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Text File | 2006-04-25 | 130KB | 5,592 lines

=head1 NAME

perlapi - autogenerated documentation for the perl public API

=head1 DESCRIPTION

This file contains the documentation of the perl public API generated by
embed.pl, specifically a listing of functions, macros, flags, and variables
that may be used by extension writers.  The interfaces of any functions that
are not listed here are subject to change without notice.  For this reason,
blindly using functions listed in proto.h is to be avoided when writing
extensions.

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

The listing is alphabetical, case insensitive.


=head1 "Gimme" Values

=over 8

=item GIMME

A backward-compatible version of C<GIMME_V> which can only return
C<G_SCALAR> or C<G_ARRAY>; in a void context, it returns C<G_SCALAR>.
Deprecated.  Use C<GIMME_V> instead.

    U32    GIMME

=for hackers
Found in file op.h

=item GIMME_V

The XSUB-writer's equivalent to Perl's C<wantarray>.  Returns C<G_VOID>,
C<G_SCALAR> or C<G_ARRAY> for void, scalar or list context,
respectively.

    U32    GIMME_V

=for hackers
Found in file op.h

=item G_ARRAY

Used to indicate list context.  See C<GIMME_V>, C<GIMME> and
L<perlcall>.

=for hackers
Found in file cop.h

=item G_DISCARD

Indicates that arguments returned from a callback should be discarded.  See
L<perlcall>.

=for hackers
Found in file cop.h

=item G_EVAL

Used to force a Perl C<eval> wrapper around a callback.  See
L<perlcall>.

=for hackers
Found in file cop.h

=item G_NOARGS

Indicates that no arguments are being sent to a callback.  See
L<perlcall>.

=for hackers
Found in file cop.h

=item G_SCALAR

Used to indicate scalar context.  See C<GIMME_V>, C<GIMME>, and
L<perlcall>.

=for hackers
Found in file cop.h

=item G_VOID

Used to indicate void context.  See C<GIMME_V> and L<perlcall>.

=for hackers
Found in file cop.h


=back

=head1 Array Manipulation Functions

=over 8

=item AvFILL

Same as C<av_len()>.  Deprecated, use C<av_len()> instead.

    int    AvFILL(AV* av)

=for hackers
Found in file av.h

=item av_clear

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

    void    av_clear(AV* ar)

=for hackers
Found in file av.c

=item av_delete

Deletes the element indexed by C<key> from the array.  Returns the
deleted element. If C<flags> equals C<G_DISCARD>, the element is freed
and null is returned.

    SV*    av_delete(AV* ar, I32 key, I32 flags)

=for hackers
Found in file av.c

=item av_exists

Returns true if the element indexed by C<key> has been initialized.

This relies on the fact that uninitialized array elements are set to
C<&PL_sv_undef>.

    bool    av_exists(AV* ar, I32 key)

=for hackers
Found in file av.c

=item av_extend

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

    void    av_extend(AV* ar, I32 key)

=for hackers
Found in file av.c

=item av_fetch

Returns the SV at the specified index in the array.  The C<key> is the
index.  If C<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 C<SV*>.

See L<perlguts/"Understanding the Magic of Tied Hashes and Arrays"> for
more information on how to use this function on tied arrays.

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

=for hackers
Found in file av.c

=item av_fill

Ensure than an array has a given number of elements, equivalent to
Perl's C<$#array = $fill;>.

    void    av_fill(AV* ar, I32 fill)

=for hackers
Found in file av.c

=item av_len

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

    I32    av_len(AV* ar)

=for hackers
Found in file av.c

=item 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)

=for hackers
Found in file av.c

=item av_pop

Pops an SV off the end of the array.  Returns C<&PL_sv_undef> if the array
is empty.

    SV*    av_pop(AV* ar)

=for hackers
Found in file av.c

=item 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)

=for hackers
Found in file av.c

=item av_shift

Shifts an SV off the beginning of the array.

    SV*    av_shift(AV* ar)

=for hackers
Found in file av.c

=item av_store

Stores an SV in an array.  The array index is specified as C<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 C<SV*>.  Note
that the caller is responsible for suitably incrementing the reference
count of C<val> before the call, and decrementing it if the function
returned NULL.

See L<perlguts/"Understanding the Magic of Tied Hashes and Arrays"> for
more information on how to use this function on tied arrays.

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

=for hackers
Found in file av.c

=item av_undef

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

    void    av_undef(AV* ar)

=for hackers
Found in file av.c

=item av_unshift

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

    void    av_unshift(AV* ar, I32 num)

=for hackers
Found in file av.c

=item get_av

Returns the AV of the specified Perl array.  If C<create> is set and the
Perl variable does not exist then it will be created.  If C<create> is not
set and the variable does not exist then NULL is returned.

NOTE: the perl_ form of this function is deprecated.

    AV*    get_av(const char* name, I32 create)

=for hackers
Found in file perl.c

=item newAV

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

    AV*    newAV()

=for hackers
Found in file av.c

=item sortsv

Sort an array. Here is an example:

    sortsv(AvARRAY(av), av_len(av)+1, Perl_sv_cmp_locale);

See lib/sort.pm for details about controlling the sorting algorithm.

    void    sortsv(SV ** array, size_t num_elts, SVCOMPARE_t cmp)

=for hackers
Found in file pp_sort.c


=back

=head1 Callback Functions

=over 8

=item call_argv

Performs a callback to the specified Perl sub.  See L<perlcall>.

NOTE: the perl_ form of this function is deprecated.

    I32    call_argv(const char* sub_name, I32 flags, char** argv)

=for hackers
Found in file perl.c

=item call_method

Performs a callback to the specified Perl method.  The blessed object must
be on the stack.  See L<perlcall>.

NOTE: the perl_ form of this function is deprecated.

    I32    call_method(const char* methname, I32 flags)

=for hackers
Found in file perl.c

=item call_pv

Performs a callback to the specified Perl sub.  See L<perlcall>.

NOTE: the perl_ form of this function is deprecated.

    I32    call_pv(const char* sub_name, I32 flags)

=for hackers
Found in file perl.c

=item call_sv

Performs a callback to the Perl sub whose name is in the SV.  See
L<perlcall>.

NOTE: the perl_ form of this function is deprecated.

    I32    call_sv(SV* sv, I32 flags)

=for hackers
Found in file perl.c

=item ENTER

Opening bracket on a callback.  See C<LEAVE> and L<perlcall>.

        ENTER;

=for hackers
Found in file scope.h

=item eval_pv

Tells Perl to C<eval> the given string and return an SV* result.

NOTE: the perl_ form of this function is deprecated.

    SV*    eval_pv(const char* p, I32 croak_on_error)

=for hackers
Found in file perl.c

=item eval_sv

Tells Perl to C<eval> the string in the SV.

NOTE: the perl_ form of this function is deprecated.

    I32    eval_sv(SV* sv, I32 flags)

=for hackers
Found in file perl.c

=item FREETMPS

Closing bracket for temporaries on a callback.  See C<SAVETMPS> and
L<perlcall>.

        FREETMPS;

=for hackers
Found in file scope.h

=item LEAVE

Closing bracket on a callback.  See C<ENTER> and L<perlcall>.

        LEAVE;

=for hackers
Found in file scope.h

=item SAVETMPS

Opening bracket for temporaries on a callback.  See C<FREETMPS> and
L<perlcall>.

        SAVETMPS;

=for hackers
Found in file scope.h


=back

=head1 Character classes

=over 8

=item isALNUM

Returns a boolean indicating whether the C C<char> is an ASCII alphanumeric
character (including underscore) or digit.

    bool    isALNUM(char ch)

=for hackers
Found in file handy.h

=item isALPHA

Returns a boolean indicating whether the C C<char> is an ASCII alphabetic
character.

    bool    isALPHA(char ch)

=for hackers
Found in file handy.h

=item isDIGIT

Returns a boolean indicating whether the C C<char> is an ASCII
digit.

    bool    isDIGIT(char ch)

=for hackers
Found in file handy.h

=item isLOWER

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

    bool    isLOWER(char ch)

=for hackers
Found in file handy.h

=item isSPACE

Returns a boolean indicating whether the C C<char> is whitespace.

    bool    isSPACE(char ch)

=for hackers
Found in file handy.h

=item isUPPER

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

    bool    isUPPER(char ch)

=for hackers
Found in file handy.h

=item toLOWER

Converts the specified character to lowercase.

    char    toLOWER(char ch)

=for hackers
Found in file handy.h

=item toUPPER

Converts the specified character to uppercase.

    char    toUPPER(char ch)

=for hackers
Found in file handy.h


=back

=head1 Cloning an interpreter

=over 8

=item perl_clone

Create and return a new interpreter by cloning the current one.

perl_clone takes these flags as parameters:

CLONEf_COPY_STACKS - is used to, well, copy the stacks also,
without it we only clone the data and zero the stacks,
with it we copy the stacks and the new perl interpreter is
ready to run at the exact same point as the previous one.
The pseudo-fork code uses COPY_STACKS while the
threads->new doesn't.

CLONEf_KEEP_PTR_TABLE
perl_clone keeps a ptr_table with the pointer of the old
variable as a key and the new variable as a value,
this allows it to check if something has been cloned and not
clone it again but rather just use the value and increase the
refcount. If KEEP_PTR_TABLE is not set then perl_clone will kill
the ptr_table using the function
C<ptr_table_free(PL_ptr_table); PL_ptr_table = NULL;>,
reason to keep it around is if you want to dup some of your own
variable who are outside the graph perl scans, example of this
code is in threads.xs create

CLONEf_CLONE_HOST
This is a win32 thing, it is ignored on unix, it tells perls
win32host code (which is c++) to clone itself, this is needed on
win32 if you want to run two threads at the same time,
if you just want to do some stuff in a separate perl interpreter
and then throw it away and return to the original one,
you don't need to do anything.

    PerlInterpreter*    perl_clone(PerlInterpreter* interp, UV flags)

=for hackers
Found in file sv.c


=back

=head1 CV Manipulation Functions

=over 8

=item CvSTASH

Returns the stash of the CV.

    HV*    CvSTASH(CV* cv)

=for hackers
Found in file cv.h

=item get_cv

Returns the CV of the specified Perl subroutine.  If C<create> is set and
the Perl subroutine does not exist then it will be declared (which has the
same effect as saying C<sub name;>).  If C<create> is not set and the
subroutine does not exist then NULL is returned.

NOTE: the perl_ form of this function is deprecated.

    CV*    get_cv(const char* name, I32 create)

=for hackers
Found in file perl.c


=back

=head1 Embedding Functions

=over 8

=item cv_undef

Clear out all the active components of a CV. This can happen either
by an explicit C<undef &foo>, or by the reference count going to zero.
In the former case, we keep the CvOUTSIDE pointer, so that any anonymous
children can still follow the full lexical scope chain.

    void    cv_undef(CV* cv)

=for hackers
Found in file op.c

=item load_module

Loads the module whose name is pointed to by the string part of name.
Note that the actual module name, not its filename, should be given.
Eg, "Foo::Bar" instead of "Foo/Bar.pm".  flags can be any of
PERL_LOADMOD_DENY, PERL_LOADMOD_NOIMPORT, or PERL_LOADMOD_IMPORT_OPS
(or 0 for no flags). ver, if specified, provides version semantics
similar to C<use Foo::Bar VERSION>.  The optional trailing SV*
arguments can be used to specify arguments to the module's import()
method, similar to C<use Foo::Bar VERSION LIST>.

    void    load_module(U32 flags, SV* name, SV* ver, ...)

