar
         SVt_PV    Scalar
         SVt_RV    Scalar
         SVt_PVAV  Array
         SVt_PVHV  Hash
         SVt_PVCV  Code
         SVt_PVGV  Glob (possible a file handle)
         SVt_PVMG  Blessed or Magical Scalar

         See the sv.h header file for more details.







                                                                        PPPPaaaaggggeeee 9999






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     BBBBlllleeeesssssssseeeedddd RRRReeeeffffeeeerrrreeeennnncccceeeessss aaaannnndddd CCCCllllaaaassssssss OOOObbbbjjjjeeeeccccttttssss

     References are also used to support object-oriented programming.  In the
     OO lexicon, an object is simply a reference that has been blessed into a
     package (or class).  Once blessed, the programmer may now use the
     reference to access the various methods in the class.

     A reference can be blessed into a package with the following function:

         SV* sv_bless(SV* sv, HV* stash);

     The sv argument must be a reference.  The stash argument specifies which
     class the reference will belong to.  See the section on _S_t_a_s_h_e_s _a_n_d _G_l_o_b_s
     for information on converting class names into stashes.

     /* Still under construction */

     Upgrades rv to reference if not already one.  Creates new SV for rv to
     point to.  If classname is non-null, the SV is blessed into the specified
     class.  SV is returned.

             SV* newSVrv(SV* rv, char* classname);

     Copies integer or double into an SV whose reference is rv.  SV is blessed
     if classname is non-null.

             SV* sv_setref_iv(SV* rv, char* classname, IV iv);
             SV* sv_setref_nv(SV* rv, char* classname, NV iv);

     Copies the pointer value (_t_h_e _a_d_d_r_e_s_s, _n_o_t _t_h_e _s_t_r_i_n_g!) into an SV whose
     reference is rv.  SV is blessed if classname is non-null.

             SV* sv_setref_pv(SV* rv, char* classname, PV iv);

     Copies string into an SV whose reference is rv.  Set length to 0 to let
     Perl calculate the string length.  SV is blessed if classname is non-
     null.

             SV* sv_setref_pvn(SV* rv, char* classname, PV iv, int length);

     Tests whether the SV is blessed into the specified class.  It does not
     check inheritance relationships.

             int  sv_isa(SV* sv, char* name);

     Tests whether the SV is a reference to a blessed object.

             int  sv_isobject(SV* sv);

     Tests whether the SV is derived from the specified class. SV can be
     either a reference to a blessed object or a string containing a class
     name. This is the function implementing the UNIVERSAL::isa functionality.



                                                                       PPPPaaaaggggeeee 11110000






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



             bool sv_derived_from(SV* sv, char* name);

     To check if you've got an object derived from a specific class you have
     to write:

             if (sv_isobject(sv) && sv_derived_from(sv, class)) { ... }


     CCCCrrrreeeeaaaattttiiiinnnngggg NNNNeeeewwww VVVVaaaarrrriiiiaaaabbbblllleeeessss

     To create a new Perl variable with an undef value which can be accessed
     from your Perl script, use the following routines, depending on the
     variable type.

         SV*  perl_get_sv("package::varname", TRUE);
         AV*  perl_get_av("package::varname", TRUE);
         HV*  perl_get_hv("package::varname", TRUE);

     Notice the use of TRUE as the second parameter.  The new variable can now
     be set, using the routines appropriate to the data type.

     There are additional macros whose values may be bitwise OR'ed with the
     TRUE argument to enable certain extra features.  Those bits are:

         GV_ADDMULTI Marks the variable as multiply defined, thus preventing the
                     "Name <varname> used only once: possible typo" warning.
         GV_ADDWARN  Issues the warning "Had to create <varname> unexpectedly" if
                     the variable did not exist before the function was called.

     If you do not specify a package name, the variable is created in the
     current package.

     RRRReeeeffffeeeerrrreeeennnncccceeee CCCCoooouuuunnnnttttssss aaaannnndddd MMMMoooorrrrttttaaaalllliiiittttyyyy

     Perl uses an reference count-driven garbage collection mechanism. SVs,
     AVs, or HVs (xV for short in the following) start their life with a
     reference count of 1.  If the reference count of an xV ever drops to 0,
     then it will be destroyed and its memory made available for reuse.

     This normally doesn't happen at the Perl level unless a variable is
     undef'ed or the last variable holding a reference to it is changed or
     overwritten.  At the internal level, however, reference counts can be
     manipulated with the following macros:

         int SvREFCNT(SV* sv);
         SV* SvREFCNT_inc(SV* sv);
         void SvREFCNT_dec(SV* sv);

     However, there is one other function which manipulates the reference
     count of its argument.  The newRV_inc function, you will recall, creates
     a reference to the specified argument.  As a side effect, it increments
     the argument's reference count.  If this is not what you want, use



                                                                       PPPPaaaaggggeeee 11111111






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     newRV_noinc instead.

     For example, imagine you want to return a reference from an XSUB
     function.  Inside the XSUB routine, you create an SV which initially has
     a reference count of one.  Then you call newRV_inc, passing it the just-
     created SV.  This returns the reference as a new SV, but the reference
     count of the SV you passed to newRV_inc has been incremented to two.  Now
     you return the reference from the XSUB routine and forget about the SV.
     But Perl hasn't!  Whenever the returned reference is destroyed, the
     reference count of the original SV is decreased to one and nothing
     happens.  The SV will hang around without any way to access it until Perl
     itself terminates.  This is a memory leak.

     The correct procedure, then, is to use newRV_noinc instead of newRV_inc.
     Then, if and when the last reference is destroyed, the reference count of
     the SV will go to zero and it will be destroyed, stopping any memory
     leak.

     There are some convenience functions available that can help with the
     destruction of xVs.  These functions introduce the concept of
     "mortality".  An xV that is mortal has had its reference count marked to
     be decremented, but not actually decremented, until "a short time later".
     Generally the term "short time later" means a single Perl statement, such
     as a call to an XSUB function.  The actual determinant for when mortal
     xVs have their reference count decremented depends on two macros,
     SAVETMPS and FREETMPS.  See the _p_e_r_l_c_a_l_l manpage and the _p_e_r_l_x_s manpage
     for more details on these macros.

     "Mortalization" then is at its simplest a deferred SvREFCNT_dec.
     However, if you mortalize a variable twice, the reference count will
     later be decremented twice.

     You should be careful about creating mortal variables.  Strange things
     can happen if you make the same value mortal within multiple contexts, or
     if you make a variable mortal multiple times.

     To create a mortal variable, use the functions:

         SV*  sv_newmortal()
         SV*  sv_2mortal(SV*)
         SV*  sv_mortalcopy(SV*)

     The first call creates a mortal SV, the second converts an existing SV to
     a mortal SV (and thus defers a call to SvREFCNT_dec), and the third
     creates a mortal copy of an existing SV.

     The mortal routines are not just for SVs -- AVs and HVs can be made
     mortal by passing their address (type-casted to SV*) to the sv_2mortal or
     sv_mortalcopy routines.






                                                                       PPPPaaaaggggeeee 11112222






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     SSSSttttaaaasssshhhheeeessss aaaannnndddd GGGGlllloooobbbbssss

     A "stash" is a hash that contains all of the different objects that are
     contained within a package.  Each key of the stash is a symbol name
     (shared by all the different types of objects that have the same name),
     and each value in the hash table is a GV (Glob Value).  This GV in turn
     contains references to the various objects of that name, including (but
     not limited to) the following:

         Scalar Value
         Array Value
         Hash Value
         I/O Handle
         Format
         Subroutine

     There is a single stash called "PL_defstash" that holds the items that
     exist in the "main" package.  To get at the items in other packages,
     append the string "::" to the package name.  The items in the "Foo"
     package are in the stash "Foo::" in PL_defstash.  The items in the
     "Bar::Baz" package are in the stash "Baz::" in "Bar::"'s stash.

     To get the stash pointer for a particular package, use the function:

         HV*  gv_stashpv(char* name, I32 create)
         HV*  gv_stashsv(SV*, I32 create)

     The first function takes a literal string, the second uses the string
     stored in the SV.  Remember that a stash is just a hash table, so you get
     back an HV*.  The create flag will create a new package if it is set.

     The name that gv_stash*v wants is the name of the package whose symbol
     table you want.  The default package is called main.  If you have
     multiply nested packages, pass their names to gv_stash*v, separated by ::
     as in the Perl language itself.

     Alternately, if you have an SV that is a blessed reference, you can find
     out the stash pointer by using:

         HV*  SvSTASH(SvRV(SV*));

     then use the following to get the package name itself:

         char*  HvNAME(HV* stash);

     If you need to bless or re-bless an object you can use the following
     function:

         SV*  sv_bless(SV*, HV* stash)

     where the first argument, an SV*, must be a reference, and the second
     argument is a stash.  The returned SV* can now be used in the same way as



                                                                       PPPPaaaaggggeeee 11113333






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     any other SV.

     For more information on references and blessings, consult the _p_e_r_l_r_e_f
     manpage.

     DDDDoooouuuubbbblllleeee----TTTTyyyyppppeeeedddd SSSSVVVVssss

     Scalar variables normally contain only one type of value, an integer,
     double, pointer, or reference.  Perl will automatically convert the
     actual scalar data from the stored type into the requested type.

     Some scalar variables contain more than one type of scalar data.  For
     example, the variable $! contains either the numeric value of errno or
     its string equivalent from either strerror or sys_errlist[].

     To force multiple data values into an SV, you must do two things: use the
     sv_set*v routines to add the additional scalar type, then set a flag so
     that Perl will believe it contains more than one type of data.  The four
     macros to set the flags are:

             SvIOK_on
             SvNOK_on
             SvPOK_on
             SvROK_on

     The particular macro you must use depends on which sv_set*v routine you
     called first.  This is because every sv_set*v routine turns on only the
     bit for the particular type of data being set, and turns off all the
     rest.

     For example, to create a new Perl variable called "dberror" that contains
     both the numeric and descriptive string error values, you could use the
     following code:

         extern int  dberror;
         extern char *dberror_list;

         SV* sv = perl_get_sv("dberror", TRUE);
         sv_setiv(sv, (IV) dberror);
         sv_setpv(sv, dberror_list[dberror]);
         SvIOK_on(sv);

     If the order of sv_setiv and sv_setpv had been reversed, then the macro
     SvPOK_on would need to be called instead of SvIOK_on.

     MMMMaaaaggggiiiicccc VVVVaaaarrrriiiiaaaabbbblllleeeessss

     [This section still under construction.  Ignore everything here.  Post no
     bills.  Everything not permitted is forbidden.]






                                                                       PPPPaaaaggggeeee 11114444






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     Any SV may be magical, that is, it has special features that a normal SV
     does not have.  These features are stored in the SV structure in a linked
     list of struct magic's, typedef'ed to MAGIC.

         struct magic {
             MAGIC*      mg_moremagic;
             MGVTBL*     mg_virtual;
             U16         mg_private;
             char        mg_type;
             U8          mg_flags;
             SV*         mg_obj;
             char*       mg_ptr;
             I32         mg_len;
         };

     Note this is current as of patchlevel 0, and could change at any time.

     AAAAssssssssiiiiggggnnnniiiinnnngggg MMMMaaaaggggiiiicccc

     Perl adds magic to an SV using the sv_magic function:

         void sv_magic(SV* sv, SV* obj, int how, char* name, I32 namlen);

     The sv argument is a pointer to the SV that is to acquire a new magical
     feature.

     If sv is not already magical, Perl uses the SvUPGRADE macro to set the
     SVt_PVMG flag for the sv.  Perl then continues by adding it to the
     beginning of the linked list of magical features.  Any prior entry of the
     same type of magic is deleted.  Note that this can be overridden, and
     multiple instances of the same type of magic can be associated with an
     SV.

     The name and namlen arguments are used to associate a string with the
     magic, typically the name of a variable. namlen is stored in the mg_len
     field and if name is non-null and namlen >= 0 a malloc'd copy of the name
     is stored in mg_ptr field.

     The sv_magic function uses how to determine which, if any, predefined
     "Magic Virtual Table" should be assigned to the mg_virtual field.  See
     the "Magic Virtual Table" section below.  The how argument is also stored
     in the mg_type field.

     The obj argument is stored in the mg_obj field of the MAGIC structure.
     If it is not the same as the sv argument, the reference count of the obj
     object is incremented.  If it is the same, or if the how argument is "#",
     or if it is a NULL pointer, then obj is merely stored, without the
     reference count being incremented.

     There is also a function to add magic to an HV:





                                                                       PPPPaaaaggggeeee 11115555






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



         void hv_magic(HV *hv, GV *gv, int how);

     This simply calls sv_magic and coerces the gv argument into an SV.