=for hackers
Found in file op.c

=item nothreadhook

Stub that provides thread hook for perl_destruct when there are
no threads.

    int    nothreadhook()

=for hackers
Found in file perl.c

=item perl_alloc

Allocates a new Perl interpreter.  See L<perlembed>.

    PerlInterpreter*    perl_alloc()

=for hackers
Found in file perl.c

=item perl_construct

Initializes a new Perl interpreter.  See L<perlembed>.

    void    perl_construct(PerlInterpreter* interp)

=for hackers
Found in file perl.c

=item perl_destruct

Shuts down a Perl interpreter.  See L<perlembed>.

    int    perl_destruct(PerlInterpreter* interp)

=for hackers
Found in file perl.c

=item perl_free

Releases a Perl interpreter.  See L<perlembed>.

    void    perl_free(PerlInterpreter* interp)

=for hackers
Found in file perl.c

=item perl_parse

Tells a Perl interpreter to parse a Perl script.  See L<perlembed>.

    int    perl_parse(PerlInterpreter* interp, XSINIT_t xsinit, int argc, char** argv, char** env)

=for hackers
Found in file perl.c

=item perl_run

Tells a Perl interpreter to run.  See L<perlembed>.

    int    perl_run(PerlInterpreter* interp)

=for hackers
Found in file perl.c

=item require_pv

Tells Perl to C<require> the file named by the string argument.  It is
analogous to the Perl code C<eval "require '$file'">.  It's even
implemented that way; consider using load_module instead.

NOTE: the perl_ form of this function is deprecated.

    void    require_pv(const char* pv)

=for hackers
Found in file perl.c


=back

=head1 Functions in file pp_pack.c


=over 8

=item packlist

The engine implementing pack() Perl function.

    void    packlist(SV *cat, char *pat, char *patend, SV **beglist, SV **endlist)

=for hackers
Found in file pp_pack.c

=item pack_cat

The engine implementing pack() Perl function. Note: parameters next_in_list and
flags are not used. This call should not be used; use packlist instead.

    void    pack_cat(SV *cat, char *pat, char *patend, SV **beglist, SV **endlist, SV ***next_in_list, U32 flags)

=for hackers
Found in file pp_pack.c

=item unpackstring

The engine implementing unpack() Perl function. C<unpackstring> puts the
extracted list items on the stack and returns the number of elements.
Issue C<PUTBACK> before and C<SPAGAIN> after the call to this function.

    I32    unpackstring(char *pat, char *patend, char *s, char *strend, U32 flags)

=for hackers
Found in file pp_pack.c

=item unpack_str

The engine implementing unpack() Perl function. Note: parameters strbeg, new_s
and ocnt are not used. This call should not be used, use unpackstring instead.

    I32    unpack_str(char *pat, char *patend, char *s, char *strbeg, char *strend, char **new_s, I32 ocnt, U32 flags)

=for hackers
Found in file pp_pack.c


=back

=head1 Global Variables

=over 8

=item PL_modglobal

C<PL_modglobal> is a general purpose, interpreter global HV for use by
extensions that need to keep information on a per-interpreter basis.
In a pinch, it can also be used as a symbol table for extensions
to share data among each other.  It is a good idea to use keys
prefixed by the package name of the extension that owns the data.

    HV*    PL_modglobal

=for hackers
Found in file intrpvar.h

=item PL_na

A convenience variable which is typically used with C<SvPV> when one
doesn't care about the length of the string.  It is usually more efficient
to either declare a local variable and use that instead or to use the
C<SvPV_nolen> macro.

    STRLEN    PL_na

=for hackers
Found in file thrdvar.h

=item PL_sv_no

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

    SV    PL_sv_no

=for hackers
Found in file intrpvar.h

=item PL_sv_undef

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

    SV    PL_sv_undef

=for hackers
Found in file intrpvar.h

=item PL_sv_yes

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

    SV    PL_sv_yes

=for hackers
Found in file intrpvar.h


=back

=head1 GV Functions

=over 8

=item GvSV

Return the SV from the GV.

    SV*    GvSV(GV* gv)

=for hackers
Found in file gv.h

=item gv_fetchmeth

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

The argument C<level> should be either 0 or -1.  If C<level==0>, as a
side-effect creates a glob with the given C<name> in the given C<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 C<"SUPER"> token as a postfix of the stash name. The
GV returned from C<gv_fetchmeth> may be a method cache entry, which is not
visible to Perl code.  So when calling C<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 C<GvCV> macro.

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

=for hackers
Found in file gv.c

=item gv_fetchmethod

See L<gv_fetchmethod_autoload>.

    GV*    gv_fetchmethod(HV* stash, const char* name)

=for hackers
Found in file gv.c

=item gv_fetchmethod_autoload

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

The third parameter of C<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 for AUTOLOAD.
Calling C<gv_fetchmethod> is equivalent to calling C<gv_fetchmethod_autoload>
with a non-zero C<autoload> parameter.

These functions grant C<"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 C<gv_fetchmeth> with
C<level==0>.  C<name> should be writable if contains C<':'> or C<'
''>. The warning against passing the GV returned by C<gv_fetchmeth> to
C<call_sv> apply equally to these functions.

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

=for hackers
Found in file gv.c

=item gv_fetchmeth_autoload

Same as gv_fetchmeth(), but looks for autoloaded subroutines too.
Returns a glob for the subroutine.

For an autoloaded subroutine without a GV, will create a GV even
if C<level < 0>.  For an autoloaded subroutine without a stub, GvCV()
of the result may be zero.

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

=for hackers
Found in file gv.c

=item gv_stashpv

Returns a pointer to the stash for a specified package.  C<name> should
be a valid UTF-8 string and must be null-terminated.  If C<create> is set
then the package will be created if it does not already exist.  If C<create>
is not set and the package does not exist then NULL is returned.

    HV*    gv_stashpv(const char* name, I32 create)

=for hackers
Found in file gv.c

=item gv_stashpvn

Returns a pointer to the stash for a specified package.  C<name> should
be a valid UTF-8 string.  The C<namelen> parameter indicates the length of
the C<name>, in bytes.  If C<create> is set then the package will be
created if it does not already exist.  If C<create> is not set and the
package does not exist then NULL is returned.

    HV*    gv_stashpvn(const char* name, U32 namelen, I32 create)

=for hackers
Found in file gv.c

=item gv_stashsv

Returns a pointer to the stash for a specified package, which must be a
valid UTF-8 string.  See C<gv_stashpv>.

    HV*    gv_stashsv(SV* sv, I32 create)

=for hackers
Found in file gv.c


=back

=head1 Handy Values

=over 8

=item Nullav

Null AV pointer.

=for hackers
Found in file av.h

=item Nullch

Null character pointer.

=for hackers
Found in file handy.h

=item Nullcv

Null CV pointer.

=for hackers
Found in file cv.h

=item Nullhv

Null HV pointer.

=for hackers
Found in file hv.h

=item Nullsv

Null SV pointer.

=for hackers
Found in file handy.h


=back

=head1 Hash Manipulation Functions

=over 8

=item get_hv

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

NOTE: the perl_ form of this function is deprecated.

    HV*    get_hv(const char* name, I32 create)

=for hackers
Found in file perl.c

=item HEf_SVKEY

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

=for hackers
Found in file hv.h

=item HeHASH

Returns the computed hash stored in the hash entry.

    U32    HeHASH(HE* he)

=for hackers
Found in file hv.h

=item HeKEY

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

    void*    HeKEY(HE* he)

=for hackers
Found in file hv.h

=item HeKLEN

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

    STRLEN    HeKLEN(HE* he)

=for hackers
Found in file hv.h

=item HePV

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

    char*    HePV(HE* he, STRLEN len)

=for hackers
Found in file hv.h

=item HeSVKEY

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

    SV*    HeSVKEY(HE* he)

=for hackers
Found in file hv.h

=item HeSVKEY_force

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

    SV*    HeSVKEY_force(HE* he)

=for hackers
Found in file hv.h

=item HeSVKEY_set

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

    SV*    HeSVKEY_set(HE* he, SV* sv)

=for hackers
Found in file hv.h

=item HeVAL

Returns the value slot (type C<SV*>) stored in the hash entry.

    SV*    HeVAL(HE* he)

=for hackers
Found in file hv.h

=item HvNAME

Returns the package name of a stash.  See C<SvSTASH>, C<CvSTASH>.

    char*    HvNAME(HV* stash)

=for hackers
Found in file hv.h

=item hv_clear

Clears a hash, making it empty.

    void    hv_clear(HV* tb)

=for hackers
Found in file hv.c

=item hv_clear_placeholders

Clears any placeholders from a hash.  If a restricted hash has any of its keys
marked as readonly and the key is subsequently deleted, the key is not actually
deleted but is marked by assigning it a value of &PL_sv_placeholder.  This tags
it so it will be ignored by future operations such as iterating over the hash,
but will still allow the hash to have a value reassigned to the key at some
future point.  This function clears any such placeholder keys from the hash.
See Hash::Util::lock_keys() for an example of its use.

    void    hv_clear_placeholders(HV* hb)

=for hackers
Found in file hv.c

=item hv_delete

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

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

=for hackers
Found in file hv.c

=item 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 C<flags> value will normally be zero;
if set to G_DISCARD then NULL will be returned.  C<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)

=for hackers
Found in file hv.c

=item hv_exists

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

    bool    hv_exists(HV* tb, const char* key, I32 klen)

=for hackers
Found in file hv.c

=item hv_exists_ent

Returns a boolean indicating whether the specified hash key exists. C<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)

=for hackers
Found in file hv.c

=item hv_fetch

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

See L<perlguts/"Understanding the Magic of Tied Hashes and Arrays"> for more
information on how to use this function on tied hashes.

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

=for hackers
Found in file hv.c

=item hv_fetch_ent

Returns the hash entry which corresponds to the specified key in the hash.
C<hash> must be a valid precomputed hash number for the given C<key>, or 0
if you want the function to compute it.  IF C<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 C<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 L<perlguts/"Understanding the Magic of Tied Hashes and Arrays"> for more
information on how to use this function on tied hashes.

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

=for hackers
Found in file hv.c

=item hv_iterinit

Prepares a starting point to traverse a hash table.  Returns the number of
keys in the hash (i.e. the same as C<HvKEYS(tb)>).  The return value is
currently only meaningful for hashes without tie magic.

NOTE: Before version 5.004_65, C<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 C<HvFILL(tb)>.


    I32    hv_iterinit(HV* tb)

=for hackers
Found in file hv.c

=item hv_iterkey

Returns the key from the current position of the hash iterator.  See
C<hv_iterinit>.

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

=for hackers
Found in file hv.c

=item hv_iterkeysv

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

    SV*    hv_iterkeysv(HE* entry)

=for hackers
Found in file hv.c

=item hv_iternext

Returns entries from a hash iterator.  See C<hv_iterinit>.

You may call C<hv_delete> or C<hv_delete_ent> on the hash entry that the
iterator currently points to, without losing your place or invalidating your
iterator.  Note that in this case the current entry is deleted from the hash
with your iterator holding the last reference to it.  Your iterator is flagged
to free the entry on the next call to C<hv_iternext>, so you must not discard
your iterator immediately else the entry will leak - call C<hv_iternext> to
trigger the resource deallocation.