     To remove the magic from an SV, call the function sv_unmagic:

         void sv_unmagic(SV *sv, int type);

     The type argument should be equal to the how value when the SV was
     initially made magical.

     MMMMaaaaggggiiiicccc VVVViiiirrrrttttuuuuaaaallll TTTTaaaabbbblllleeeessss

     The mg_virtual field in the MAGIC structure is a pointer to a MGVTBL,
     which is a structure of function pointers and stands for "Magic Virtual
     Table" to handle the various operations that might be applied to that
     variable.

     The MGVTBL has five pointers to the following routine types:

         int  (*svt_get)(SV* sv, MAGIC* mg);
         int  (*svt_set)(SV* sv, MAGIC* mg);
         U32  (*svt_len)(SV* sv, MAGIC* mg);
         int  (*svt_clear)(SV* sv, MAGIC* mg);
         int  (*svt_free)(SV* sv, MAGIC* mg);

     This MGVTBL structure is set at compile-time in perl.h and there are
     currently 19 types (or 21 with overloading turned on).  These different
     structures contain pointers to various routines that perform additional
     actions depending on which function is being called.

         Function pointer    Action taken
         ----------------    ------------
         svt_get             Do something after the value of the SV is retrieved.
         svt_set             Do something after the SV is assigned a value.
         svt_len             Report on the SV's length.
         svt_clear           Clear something the SV represents.
         svt_free            Free any extra storage associated with the SV.

     For instance, the MGVTBL structure called vtbl_sv (which corresponds to
     an mg_type of '\0') contains:

         { magic_get, magic_set, magic_len, 0, 0 }

     Thus, when an SV is determined to be magical and of type '\0', if a get
     operation is being performed, the routine magic_get is called.  All the
     various routines for the various magical types begin with magic_.

     The current kinds of Magic Virtual Tables are:






                                                                       PPPPaaaaggggeeee 11116666






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



         mg_type  MGVTBL              Type of magic
         -------  ------              ----------------------------
         \0       vtbl_sv             Special scalar variable
         A        vtbl_amagic         %OVERLOAD hash
         a        vtbl_amagicelem     %OVERLOAD hash element
         c        (none)              Holds overload table (AMT) on stash
         B        vtbl_bm             Boyer-Moore (fast string search)
         E        vtbl_env            %ENV hash
         e        vtbl_envelem        %ENV hash element
         f        vtbl_fm             Formline ('compiled' format)
         g        vtbl_mglob          m//g target / study()ed string
         I        vtbl_isa            @ISA array
         i        vtbl_isaelem        @ISA array element
         k        vtbl_nkeys          scalar(keys()) lvalue
         L        (none)              Debugger %_<filename
         l        vtbl_dbline         Debugger %_<filename element
         o        vtbl_collxfrm       Locale transformation
         P        vtbl_pack           Tied array or hash
         p        vtbl_packelem       Tied array or hash element
         q        vtbl_packelem       Tied scalar or handle
         S        vtbl_sig            %SIG hash
         s        vtbl_sigelem        %SIG hash element
         t        vtbl_taint          Taintedness
         U        vtbl_uvar           Available for use by extensions
         v        vtbl_vec            vec() lvalue
         x        vtbl_substr         substr() lvalue
         y        vtbl_defelem        Shadow "foreach" iterator variable /
                                       smart parameter vivification
         *        vtbl_glob           GV (typeglob)
         #        vtbl_arylen         Array length ($#ary)
         .        vtbl_pos            pos() lvalue
         ~        (none)              Available for use by extensions

     When an uppercase and lowercase letter both exist in the table, then the
     uppercase letter is used to represent some kind of composite type (a list
     or a hash), and the lowercase letter is used to represent an element of
     that composite type.

     The '~' and 'U' magic types are defined specifically for use by
     extensions and will not be used by perl itself.  Extensions can use '~'
     magic to 'attach' private information to variables (typically objects).
     This is especially useful because there is no way for normal perl code to
     corrupt this private information (unlike using extra elements of a hash
     object).

     Similarly, 'U' magic can be used much like _t_i_e() to call a C function any
     time a scalar's value is used or changed.  The MAGIC's mg_ptr field
     points to a ufuncs structure:







                                                                       PPPPaaaaggggeeee 11117777






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



         struct ufuncs {
             I32 (*uf_val)(IV, SV*);
             I32 (*uf_set)(IV, SV*);
             IV uf_index;
         };

     When the SV is read from or written to, the uf_val or uf_set function
     will be called with uf_index as the first arg and a pointer to the SV as
     the second.  A simple example of how to add 'U' magic is shown below.
     Note that the ufuncs structure is copied by sv_magic, so you can safely
     allocate it on the stack.

         void
         Umagic(sv)
             SV *sv;
         PREINIT:
             struct ufuncs uf;
         CODE:
             uf.uf_val   = &my_get_fn;
             uf.uf_set   = &my_set_fn;
             uf.uf_index = 0;
             sv_magic(sv, 0, 'U', (char*)&uf, sizeof(uf));

     Note that because multiple extensions may be using '~' or 'U' magic, it
     is important for extensions to take extra care to avoid conflict.
     Typically only using the magic on objects blessed into the same class as
     the extension is sufficient.  For '~' magic, it may also be appropriate
     to add an I32 'signature' at the top of the private data area and check
     that.

     Also note that the sv_set*() and sv_cat*() functions described earlier do
     nnnnooootttt invoke 'set' magic on their targets.  This must be done by the user
     either by calling the SvSETMAGIC() macro after calling these functions,
     or by using one of the sv_set*_mg() or sv_cat*_mg() functions.
     Similarly, generic C code must call the SvGETMAGIC() macro to invoke any
     'get' magic if they use an SV obtained from external sources in functions
     that don't handle magic.  the section on _A_P_I _L_I_S_T_I_N_G later in this
     document identifies such functions.  For example, calls to the sv_cat*()
     functions typically need to be followed by SvSETMAGIC(), but they don't
     need a prior SvGETMAGIC() since their implementation handles 'get' magic.

     FFFFiiiinnnnddddiiiinnnngggg MMMMaaaaggggiiiicccc

         MAGIC* mg_find(SV*, int type); /* Finds the magic pointer of that type */

     This routine returns a pointer to the MAGIC structure stored in the SV.
     If the SV does not have that magical feature, NULL is returned.  Also, if
     the SV is not of type SVt_PVMG, Perl may core dump.

         int mg_copy(SV* sv, SV* nsv, char* key, STRLEN klen);

     This routine checks to see what types of magic sv has.  If the mg_type



                                                                       PPPPaaaaggggeeee 11118888






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     field is an uppercase letter, then the mg_obj is copied to nsv, but the
     mg_type field is changed to be the lowercase letter.

     UUUUnnnnddddeeeerrrrssssttttaaaannnnddddiiiinnnngggg tttthhhheeee MMMMaaaaggggiiiicccc ooooffff TTTTiiiieeeedddd HHHHaaaasssshhhheeeessss aaaannnndddd AAAArrrrrrrraaaayyyyssss

     Tied hashes and arrays are magical beasts of the 'P' magic type.

     WARNING: As of the 5.004 release, proper usage of the array and hash
     access functions requires understanding a few caveats.  Some of these
     caveats are actually considered bugs in the API, to be fixed in later
     releases, and are bracketed with [MAYCHANGE] below. If you find yourself
     actually applying such information in this section, be aware that the
     behavior may change in the future, umm, without warning.

     The perl tie function associates a variable with an object that
     implements the various GET, SET etc methods.  To perform the equivalent
     of the perl tie function from an XSUB, you must mimic this behaviour.
     The code below carries out the necessary steps - firstly it creates a new
     hash, and then creates a second hash which it blesses into the class
     which will implement the tie methods. Lastly it ties the two hashes
     together, and returns a reference to the new tied hash.  Note that the
     code below does NOT call the TIEHASH method in the MyTie class - see the
     section on _C_a_l_l_i_n_g _P_e_r_l _R_o_u_t_i_n_e_s _f_r_o_m _w_i_t_h_i_n _C _P_r_o_g_r_a_m_s for details on
     how to do this.

         SV*
         mytie()
         PREINIT:
             HV *hash;
             HV *stash;
             SV *tie;
         CODE:
             hash = newHV();
             tie = newRV_noinc((SV*)newHV());
             stash = gv_stashpv("MyTie", TRUE);
             sv_bless(tie, stash);
             hv_magic(hash, tie, 'P');
             RETVAL = newRV_noinc(hash);
         OUTPUT:
             RETVAL

     The av_store function, when given a tied array argument, merely copies
     the magic of the array onto the value to be "stored", using mg_copy.  It
     may also return NULL, indicating that the value did not actually need to
     be stored in the array.  [MAYCHANGE] After a call to av_store on a tied
     array, the caller will usually need to call mg_set(val) to actually
     invoke the perl level "STORE" method on the TIEARRAY object.  If av_store
     did return NULL, a call to SvREFCNT_dec(val) will also be usually
     necessary to avoid a memory leak. [/MAYCHANGE]






                                                                       PPPPaaaaggggeeee 11119999






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     The previous paragraph is applicable verbatim to tied hash access using
     the hv_store and hv_store_ent functions as well.

     av_fetch and the corresponding hash functions hv_fetch and hv_fetch_ent
     actually return an undefined mortal value whose magic has been
     initialized using mg_copy.  Note the value so returned does not need to
     be deallocated, as it is already mortal.  [MAYCHANGE] But you will need
     to call mg_get() on the returned value in order to actually invoke the
     perl level "FETCH" method on the underlying TIE object.  Similarly, you
     may also call mg_set() on the return value after possibly assigning a
     suitable value to it using sv_setsv,  which will invoke the "STORE"
     method on the TIE object. [/MAYCHANGE]

     [MAYCHANGE] In other words, the array or hash fetch/store functions don't
     really fetch and store actual values in the case of tied arrays and
     hashes.  They merely call mg_copy to attach magic to the values that were
     meant to be "stored" or "fetched".  Later calls to mg_get and mg_set
     actually do the job of invoking the TIE methods on the underlying
     objects.  Thus the magic mechanism currently implements a kind of lazy
     access to arrays and hashes.

     Currently (as of perl version 5.004), use of the hash and array access
     functions requires the user to be aware of whether they are operating on
     "normal" hashes and arrays, or on their tied variants.  The API may be
     changed to provide more transparent access to both tied and normal data
     types in future versions.  [/MAYCHANGE]

     You would do well to understand that the TIEARRAY and TIEHASH interfaces
     are mere sugar to invoke some perl method calls while using the uniform
     hash and array syntax.  The use of this sugar imposes some overhead
     (typically about two to four extra opcodes per FETCH/STORE operation, in
     addition to the creation of all the mortal variables required to invoke
     the methods).  This overhead will be comparatively small if the TIE
     methods are themselves substantial, but if they are only a few statements
     long, the overhead will not be insignificant.

     LLLLooooccccaaaalllliiiizzzziiiinnnngggg cccchhhhaaaannnnggggeeeessss

     Perl has a very handy construction

       {
         local $var = 2;
         ...
       }

     This construction is _a_p_p_r_o_x_i_m_a_t_e_l_y equivalent to









                                                                       PPPPaaaaggggeeee 22220000






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



       {
         my $oldvar = $var;
         $var = 2;
         ...
         $var = $oldvar;
       }

     The biggest difference is that the first construction would reinstate the
     initial value of $var, irrespective of how control exits the block: goto,
     return, die/eval etc. It is a little bit more efficient as well.

     There is a way to achieve a similar task from C via Perl API: create a
     _p_s_e_u_d_o-_b_l_o_c_k, and arrange for some changes to be automatically undone at
     the end of it, either explicit, or via a non-local exit (via _d_i_e()). A
     _b_l_o_c_k-like construct is created by a pair of ENTER/LEAVE macros (see the
     section on _R_e_t_u_r_n_i_n_g _a _S_c_a_l_a_r in the _p_e_r_l_c_a_l_l manpage).  Such a construct
     may be created specially for some important localized task, or an
     existing one (like boundaries of enclosing Perl subroutine/block, or an
     existing pair for freeing TMPs) may be used. (In the second case the
     overhead of additional localization must be almost negligible.) Note that
     any XSUB is automatically enclosed in an ENTER/LEAVE pair.

     Inside such a _p_s_e_u_d_o-_b_l_o_c_k the following service is available:

     SAVEINT(int i)

     SAVEIV(IV i)

     SAVEI32(I32 i)

     SAVELONG(long i)
          These macros arrange things to restore the value of integer variable
          i at the end of enclosing _p_s_e_u_d_o-_b_l_o_c_k.

     SAVESPTR(s)

     SAVEPPTR(p)
          These macros arrange things to restore the value of pointers s and
          p. s must be a pointer of a type which survives conversion to SV*
          and back, p should be able to survive conversion to char* and back.

     SAVEFREESV(SV *sv)
          The refcount of sv would be decremented at the end of _p_s_e_u_d_o-_b_l_o_c_k.
          This is similar to sv_2mortal, which should (?) be used instead.

     SAVEFREEOP(OP *op)
          The OP * is _o_p__f_r_e_e()ed at the end of _p_s_e_u_d_o-_b_l_o_c_k.

     SAVEFREEPV(p)
          The chunk of memory which is pointed to by p is _S_a_f_e_f_r_e_e()ed at the
          end of _p_s_e_u_d_o-_b_l_o_c_k.




                                                                       PPPPaaaaggggeeee 22221111






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     SAVECLEARSV(SV *sv)
          Clears a slot in the current scratchpad which corresponds to sv at
          the end of _p_s_e_u_d_o-_b_l_o_c_k.

     SAVEDELETE(HV *hv, char *key, I32 length)
          The key key of hv is deleted at the end of _p_s_e_u_d_o-_b_l_o_c_k. The string
          pointed to by key is _S_a_f_e_f_r_e_e()ed.  If one has a _k_e_y in short-lived
          storage, the corresponding string may be reallocated like this:

            SAVEDELETE(PL_defstash, savepv(tmpbuf), strlen(tmpbuf));


     SAVEDESTRUCTOR(f,p)
          At the end of _p_s_e_u_d_o-_b_l_o_c_k the function f is called with the only
          argument (of type void*) p.

     SAVESTACK_POS()
          The current offset on the Perl internal stack (cf. SP) is restored
          at the end of _p_s_e_u_d_o-_b_l_o_c_k.

     The following API list contains functions, thus one needs to provide
     pointers to the modifiable data explicitly (either C pointers, or Perlish
     GV *s).  Where the above macros take int, a similar function takes int *.

     SV* save_scalar(GV *gv)
          Equivalent to Perl code local $gv.

     AV* save_ary(GV *gv)

     HV* save_hash(GV *gv)
          Similar to save_scalar, but localize @gv and %gv.

     void save_item(SV *item)
          Duplicates the current value of SV, on the exit from the current
          ENTER/LEAVE _p_s_e_u_d_o-_b_l_o_c_k will restore the value of SV using the
          stored value.

     void save_list(SV **sarg, I32 maxsarg)
          A variant of save_item which takes multiple arguments via an array
          sarg of SV* of length maxsarg.

     SV* save_svref(SV **sptr)
          Similar to save_scalar, but will reinstate a SV *.

     void save_aptr(AV **aptr)

     void save_hptr(HV **hptr)
          Similar to save_svref, but localize AV * and HV *.

     The Alias module implements localization of the basic types within the
     _c_a_l_l_e_r'_s _s_c_o_p_e.  People who are interested in how to localize things in
     the containing scope should take a look there too.



                                                                       PPPPaaaaggggeeee 22222222






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



SSSSuuuubbbbrrrroooouuuuttttiiiinnnneeeessss
     XXXXSSSSUUUUBBBBssss aaaannnndddd tttthhhheeee AAAArrrrgggguuuummmmeeeennnntttt SSSSttttaaaacccckkkk

     The XSUB mechanism is a simple way for Perl programs to access C
     subroutines.  An XSUB routine will have a stack that contains the
     arguments from the Perl program, and a way to map from the Perl data
     structures to a C equivalent.

     The stack arguments are accessible through the ST(n) macro, which returns
     the n'th stack argument.  Argument 0 is the first argument passed in the
     Perl subroutine call.  These arguments are SV*, and can be used anywhere
     an SV* is used.

     Most of the time, output from the C routine can be handled through use of
     the RETVAL and OUTPUT directives.  However, there are some cases where
     the argument stack is not already long enough to handle all the return
     values.  An example is the POSIX _t_z_n_a_m_e() call, which takes no arguments,
     but returns two, the local time zone's standard and summer time
     abbreviations.

     To handle this situation, the PPCODE directive is used and the stack is
     extended using the macro:

         EXTEND(SP, num);

     where SP is the macro that represents the local copy of the stack
     pointer, and num is the number of elements the stack should be extended
     by.

     Now that there is room on the stack, values can be pushed on it using the
     macros to push IVs, doubles, strings, and SV pointers respectively:

         PUSHi(IV)
         PUSHn(double)
         PUSHp(char*, I32)
         PUSHs(SV*)

     And now the Perl program calling tzname, the two values will be assigned
     as in:

         ($standard_abbrev, $summer_abbrev) = POSIX::tzname;

     An alternate (and possibly simpler) method to pushing values on the stack
     is to use the macros:

         XPUSHi(IV)
         XPUSHn(double)
         XPUSHp(char*, I32)
         XPUSHs(SV*)

     These macros automatically adjust the stack for you, if needed.  Thus,
     you do not need to call EXTEND to extend the stack.



                                                                       PPPPaaaaggggeeee 22223333






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     For more information, consult the _p_e_r_l_x_s manpage and the _p_e_r_l_x_s_t_u_t
     manpage.

     CCCCaaaalllllllliiiinnnngggg PPPPeeeerrrrllll RRRRoooouuuuttttiiiinnnneeeessss ffffrrrroooommmm wwwwiiiitttthhhhiiiinnnn CCCC PPPPrrrrooooggggrrrraaaammmmssss

     There are four routines that can be used to call a Perl subroutine from
     within a C program.  These four are:

         I32  perl_call_sv(SV*, I32);
         I32  perl_call_pv(char*, I32);
         I32  perl_call_method(char*, I32);
         I32  perl_call_argv(char*, I32, register char**);

     The routine most often used is perl_call_sv.  The SV* argument contains
     either the name of the Perl subroutine to be called, or a reference to
     the subroutine.  The second argument consists of flags that control the
     context in which the subroutine is called, whether or not the subroutine
     is being passed arguments, how errors should be trapped, and how to treat
     return values.

     All four routines return the number of arguments that the subroutine
     returned on the Perl stack.

     When using any of these routines (except perl_call_argv), the programmer
     must manipulate the Perl stack.  These include the following macros and
     functions:

         dSP
         SP
         PUSHMARK()
         PUTBACK
         SPAGAIN
         ENTER
         SAVETMPS
         FREETMPS
         LEAVE
         XPUSH*()
         POP*()

     For a detailed description of calling conventions from C to Perl, consult
     the _p_e_r_l_c_a_l_l manpage.

     MMMMeeeemmmmoooorrrryyyy AAAAllllllllooooccccaaaattttiiiioooonnnn

     It is suggested that you use the version of malloc that is distributed
     with Perl.  It keeps pools of various sizes of unallocated memory in
     order to satisfy allocation requests more quickly.  However, on some
     platforms, it may cause spurious malloc or free errors.

         New(x, pointer, number, type);
         Newc(x, pointer, number, type, cast);
         Newz(x, pointer, number, type);



                                                                       PPPPaaaaggggeeee 22224444






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     These three macros are used to initially allocate memory.

     The first argument x was a "magic cookie" that was used to keep track of
     who called the macro, to help when debugging memory problems.  However,
     the current code makes no use of this feature (most Perl developers now
     use run-time memory checkers), so this argument can be any number.

     The second argument pointer should be the name of a variable that will
     point to the newly allocated memory.

     The third and fourth arguments number and type specify how many of the
     specified type of data structure should be allocated.  The argument type
     is passed to sizeof.  The final argument to Newc, cast, should be used if
     the pointer argument is different from the type argument.

     Unlike the New and Newc macros, the Newz macro calls memzero to zero out
     all the newly allocated memory.

         Renew(pointer, number, type);
         Renewc(pointer, number, type, cast);
         Safefree(pointer)

     These three macros are used to change a memory buffer size or to free a
     piece of memory no longer needed.  The arguments to Renew and Renewc
     match those of New and Newc with the exception of not needing the "magic
     cookie" argument.

         Move(source, dest, number, type);
         Copy(source, dest, number, type);
         Zero(dest, number, type);

     These three macros are used to move, copy, or zero out previously
     allocated memory.  The source and dest arguments point to the source and
     destination starting points.  Perl will move, copy, or zero out number
     instances of the size of the type data structure (using the sizeof
     function).

     PPPPeeeerrrrllllIIIIOOOO

     The most recent development releases of Perl has been experimenting with
     removing Perl's dependency on the "normal" standard I/O suite and
     allowing other stdio implementations to be used.  This involves creating
     a new abstraction layer that then calls whichever implementation of stdio
     Perl was compiled with.  All XSUBs should now use the functions in the
     PerlIO abstraction layer and not make any assumptions about what kind of
     stdio is being used.

     For a complete description of the PerlIO abstraction, consult the
     _p_e_r_l_a_p_i_o manpage.






                                                                       PPPPaaaaggggeeee 22225555






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     PPPPuuuuttttttttiiiinnnngggg aaaa CCCC vvvvaaaalllluuuueeee oooonnnn PPPPeeeerrrrllll ssssttttaaaacccckkkk

     A lot of opcodes (this is an elementary operation in the internal perl
     stack machine) put an SV* on the stack. However, as an optimization the
     corresponding SV is (usually) not recreated each time. The opcodes reuse
     specially assigned SVs (_t_a_r_g_e_ts) which are (as a corollary) not
     constantly freed/created.

     Each of the targets is created only once (but see the section on
     _S_c_r_a_t_c_h_p_a_d_s _a_n_d _r_e_c_u_r_s_i_o_n below), and when an opcode needs to put an
     integer, a double, or a string on stack, it just sets the corresponding
     parts of its _t_a_r_g_e_t and puts the _t_a_r_g_e_t on stack.

     The macro to put this target on stack is PUSHTARG, and it is directly
     used in some opcodes, as well as indirectly in zillions of others, which
     use it via (X)PUSH[pni].

     SSSSccccrrrraaaattttcccchhhhppppaaaaddddssss

     The question remains on when the SVs which are _t_a_r_g_e_ts for opcodes are
     created. The answer is that they are created when the current unit -- a
     subroutine or a file (for opcodes for statements outside of subroutines)
     -- is compiled. During this time a special anonymous Perl array is
     created, which is called a scratchpad for the current unit.

     A scratchpad keeps SVs which are lexicals for the current unit and are
     targets for opcodes. One can deduce that an SV lives on a scratchpad by
     looking on its flags: lexicals have SVs_PADMY set, and _t_a_r_g_e_ts have
     SVs_PADTMP set.

     The correspondence between OPs and _t_a_r_g_e_ts is not 1-to-1. Different OPs
     in the compile tree of the unit can use the same target, if this would
     not conflict with the expected life of the temporary.

     SSSSccccrrrraaaattttcccchhhhppppaaaaddddssss aaaannnndddd rrrreeeeccccuuuurrrrssssiiiioooonnnn

     In fact it is not 100% true that a compiled unit contains a pointer to
     the scratchpad AV. In fact it contains a pointer to an AV of (initially)
     one element, and this element is the scratchpad AV. Why do we need an
     extra level of indirection?

     The answer is rrrreeeeccccuuuurrrrssssiiiioooonnnn, and maybe (sometime soon) tttthhhhrrrreeeeaaaaddddssss. Both these
     can create several execution pointers going into the same subroutine. For
     the subroutine-child not write over the temporaries for the subroutine-
     parent (lifespan of which covers the call to the child), the parent and
     the child should have different scratchpads. (_A_n_d the lexicals should be
     separate anyway!)

     So each subroutine is born with an array of scratchpads (of length 1).
     On each entry to the subroutine it is checked that the current depth of
     the recursion is not more than the length of this array, and if it is,
     new scratchpad is created and pushed into the array.



                                                                       PPPPaaaaggggeeee 22226666






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     The _t_a_r_g_e_ts on this scratchpad are undefs, but they are already marked
     with correct flags.

CCCCoooommmmppppiiiilllleeeedddd ccccooooddddeeee
     CCCCooooddddeeee ttttrrrreeeeeeee

     Here we describe the internal form your code is converted to by Perl.
     Start with a simple example:

       $a = $b + $c;

     This is converted to a tree similar to this one:

                  assign-to
                /           \
               +             $a
             /   \
           $b     $c

     (but slightly more complicated).  This tree reflects the way Perl parsed
     your code, but has nothing to do with the execution order.  There is an
     additional "thread" going through the nodes of the tree which shows the
     order of execution of the nodes.  In our simplified example above it
     looks like:

          $b ---> $c ---> + ---> $a ---> assign-to

     But with the actual compile tree for $a = $b + $c it is different:  some
     nodes _o_p_t_i_m_i_z_e_d _a_w_a_y.  As a corollary, though the actual tree contains
     more nodes than our simplified example, the execution order is the same
     as in our example.