    HE*    hv_iternext(HV* tb)

=for hackers
Found in file hv.c

=item hv_iternextsv

Performs an C<hv_iternext>, C<hv_iterkey>, and C<hv_iterval> in one
operation.

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

=for hackers
Found in file hv.c

=item hv_iternext_flags

Returns entries from a hash iterator.  See C<hv_iterinit> and C<hv_iternext>.
The C<flags> value will normally be zero; if HV_ITERNEXT_WANTPLACEHOLDERS is
set the placeholders keys (for restricted hashes) will be returned in addition
to normal keys. By default placeholders are automatically skipped over.
Currently a placeholder is implemented with a value that is
C<&Perl_sv_placeholder>. Note that the implementation of placeholders and
restricted hashes may change, and the implementation currently is
insufficiently abstracted for any change to be tidy.

NOTE: this function is experimental and may change or be
removed without notice.

    HE*    hv_iternext_flags(HV* tb, I32 flags)

=for hackers
Found in file hv.c

=item hv_iterval

Returns the value from the current position of the hash iterator.  See
C<hv_iterkey>.

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

=for hackers
Found in file hv.c

=item hv_magic

Adds magic to a hash.  See C<sv_magic>.

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

=for hackers
Found in file hv.c

=item hv_scalar

Evaluates the hash in scalar context and returns the result. Handles magic when the hash is tied.

    SV*    hv_scalar(HV* hv)

=for hackers
Found in file hv.c

=item hv_store

Stores an SV in a hash.  The hash key is specified as C<key> and C<klen> is
the length of the key.  The C<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 C<SV*>.  Note that the caller is
responsible for suitably incrementing the reference count of C<val> before
the call, and decrementing it if the function returned NULL.  Effectively
a successful hv_store takes ownership of one reference to C<val>.  This is
usually what you want; a newly created SV has a reference count of one, so
if all your code does is create SVs then store them in a hash, hv_store
will own the only reference to the new SV, and your code doesn't need to do
anything further to tidy up.  hv_store is not implemented as a call to
hv_store_ent, and does not create a temporary SV for the key, so if your
key data is not already in SV form then use hv_store in preference to
hv_store_ent.

See L<perlguts/"Understanding the Magic of Tied Hashes and Arrays"> for more
information on how to use this function on tied hashes.

    SV**    hv_store(HV* tb, const char* key, I32 klen, SV* val, U32 hash)

=for hackers
Found in file hv.c

=item hv_store_ent

Stores C<val> in a hash.  The hash key is specified as C<key>.  The C<hash>
parameter is the precomputed hash value; if it is zero then 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 C<He?> macros
described here.  Note that the caller is responsible for suitably
incrementing the reference count of C<val> before the call, and
decrementing it if the function returned NULL.  Effectively a successful
hv_store_ent takes ownership of one reference to C<val>.  This is
usually what you want; a newly created SV has a reference count of one, so
if all your code does is create SVs then store them in a hash, hv_store
will own the only reference to the new SV, and your code doesn't need to do
anything further to tidy up.  Note that hv_store_ent only reads the C<key>;
unlike C<val> it does not take ownership of it, so maintaining the correct
reference count on C<key> is entirely the caller's responsibility.  hv_store
is not implemented as a call to hv_store_ent, and does not create a temporary
SV for the key, so if your key data is not already in SV form then use
hv_store in preference to hv_store_ent.

See L<perlguts/"Understanding the Magic of Tied Hashes and Arrays"> for more
information on how to use this function on tied hashes.

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

=for hackers
Found in file hv.c

=item hv_undef

Undefines the hash.

    void    hv_undef(HV* tb)

=for hackers
Found in file hv.c

=item newHV

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

    HV*    newHV()

=for hackers
Found in file hv.c


=back

=head1 Magical Functions

=over 8

=item mg_clear

Clear something magical that the SV represents.  See C<sv_magic>.

    int    mg_clear(SV* sv)

=for hackers
Found in file mg.c

=item mg_copy

Copies the magic from one SV to another.  See C<sv_magic>.

    int    mg_copy(SV* sv, SV* nsv, const char* key, I32 klen)

=for hackers
Found in file mg.c

=item mg_find

Finds the magic pointer for type matching the SV.  See C<sv_magic>.

    MAGIC*    mg_find(SV* sv, int type)

=for hackers
Found in file mg.c

=item mg_free

Free any magic storage used by the SV.  See C<sv_magic>.

    int    mg_free(SV* sv)

=for hackers
Found in file mg.c

=item mg_get

Do magic after a value is retrieved from the SV.  See C<sv_magic>.

    int    mg_get(SV* sv)

=for hackers
Found in file mg.c

=item mg_length

Report on the SV's length.  See C<sv_magic>.

    U32    mg_length(SV* sv)

=for hackers
Found in file mg.c

=item mg_magical

Turns on the magical status of an SV.  See C<sv_magic>.

    void    mg_magical(SV* sv)

=for hackers
Found in file mg.c

=item mg_set

Do magic after a value is assigned to the SV.  See C<sv_magic>.

    int    mg_set(SV* sv)

=for hackers
Found in file mg.c

=item SvGETMAGIC

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

    void    SvGETMAGIC(SV* sv)

=for hackers
Found in file sv.h

=item SvLOCK

Arranges for a mutual exclusion lock to be obtained on sv if a suitable module
has been loaded.

    void    SvLOCK(SV* sv)

=for hackers
Found in file sv.h

=item SvSETMAGIC

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

    void    SvSETMAGIC(SV* sv)

=for hackers
Found in file sv.h

=item SvSetMagicSV

Like C<SvSetSV>, but does any set magic required afterwards.

    void    SvSetMagicSV(SV* dsb, SV* ssv)

=for hackers
Found in file sv.h

=item SvSetMagicSV_nosteal

Like C<SvSetSV_nosteal>, but does any set magic required afterwards.

    void    SvSetMagicSV_nosteal(SV* dsv, SV* ssv)

=for hackers
Found in file sv.h

=item SvSetSV

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

    void    SvSetSV(SV* dsb, SV* ssv)

=for hackers
Found in file sv.h

=item SvSetSV_nosteal

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

    void    SvSetSV_nosteal(SV* dsv, SV* ssv)

=for hackers
Found in file sv.h

=item SvSHARE

Arranges for sv to be shared between threads if a suitable module
has been loaded.

    void    SvSHARE(SV* sv)

=for hackers
Found in file sv.h

=item SvUNLOCK

Releases a mutual exclusion lock on sv if a suitable module
has been loaded.

    void    SvUNLOCK(SV* sv)

=for hackers
Found in file sv.h


=back

=head1 Memory Management

=over 8

=item Copy

The XSUB-writer's interface to the C C<memcpy> function.  The C<src> is the
source, C<dest> is the destination, C<nitems> is the number of items, and C<type> is
the type.  May fail on overlapping copies.  See also C<Move>.

    void    Copy(void* src, void* dest, int nitems, type)

=for hackers
Found in file handy.h

=item CopyD

Like C<Copy> but returns dest. Useful for encouraging compilers to tail-call
optimise.

    void *    CopyD(void* src, void* dest, int nitems, type)

=for hackers
Found in file handy.h

=item Move

The XSUB-writer's interface to the C C<memmove> function.  The C<src> is the
source, C<dest> is the destination, C<nitems> is the number of items, and C<type> is
the type.  Can do overlapping moves.  See also C<Copy>.

    void    Move(void* src, void* dest, int nitems, type)

=for hackers
Found in file handy.h

=item MoveD

Like C<Move> but returns dest. Useful for encouraging compilers to tail-call
optimise.

    void *    MoveD(void* src, void* dest, int nitems, type)

=for hackers
Found in file handy.h

=item New

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

    void    New(int id, void* ptr, int nitems, type)

=for hackers
Found in file handy.h

=item Newc

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

    void    Newc(int id, void* ptr, int nitems, type, cast)

=for hackers
Found in file handy.h

=item Newz

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

    void    Newz(int id, void* ptr, int nitems, type)

=for hackers
Found in file handy.h

=item Poison

Fill up memory with a pattern (byte 0xAB over and over again) that
hopefully catches attempts to access uninitialized memory.

    void    Poison(void* dest, int nitems, type)

=for hackers
Found in file handy.h

=item Renew

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

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

=for hackers
Found in file handy.h

=item Renewc

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

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

=for hackers
Found in file handy.h

=item Safefree

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

    void    Safefree(void* ptr)

=for hackers
Found in file handy.h

=item savepv

Perl's version of C<strdup()>. Returns a pointer to a newly allocated
string which is a duplicate of C<pv>. The size of the string is
determined by C<strlen()>. The memory allocated for the new string can
be freed with the C<Safefree()> function.

    char*    savepv(const char* pv)

=for hackers
Found in file util.c

=item savepvn

Perl's version of what C<strndup()> would be if it existed. Returns a
pointer to a newly allocated string which is a duplicate of the first
C<len> bytes from C<pv>. The memory allocated for the new string can be
freed with the C<Safefree()> function.

    char*    savepvn(const char* pv, I32 len)

=for hackers
Found in file util.c

=item savesharedpv

A version of C<savepv()> which allocates the duplicate string in memory
which is shared between threads.

    char*    savesharedpv(const char* pv)

=for hackers
Found in file util.c

=item savesvpv

A version of C<savepv()>/C<savepvn()> which gets the string to duplicate from
the passed in SV using C<SvPV()>

    char*    savesvpv(SV* sv)

=for hackers
Found in file util.c

=item StructCopy

This is an architecture-independent macro to copy one structure to another.

    void    StructCopy(type src, type dest, type)

=for hackers
Found in file handy.h

=item Zero

The XSUB-writer's interface to the C C<memzero> function.  The C<dest> is the
destination, C<nitems> is the number of items, and C<type> is the type.

    void    Zero(void* dest, int nitems, type)

=for hackers
Found in file handy.h

=item ZeroD

Like C<Zero> but returns dest. Useful for encouraging compilers to tail-call
optimise.

    void *    ZeroD(void* dest, int nitems, type)

=for hackers
Found in file handy.h


=back

=head1 Miscellaneous Functions

=over 8

=item fbm_compile

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

    void    fbm_compile(SV* sv, U32 flags)

=for hackers
Found in file util.c

=item fbm_instr

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

    char*    fbm_instr(unsigned char* big, unsigned char* bigend, SV* littlesv, U32 flags)

=for hackers
Found in file util.c

=item form

Takes a sprintf-style format pattern and conventional
(non-SV) arguments and returns the formatted string.

    (char *) Perl_form(pTHX_ const char* pat, ...)

can be used any place a string (char *) is required:

    char * s = Perl_form("%d.%d",major,minor);

Uses a single private buffer so if you want to format several strings you
must explicitly copy the earlier strings away (and free the copies when you
are done).

    char*    form(const char* pat, ...)