     EEEExxxxaaaammmmiiiinnnniiiinnnngggg tttthhhheeee ttttrrrreeeeeeee

     If you have your perl compiled for debugging (usually done with -D
     optimize=-g on Configure command line), you may examine the compiled tree
     by specifying -Dx on the Perl command line.  The output takes several
     lines per node, and for $b+$c it looks like this:

















                                                                       PPPPaaaaggggeeee 22227777






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



         5           TYPE = add  ===> 6
                     TARG = 1
                     FLAGS = (SCALAR,KIDS)
                     {
                         TYPE = null  ===> (4)
                           (was rv2sv)
                         FLAGS = (SCALAR,KIDS)
                         {
         3                   TYPE = gvsv  ===> 4
                             FLAGS = (SCALAR)
                             GV = main::b
                         }
                     }
                     {
                         TYPE = null  ===> (5)
                           (was rv2sv)
                         FLAGS = (SCALAR,KIDS)
                         {
         4                   TYPE = gvsv  ===> 5
                             FLAGS = (SCALAR)
                             GV = main::c
                         }
                     }

     This tree has 5 nodes (one per TYPE specifier), only 3 of them are not
     optimized away (one per number in the left column).  The immediate
     children of the given node correspond to {} pairs on the same level of
     indentation, thus this listing corresponds to the tree:

                        add
                      /     \
                    null    null
                     |       |
                    gvsv    gvsv

     The execution order is indicated by ===> marks, thus it is 3 4 5 6 (node
     6 is not included into above listing), i.e., gvsv gvsv add whatever.

     CCCCoooommmmppppiiiilllleeee ppppaaaassssssss 1111:::: cccchhhheeeecccckkkk rrrroooouuuuttttiiiinnnneeeessss

     The tree is created by the _p_s_e_u_d_o-_c_o_m_p_i_l_e_r while yacc code feeds it the
     constructions it recognizes. Since yacc works bottom-up, so does the
     first pass of perl compilation.

     What makes this pass interesting for perl developers is that some
     optimization may be performed on this pass.  This is optimization by so-
     called _c_h_e_c_k _r_o_u_t_i_n_e_s.  The correspondence between node names and
     corresponding check routines is described in _o_p_c_o_d_e._p_l (do not forget to
     run make regen_headers if you modify this file).






                                                                       PPPPaaaaggggeeee 22228888






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     A check routine is called when the node is fully constructed except for
     the execution-order thread.  Since at this time there are no back-links
     to the currently constructed node, one can do most any operation to the
     top-level node, including freeing it and/or creating new nodes
     above/below it.

     The check routine returns the node which should be inserted into the tree
     (if the top-level node was not modified, check routine returns its
     argument).

     By convention, check routines have names ck_*. They are usually called
     from new*OP subroutines (or convert) (which in turn are called from
     _p_e_r_l_y._y).

     CCCCoooommmmppppiiiilllleeee ppppaaaassssssss 1111aaaa:::: ccccoooonnnnssssttttaaaannnntttt ffffoooollllddddiiiinnnngggg

     Immediately after the check routine is called the returned node is
     checked for being compile-time executable.  If it is (the value is judged
     to be constant) it is immediately executed, and a _c_o_n_s_t_a_n_t node with the
     "return value" of the corresponding subtree is substituted instead.  The
     subtree is deleted.

     If constant folding was not performed, the execution-order thread is
     created.

     CCCCoooommmmppppiiiilllleeee ppppaaaassssssss 2222:::: ccccoooonnnntttteeeexxxxtttt pppprrrrooooppppaaaaggggaaaattttiiiioooonnnn

     When a context for a part of compile tree is known, it is propagated down
     through the tree.  At this time the context can have 5 values (instead of
     2 for runtime context): void, boolean, scalar, list, and lvalue.  In
     contrast with the pass 1 this pass is processed from top to bottom: a
     node's context determines the context for its children.

     Additional context-dependent optimizations are performed at this time.
     Since at this moment the compile tree contains back-references (via
     "thread" pointers), nodes cannot be _f_r_e_e()d now.  To allow optimized-away
     nodes at this stage, such nodes are _n_u_l_l()ified instead of _f_r_e_e()ing
     (i.e. their type is changed to OP_NULL).

     CCCCoooommmmppppiiiilllleeee ppppaaaassssssss 3333:::: ppppeeeeeeeepppphhhhoooolllleeee ooooppppttttiiiimmmmiiiizzzzaaaattttiiiioooonnnn

     After the compile tree for a subroutine (or for an eval or a file) is
     created, an additional pass over the code is performed. This pass is
     neither top-down or bottom-up, but in the execution order (with
     additional complications for conditionals).  These optimizations are done
     in the subroutine _p_e_e_p().  Optimizations performed at this stage are
     subject to the same restrictions as in the pass 2.

AAAAPPPPIIII LLLLIIIISSSSTTTTIIIINNNNGGGG
     This is a listing of functions, macros, flags, and variables that may be
     useful to extension writers or that may be found while reading other
     extensions.



                                                                       PPPPaaaaggggeeee 22229999






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     Note that all Perl API global variables must be referenced with the PL_
     prefix.  Some macros are provided for compatibility with the older,
     unadorned names, but this support will be removed in a future release.

     It is strongly recommended that all Perl API functions that don't begin
     with perl be referenced with an explicit Perl_ prefix.

     The sort order of the listing is case insensitive, with any occurrences
     of '_' ignored for the the purpose of sorting.

     av_clear
             Clears an array, making it empty.  Does not free the memory used
             by the array itself.

                     void    av_clear (AV* ar)


     av_extend
             Pre-extend an array.  The key is the index to which the array
             should be extended.

                     void    av_extend (AV* ar, I32 key)


     av_fetch
             Returns the SV at the specified index in the array.  The key is
             the index.  If lval is set then the fetch will be part of a
             store.  Check that the return value is non-null before
             dereferencing it to a SV*.

             See the section on _U_n_d_e_r_s_t_a_n_d_i_n_g _t_h_e _M_a_g_i_c _o_f _T_i_e_d _H_a_s_h_e_s _a_n_d
             _A_r_r_a_y_s for more information on how to use this function on tied
             arrays.

                     SV**    av_fetch (AV* ar, I32 key, I32 lval)


     AvFILL  Same as av_len().  Deprecated, use av_len() instead.

     av_len  Returns the highest index in the array.  Returns -1 if the array
             is empty.

                     I32     av_len (AV* ar)


     av_make Creates a new AV and populates it with a list of SVs.  The SVs
             are copied into the array, so they may be freed after the call to
             av_make.  The new AV will have a reference count of 1.

                     AV*     av_make (I32 size, SV** svp)





                                                                       PPPPaaaaggggeeee 33330000






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     av_pop  Pops an SV off the end of the array.  Returns &PL_sv_undef if the
             array is empty.

                     SV*     av_pop (AV* ar)


     av_push Pushes an SV onto the end of the array.  The array will grow
             automatically to accommodate the addition.

                     void    av_push (AV* ar, SV* val)


     av_shift
             Shifts an SV off the beginning of the array.

                     SV*     av_shift (AV* ar)


     av_store
             Stores an SV in an array.  The array index is specified as key.
             The return value will be NULL if the operation failed or if the
             value did not need to be actually stored within the array (as in
             the case of tied arrays).  Otherwise it can be dereferenced to
             get the original SV*.  Note that the caller is responsible for
             suitably incrementing the reference count of val before the call,
             and decrementing it if the function returned NULL.

             See the section on _U_n_d_e_r_s_t_a_n_d_i_n_g _t_h_e _M_a_g_i_c _o_f _T_i_e_d _H_a_s_h_e_s _a_n_d
             _A_r_r_a_y_s for more information on how to use this function on tied
             arrays.

                     SV**    av_store (AV* ar, I32 key, SV* val)


     av_undef
             Undefines the array.  Frees the memory used by the array itself.

                     void    av_undef (AV* ar)


     av_unshift
             Unshift the given number of undef values onto the beginning of
             the array.  The array will grow automatically to accommodate the
             addition.  You must then use av_store to assign values to these
             new elements.

                     void    av_unshift (AV* ar, I32 num)


     CLASS   Variable which is setup by xsubpp to indicate the class name for
             a C++ XS constructor.  This is always a char*.  See THIS and the
             section on _U_s_i_n_g _X_S _W_i_t_h _C++ in the _p_e_r_l_x_s manpage.



                                                                       PPPPaaaaggggeeee 33331111






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     Copy    The XSUB-writer's interface to the C memcpy function.  The s is
             the source, d is the destination, n is the number of items, and t
             is the type.  May fail on overlapping copies.  See also Move.

                     void    Copy( s, d, n, t )


     croak   This is the XSUB-writer's interface to Perl's die function.  Use
             this function the same way you use the C printf function.  See
             warn.

     CvSTASH Returns the stash of the CV.

                     HV*     CvSTASH( SV* sv )


     PL_DBsingle
             When Perl is run in debugging mode, with the ----dddd switch, this SV
             is a boolean which indicates whether subs are being single-
             stepped.  Single-stepping is automatically turned on after every
             step.  This is the C variable which corresponds to Perl's
             $DB::single variable.  See PL_DBsub.

     PL_DBsub
             When Perl is run in debugging mode, with the ----dddd switch, this GV
             contains the SV which holds the name of the sub being debugged.
             This is the C variable which corresponds to Perl's $DB::sub
             variable.  See PL_DBsingle.  The sub name can be found by

                     SvPV( GvSV( PL_DBsub ), PL_na )


     PL_DBtrace
             Trace variable used when Perl is run in debugging mode, with the
             ----dddd switch.  This is the C variable which corresponds to Perl's
             $DB::trace variable.  See PL_DBsingle.

     dMARK   Declare a stack marker variable, mark, for the XSUB.  See MARK
             and dORIGMARK.

     dORIGMARK
             Saves the original stack mark for the XSUB.  See ORIGMARK.

     PL_dowarn
             The C variable which corresponds to Perl's $^W warning variable.

     dSP     Declares a local copy of perl's stack pointer for the XSUB,
             available via the SP macro.  See SP.

     dXSARGS Sets up stack and mark pointers for an XSUB, calling dSP and
             dMARK.  This is usually handled automatically by xsubpp.
             Declares the items variable to indicate the number of items on



                                                                       PPPPaaaaggggeeee 33332222






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



             the stack.

     dXSI32  Sets up the ix variable for an XSUB which has aliases.  This is
             usually handled automatically by xsubpp.

     do_binmode
             Switches filehandle to binmode.  iotype is what IoTYPE(io) would
             contain.

                     do_binmode(fp, iotype, TRUE);


     ENTER   Opening bracket on a callback.  See LEAVE and the _p_e_r_l_c_a_l_l
             manpage.

                     ENTER;


     EXTEND  Used to extend the argument stack for an XSUB's return values.

                     EXTEND( sp, int x )


     fbm_compile
             Analyses the string in order to make fast searches on it using
             _f_b_m__i_n_s_t_r() -- the Boyer-Moore algorithm.

                     void    fbm_compile(SV* sv, U32 flags)


     fbm_instr
             Returns the location of the SV in the string delimited by str and
             strend.  It returns Nullch if the string can't be found.  The sv
             does not have to be fbm_compiled, but the search will not be as
             fast then.

                     char*   fbm_instr(char *str, char *strend, SV *sv, U32 flags)


     FREETMPS
             Closing bracket for temporaries on a callback.  See SAVETMPS and
             the _p_e_r_l_c_a_l_l manpage.

                     FREETMPS;


     G_ARRAY Used to indicate array context.  See GIMME_V, GIMME and the
             _p_e_r_l_c_a_l_l manpage.

     G_DISCARD
             Indicates that arguments returned from a callback should be
             discarded.  See the _p_e_r_l_c_a_l_l manpage.



                                                                       PPPPaaaaggggeeee 33333333






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     G_EVAL  Used to force a Perl eval wrapper around a callback.  See the
             _p_e_r_l_c_a_l_l manpage.

     GIMME   A backward-compatible version of GIMME_V which can only return
             G_SCALAR or G_ARRAY; in a void context, it returns G_SCALAR.

     GIMME_V The XSUB-writer's equivalent to Perl's wantarray.  Returns
             G_VOID, G_SCALAR or G_ARRAY for void, scalar or array context,
             respectively.

     G_NOARGS
             Indicates that no arguments are being sent to a callback.  See
             the _p_e_r_l_c_a_l_l manpage.

     G_SCALAR
             Used to indicate scalar context.  See GIMME_V, GIMME, and the
             _p_e_r_l_c_a_l_l manpage.

     gv_fetchmeth
             Returns the glob with the given name and a defined subroutine or
             NULL.  The glob lives in the given stash, or in the stashes
             accessible via @ISA and @UNIVERSAL.