=for hackers
Found in file util.c

=item getcwd_sv

Fill the sv with current working directory

    int    getcwd_sv(SV* sv)

=for hackers
Found in file util.c

=item strEQ

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

    bool    strEQ(char* s1, char* s2)

=for hackers
Found in file handy.h

=item strGE

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

    bool    strGE(char* s1, char* s2)

=for hackers
Found in file handy.h

=item strGT

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

    bool    strGT(char* s1, char* s2)

=for hackers
Found in file handy.h

=item strLE

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

    bool    strLE(char* s1, char* s2)

=for hackers
Found in file handy.h

=item strLT

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

    bool    strLT(char* s1, char* s2)

=for hackers
Found in file handy.h

=item strNE

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

    bool    strNE(char* s1, char* s2)

=for hackers
Found in file handy.h

=item strnEQ

Test two strings to see if they are equal.  The C<len> parameter indicates
the number of bytes to compare.  Returns true or false. (A wrapper for
C<strncmp>).

    bool    strnEQ(char* s1, char* s2, STRLEN len)

=for hackers
Found in file handy.h

=item strnNE

Test two strings to see if they are different.  The C<len> parameter
indicates the number of bytes to compare.  Returns true or false. (A
wrapper for C<strncmp>).

    bool    strnNE(char* s1, char* s2, STRLEN len)

=for hackers
Found in file handy.h

=item sv_nolocking

Dummy routine which "locks" an SV when there is no locking module present.
Exists to avoid test for a NULL function pointer and because it could potentially warn under
some level of strict-ness.

    void    sv_nolocking(SV *)

=for hackers
Found in file util.c

=item sv_nosharing

Dummy routine which "shares" an SV when there is no sharing module present.
Exists to avoid test for a NULL function pointer and because it could potentially warn under
some level of strict-ness.

    void    sv_nosharing(SV *)

=for hackers
Found in file util.c

=item sv_nounlocking

Dummy routine which "unlocks" an SV when there is no locking module present.
Exists to avoid test for a NULL function pointer and because it could potentially warn under
some level of strict-ness.

    void    sv_nounlocking(SV *)

=for hackers
Found in file util.c


=back

=head1 Numeric functions

=over 8

=item grok_bin

converts a string representing a binary number to numeric form.

On entry I<start> and I<*len> give the string to scan, I<*flags> gives
conversion flags, and I<result> should be NULL or a pointer to an NV.
The scan stops at the end of the string, or the first invalid character.
Unless C<PERL_SCAN_SILENT_ILLDIGIT> is set in I<*flags>, encountering an
invalid character will also trigger a warning.
On return I<*len> is set to the length of the scanned string,
and I<*flags> gives output flags.

If the value is <= UV_MAX it is returned as a UV, the output flags are clear,
and nothing is written to I<*result>. If the value is > UV_MAX C<grok_bin>
returns UV_MAX, sets C<PERL_SCAN_GREATER_THAN_UV_MAX> in the output flags,
and writes the value to I<*result> (or the value is discarded if I<result>
is NULL).

The binary number may optionally be prefixed with "0b" or "b" unless
C<PERL_SCAN_DISALLOW_PREFIX> is set in I<*flags> on entry. If
C<PERL_SCAN_ALLOW_UNDERSCORES> is set in I<*flags> then the binary
number may use '_' characters to separate digits.

    UV    grok_bin(char* start, STRLEN* len, I32* flags, NV *result)

=for hackers
Found in file numeric.c

=item grok_hex

converts a string representing a hex number to numeric form.

On entry I<start> and I<*len> give the string to scan, I<*flags> gives
conversion flags, and I<result> should be NULL or a pointer to an NV.
The scan stops at the end of the string, or the first invalid character.
Unless C<PERL_SCAN_SILENT_ILLDIGIT> is set in I<*flags>, encountering an
invalid character will also trigger a warning.
On return I<*len> is set to the length of the scanned string,
and I<*flags> gives output flags.

If the value is <= UV_MAX it is returned as a UV, the output flags are clear,
and nothing is written to I<*result>. If the value is > UV_MAX C<grok_hex>
returns UV_MAX, sets C<PERL_SCAN_GREATER_THAN_UV_MAX> in the output flags,
and writes the value to I<*result> (or the value is discarded if I<result>
is NULL).

The hex number may optionally be prefixed with "0x" or "x" unless
C<PERL_SCAN_DISALLOW_PREFIX> is set in I<*flags> on entry. If
C<PERL_SCAN_ALLOW_UNDERSCORES> is set in I<*flags> then the hex
number may use '_' characters to separate digits.

    UV    grok_hex(char* start, STRLEN* len, I32* flags, NV *result)

=for hackers
Found in file numeric.c

=item grok_number

Recognise (or not) a number.  The type of the number is returned
(0 if unrecognised), otherwise it is a bit-ORed combination of
IS_NUMBER_IN_UV, IS_NUMBER_GREATER_THAN_UV_MAX, IS_NUMBER_NOT_INT,
IS_NUMBER_NEG, IS_NUMBER_INFINITY, IS_NUMBER_NAN (defined in perl.h).

If the value of the number can fit an in UV, it is returned in the *valuep
IS_NUMBER_IN_UV will be set to indicate that *valuep is valid, IS_NUMBER_IN_UV
will never be set unless *valuep is valid, but *valuep may have been assigned
to during processing even though IS_NUMBER_IN_UV is not set on return.
If valuep is NULL, IS_NUMBER_IN_UV will be set for the same cases as when
valuep is non-NULL, but no actual assignment (or SEGV) will occur.

IS_NUMBER_NOT_INT will be set with IS_NUMBER_IN_UV if trailing decimals were
seen (in which case *valuep gives the true value truncated to an integer), and
IS_NUMBER_NEG if the number is negative (in which case *valuep holds the
absolute value).  IS_NUMBER_IN_UV is not set if e notation was used or the
number is larger than a UV.

    int    grok_number(const char *pv, STRLEN len, UV *valuep)

=for hackers
Found in file numeric.c

=item grok_numeric_radix

Scan and skip for a numeric decimal separator (radix).

    bool    grok_numeric_radix(const char **sp, const char *send)

=for hackers
Found in file numeric.c

=item grok_oct

converts a string representing an octal number to numeric form.

On entry I<start> and I<*len> give the string to scan, I<*flags> gives
conversion flags, and I<result> should be NULL or a pointer to an NV.
The scan stops at the end of the string, or the first invalid character.
Unless C<PERL_SCAN_SILENT_ILLDIGIT> is set in I<*flags>, encountering an
invalid character will also trigger a warning.
On return I<*len> is set to the length of the scanned string,
and I<*flags> gives output flags.

If the value is <= UV_MAX it is returned as a UV, the output flags are clear,
and nothing is written to I<*result>. If the value is > UV_MAX C<grok_oct>
returns UV_MAX, sets C<PERL_SCAN_GREATER_THAN_UV_MAX> in the output flags,
and writes the value to I<*result> (or the value is discarded if I<result>
is NULL).

If C<PERL_SCAN_ALLOW_UNDERSCORES> is set in I<*flags> then the octal
number may use '_' characters to separate digits.

    UV    grok_oct(char* start, STRLEN* len, I32* flags, NV *result)

=for hackers
Found in file numeric.c

=item scan_bin

For backwards compatibility. Use C<grok_bin> instead.

    NV    scan_bin(char* start, STRLEN len, STRLEN* retlen)

=for hackers
Found in file numeric.c

=item scan_hex

For backwards compatibility. Use C<grok_hex> instead.

    NV    scan_hex(char* start, STRLEN len, STRLEN* retlen)

=for hackers
Found in file numeric.c

=item scan_oct

For backwards compatibility. Use C<grok_oct> instead.

    NV    scan_oct(char* start, STRLEN len, STRLEN* retlen)

=for hackers
Found in file numeric.c


=back

=head1 Optree Manipulation Functions

=over 8

=item cv_const_sv

If C<cv> is a constant sub eligible for inlining. returns the constant
value returned by the sub.  Otherwise, returns NULL.

Constant subs can be created with C<newCONSTSUB> or as described in
L<perlsub/"Constant Functions">.

    SV*    cv_const_sv(CV* cv)

=for hackers
Found in file op.c

=item newCONSTSUB

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

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

=for hackers
Found in file op.c

=item newXS

Used by C<xsubpp> to hook up XSUBs as Perl subs.

=for hackers
Found in file op.c


=back

=head1 Pad Data Structures

=over 8

=item pad_sv

Get the value at offset po in the current pad.
Use macro PAD_SV instead of calling this function directly.

    SV*    pad_sv(PADOFFSET po)

=for hackers
Found in file pad.c


=back

=head1 Stack Manipulation Macros

=over 8

=item dMARK

Declare a stack marker variable, C<mark>, for the XSUB.  See C<MARK> and
C<dORIGMARK>.

        dMARK;

=for hackers
Found in file pp.h

=item dORIGMARK

Saves the original stack mark for the XSUB.  See C<ORIGMARK>.

        dORIGMARK;

=for hackers
Found in file pp.h

=item dSP

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

        dSP;

=for hackers
Found in file pp.h

=item EXTEND

Used to extend the argument stack for an XSUB's return values. Once
used, guarantees that there is room for at least C<nitems> to be pushed
onto the stack.

    void    EXTEND(SP, int nitems)

=for hackers
Found in file pp.h

=item MARK

Stack marker variable for the XSUB.  See C<dMARK>.

=for hackers
Found in file pp.h

=item mPUSHi

Push an integer onto the stack.  The stack must have room for this element.
Handles 'set' magic.  Does not use C<TARG>.  See also C<PUSHi>, C<mXPUSHi>
and C<XPUSHi>.

    void    mPUSHi(IV iv)

=for hackers
Found in file pp.h

=item mPUSHn

Push a double onto the stack.  The stack must have room for this element.
Handles 'set' magic.  Does not use C<TARG>.  See also C<PUSHn>, C<mXPUSHn>
and C<XPUSHn>.

    void    mPUSHn(NV nv)

=for hackers
Found in file pp.h

=item mPUSHp

Push a string onto the stack.  The stack must have room for this element.
The C<len> indicates the length of the string.  Handles 'set' magic.  Does
not use C<TARG>.  See also C<PUSHp>, C<mXPUSHp> and C<XPUSHp>.

    void    mPUSHp(char* str, STRLEN len)

=for hackers
Found in file pp.h

=item mPUSHu

Push an unsigned integer onto the stack.  The stack must have room for this
element.  Handles 'set' magic.  Does not use C<TARG>.  See also C<PUSHu>,
C<mXPUSHu> and C<XPUSHu>.

    void    mPUSHu(UV uv)

=for hackers
Found in file pp.h

=item mXPUSHi

Push an integer onto the stack, extending the stack if necessary.  Handles
'set' magic.  Does not use C<TARG>.  See also C<XPUSHi>, C<mPUSHi> and
C<PUSHi>.

    void    mXPUSHi(IV iv)

=for hackers
Found in file pp.h

=item mXPUSHn

Push a double onto the stack, extending the stack if necessary.  Handles
'set' magic.  Does not use C<TARG>.  See also C<XPUSHn>, C<mPUSHn> and
C<PUSHn>.

    void    mXPUSHn(NV nv)

=for hackers
Found in file pp.h

=item mXPUSHp

Push a string onto the stack, extending the stack if necessary.  The C<len>
indicates the length of the string.  Handles 'set' magic.  Does not use
C<TARG>.  See also C<XPUSHp>, C<mPUSHp> and C<PUSHp>.

    void    mXPUSHp(char* str, STRLEN len)

=for hackers
Found in file pp.h

=item mXPUSHu

Push an unsigned integer onto the stack, extending the stack if necessary.
Handles 'set' magic.  Does not use C<TARG>.  See also C<XPUSHu>, C<mPUSHu>
and C<PUSHu>.

    void    mXPUSHu(UV uv)

=for hackers
Found in file pp.h

=item ORIGMARK

The original stack mark for the XSUB.  See C<dORIGMARK>.