             The argument level should be either 0 or -1.  If level==0, as a
             side-effect creates a glob with the given name in the given stash
             which in the case of success contains an alias for the
             subroutine, and sets up caching info for this glob.  Similarly
             for all the searched stashes.

             This function grants "SUPER" token as a postfix of the stash
             name.

             The GV returned from gv_fetchmeth may be a method cache entry,
             which is not visible to Perl code.  So when calling perl_call_sv,
             you should not use the GV directly; instead, you should use the
             method's CV, which can be obtained from the GV with the GvCV
             macro.

                     GV*     gv_fetchmeth (HV* stash, char* name, STRLEN len, I32 level)


     gv_fetchmethod

     gv_fetchmethod_autoload
             Returns the glob which contains the subroutine to call to invoke
             the method on the stash.  In fact in the presense of autoloading
             this may be the glob for "AUTOLOAD".  In this case the
             corresponding variable $AUTOLOAD is already setup.

             The third parameter of gv_fetchmethod_autoload determines whether
             AUTOLOAD lookup is performed if the given method is not present:
             non-zero means yes, look for AUTOLOAD; zero means no, don't look



                                                                       PPPPaaaaggggeeee 33334444






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



             for AUTOLOAD.  Calling gv_fetchmethod is equivalent to calling
             gv_fetchmethod_autoload with a non-zero autoload parameter.

             These functions grant "SUPER" token as a prefix of the method
             name.

             Note that if you want to keep the returned glob for a long time,
             you need to check for it being "AUTOLOAD", since at the later
             time the call may load a different subroutine due to $AUTOLOAD
             changing its value.  Use the glob created via a side effect to do
             this.

             These functions have the same side-effects and as gv_fetchmeth
             with level==0.  name should be writable if contains ':' or '\''.
             The warning against passing the GV returned by gv_fetchmeth to
             perl_call_sv apply equally to these functions.

                     GV*     gv_fetchmethod (HV* stash, char* name)
                     GV*     gv_fetchmethod_autoload (HV* stash, char* name, I32 autoload)


     G_VOID  Used to indicate void context.  See GIMME_V and the _p_e_r_l_c_a_l_l
             manpage.

     gv_stashpv
             Returns a pointer to the stash for a specified package.  If
             create is set then the package will be created if it does not
             already exist.  If create is not set and the package does not
             exist then NULL is returned.

                     HV*     gv_stashpv (char* name, I32 create)


     gv_stashsv
             Returns a pointer to the stash for a specified package.  See
             gv_stashpv.

                     HV*     gv_stashsv (SV* sv, I32 create)


     GvSV    Return the SV from the GV.

     HEf_SVKEY
             This flag, used in the length slot of hash entries and magic
             structures, specifies the structure contains a SV* pointer where
             a char* pointer is to be expected. (For information only--not to
             be used).

     HeHASH  Returns the computed hash stored in the hash entry.

                     U32     HeHASH(HE* he)




                                                                       PPPPaaaaggggeeee 33335555






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     HeKEY   Returns the actual pointer stored in the key slot of the hash
             entry.  The pointer may be either char* or SV*, depending on the
             value of HeKLEN().  Can be assigned to.  The HePV() or HeSVKEY()
             macros are usually preferable for finding the value of a key.

                     char*   HeKEY(HE* he)


     HeKLEN  If this is negative, and amounts to HEf_SVKEY, it indicates the
             entry holds an SV* key.  Otherwise, holds the actual length of
             the key.  Can be assigned to. The HePV() macro is usually
             preferable for finding key lengths.

                     int     HeKLEN(HE* he)


     HePV    Returns the key slot of the hash entry as a char* value, doing
             any necessary dereferencing of possibly SV* keys.  The length of
             the string is placed in len (this is a macro, so do _n_o_t use
             &len).  If you do not care about what the length of the key is,
             you may use the global variable PL_na.  Remember though, that
             hash keys in perl are free to contain embedded nulls, so using
             strlen() or similar is not a good way to find the length of hash
             keys.  This is very similar to the SvPV() macro described
             elsewhere in this document.

                     char*   HePV(HE* he, STRLEN len)


     HeSVKEY Returns the key as an SV*, or Nullsv if the hash entry does not
             contain an SV* key.

                     HeSVKEY(HE* he)


     HeSVKEY_force
             Returns the key as an SV*.  Will create and return a temporary
             mortal SV* if the hash entry contains only a char* key.

                     HeSVKEY_force(HE* he)


     HeSVKEY_set
             Sets the key to a given SV*, taking care to set the appropriate
             flags to indicate the presence of an SV* key, and returns the
             same SV*.

                     HeSVKEY_set(HE* he, SV* sv)







                                                                       PPPPaaaaggggeeee 33336666






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     HeVAL   Returns the value slot (type SV*) stored in the hash entry.

                     HeVAL(HE* he)


     hv_clear
             Clears a hash, making it empty.

                     void    hv_clear (HV* tb)


     hv_delete
             Deletes a key/value pair in the hash.  The value SV is removed
             from the hash and returned to the caller.  The klen is the length
             of the key.  The flags value will normally be zero; if set to
             G_DISCARD then NULL will be returned.

                     SV*     hv_delete (HV* tb, char* key, U32 klen, I32 flags)


     hv_delete_ent
             Deletes a key/value pair in the hash.  The value SV is removed
             from the hash and returned to the caller.  The flags value will
             normally be zero; if set to G_DISCARD then NULL will be returned.
             hash can be a valid precomputed hash value, or 0 to ask for it to
             be computed.

                     SV*     hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash)


     hv_exists
             Returns a boolean indicating whether the specified hash key
             exists.  The klen is the length of the key.

                     bool    hv_exists (HV* tb, char* key, U32 klen)


     hv_exists_ent
             Returns a boolean indicating whether the specified hash key
             exists. hash can be a valid precomputed hash value, or 0 to ask
             for it to be computed.

                     bool    hv_exists_ent (HV* tb, SV* key, U32 hash)


     hv_fetch
             Returns the SV which corresponds to the specified key in the
             hash.  The klen is the length of the key.  If lval is set then
             the fetch will be part of a store.  Check that the return value
             is non-null before dereferencing it to a SV*.

             See the section on _U_n_d_e_r_s_t_a_n_d_i_n_g _t_h_e _M_a_g_i_c _o_f _T_i_e_d _H_a_s_h_e_s _a_n_d



                                                                       PPPPaaaaggggeeee 33337777






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



             _A_r_r_a_y_s for more information on how to use this function on tied
             hashes.

                     SV**    hv_fetch (HV* tb, char* key, U32 klen, I32 lval)


     hv_fetch_ent
             Returns the hash entry which corresponds to the specified key in
             the hash.  hash must be a valid precomputed hash number for the
             given key, or 0 if you want the function to compute it.  IF lval
             is set then the fetch will be part of a store.  Make sure the
             return value is non-null before accessing it.  The return value
             when tb is a tied hash is a pointer to a static location, so be
             sure to make a copy of the structure if you need to store it
             somewhere.

             See the section on _U_n_d_e_r_s_t_a_n_d_i_n_g _t_h_e _M_a_g_i_c _o_f _T_i_e_d _H_a_s_h_e_s _a_n_d
             _A_r_r_a_y_s for more information on how to use this function on tied
             hashes.

                     HE*     hv_fetch_ent  (HV* tb, SV* key, I32 lval, U32 hash)


     hv_iterinit
             Prepares a starting point to traverse a hash table.

                     I32     hv_iterinit (HV* tb)

             Returns the number of keys in the hash (i.e. the same as
             HvKEYS(tb)).  The return value is currently only meaningful for
             hashes without tie magic.

             NOTE: Before version 5.004_65, hv_iterinit used to return the
             number of hash buckets that happen to be in use.  If you still
             need that esoteric value, you can get it through the macro
             HvFILL(tb).

     hv_iterkey
             Returns the key from the current position of the hash iterator.
             See hv_iterinit.

                     char*   hv_iterkey (HE* entry, I32* retlen)


     hv_iterkeysv
             Returns the key as an SV* from the current position of the hash
             iterator.  The return value will always be a mortal copy of the
             key.  Also see hv_iterinit.

                     SV*     hv_iterkeysv  (HE* entry)





                                                                       PPPPaaaaggggeeee 33338888






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     hv_iternext
             Returns entries from a hash iterator.  See hv_iterinit.

                     HE*     hv_iternext (HV* tb)


     hv_iternextsv
             Performs an hv_iternext, hv_iterkey, and hv_iterval in one
             operation.

                     SV*     hv_iternextsv (HV* hv, char** key, I32* retlen)


     hv_iterval
             Returns the value from the current position of the hash iterator.
             See hv_iterkey.

                     SV*     hv_iterval (HV* tb, HE* entry)


     hv_magic
             Adds magic to a hash.  See sv_magic.

                     void    hv_magic (HV* hv, GV* gv, int how)


     HvNAME  Returns the package name of a stash.  See SvSTASH, CvSTASH.

                     char*   HvNAME (HV* stash)


     hv_store
             Stores an SV in a hash.  The hash key is specified as key and
             klen is the length of the key.  The hash parameter is the
             precomputed hash value; if it is zero then Perl will compute it.
             The return value will be NULL if the operation failed or if the
             value did not need to be actually stored within the hash (as in
             the case of tied hashes).  Otherwise it can be dereferenced to
             get the original SV*.  Note that the caller is responsible for
             suitably incrementing the reference count of val before the call,
             and decrementing it if the function returned NULL.

             See the section on _U_n_d_e_r_s_t_a_n_d_i_n_g _t_h_e _M_a_g_i_c _o_f _T_i_e_d _H_a_s_h_e_s _a_n_d
             _A_r_r_a_y_s for more information on how to use this function on tied
             hashes.

                     SV**    hv_store (HV* tb, char* key, U32 klen, SV* val, U32 hash)


     hv_store_ent
             Stores val in a hash.  The hash key is specified as key.  The
             hash parameter is the precomputed hash value; if it is zero then



                                                                       PPPPaaaaggggeeee 33339999






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



             Perl will compute it.  The return value is the new hash entry so
             created.  It will be NULL if the operation failed or if the value
             did not need to be actually stored within the hash (as in the
             case of tied hashes).  Otherwise the contents of the return value
             can be accessed using the He??? macros described here.  Note that
             the caller is responsible for suitably incrementing the reference
             count of val before the call, and decrementing it if the function
             returned NULL.

             See the section on _U_n_d_e_r_s_t_a_n_d_i_n_g _t_h_e _M_a_g_i_c _o_f _T_i_e_d _H_a_s_h_e_s _a_n_d
             _A_r_r_a_y_s for more information on how to use this function on tied
             hashes.

                     HE*     hv_store_ent  (HV* tb, SV* key, SV* val, U32 hash)


     hv_undef
             Undefines the hash.

                     void    hv_undef (HV* tb)


     isALNUM Returns a boolean indicating whether the C char is an ascii
             alphanumeric character or digit.

                     int     isALNUM (char c)


     isALPHA Returns a boolean indicating whether the C char is an ascii
             alphabetic character.

                     int     isALPHA (char c)


     isDIGIT Returns a boolean indicating whether the C char is an ascii
             digit.

                     int     isDIGIT (char c)


     isLOWER Returns a boolean indicating whether the C char is a lowercase
             character.

                     int     isLOWER (char c)


     isSPACE Returns a boolean indicating whether the C char is whitespace.

                     int     isSPACE (char c)






                                                                       PPPPaaaaggggeeee 44440000






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     isUPPER Returns a boolean indicating whether the C char is an uppercase
             character.

                     int     isUPPER (char c)


     items   Variable which is setup by xsubpp to indicate the number of items
             on the stack.  See the section on _V_a_r_i_a_b_l_e-_l_e_n_g_t_h _P_a_r_a_m_e_t_e_r _L_i_s_t_s
             in the _p_e_r_l_x_s manpage.

     ix      Variable which is setup by xsubpp to indicate which of an XSUB's
             aliases was used to invoke it.  See the section on _T_h_e _A_L_I_A_S:
             _K_e_y_w_o_r_d in the _p_e_r_l_x_s manpage.

     LEAVE   Closing bracket on a callback.  See ENTER and the _p_e_r_l_c_a_l_l
             manpage.

                     LEAVE;


     looks_like_number
             Test if an the content of an SV looks like a number (or is a
             number).

                     int     looks_like_number(SV*)


     MARK    Stack marker variable for the XSUB.  See dMARK.

     mg_clear
             Clear something magical that the SV represents.  See sv_magic.

                     int     mg_clear (SV* sv)


     mg_copy Copies the magic from one SV to another.  See sv_magic.

                     int     mg_copy (SV *, SV *, char *, STRLEN)


     mg_find Finds the magic pointer for type matching the SV.  See sv_magic.

                     MAGIC*  mg_find (SV* sv, int type)


     mg_free Free any magic storage used by the SV.  See sv_magic.

                     int     mg_free (SV* sv)







                                                                       PPPPaaaaggggeeee 44441111






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     mg_get  Do magic after a value is retrieved from the SV.  See sv_magic.

                     int     mg_get (SV* sv)


     mg_len  Report on the SV's length.  See sv_magic.

                     U32     mg_len (SV* sv)


     mg_magical
             Turns on the magical status of an SV.  See sv_magic.

                     void    mg_magical (SV* sv)


     mg_set  Do magic after a value is assigned to the SV.  See sv_magic.

                     int     mg_set (SV* sv)


     Move    The XSUB-writer's interface to the C memmove function.  The s is
             the source, d is the destination, n is the number of items, and t
             is the type.  Can do overlapping moves.  See also Copy.

                     void    Move( s, d, n, t )


     PL_na   A variable which may be used with SvPV to tell Perl to calculate
             the string length.

     New     The XSUB-writer's interface to the C malloc function.

                     void*   New( x, void *ptr, int size, type )


     newAV   Creates a new AV.  The reference count is set to 1.

                     AV*     newAV (void)


     Newc    The XSUB-writer's interface to the C malloc function, with cast.

                     void*   Newc( x, void *ptr, int size, type, cast )


     newCONSTSUB
             Creates a constant sub equivalent to Perl sub FOO () { 123 }
             which is eligible for inlining at compile-time.

                     void    newCONSTSUB(HV* stash, char* name, SV* sv)




                                                                       PPPPaaaaggggeeee 44442222






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     newHV   Creates a new HV.  The reference count is set to 1.

                     HV*     newHV (void)


     newRV_inc
             Creates an RV wrapper for an SV.  The reference count for the
             original SV is incremented.

                     SV*     newRV_inc (SV* ref)

             For historical reasons, "newRV" is a synonym for "newRV_inc".

     newRV_noinc
             Creates an RV wrapper for an SV.  The reference count for the
             original SV is nnnnooootttt incremented.

                     SV*     newRV_noinc (SV* ref)


     NEWSV   Creates a new SV.  A non-zero len parameter indicates the number
             of bytes of preallocated string space the SV should have.  An
             extra byte for a tailing NUL is also reserved.  (SvPOK is not set
             for the SV even if string space is allocated.)  The reference
             count for the new SV is set to 1.  id is an integer id between 0
             and 1299 (used to identify leaks).

                     SV*     NEWSV (int id, STRLEN len)


     newSViv Creates a new SV and copies an integer into it.  The reference
             count for the SV is set to 1.

                     SV*     newSViv (IV i)


     newSVnv Creates a new SV and copies a double into it.  The reference
             count for the SV is set to 1.

                     SV*     newSVnv (NV i)


     newSVpv Creates a new SV and copies a string into it.  The reference
             count for the SV is set to 1.  If len is zero then Perl will
             compute the length.

                     SV*     newSVpv (char* s, STRLEN len)


     newSVpvf
             Creates a new SV an initialize it with the string formatted like
             sprintf.



                                                                       PPPPaaaaggggeeee 44443333






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



                     SV*     newSVpvf(const char* pat, ...);


     newSVpvn
             Creates a new SV and copies a string into it.  The reference
             count for the SV is set to 1.  If len is zero then Perl will
             create a zero length string.

                     SV*     newSVpvn (char* s, STRLEN len)


     newSVrv Creates a new SV for the RV, rv, to point to.  If rv is not an RV
             then it will be upgraded to one.  If classname is non-null then
             the new SV will be blessed in the specified package.  The new SV
             is returned and its reference count is 1.

                     SV*     newSVrv (SV* rv, char* classname)


     newSVsv Creates a new SV which is an exact duplicate of the original SV.

                     SV*     newSVsv (SV* old)


     newXS   Used by xsubpp to hook up XSUBs as Perl subs.

     newXSproto
             Used by xsubpp to hook up XSUBs as Perl subs.  Adds Perl
             prototypes to the subs.

     Newz    The XSUB-writer's interface to the C malloc function.  The
             allocated memory is zeroed with memzero.

                     void*   Newz( x, void *ptr, int size, type )


     Nullav  Null AV pointer.

     Nullch  Null character pointer.

     Nullcv  Null CV pointer.

     Nullhv  Null HV pointer.

     Nullsv  Null SV pointer.

     ORIGMARK
             The original stack mark for the XSUB.  See dORIGMARK.

     perl_alloc
             Allocates a new Perl interpreter.  See the _p_e_r_l_e_m_b_e_d manpage.




                                                                       PPPPaaaaggggeeee 44444444






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     perl_call_argv
             Performs a callback to the specified Perl sub.  See the _p_e_r_l_c_a_l_l
             manpage.

                     I32     perl_call_argv (char* subname, I32 flags, char** argv)


     perl_call_method
             Performs a callback to the specified Perl method.  The blessed
             object must be on the stack.  See the _p_e_r_l_c_a_l_l manpage.

                     I32     perl_call_method (char* methname, I32 flags)


     perl_call_pv
             Performs a callback to the specified Perl sub.  See the _p_e_r_l_c_a_l_l
             manpage.

                     I32     perl_call_pv (char* subname, I32 flags)


     perl_call_sv
             Performs a callback to the Perl sub whose name is in the SV.  See
             the _p_e_r_l_c_a_l_l manpage.

                     I32     perl_call_sv (SV* sv, I32 flags)


     perl_construct
             Initializes a new Perl interpreter.  See the _p_e_r_l_e_m_b_e_d manpage.

     perl_destruct
             Shuts down a Perl interpreter.  See the _p_e_r_l_e_m_b_e_d manpage.

     perl_eval_sv
             Tells Perl to eval the string in the SV.

                     I32     perl_eval_sv (SV* sv, I32 flags)


     perl_eval_pv
             Tells Perl to eval the given string and return an SV* result.

                     SV*     perl_eval_pv (char* p, I32 croak_on_error)


     perl_free
             Releases a Perl interpreter.  See the _p_e_r_l_e_m_b_e_d manpage.

     perl_get_av
             Returns the AV of the specified Perl array.  If create is set and
             the Perl variable does not exist then it will be created.  If



                                                                       PPPPaaaaggggeeee 44445555






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



             create is not set and the variable does not exist then NULL is
             returned.

                     AV*     perl_get_av (char* name, I32 create)


     perl_get_cv
             Returns the CV of the specified Perl sub.  If create is set and
             the Perl variable does not exist then it will be created.  If
             create is not set and the variable does not exist then NULL is
             returned.

                     CV*     perl_get_cv (char* name, I32 create)


     perl_get_hv
             Returns the HV of the specified Perl hash.  If create is set and
             the Perl variable does not exist then it will be created.  If
             create is not set and the variable does not exist then NULL is
             returned.

                     HV*     perl_get_hv (char* name, I32 create)


     perl_get_sv
             Returns the SV of the specified Perl scalar.  If create is set
             and the Perl variable does not exist then it will be created.  If
             create is not set and the variable does not exist then NULL is
             returned.

                     SV*     perl_get_sv (char* name, I32 create)


     perl_parse
             Tells a Perl interpreter to parse a Perl script.  See the
             _p_e_r_l_e_m_b_e_d manpage.

     perl_require_pv
             Tells Perl to require a module.

                     void    perl_require_pv (char* pv)


     perl_run
             Tells a Perl interpreter to run.  See the _p_e_r_l_e_m_b_e_d manpage.

     POPi    Pops an integer off the stack.

                     int     POPi()






                                                                       PPPPaaaaggggeeee 44446666






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     POPl    Pops a long off the stack.

                     long    POPl()


     POPp    Pops a string off the stack.

                     char*   POPp()


     POPn    Pops a double off the stack.

                     double  POPn()


     POPs    Pops an SV off the stack.

                     SV*     POPs()


     PUSHMARK
             Opening bracket for arguments on a callback.  See PUTBACK and the
             _p_e_r_l_c_a_l_l manpage.

                     PUSHMARK(p)


     PUSHi   Push an integer onto the stack.  The stack must have room for
             this element.  Handles 'set' magic.  See XPUSHi.

                     void    PUSHi(int d)


     PUSHn   Push a double onto the stack.  The stack must have room for this
             element.  Handles 'set' magic.  See XPUSHn.

                     void    PUSHn(double d)


     PUSHp   Push a string onto the stack.  The stack must have room for this
             element.  The len indicates the length of the string.  Handles
             'set' magic.  See XPUSHp.

                     void    PUSHp(char *c, int len )


     PUSHs   Push an SV onto the stack.  The stack must have room for this
             element.  Does not handle 'set' magic.  See XPUSHs.

                     void    PUSHs(sv)





                                                                       PPPPaaaaggggeeee 44447777






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     PUSHu   Push an unsigned integer onto the stack.  The stack must have
             room for this element.  See XPUSHu.

                     void    PUSHu(unsigned int d)


     PUTBACK Closing bracket for XSUB arguments.  This is usually handled by
             xsubpp.  See PUSHMARK and the _p_e_r_l_c_a_l_l manpage for other uses.

                     PUTBACK;


     Renew   The XSUB-writer's interface to the C realloc function.

                     void*   Renew( void *ptr, int size, type )


     Renewc  The XSUB-writer's interface to the C realloc function, with cast.

                     void*   Renewc( void *ptr, int size, type, cast )


     RETVAL  Variable which is setup by xsubpp to hold the return value for an
             XSUB.  This is always the proper type for the XSUB.  See the
             section on _T_h_e _R_E_T_V_A_L _V_a_r_i_a_b_l_e in the _p_e_r_l_x_s manpage.

     safefree
             The XSUB-writer's interface to the C free function.

     safemalloc
             The XSUB-writer's interface to the C malloc function.

     saferealloc
             The XSUB-writer's interface to the C realloc function.

     savepv  Copy a string to a safe spot.  This does not use an SV.

                     char*   savepv (char* sv)


     savepvn Copy a string to a safe spot.  The len indicates number of bytes
             to copy.  This does not use an SV.

                     char*   savepvn (char* sv, I32 len)


     SAVETMPS
             Opening bracket for temporaries on a callback.  See FREETMPS and
             the _p_e_r_l_c_a_l_l manpage.

                     SAVETMPS;




                                                                       PPPPaaaaggggeeee 44448888






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     SP      Stack pointer.  This is usually handled by xsubpp.  See dSP and
             SPAGAIN.

     SPAGAIN Refetch the stack pointer.  Used after a callback.  See the
             _p_e_r_l_c_a_l_l manpage.

                     SPAGAIN;


     ST      Used to access elements on the XSUB's stack.

                     SV*     ST(int x)


     strEQ   Test two strings to see if they are equal.  Returns true or
             false.

                     int     strEQ( char *s1, char *s2 )


     strGE   Test two strings to see if the first, s1, is greater than or
             equal to the second, s2.  Returns true or false.

                     int     strGE( char *s1, char *s2 )


     strGT   Test two strings to see if the first, s1, is greater than the
             second, s2.  Returns true or false.

                     int     strGT( char *s1, char *s2 )


     strLE   Test two strings to see if the first, s1, is less than or equal
             to the second, s2.  Returns true or false.

                     int     strLE( char *s1, char *s2 )


     strLT   Test two strings to see if the first, s1, is less than the
             second, s2.  Returns true or false.

                     int     strLT( char *s1, char *s2 )


     strNE   Test two strings to see if they are different.  Returns true or
             false.

                     int     strNE( char *s1, char *s2 )







                                                                       PPPPaaaaggggeeee 44449999






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     strnEQ  Test two strings to see if they are equal.  The len parameter
             indicates the number of bytes to compare.  Returns true or false.

                     int     strnEQ( char *s1, char *s2 )


     strnNE  Test two strings to see if they are different.  The len parameter
             indicates the number of bytes to compare.  Returns true or false.

                     int     strnNE( char *s1, char *s2, int len )


     sv_2mortal
             Marks an SV as mortal.  The SV will be destroyed when the current
             context ends.

                     SV*     sv_2mortal (SV* sv)


     sv_bless
             Blesses an SV into a specified package.  The SV must be an RV.
             The package must be designated by its stash (see gv_stashpv()).
             The reference count of the SV is unaffected.