=for hackers
Found in file pp.h

=item POPi

Pops an integer off the stack.

    IV    POPi

=for hackers
Found in file pp.h

=item POPl

Pops a long off the stack.

    long    POPl

=for hackers
Found in file pp.h

=item POPn

Pops a double off the stack.

    NV    POPn

=for hackers
Found in file pp.h

=item POPp

Pops a string off the stack. Deprecated. New code should provide
a STRLEN n_a and use POPpx.

    char*    POPp

=for hackers
Found in file pp.h

=item POPpbytex

Pops a string off the stack which must consist of bytes i.e. characters < 256.
Requires a variable STRLEN n_a in scope.

    char*    POPpbytex

=for hackers
Found in file pp.h

=item POPpx

Pops a string off the stack.
Requires a variable STRLEN n_a in scope.

    char*    POPpx

=for hackers
Found in file pp.h

=item POPs

Pops an SV off the stack.

    SV*    POPs

=for hackers
Found in file pp.h

=item PUSHi

Push an integer onto the stack.  The stack must have room for this element.
Handles 'set' magic.  Uses C<TARG>, so C<dTARGET> or C<dXSTARG> should be
called to declare it.  Do not call multiple C<TARG>-oriented macros to
return lists from XSUB's - see C<mPUSHi> instead.  See also C<XPUSHi> and
C<mXPUSHi>.

    void    PUSHi(IV iv)

=for hackers
Found in file pp.h

=item PUSHMARK

Opening bracket for arguments on a callback.  See C<PUTBACK> and
L<perlcall>.

    void    PUSHMARK(SP)

=for hackers
Found in file pp.h

=item PUSHmortal

Push a new mortal SV onto the stack.  The stack must have room for this
element.  Does not handle 'set' magic.  Does not use C<TARG>.  See also
C<PUSHs>, C<XPUSHmortal> and C<XPUSHs>.

    void    PUSHmortal()

=for hackers
Found in file pp.h

=item PUSHn

Push a double onto the stack.  The stack must have room for this element.
Handles 'set' magic.  Uses C<TARG>, so C<dTARGET> or C<dXSTARG> should be
called to declare it.  Do not call multiple C<TARG>-oriented macros to
return lists from XSUB's - see C<mPUSHn> instead.  See also C<XPUSHn> and
C<mXPUSHn>.

    void    PUSHn(NV nv)

=for hackers
Found in file pp.h

=item PUSHp

Push a string onto the stack.  The stack must have room for this element.
The C<len> indicates the length of the string.  Handles 'set' magic.  Uses
C<TARG>, so C<dTARGET> or C<dXSTARG> should be called to declare it.  Do not
call multiple C<TARG>-oriented macros to return lists from XSUB's - see
C<mPUSHp> instead.  See also C<XPUSHp> and C<mXPUSHp>.

    void    PUSHp(char* str, STRLEN len)

=for hackers
Found in file pp.h

=item PUSHs

Push an SV onto the stack.  The stack must have room for this element.
Does not handle 'set' magic.  Does not use C<TARG>.  See also C<PUSHmortal>,
C<XPUSHs> and C<XPUSHmortal>.

    void    PUSHs(SV* sv)

=for hackers
Found in file pp.h

=item PUSHu

Push an unsigned integer onto the stack.  The stack must have room for this
element.  Handles 'set' magic.  Uses C<TARG>, so C<dTARGET> or C<dXSTARG>
should be called to declare it.  Do not call multiple C<TARG>-oriented
macros to return lists from XSUB's - see C<mPUSHu> instead.  See also
C<XPUSHu> and C<mXPUSHu>.

    void    PUSHu(UV uv)

=for hackers
Found in file pp.h

=item PUTBACK

Closing bracket for XSUB arguments.  This is usually handled by C<xsubpp>.
See C<PUSHMARK> and L<perlcall> for other uses.

        PUTBACK;

=for hackers
Found in file pp.h

=item SP

Stack pointer.  This is usually handled by C<xsubpp>.  See C<dSP> and
C<SPAGAIN>.

=for hackers
Found in file pp.h

=item SPAGAIN

Refetch the stack pointer.  Used after a callback.  See L<perlcall>.

        SPAGAIN;

=for hackers
Found in file pp.h

=item XPUSHi

Push an integer onto the stack, extending the stack if necessary.  Handles
'set' magic.  Uses C<TARG>, so C<dTARGET> or C<dXSTARG> should be called to
declare it.  Do not call multiple C<TARG>-oriented macros to return lists
from XSUB's - see C<mXPUSHi> instead.  See also C<PUSHi> and C<mPUSHi>.

    void    XPUSHi(IV iv)

=for hackers
Found in file pp.h

=item XPUSHmortal

Push a new mortal SV onto the stack, extending the stack if necessary.  Does
not handle 'set' magic.  Does not use C<TARG>.  See also C<XPUSHs>,
C<PUSHmortal> and C<PUSHs>.

    void    XPUSHmortal()

=for hackers
Found in file pp.h

=item XPUSHn

Push a double onto the stack, extending the stack if necessary.  Handles
'set' magic.  Uses C<TARG>, so C<dTARGET> or C<dXSTARG> should be called to
declare it.  Do not call multiple C<TARG>-oriented macros to return lists
from XSUB's - see C<mXPUSHn> instead.  See also C<PUSHn> and C<mPUSHn>.

    void    XPUSHn(NV nv)

=for hackers
Found in file pp.h

=item XPUSHp

Push a string onto the stack, extending the stack if necessary.  The C<len>
indicates the length of the string.  Handles 'set' magic.  Uses C<TARG>, so
C<dTARGET> or C<dXSTARG> should be called to declare it.  Do not call
multiple C<TARG>-oriented macros to return lists from XSUB's - see
C<mXPUSHp> instead.  See also C<PUSHp> and C<mPUSHp>.

    void    XPUSHp(char* str, STRLEN len)

=for hackers
Found in file pp.h

=item XPUSHs

Push an SV onto the stack, extending the stack if necessary.  Does not
handle 'set' magic.  Does not use C<TARG>.  See also C<XPUSHmortal>,
C<PUSHs> and C<PUSHmortal>.

    void    XPUSHs(SV* sv)

=for hackers
Found in file pp.h

=item XPUSHu

Push an unsigned integer onto the stack, extending the stack if necessary.
Handles 'set' magic.  Uses C<TARG>, so C<dTARGET> or C<dXSTARG> should be
called to declare it.  Do not call multiple C<TARG>-oriented macros to
return lists from XSUB's - see C<mXPUSHu> instead.  See also C<PUSHu> and
C<mPUSHu>.

    void    XPUSHu(UV uv)

=for hackers
Found in file pp.h

=item XSRETURN

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

    void    XSRETURN(int nitems)

=for hackers
Found in file XSUB.h

=item XSRETURN_EMPTY

Return an empty list from an XSUB immediately.

        XSRETURN_EMPTY;

=for hackers
Found in file XSUB.h

=item XSRETURN_IV

Return an integer from an XSUB immediately.  Uses C<XST_mIV>.

    void    XSRETURN_IV(IV iv)

=for hackers
Found in file XSUB.h

=item XSRETURN_NO

Return C<&PL_sv_no> from an XSUB immediately.  Uses C<XST_mNO>.

        XSRETURN_NO;

=for hackers
Found in file XSUB.h

=item XSRETURN_NV

Return a double from an XSUB immediately.  Uses C<XST_mNV>.

    void    XSRETURN_NV(NV nv)

=for hackers
Found in file XSUB.h

=item XSRETURN_PV

Return a copy of a string from an XSUB immediately.  Uses C<XST_mPV>.

    void    XSRETURN_PV(char* str)

=for hackers
Found in file XSUB.h

=item XSRETURN_UNDEF

Return C<&PL_sv_undef> from an XSUB immediately.  Uses C<XST_mUNDEF>.

        XSRETURN_UNDEF;

=for hackers
Found in file XSUB.h

=item XSRETURN_UV

Return an integer from an XSUB immediately.  Uses C<XST_mUV>.

    void    XSRETURN_UV(IV uv)

=for hackers
Found in file XSUB.h

=item XSRETURN_YES

Return C<&PL_sv_yes> from an XSUB immediately.  Uses C<XST_mYES>.

        XSRETURN_YES;

=for hackers
Found in file XSUB.h

=item XST_mIV

Place an integer into the specified position C<pos> on the stack.  The
value is stored in a new mortal SV.

    void    XST_mIV(int pos, IV iv)

=for hackers
Found in file XSUB.h

=item XST_mNO

Place C<&PL_sv_no> into the specified position C<pos> on the
stack.

    void    XST_mNO(int pos)

=for hackers
Found in file XSUB.h

=item XST_mNV

Place a double into the specified position C<pos> on the stack.  The value
is stored in a new mortal SV.

    void    XST_mNV(int pos, NV nv)

=for hackers
Found in file XSUB.h

=item XST_mPV

Place a copy of a string into the specified position C<pos> on the stack.
The value is stored in a new mortal SV.

    void    XST_mPV(int pos, char* str)

=for hackers
Found in file XSUB.h

=item XST_mUNDEF

Place C<&PL_sv_undef> into the specified position C<pos> on the
stack.

    void    XST_mUNDEF(int pos)

=for hackers
Found in file XSUB.h

=item XST_mYES

Place C<&PL_sv_yes> into the specified position C<pos> on the
stack.

    void    XST_mYES(int pos)

=for hackers
Found in file XSUB.h


=back

=head1 SV Flags

=over 8

=item svtype

An enum of flags for Perl types.  These are found in the file B<sv.h>
in the C<svtype> enum.  Test these flags with the C<SvTYPE> macro.

=for hackers
Found in file sv.h

=item SVt_IV

Integer type flag for scalars.  See C<svtype>.

=for hackers
Found in file sv.h

=item SVt_NV

Double type flag for scalars.  See C<svtype>.

=for hackers
Found in file sv.h

=item SVt_PV

Pointer type flag for scalars.  See C<svtype>.

=for hackers
Found in file sv.h

=item SVt_PVAV

Type flag for arrays.  See C<svtype>.

=for hackers
Found in file sv.h

=item SVt_PVCV

Type flag for code refs.  See C<svtype>.

=for hackers
Found in file sv.h

=item SVt_PVHV

Type flag for hashes.  See C<svtype>.

=for hackers
Found in file sv.h

=item SVt_PVMG

Type flag for blessed scalars.  See C<svtype>.

=for hackers
Found in file sv.h


=back

=head1 SV Manipulation Functions

=over 8

=item get_sv

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

NOTE: the perl_ form of this function is deprecated.

    SV*    get_sv(const char* name, I32 create)

=for hackers
Found in file perl.c

=item looks_like_number

Test if the content of an SV looks like a number (or is a number).
C<Inf> and C<Infinity> are treated as numbers (so will not issue a
non-numeric warning), even if your atof() doesn't grok them.

    I32    looks_like_number(SV* sv)

=for hackers
Found in file sv.c

=item newRV_inc

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

    SV*    newRV_inc(SV* sv)

=for hackers
Found in file sv.h

=item newRV_noinc

Creates an RV wrapper for an SV.  The reference count for the original
SV is B<not> incremented.

    SV*    newRV_noinc(SV *sv)

=for hackers
Found in file sv.c

=item NEWSV

Creates a new SV.  A non-zero C<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.
C<id> is an integer id between 0 and 1299 (used to identify leaks).

    SV*    NEWSV(int id, STRLEN len)

=for hackers
Found in file handy.h

=item newSV

Create a new null SV, or if len > 0, create a new empty SVt_PV type SV
with an initial PV allocation of len+1. Normally accessed via the C<NEWSV>
macro.

    SV*    newSV(STRLEN len)

=for hackers
Found in file sv.c

=item 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)

=for hackers
Found in file sv.c

=item newSVnv

Creates a new SV and copies a floating point value into it.
The reference count for the SV is set to 1.

    SV*    newSVnv(NV n)

=for hackers
Found in file sv.c

=item newSVpv

Creates a new SV and copies a string into it.  The reference count for the
SV is set to 1.  If C<len> is zero, Perl will compute the length using
strlen().  For efficiency, consider using C<newSVpvn> instead.

    SV*    newSVpv(const char* s, STRLEN len)

=for hackers
Found in file sv.c

=item newSVpvf

Creates a new SV and initializes it with the string formatted like
C<sprintf>.

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

=for hackers
Found in file sv.c

=item newSVpvn

Creates a new SV and copies a string into it.  The reference count for the
SV is set to 1.  Note that if C<len> is zero, Perl will create a zero length
string.  You are responsible for ensuring that the source string is at least
C<len> bytes long.  If the C<s> argument is NULL the new SV will be undefined.

    SV*    newSVpvn(const char* s, STRLEN len)

=for hackers
Found in file sv.c

=item newSVpvn_share

Creates a new SV with its SvPVX pointing to a shared string in the string
table. If the string does not already exist in the table, it is created
first.  Turns on READONLY and FAKE.  The string's hash is stored in the UV
slot of the SV; if the C<hash> parameter is non-zero, that value is used;
otherwise the hash is computed.  The idea here is that as the string table
is used for shared hash keys these strings will have SvPVX == HeKEY and
hash lookup will avoid string compare.

    SV*    newSVpvn_share(const char* s, I32 len, U32 hash)

=for hackers
Found in file sv.c

=item newSVrv

Creates a new SV for the RV, C<rv>, to point to.  If C<rv> is not an RV then
it will be upgraded to one.  If C<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, const char* classname)

=for hackers
Found in file sv.c

=item newSVsv

Creates a new SV which is an exact duplicate of the original SV.
(Uses C<sv_setsv>).

    SV*    newSVsv(SV* old)

=for hackers
Found in file sv.c

=item newSVuv

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

    SV*    newSVuv(UV u)

=for hackers
Found in file sv.c

=item SvCUR

Returns the length of the string which is in the SV.  See C<SvLEN>.

    STRLEN    SvCUR(SV* sv)

=for hackers
Found in file sv.h

=item SvCUR_set

Set the length of the string which is in the SV.  See C<SvCUR>.

    void    SvCUR_set(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvEND

Returns a pointer to the last character in the string which is in the SV.
See C<SvCUR>.  Access the character as *(SvEND(sv)).

    char*    SvEND(SV* sv)

=for hackers
Found in file sv.h

=item 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 C<sv_grow> to perform the expansion if necessary.
Returns a pointer to the character buffer.

    char *    SvGROW(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvIOK

Returns a boolean indicating whether the SV contains an integer.

    bool    SvIOK(SV* sv)

=for hackers
Found in file sv.h

=item SvIOKp

Returns a boolean indicating whether the SV contains an integer.  Checks
the B<private> setting.  Use C<SvIOK>.

    bool    SvIOKp(SV* sv)

=for hackers
Found in file sv.h

=item SvIOK_notUV

Returns a boolean indicating whether the SV contains a signed integer.

    bool    SvIOK_notUV(SV* sv)

=for hackers
Found in file sv.h

=item SvIOK_off

Unsets the IV status of an SV.

    void    SvIOK_off(SV* sv)

=for hackers
Found in file sv.h

=item SvIOK_on

Tells an SV that it is an integer.

    void    SvIOK_on(SV* sv)

=for hackers
Found in file sv.h

=item SvIOK_only

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

    void    SvIOK_only(SV* sv)

=for hackers
Found in file sv.h

=item SvIOK_only_UV

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

    void    SvIOK_only_UV(SV* sv)

=for hackers
Found in file sv.h

=item SvIOK_UV

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

    bool    SvIOK_UV(SV* sv)

=for hackers
Found in file sv.h

=item SvIsCOW

Returns a boolean indicating whether the SV is Copy-On-Write. (either shared
hash key scalars, or full Copy On Write scalars if 5.9.0 is configured for
COW)

    bool    SvIsCOW(SV* sv)

=for hackers
Found in file sv.h

=item SvIsCOW_shared_hash

Returns a boolean indicating whether the SV is Copy-On-Write shared hash key
scalar.

    bool    SvIsCOW_shared_hash(SV* sv)

=for hackers
Found in file sv.h

=item SvIV

Coerces the given SV to an integer and returns it. See  C<SvIVx> for a
version which guarantees to evaluate sv only once.

    IV    SvIV(SV* sv)

=for hackers
Found in file sv.h

=item SvIVX

Returns the raw value in the SV's IV slot, without checks or conversions.
Only use when you are sure SvIOK is true. See also C<SvIV()>.

    IV    SvIVX(SV* sv)

=for hackers
Found in file sv.h

=item SvIVx

Coerces the given SV to an integer and returns it. Guarantees to evaluate
sv only once. Use the more efficient C<SvIV> otherwise.

    IV    SvIVx(SV* sv)

=for hackers
Found in file sv.h

=item SvLEN

Returns the size of the string buffer in the SV, not including any part
attributable to C<SvOOK>.  See C<SvCUR>.

    STRLEN    SvLEN(SV* sv)

=for hackers
Found in file sv.h

=item SvNIOK

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

    bool    SvNIOK(SV* sv)

=for hackers
Found in file sv.h

=item SvNIOKp

Returns a boolean indicating whether the SV contains a number, integer or
double.  Checks the B<private> setting.  Use C<SvNIOK>.

    bool    SvNIOKp(SV* sv)

=for hackers
Found in file sv.h

=item SvNIOK_off

Unsets the NV/IV status of an SV.

    void    SvNIOK_off(SV* sv)

=for hackers
Found in file sv.h

=item SvNOK

Returns a boolean indicating whether the SV contains a double.

    bool    SvNOK(SV* sv)

=for hackers
Found in file sv.h

=item SvNOKp

Returns a boolean indicating whether the SV contains a double.  Checks the
B<private> setting.  Use C<SvNOK>.

    bool    SvNOKp(SV* sv)

=for hackers
Found in file sv.h

=item SvNOK_off

Unsets the NV status of an SV.

    void    SvNOK_off(SV* sv)

=for hackers
Found in file sv.h

=item SvNOK_on

Tells an SV that it is a double.

    void    SvNOK_on(SV* sv)

=for hackers
Found in file sv.h

=item SvNOK_only

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

    void    SvNOK_only(SV* sv)

=for hackers
Found in file sv.h

=item SvNV

Coerce the given SV to a double and return it. See  C<SvNVx> for a version
which guarantees to evaluate sv only once.

    NV    SvNV(SV* sv)

=for hackers
Found in file sv.h

=item SvNVX

Returns the raw value in the SV's NV slot, without checks or conversions.
Only use when you are sure SvNOK is true. See also C<SvNV()>.

    NV    SvNVX(SV* sv)

=for hackers
Found in file sv.h

=item SvNVx

Coerces the given SV to a double and returns it. Guarantees to evaluate
sv only once. Use the more efficient C<SvNV> otherwise.

    NV    SvNVx(SV* sv)

=for hackers
Found in file sv.h

=item SvOK

Returns a boolean indicating whether the value is an SV. It also tells
whether the value is defined or not.

    bool    SvOK(SV* sv)

=for hackers
Found in file sv.h

=item 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).

    bool    SvOOK(SV* sv)

=for hackers
Found in file sv.h

=item SvPOK

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

    bool    SvPOK(SV* sv)

=for hackers
Found in file sv.h

=item SvPOKp

Returns a boolean indicating whether the SV contains a character string.
Checks the B<private> setting.  Use C<SvPOK>.

    bool    SvPOKp(SV* sv)

=for hackers
Found in file sv.h

=item SvPOK_off

Unsets the PV status of an SV.

    void    SvPOK_off(SV* sv)

=for hackers
Found in file sv.h

=item SvPOK_on

Tells an SV that it is a string.

    void    SvPOK_on(SV* sv)

=for hackers
Found in file sv.h

=item SvPOK_only

Tells an SV that it is a string and disables all other OK bits.
Will also turn off the UTF-8 status.

    void    SvPOK_only(SV* sv)

=for hackers
Found in file sv.h

=item SvPOK_only_UTF8

Tells an SV that it is a string and disables all other OK bits,
and leaves the UTF-8 status as it was.

    void    SvPOK_only_UTF8(SV* sv)

=for hackers
Found in file sv.h

=item 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.  The SV may cache the
stringified version becoming C<SvPOK>.  Handles 'get' magic. See also
C<SvPVx> for a version which guarantees to evaluate sv only once.

    char*    SvPV(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVbyte

Like C<SvPV>, but converts sv to byte representation first if necessary.

    char*    SvPVbyte(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVbytex

Like C<SvPV>, but converts sv to byte representation first if necessary.
Guarantees to evaluate sv only once; use the more efficient C<SvPVbyte>
otherwise.

    char*    SvPVbytex(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVbytex_force

Like C<SvPV_force>, but converts sv to byte representation first if necessary.
Guarantees to evaluate sv only once; use the more efficient C<SvPVbyte_force>
otherwise.

    char*    SvPVbytex_force(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVbyte_force

Like C<SvPV_force>, but converts sv to byte representation first if necessary.

    char*    SvPVbyte_force(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVbyte_nolen

Like C<SvPV_nolen>, but converts sv to byte representation first if necessary.

    char*    SvPVbyte_nolen(SV* sv)

=for hackers
Found in file sv.h

=item SvPVutf8

Like C<SvPV>, but converts sv to utf8 first if necessary.

    char*    SvPVutf8(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVutf8x

Like C<SvPV>, but converts sv to utf8 first if necessary.
Guarantees to evaluate sv only once; use the more efficient C<SvPVutf8>
otherwise.

    char*    SvPVutf8x(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVutf8x_force

Like C<SvPV_force>, but converts sv to utf8 first if necessary.
Guarantees to evaluate sv only once; use the more efficient C<SvPVutf8_force>
otherwise.

    char*    SvPVutf8x_force(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVutf8_force

Like C<SvPV_force>, but converts sv to utf8 first if necessary.

    char*    SvPVutf8_force(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPVutf8_nolen

Like C<SvPV_nolen>, but converts sv to utf8 first if necessary.

    char*    SvPVutf8_nolen(SV* sv)

=for hackers
Found in file sv.h

=item SvPVX

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

    char*    SvPVX(SV* sv)

=for hackers
Found in file sv.h

=item SvPVx

A version of C<SvPV> which guarantees to evaluate sv only once.

    char*    SvPVx(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPV_force

Like C<SvPV> but will force the SV into containing just a string
(C<SvPOK_only>).  You want force if you are going to update the C<SvPVX>
directly.

    char*    SvPV_force(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPV_force_nomg

Like C<SvPV> but will force the SV into containing just a string
(C<SvPOK_only>).  You want force if you are going to update the C<SvPVX>
directly. Doesn't process magic.

    char*    SvPV_force_nomg(SV* sv, STRLEN len)

=for hackers
Found in file sv.h

=item SvPV_nolen

Returns a pointer to the string in the SV, or a stringified form of
the SV if the SV does not contain a string.  The SV may cache the
stringified form becoming C<SvPOK>.  Handles 'get' magic.

    char*    SvPV_nolen(SV* sv)

=for hackers
Found in file sv.h

=item SvREFCNT

Returns the value of the object's reference count.