                     SV*     sv_bless (SV* sv, HV* stash)


     sv_catpv
             Concatenates the string onto the end of the string which is in
             the SV.  Handles 'get' magic, but not 'set' magic.  See
             sv_catpv_mg.

                     void    sv_catpv (SV* sv, char* ptr)


     sv_catpv_mg
             Like sv_catpv, but also handles 'set' magic.

                     void    sv_catpvn (SV* sv, char* ptr)


     sv_catpvn
             Concatenates the string onto the end of the string which is in
             the SV.  The len indicates number of bytes to copy.  Handles
             'get' magic, but not 'set' magic.  See sv_catpvn_mg.

                     void    sv_catpvn (SV* sv, char* ptr, STRLEN len)


     sv_catpvn_mg
             Like sv_catpvn, but also handles 'set' magic.




                                                                       PPPPaaaaggggeeee 55550000






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



                     void    sv_catpvn_mg (SV* sv, char* ptr, STRLEN len)


     sv_catpvf
             Processes its arguments like sprintf and appends the formatted
             output to an SV.  Handles 'get' magic, but not 'set' magic.
             SvSETMAGIC() must typically be called after calling this function
             to handle 'set' magic.

                     void    sv_catpvf (SV* sv, const char* pat, ...)


     sv_catpvf_mg
             Like sv_catpvf, but also handles 'set' magic.

                     void    sv_catpvf_mg (SV* sv, const char* pat, ...)


     sv_catsv
             Concatenates the string from SV ssv onto the end of the string in
             SV dsv.  Handles 'get' magic, but not 'set' magic.  See
             sv_catsv_mg.

                     void    sv_catsv (SV* dsv, SV* ssv)


     sv_catsv_mg
             Like sv_catsv, but also handles 'set' magic.

                     void    sv_catsv_mg (SV* dsv, SV* ssv)


     sv_chop Efficient removal of characters from the beginning of the string
             buffer.  _S_v_P_O_K(sv) must be true and the ptr must be a pointer to
             somewhere inside the string buffer.  The ptr becomes the first
             character of the adjusted string.

                     void    sv_chop(SV* sv, char *ptr)


     sv_cmp  Compares the strings in two SVs.  Returns -1, 0, or 1 indicating
             whether the string in sv1 is less than, equal to, or greater than
             the string in sv2.

                     I32     sv_cmp (SV* sv1, SV* sv2)


     SvCUR   Returns the length of the string which is in the SV.  See SvLEN.

                     int     SvCUR (SV* sv)





                                                                       PPPPaaaaggggeeee 55551111






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     SvCUR_set
             Set the length of the string which is in the SV.  See SvCUR.

                     void    SvCUR_set (SV* sv, int val )


     sv_dec  Auto-decrement of the value in the SV.

                     void    sv_dec (SV* sv)


     sv_derived_from
             Returns a boolean indicating whether the SV is a subclass of the
             specified class.

                     int     sv_derived_from(SV* sv, char* class)


     sv_derived_from
             Returns a boolean indicating whether the SV is derived from the
             specified class.  This is the function that implements
             UNIVERSAL::isa.  It works for class names as well as for objects.

                     bool    sv_derived_from _((SV* sv, char* name));


     SvEND   Returns a pointer to the last character in the string which is in
             the SV.  See SvCUR.  Access the character as

                     char*   SvEND(sv)


     sv_eq   Returns a boolean indicating whether the strings in the two SVs
             are identical.

                     I32     sv_eq (SV* sv1, SV* sv2)


     SvGETMAGIC
             Invokes mg_get on an SV if it has 'get' magic.  This macro
             evaluates its argument more than once.

                     void    SvGETMAGIC( SV *sv )


     SvGROW  Expands the character buffer in the SV so that it has room for
             the indicated number of bytes (remember to reserve space for an
             extra trailing NUL character).  Calls sv_grow to perform the
             expansion if necessary.  Returns a pointer to the character
             buffer.

                     char*   SvGROW( SV* sv, STRLEN len )



                                                                       PPPPaaaaggggeeee 55552222






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     sv_grow Expands the character buffer in the SV.  This will use sv_unref
             and will upgrade the SV to SVt_PV.  Returns a pointer to the
             character buffer.  Use SvGROW.

     sv_inc  Auto-increment of the value in the SV.

                     void    sv_inc (SV* sv)


     sv_insert
             Inserts a string at the specified offset/length within the SV.
             Similar to the Perl _s_u_b_s_t_r() function.

                     void    sv_insert(SV *sv, STRLEN offset, STRLEN len,
                                       char *str, STRLEN strlen)


     SvIOK   Returns a boolean indicating whether the SV contains an integer.

                     int     SvIOK (SV* SV)


     SvIOK_off
             Unsets the IV status of an SV.

                     void    SvIOK_off (SV* sv)


     SvIOK_on
             Tells an SV that it is an integer.

                     void    SvIOK_on (SV* sv)


     SvIOK_only
             Tells an SV that it is an integer and disables all other OK bits.

                     void    SvIOK_only (SV* sv)


     SvIOKp  Returns a boolean indicating whether the SV contains an integer.
             Checks the pppprrrriiiivvvvaaaatttteeee setting.  Use SvIOK.

                     int     SvIOKp (SV* SV)


     sv_isa  Returns a boolean indicating whether the SV is blessed into the
             specified class.  This does not check for subtypes; use
             sv_derived_from to verify an inheritance relationship.

                     int     sv_isa (SV* sv, char* name)




                                                                       PPPPaaaaggggeeee 55553333






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     sv_isobject
             Returns a boolean indicating whether the SV is an RV pointing to
             a blessed object.  If the SV is not an RV, or if the object is
             not blessed, then this will return false.

                     int     sv_isobject (SV* sv)


     SvIV    Returns the integer which is in the SV.

                     int SvIV (SV* sv)


     SvIVX   Returns the integer which is stored in the SV.

                     int     SvIVX (SV* sv)


     SvLEN   Returns the size of the string buffer in the SV.  See SvCUR.

                     int     SvLEN (SV* sv)


     sv_len  Returns the length of the string in the SV.  Use SvCUR.

                     STRLEN  sv_len (SV* sv)


     sv_magic
             Adds magic to an SV.

                     void    sv_magic (SV* sv, SV* obj, int how, char* name, I32 namlen)


     sv_mortalcopy
             Creates a new SV which is a copy of the original SV.  The new SV
             is marked as mortal.

                     SV*     sv_mortalcopy (SV* oldsv)


     sv_newmortal
             Creates a new SV which is mortal.  The reference count of the SV
             is set to 1.

                     SV*     sv_newmortal (void)


     SvNIOK  Returns a boolean indicating whether the SV contains a number,
             integer or double.

                     int     SvNIOK (SV* SV)



                                                                       PPPPaaaaggggeeee 55554444






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     SvNIOK_off
             Unsets the NV/IV status of an SV.

                     void    SvNIOK_off (SV* sv)


     SvNIOKp Returns a boolean indicating whether the SV contains a number,
             integer or double.  Checks the pppprrrriiiivvvvaaaatttteeee setting.  Use SvNIOK.

                     int     SvNIOKp (SV* SV)


     PL_sv_no
             This is the false SV.  See PL_sv_yes.  Always refer to this as
             &PL_sv_no.

     SvNOK   Returns a boolean indicating whether the SV contains a double.

                     int     SvNOK (SV* SV)


     SvNOK_off
             Unsets the NV status of an SV.

                     void    SvNOK_off (SV* sv)


     SvNOK_on
             Tells an SV that it is a double.

                     void    SvNOK_on (SV* sv)


     SvNOK_only
             Tells an SV that it is a double and disables all other OK bits.

                     void    SvNOK_only (SV* sv)


     SvNOKp  Returns a boolean indicating whether the SV contains a double.
             Checks the pppprrrriiiivvvvaaaatttteeee setting.  Use SvNOK.

                     int     SvNOKp (SV* SV)


     SvNV    Returns the double which is stored in the SV.

                     double  SvNV (SV* sv)







                                                                       PPPPaaaaggggeeee 55555555






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     SvNVX   Returns the double which is stored in the SV.

                     double  SvNVX (SV* sv)


     SvOK    Returns a boolean indicating whether the value is an SV.

                     int     SvOK (SV* sv)


     SvOOK   Returns a boolean indicating whether the SvIVX is a valid offset
             value for the SvPVX.  This hack is used internally to speed up
             removal of characters from the beginning of a SvPV.  When SvOOK
             is true, then the start of the allocated string buffer is really
             (SvPVX - SvIVX).

                     int     SvOOK(SV* sv)


     SvPOK   Returns a boolean indicating whether the SV contains a character
             string.

                     int     SvPOK (SV* SV)


     SvPOK_off
             Unsets the PV status of an SV.

                     void    SvPOK_off (SV* sv)


     SvPOK_on
             Tells an SV that it is a string.

                     void    SvPOK_on (SV* sv)


     SvPOK_only
             Tells an SV that it is a string and disables all other OK bits.

                     void    SvPOK_only (SV* sv)


     SvPOKp  Returns a boolean indicating whether the SV contains a character
             string.  Checks the pppprrrriiiivvvvaaaatttteeee setting.  Use SvPOK.

                     int     SvPOKp (SV* SV)


     SvPV    Returns a pointer to the string in the SV, or a stringified form
             of the SV if the SV does not contain a string.  If len is PL_na
             then Perl will handle the length on its own.  Handles 'get'



                                                                       PPPPaaaaggggeeee 55556666






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



             magic.

                     char*   SvPV (SV* sv, int len )


     SvPV_force
             Like <SvPV> but will force the SV into becoming a string (SvPOK).
             You want force if you are going to update the SvPVX directly.

                     char*   SvPV_force(SV* sv, int len)


     SvPVX   Returns a pointer to the string in the SV.  The SV must contain a
             string.

                     char*   SvPVX (SV* sv)


     SvREFCNT
             Returns the value of the object's reference count.

                     int     SvREFCNT (SV* sv)


     SvREFCNT_dec
             Decrements the reference count of the given SV.

                     void    SvREFCNT_dec (SV* sv)


     SvREFCNT_inc
             Increments the reference count of the given SV.

                     void    SvREFCNT_inc (SV* sv)


     SvROK   Tests if the SV is an RV.

                     int     SvROK (SV* sv)


     SvROK_off
             Unsets the RV status of an SV.

                     void    SvROK_off (SV* sv)


     SvROK_on
             Tells an SV that it is an RV.

                     void    SvROK_on (SV* sv)




                                                                       PPPPaaaaggggeeee 55557777






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     SvRV    Dereferences an RV to return the SV.

                     SV*     SvRV (SV* sv)


     SvSETMAGIC
             Invokes mg_set on an SV if it has 'set' magic.  This macro
             evaluates its argument more than once.

                     void    SvSETMAGIC( SV *sv )


     sv_setiv
             Copies an integer into the given SV.  Does not handle 'set'
             magic.  See sv_setiv_mg.

                     void    sv_setiv (SV* sv, IV num)


     sv_setiv_mg
             Like sv_setiv, but also handles 'set' magic.

                     void    sv_setiv_mg (SV* sv, IV num)


     sv_setnv
             Copies a double into the given SV.  Does not handle 'set' magic.
             See sv_setnv_mg.

                     void    sv_setnv (SV* sv, double num)


     sv_setnv_mg
             Like sv_setnv, but also handles 'set' magic.

                     void    sv_setnv_mg (SV* sv, double num)


     sv_setpv
             Copies a string into an SV.  The string must be null-terminated.
             Does not handle 'set' magic.  See sv_setpv_mg.

                     void    sv_setpv (SV* sv, char* ptr)


     sv_setpv_mg
             Like sv_setpv, but also handles 'set' magic.

                     void    sv_setpv_mg (SV* sv, char* ptr)






                                                                       PPPPaaaaggggeeee 55558888






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     sv_setpviv
             Copies an integer into the given SV, also updating its string
             value.  Does not handle 'set' magic.  See sv_setpviv_mg.

                     void    sv_setpviv (SV* sv, IV num)


     sv_setpviv_mg
             Like sv_setpviv, but also handles 'set' magic.

                     void    sv_setpviv_mg (SV* sv, IV num)


     sv_setpvn
             Copies a string into an SV.  The len parameter indicates the
             number of bytes to be copied.  Does not handle 'set' magic.  See
             sv_setpvn_mg.

                     void    sv_setpvn (SV* sv, char* ptr, STRLEN len)


     sv_setpvn_mg
             Like sv_setpvn, but also handles 'set' magic.

                     void    sv_setpvn_mg (SV* sv, char* ptr, STRLEN len)


     sv_setpvf
             Processes its arguments like sprintf and sets an SV to the
             formatted output.  Does not handle 'set' magic.  See
             sv_setpvf_mg.

                     void    sv_setpvf (SV* sv, const char* pat, ...)


     sv_setpvf_mg
             Like sv_setpvf, but also handles 'set' magic.

                     void    sv_setpvf_mg (SV* sv, const char* pat, ...)


     sv_setref_iv
             Copies an integer into a new SV, optionally blessing the SV.  The
             rv argument will be upgraded to an RV.  That RV will be modified
             to point to the new SV.  The classname argument indicates the
             package for the blessing.  Set classname to Nullch to avoid the
             blessing.  The new SV will be returned and will have a reference
             count of 1.