    U32    SvREFCNT(SV* sv)

=for hackers
Found in file sv.h

=item SvREFCNT_dec

Decrements the reference count of the given SV.

    void    SvREFCNT_dec(SV* sv)

=for hackers
Found in file sv.h

=item SvREFCNT_inc

Increments the reference count of the given SV.

    SV*    SvREFCNT_inc(SV* sv)

=for hackers
Found in file sv.h

=item SvROK

Tests if the SV is an RV.

    bool    SvROK(SV* sv)

=for hackers
Found in file sv.h

=item SvROK_off

Unsets the RV status of an SV.

    void    SvROK_off(SV* sv)

=for hackers
Found in file sv.h

=item SvROK_on

Tells an SV that it is an RV.

    void    SvROK_on(SV* sv)

=for hackers
Found in file sv.h

=item SvRV

Dereferences an RV to return the SV.

    SV*    SvRV(SV* sv)

=for hackers
Found in file sv.h

=item SvSTASH

Returns the stash of the SV.

    HV*    SvSTASH(SV* sv)

=for hackers
Found in file sv.h

=item SvTAINT

Taints an SV if tainting is enabled.

    void    SvTAINT(SV* sv)

=for hackers
Found in file sv.h

=item SvTAINTED

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

    bool    SvTAINTED(SV* sv)

=for hackers
Found in file sv.h

=item SvTAINTED_off

Untaints an SV. Be I<very> 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 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)

=for hackers
Found in file sv.h

=item SvTAINTED_on

Marks an SV as tainted if tainting is enabled.

    void    SvTAINTED_on(SV* sv)

=for hackers
Found in file sv.h

=item SvTRUE

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

    bool    SvTRUE(SV* sv)

=for hackers
Found in file sv.h

=item SvTYPE

Returns the type of the SV.  See C<svtype>.

    svtype    SvTYPE(SV* sv)

=for hackers
Found in file sv.h

=item SvUOK

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

    void    SvUOK(SV* sv)

=for hackers
Found in file sv.h

=item SvUPGRADE

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

    void    SvUPGRADE(SV* sv, svtype type)

=for hackers
Found in file sv.h

=item SvUTF8

Returns a boolean indicating whether the SV contains UTF-8 encoded data.

    bool    SvUTF8(SV* sv)

=for hackers
Found in file sv.h

=item SvUTF8_off

Unsets the UTF-8 status of an SV.

    void    SvUTF8_off(SV *sv)

=for hackers
Found in file sv.h

=item SvUTF8_on

Turn on the UTF-8 status of an SV (the data is not changed, just the flag).
Do not use frivolously.

    void    SvUTF8_on(SV *sv)

=for hackers
Found in file sv.h

=item SvUV

Coerces the given SV to an unsigned integer and returns it.  See C<SvUVx>
for a version which guarantees to evaluate sv only once.

    UV    SvUV(SV* sv)

=for hackers
Found in file sv.h

=item SvUVX

Returns the raw value in the SV's UV slot, without checks or conversions.
Only use when you are sure SvIOK is true. See also C<SvUV()>.

    UV    SvUVX(SV* sv)

=for hackers
Found in file sv.h

=item SvUVx

Coerces the given SV to an unsigned integer and returns it. Guarantees to
evaluate sv only once. Use the more efficient C<SvUV> otherwise.

    UV    SvUVx(SV* sv)

=for hackers
Found in file sv.h

=item sv_2bool

This function is only called on magical items, and is only used by
sv_true() or its macro equivalent.

    bool    sv_2bool(SV* sv)

=for hackers
Found in file sv.c

=item sv_2cv

Using various gambits, try to get a CV from an SV; in addition, try if
possible to set C<*st> and C<*gvp> to the stash and GV associated with it.

    CV*    sv_2cv(SV* sv, HV** st, GV** gvp, I32 lref)

=for hackers
Found in file sv.c

=item sv_2io

Using various gambits, try to get an IO from an SV: the IO slot if its a
GV; or the recursive result if we're an RV; or the IO slot of the symbol
named after the PV if we're a string.

    IO*    sv_2io(SV* sv)

=for hackers
Found in file sv.c

=item sv_2iv

Return the integer value of an SV, doing any necessary string conversion,
magic etc. Normally used via the C<SvIV(sv)> and C<SvIVx(sv)> macros.

    IV    sv_2iv(SV* sv)

=for hackers
Found in file sv.c

=item sv_2mortal

Marks an existing SV as mortal.  The SV will be destroyed "soon", either
by an explicit call to FREETMPS, or by an implicit call at places such as
statement boundaries.  SvTEMP() is turned on which means that the SV's
string buffer can be "stolen" if this SV is copied. See also C<sv_newmortal>
and C<sv_mortalcopy>.

    SV*    sv_2mortal(SV* sv)

=for hackers
Found in file sv.c

=item sv_2nv

Return the num value of an SV, doing any necessary string or integer
conversion, magic etc. Normally used via the C<SvNV(sv)> and C<SvNVx(sv)>
macros.

    NV    sv_2nv(SV* sv)

=for hackers
Found in file sv.c

=item sv_2pvbyte

Return a pointer to the byte-encoded representation of the SV, and set *lp
to its length.  May cause the SV to be downgraded from UTF-8 as a
side-effect.

Usually accessed via the C<SvPVbyte> macro.

    char*    sv_2pvbyte(SV* sv, STRLEN* lp)

=for hackers
Found in file sv.c

=item sv_2pvbyte_nolen

Return a pointer to the byte-encoded representation of the SV.
May cause the SV to be downgraded from UTF-8 as a side-effect.

Usually accessed via the C<SvPVbyte_nolen> macro.

    char*    sv_2pvbyte_nolen(SV* sv)

=for hackers
Found in file sv.c

=item sv_2pvutf8

Return a pointer to the UTF-8-encoded representation of the SV, and set *lp
to its length.  May cause the SV to be upgraded to UTF-8 as a side-effect.

Usually accessed via the C<SvPVutf8> macro.

    char*    sv_2pvutf8(SV* sv, STRLEN* lp)

=for hackers
Found in file sv.c

=item sv_2pvutf8_nolen

Return a pointer to the UTF-8-encoded representation of the SV.
May cause the SV to be upgraded to UTF-8 as a side-effect.

Usually accessed via the C<SvPVutf8_nolen> macro.

    char*    sv_2pvutf8_nolen(SV* sv)

=for hackers
Found in file sv.c

=item sv_2pv_flags

Returns a pointer to the string value of an SV, and sets *lp to its length.
If flags includes SV_GMAGIC, does an mg_get() first. Coerces sv to a string
if necessary.
Normally invoked via the C<SvPV_flags> macro. C<sv_2pv()> and C<sv_2pv_nomg>
usually end up here too.

    char*    sv_2pv_flags(SV* sv, STRLEN* lp, I32 flags)

=for hackers
Found in file sv.c

=item sv_2pv_nolen

Like C<sv_2pv()>, but doesn't return the length too. You should usually
use the macro wrapper C<SvPV_nolen(sv)> instead.
    char*    sv_2pv_nolen(SV* sv)

=for hackers
Found in file sv.c

=item sv_2uv

Return the unsigned integer value of an SV, doing any necessary string
conversion, magic etc. Normally used via the C<SvUV(sv)> and C<SvUVx(sv)>
macros.

    UV    sv_2uv(SV* sv)

=for hackers
Found in file sv.c

=item sv_backoff

Remove any string offset. You should normally use the C<SvOOK_off> macro
wrapper instead.

    int    sv_backoff(SV* sv)

=for hackers
Found in file sv.c

=item sv_bless

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

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

=for hackers
Found in file sv.c

=item sv_catpv

Concatenates the string onto the end of the string which is in the SV.
If the SV has the UTF-8 status set, then the bytes appended should be
valid UTF-8.  Handles 'get' magic, but not 'set' magic.  See C<sv_catpv_mg>.

    void    sv_catpv(SV* sv, const char* ptr)

=for hackers
Found in file sv.c

=item sv_catpvf

Processes its arguments like C<sprintf> and appends the formatted
output to an SV.  If the appended data contains "wide" characters
(including, but not limited to, SVs with a UTF-8 PV formatted with %s,
and characters >255 formatted with %c), the original SV might get
upgraded to UTF-8.  Handles 'get' magic, but not 'set' magic.  See
C<sv_catpvf_mg>. If the original SV was UTF-8, the pattern should be
valid UTF-8; if the original SV was bytes, the pattern should be too.

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

=for hackers
Found in file sv.c

=item sv_catpvf_mg

Like C<sv_catpvf>, but also handles 'set' magic.

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

=for hackers
Found in file sv.c

=item sv_catpvn

Concatenates the string onto the end of the string which is in the SV.  The
C<len> indicates number of bytes to copy.  If the SV has the UTF-8
status set, then the bytes appended should be valid UTF-8.
Handles 'get' magic, but not 'set' magic.  See C<sv_catpvn_mg>.

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

=for hackers
Found in file sv.c

=item sv_catpvn_flags

Concatenates the string onto the end of the string which is in the SV.  The
C<len> indicates number of bytes to copy.  If the SV has the UTF-8
status set, then the bytes appended should be valid UTF-8.
If C<flags> has C<SV_GMAGIC> bit set, will C<mg_get> on C<dsv> if
appropriate, else not. C<sv_catpvn> and C<sv_catpvn_nomg> are implemented
in terms of this function.

    void    sv_catpvn_flags(SV* sv, const char* ptr, STRLEN len, I32 flags)

=for hackers
Found in file sv.c

=item sv_catpvn_mg

Like C<sv_catpvn>, but also handles 'set' magic.