                     SV*     sv_setref_iv (SV *rv, char *classname, IV iv)





                                                                       PPPPaaaaggggeeee 55559999






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     sv_setref_nv
             Copies a double into a new SV, optionally blessing the SV.  The
             rv argument will be upgraded to an RV.  That RV will be modified
             to point to the new SV.  The classname argument indicates the
             package for the blessing.  Set classname to Nullch to avoid the
             blessing.  The new SV will be returned and will have a reference
             count of 1.

                     SV*     sv_setref_nv (SV *rv, char *classname, double nv)


     sv_setref_pv
             Copies a pointer into a new SV, optionally blessing the SV.  The
             rv argument will be upgraded to an RV.  That RV will be modified
             to point to the new SV.  If the pv argument is NULL then
             PL_sv_undef will be placed into the SV.  The classname argument
             indicates the package for the blessing.  Set classname to Nullch
             to avoid the blessing.  The new SV will be returned and will have
             a reference count of 1.

                     SV*     sv_setref_pv (SV *rv, char *classname, void* pv)

             Do not use with integral Perl types such as HV, AV, SV, CV,
             because those objects will become corrupted by the pointer copy
             process.

             Note that sv_setref_pvn copies the string while this copies the
             pointer.

     sv_setref_pvn
             Copies a string into a new SV, optionally blessing the SV.  The
             length of the string must be specified with n.  The rv argument
             will be upgraded to an RV.  That RV will be modified to point to
             the new SV.  The classname argument indicates the package for the
             blessing.  Set classname to Nullch to avoid the blessing.  The
             new SV will be returned and will have a reference count of 1.

                     SV*     sv_setref_pvn (SV *rv, char *classname, char* pv, I32 n)

             Note that sv_setref_pv copies the pointer while this copies the
             string.

     SvSetSV Calls sv_setsv if dsv is not the same as ssv.  May evaluate
             arguments more than once.

                     void    SvSetSV (SV* dsv, SV* ssv)


     SvSetSV_nosteal
             Calls a non-destructive version of sv_setsv if dsv is not the
             same as ssv.  May evaluate arguments more than once.




                                                                       PPPPaaaaggggeeee 66660000






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



                     void    SvSetSV_nosteal (SV* dsv, SV* ssv)


     sv_setsv
             Copies the contents of the source SV ssv into the destination SV
             dsv.  The source SV may be destroyed if it is mortal.  Does not
             handle 'set' magic.  See the macro forms SvSetSV, SvSetSV_nosteal
             and sv_setsv_mg.

                     void    sv_setsv (SV* dsv, SV* ssv)


     sv_setsv_mg
             Like sv_setsv, but also handles 'set' magic.

                     void    sv_setsv_mg (SV* dsv, SV* ssv)


     sv_setuv
             Copies an unsigned integer into the given SV.  Does not handle
             'set' magic.  See sv_setuv_mg.

                     void    sv_setuv (SV* sv, UV num)


     sv_setuv_mg
             Like sv_setuv, but also handles 'set' magic.

                     void    sv_setuv_mg (SV* sv, UV num)


     SvSTASH Returns the stash of the SV.

                     HV*     SvSTASH (SV* sv)


     SvTAINT Taints an SV if tainting is enabled

                     void    SvTAINT (SV* sv)


     SvTAINTED
             Checks to see if an SV is tainted. Returns TRUE if it is, FALSE
             if not.

                     int     SvTAINTED (SV* sv)


     SvTAINTED_off
             Untaints an SV. Be _v_e_r_y careful with this routine, as it short-
             circuits some of Perl's fundamental security features. XS module
             authors should not use this function unless they fully understand



                                                                       PPPPaaaaggggeeee 66661111






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



             all the implications of unconditionally untainting the value.
             Untainting should be done in the standard perl fashion, via a
             carefully crafted regexp, rather than directly untainting
             variables.

                     void    SvTAINTED_off (SV* sv)


     SvTAINTED_on
             Marks an SV as tainted.

                     void    SvTAINTED_on (SV* sv)


     SVt_IV  Integer type flag for scalars.  See svtype.

     SVt_PV  Pointer type flag for scalars.  See svtype.

     SVt_PVAV
             Type flag for arrays.  See svtype.

     SVt_PVCV
             Type flag for code refs.  See svtype.

     SVt_PVHV
             Type flag for hashes.  See svtype.

     SVt_PVMG
             Type flag for blessed scalars.  See svtype.

     SVt_NV  Double type flag for scalars.  See svtype.

     SvTRUE  Returns a boolean indicating whether Perl would evaluate the SV
             as true or false, defined or undefined.  Does not handle 'get'
             magic.

                     int     SvTRUE (SV* sv)


     SvTYPE  Returns the type of the SV.  See svtype.

                     svtype  SvTYPE (SV* sv)


     svtype  An enum of flags for Perl types.  These are found in the file
             ssssvvvv....hhhh in the svtype enum.  Test these flags with the SvTYPE macro.

     PL_sv_undef
             This is the undef SV.  Always refer to this as &PL_sv_undef.






                                                                       PPPPaaaaggggeeee 66662222






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     sv_unref
             Unsets the RV status of the SV, and decrements the reference
             count of whatever was being referenced by the RV.  This can
             almost be thought of as a reversal of newSVrv.  See SvROK_off.

                     void    sv_unref (SV* sv)


     SvUPGRADE
             Used to upgrade an SV to a more complex form.  Uses sv_upgrade to
             perform the upgrade if necessary.  See svtype.

                     bool    SvUPGRADE (SV* sv, svtype mt)


     sv_upgrade
             Upgrade an SV to a more complex form.  Use SvUPGRADE.  See
             svtype.

     sv_usepvn
             Tells an SV to use ptr to find its string value.  Normally the
             string is stored inside the SV but sv_usepvn allows the SV to use
             an outside string.  The ptr should point to memory that was
             allocated by malloc.  The string length, len, must be supplied.
             This function will realloc the memory pointed to by ptr, so that
             pointer should not be freed or used by the programmer after
             giving it to sv_usepvn.  Does not handle 'set' magic.  See
             sv_usepvn_mg.

                     void    sv_usepvn (SV* sv, char* ptr, STRLEN len)


     sv_usepvn_mg
             Like sv_usepvn, but also handles 'set' magic.

                     void    sv_usepvn_mg (SV* sv, char* ptr, STRLEN len)


     sv_vcatpvfn(sv, pat, patlen, args, svargs, svmax, used_locale)
             Processes its arguments like vsprintf and appends the formatted
             output to an SV.  Uses an array of SVs if the C style variable
             argument list is missing (NULL).  Indicates if locale information
             has been used for formatting.

                     void    sv_catpvfn _((SV* sv, const char* pat, STRLEN patlen,
                                           va_list *args, SV **svargs, I32 svmax,
                                           bool *used_locale));


     sv_vsetpvfn(sv, pat, patlen, args, svargs, svmax, used_locale)
             Works like vcatpvfn but copies the text into the SV instead of
             appending it.



                                                                       PPPPaaaaggggeeee 66663333






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



                     void    sv_setpvfn _((SV* sv, const char* pat, STRLEN patlen,
                                           va_list *args, SV **svargs, I32 svmax,
                                           bool *used_locale));


     SvUV    Returns the unsigned integer which is in the SV.

                     UV      SvUV(SV* sv)


     SvUVX   Returns the unsigned integer which is stored in the SV.

                     UV      SvUVX(SV* sv)


     PL_sv_yes
             This is the true SV.  See PL_sv_no.  Always refer to this as
             &PL_sv_yes.

     THIS    Variable which is setup by xsubpp to designate the object in a
             C++ XSUB.  This is always the proper type for the C++ object.
             See CLASS and the section on _U_s_i_n_g _X_S _W_i_t_h _C++ in the _p_e_r_l_x_s
             manpage.

     toLOWER Converts the specified character to lowercase.

                     int     toLOWER (char c)


     toUPPER Converts the specified character to uppercase.

                     int     toUPPER (char c)


     warn    This is the XSUB-writer's interface to Perl's warn function.  Use
             this function the same way you use the C printf function.  See
             croak().

     XPUSHi  Push an integer onto the stack, extending the stack if necessary.
             Handles 'set' magic. See PUSHi.

                     XPUSHi(int d)


     XPUSHn  Push a double onto the stack, extending the stack if necessary.
             Handles 'set' magic.  See PUSHn.

                     XPUSHn(double d)







                                                                       PPPPaaaaggggeeee 66664444






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     XPUSHp  Push a string onto the stack, extending the stack if necessary.
             The len indicates the length of the string.  Handles 'set' magic.
             See PUSHp.

                     XPUSHp(char *c, int len)


     XPUSHs  Push an SV onto the stack, extending the stack if necessary.
             Does not handle 'set' magic.  See PUSHs.

                     XPUSHs(sv)


     XPUSHu  Push an unsigned integer onto the stack, extending the stack if
             necessary.  See PUSHu.

     XS      Macro to declare an XSUB and its C parameter list.  This is
             handled by xsubpp.

     XSRETURN
             Return from XSUB, indicating number of items on the stack.  This
             is usually handled by xsubpp.

                     XSRETURN(int x)


     XSRETURN_EMPTY
             Return an empty list from an XSUB immediately.

                     XSRETURN_EMPTY;


     XSRETURN_IV
             Return an integer from an XSUB immediately.  Uses XST_mIV.

                     XSRETURN_IV(IV v)


     XSRETURN_NO
             Return &PL_sv_no from an XSUB immediately.  Uses XST_mNO.

                     XSRETURN_NO;


     XSRETURN_NV
             Return an double from an XSUB immediately.  Uses XST_mNV.

                     XSRETURN_NV(NV v)







                                                                       PPPPaaaaggggeeee 66665555






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     XSRETURN_PV
             Return a copy of a string from an XSUB immediately.  Uses
             XST_mPV.

                     XSRETURN_PV(char *v)


     XSRETURN_UNDEF
             Return &PL_sv_undef from an XSUB immediately.  Uses XST_mUNDEF.

                     XSRETURN_UNDEF;


     XSRETURN_YES
             Return &PL_sv_yes from an XSUB immediately.  Uses XST_mYES.

                     XSRETURN_YES;


     XST_mIV Place an integer into the specified position i on the stack.  The
             value is stored in a new mortal SV.

                     XST_mIV( int i, IV v )


     XST_mNV Place a double into the specified position i on the stack.  The
             value is stored in a new mortal SV.

                     XST_mNV( int i, NV v )


     XST_mNO Place &PL_sv_no into the specified position i on the stack.

                     XST_mNO( int i )


     XST_mPV Place a copy of a string into the specified position i on the
             stack.  The value is stored in a new mortal SV.

                     XST_mPV( int i, char *v )


     XST_mUNDEF
             Place &PL_sv_undef into the specified position i on the stack.

                     XST_mUNDEF( int i )


     XST_mYES
             Place &PL_sv_yes into the specified position i on the stack.

                     XST_mYES( int i )



                                                                       PPPPaaaaggggeeee 66666666






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))



     XS_VERSION
             The version identifier for an XS module.  This is usually handled
             automatically by ExtUtils::MakeMaker.  See XS_VERSION_BOOTCHECK.

     XS_VERSION_BOOTCHECK
             Macro to verify that a PM module's $VERSION variable matches the
             XS module's XS_VERSION variable.  This is usually handled
             automatically by xsubpp.  See the section on _T_h_e _V_E_R_S_I_O_N_C_H_E_C_K:
             _K_e_y_w_o_r_d in the _p_e_r_l_x_s manpage.

     Zero    The XSUB-writer's interface to the C memzero function.  The d is
             the destination, n is the number of items, and t is the type.

                     void    Zero( d, n, t )


AAAAUUUUTTTTHHHHOOOORRRRSSSS
     Until May 1997, this document was maintained by Jeff Okamoto
     <[e-mail]>.  It is now maintained as part of Perl itself.

     With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
     Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil
     Bowers, Matthew Green, Tim Bunce, Spider Boardman, Ulrich Pfeifer,
     Stephen McCamant, and Gurusamy Sarathy.

     API Listing originally by Dean Roehrich <[e-mail]>.





























                                                                       PPPPaaaaggggeeee 66667777






PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))                                                        PPPPEEEERRRRLLLLGGGGUUUUTTTTSSSS((((1111))))























































                                                                       PPPPaaaaggggeeee 66668888