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

=for hackers
Found in file sv.c

=item sv_catpvn_nomg

Like C<sv_catpvn> but doesn't process magic.

    void    sv_catpvn_nomg(SV* sv, const char* ptr, STRLEN len)

=for hackers
Found in file sv.h

=item sv_catpv_mg

Like C<sv_catpv>, but also handles 'set' magic.

    void    sv_catpv_mg(SV *sv, const char *ptr)

=for hackers
Found in file sv.c

=item sv_catsv

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

    void    sv_catsv(SV* dsv, SV* ssv)

=for hackers
Found in file sv.c

=item sv_catsv_flags

Concatenates the string from SV C<ssv> onto the end of the string in
SV C<dsv>.  Modifies C<dsv> but not C<ssv>.  If C<flags> has C<SV_GMAGIC>
bit set, will C<mg_get> on the SVs if appropriate, else not. C<sv_catsv>
and C<sv_catsv_nomg> are implemented in terms of this function.

    void    sv_catsv_flags(SV* dsv, SV* ssv, I32 flags)

=for hackers
Found in file sv.c

=item sv_catsv_mg

Like C<sv_catsv>, but also handles 'set' magic.

    void    sv_catsv_mg(SV *dstr, SV *sstr)

=for hackers
Found in file sv.c

=item sv_catsv_nomg

Like C<sv_catsv> but doesn't process magic.

    void    sv_catsv_nomg(SV* dsv, SV* ssv)

=for hackers
Found in file sv.h

=item sv_chop

Efficient removal of characters from the beginning of the string buffer.
SvPOK(sv) must be true and the C<ptr> must be a pointer to somewhere inside
the string buffer.  The C<ptr> becomes the first character of the adjusted
string. Uses the "OOK hack".
Beware: after this function returns, C<ptr> and SvPVX(sv) may no longer
refer to the same chunk of data.

    void    sv_chop(SV* sv, char* ptr)

=for hackers
Found in file sv.c

=item sv_clear

Clear an SV: call any destructors, free up any memory used by the body,
and free the body itself. The SV's head is I<not> freed, although
its type is set to all 1's so that it won't inadvertently be assumed
to be live during global destruction etc.
This function should only be called when REFCNT is zero. Most of the time
you'll want to call C<sv_free()> (or its macro wrapper C<SvREFCNT_dec>)
instead.

    void    sv_clear(SV* sv)

=for hackers
Found in file sv.c

=item sv_cmp

Compares the strings in two SVs.  Returns -1, 0, or 1 indicating whether the
string in C<sv1> is less than, equal to, or greater than the string in
C<sv2>. Is UTF-8 and 'use bytes' aware, handles get magic, and will
coerce its args to strings if necessary.  See also C<sv_cmp_locale>.

    I32    sv_cmp(SV* sv1, SV* sv2)

=for hackers
Found in file sv.c

=item sv_cmp_locale

Compares the strings in two SVs in a locale-aware manner. Is UTF-8 and
'use bytes' aware, handles get magic, and will coerce its args to strings
if necessary.  See also C<sv_cmp_locale>.  See also C<sv_cmp>.

    I32    sv_cmp_locale(SV* sv1, SV* sv2)

=for hackers
Found in file sv.c

=item sv_collxfrm

Add Collate Transform magic to an SV if it doesn't already have it.

Any scalar variable may carry PERL_MAGIC_collxfrm magic that contains the
scalar data of the variable, but transformed to such a format that a normal
memory comparison can be used to compare the data according to the locale
settings.

    char*    sv_collxfrm(SV* sv, STRLEN* nxp)

=for hackers
Found in file sv.c

=item sv_copypv

Copies a stringified representation of the source SV into the
destination SV.  Automatically performs any necessary mg_get and
coercion of numeric values into strings.  Guaranteed to preserve
UTF-8 flag even from overloaded objects.  Similar in nature to
sv_2pv[_flags] but operates directly on an SV instead of just the
string.  Mostly uses sv_2pv_flags to do its work, except when that
would lose the UTF-8'ness of the PV.

    void    sv_copypv(SV* dsv, SV* ssv)

=for hackers
Found in file sv.c

=item sv_dec

Auto-decrement of the value in the SV, doing string to numeric conversion
if necessary. Handles 'get' magic.

    void    sv_dec(SV* sv)

=for hackers
Found in file sv.c

=item sv_derived_from

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

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

=for hackers
Found in file universal.c

=item sv_eq

Returns a boolean indicating whether the strings in the two SVs are
identical. Is UTF-8 and 'use bytes' aware, handles get magic, and will
coerce its args to strings if necessary.

    I32    sv_eq(SV* sv1, SV* sv2)

=for hackers
Found in file sv.c

=item sv_force_normal

Undo various types of fakery on an SV: if the PV is a shared string, make
a private copy; if we're a ref, stop refing; if we're a glob, downgrade to
an xpvmg. See also C<sv_force_normal_flags>.

    void    sv_force_normal(SV *sv)

=for hackers
Found in file sv.c

=item sv_force_normal_flags

Undo various types of fakery on an SV: if the PV is a shared string, make
a private copy; if we're a ref, stop refing; if we're a glob, downgrade to
an xpvmg. The C<flags> parameter gets passed to  C<sv_unref_flags()>
when unrefing. C<sv_force_normal> calls this function with flags set to 0.

    void    sv_force_normal_flags(SV *sv, U32 flags)

=for hackers
Found in file sv.c

=item sv_free

Decrement an SV's reference count, and if it drops to zero, call
C<sv_clear> to invoke destructors and free up any memory used by
the body; finally, deallocate the SV's head itself.
Normally called via a wrapper macro C<SvREFCNT_dec>.

    void    sv_free(SV* sv)

=for hackers
Found in file sv.c

=item sv_gets

Get a line from the filehandle and store it into the SV, optionally
appending to the currently-stored string.

    char*    sv_gets(SV* sv, PerlIO* fp, I32 append)

=for hackers
Found in file sv.c

=item sv_grow

Expands the character buffer in the SV.  If necessary, uses C<sv_unref> and
upgrades the SV to C<SVt_PV>.  Returns a pointer to the character buffer.
Use the C<SvGROW> wrapper instead.

    char*    sv_grow(SV* sv, STRLEN newlen)

=for hackers
Found in file sv.c

=item sv_inc

Auto-increment of the value in the SV, doing string to numeric conversion
if necessary. Handles 'get' magic.

    void    sv_inc(SV* sv)

=for hackers
Found in file sv.c

=item sv_insert

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

    void    sv_insert(SV* bigsv, STRLEN offset, STRLEN len, char* little, STRLEN littlelen)

=for hackers
Found in file sv.c

=item sv_isa

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

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

=for hackers
Found in file sv.c

=item 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)

=for hackers
Found in file sv.c

=item sv_iv

A private implementation of the C<SvIVx> macro for compilers which can't
cope with complex macro expressions. Always use the macro instead.

    IV    sv_iv(SV* sv)

=for hackers
Found in file sv.c

=item sv_len

Returns the length of the string in the SV. Handles magic and type
coercion.  See also C<SvCUR>, which gives raw access to the xpv_cur slot.

    STRLEN    sv_len(SV* sv)

=for hackers
Found in file sv.c

=item sv_len_utf8

Returns the number of characters in the string in an SV, counting wide
UTF-8 bytes as a single character. Handles magic and type coercion.

    STRLEN    sv_len_utf8(SV* sv)

=for hackers
Found in file sv.c

=item sv_magic

Adds magic to an SV. First upgrades C<sv> to type C<SVt_PVMG> if necessary,
then adds a new magic item of type C<how> to the head of the magic list.

See C<sv_magicext> (which C<sv_magic> now calls) for a description of the
handling of the C<name> and C<namlen> arguments.

You need to use C<sv_magicext> to add magic to SvREADONLY SVs and also
to add more than one instance of the same 'how'.

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

=for hackers
Found in file sv.c

=item sv_magicext

Adds magic to an SV, upgrading it if necessary. Applies the
supplied vtable and returns a pointer to the magic added.

Note that C<sv_magicext> will allow things that C<sv_magic> will not.
In particular, you can add magic to SvREADONLY SVs, and add more than
one instance of the same 'how'.

If C<namlen> is greater than zero then a C<savepvn> I<copy> of C<name> is
stored, if C<namlen> is zero then C<name> is stored as-is and - as another
special case - if C<(name && namlen == HEf_SVKEY)> then C<name> is assumed
to contain an C<SV*> and is stored as-is with its REFCNT incremented.

(This is now used as a subroutine by C<sv_magic>.)

    MAGIC *    sv_magicext(SV* sv, SV* obj, int how, MGVTBL *vtbl, const char* name, I32 namlen)

=for hackers
Found in file sv.c

=item sv_mortalcopy

Creates a new SV which is a copy of the original SV (using C<sv_setsv>).
The new SV is marked as mortal. It will be destroyed "soon", either by an
explicit call to FREETMPS, or by an implicit call at places such as
statement boundaries.  See also C<sv_newmortal> and C<sv_2mortal>.

    SV*    sv_mortalcopy(SV* oldsv)

=for hackers
Found in file sv.c

=item sv_newmortal

Creates a new null SV which is mortal.  The reference count of the SV is
set to 1. It will be destroyed "soon", either by an explicit call to
FREETMPS, or by an implicit call at places such as statement boundaries.
See also C<sv_mortalcopy> and C<sv_2mortal>.

    SV*    sv_newmortal()

=for hackers
Found in file sv.c

=item sv_newref

Increment an SV's reference count. Use the C<SvREFCNT_inc()> wrapper
instead.

    SV*    sv_newref(SV* sv)

=for hackers
Found in file sv.c

=item sv_nv

A private implementation of the C<SvNVx> macro for compilers which can't
cope with complex macro expressions. Always use the macro instead.

    NV    sv_nv(SV* sv)

=for hackers
Found in file sv.c

=item sv_pos_b2u

Converts the value pointed to by offsetp from a count of bytes from the
start of the string, to a count of the equivalent number of UTF-8 chars.
Handles magic and type coercion.

    void    sv_pos_b2u(SV* sv, I32* offsetp)

=for hackers
Found in file sv.c

=item sv_pos_u2b

Converts the value pointed to by offsetp from a count of UTF-8 chars from
the start of the string, to a count of the equivalent number of bytes; if
lenp is non-zero, it does the same to lenp, but this time starting from
the offset, rather than from the start of the string. Handles magic and
type coercion.

    void    sv_pos_u2b(SV* sv, I32* offsetp, I32* lenp)

=for hackers
Found in file sv.c

=item sv_pv

Use the C<SvPV_nolen> macro instead

    char*    sv_pv(SV *sv)

=for hackers
Found in file sv.c

=item sv_pvbyte

Use C<SvPVbyte_nolen> instead.

    char*    sv_pvbyte(SV *sv)

=for hackers
Found in file sv.c

=item sv_pvbyten

A private implementation of the C<SvPVbyte> macro for compilers
which can't cope with complex macro expressions. Always use the macro
instead.

    char*    sv_pvbyten(SV *sv, STRLEN *len)

=for hackers
Found in file sv.c

=item sv_pvbyten_force

A private implementation of the C<SvPVbytex_force> macro for compilers
which can't cope with complex macro expressions. Always use the macro
instead.

    char*    sv_pvbyten_force(SV* sv, STRLEN* lp)

=for hackers
Found in file sv.c

=item sv_pvn

A private implementation of the C<SvPV> macro for compilers which can't
cope with complex macro expressions. Always use the macro instead.

    char*    sv_pvn(SV *sv, STRLEN *len)

=for hackers
Found in file sv.c

=item sv_pvn_force

Get a sensible string out of the SV somehow.
A private implementation of the C<SvPV_force> macro for compilers which
can't cope with complex macro expressions. Always use the macro instead.

    char*    sv_pvn_force(SV* sv, STRLEN* lp)

=for hackers
Found in file sv.c

=item sv_pvn_force_flags

Get a sensible string out of the SV somehow.
If C<flags> has C<SV_GMAGIC> bit set, will C<mg_get> on C<sv> if
appropriate, else not. C<sv_pvn_force> and C<sv_pvn_force_nomg> are
implemented in terms of this function.
You normally want to use the various wrapper macros instead: see
C<SvPV_force> and C<SvPV_force_nomg>

    char*    sv_pvn_force_flags(SV* sv, STRLEN* lp, I32 flags)

=for hackers
Found in file sv.c

=item sv_pvutf8

Use the C<SvPVutf8_nolen> macro instead

    char*    sv_pvutf8(SV *sv)

=for hackers
Found in file sv.c

=item sv_pvutf8n

A private implementation of the C<SvPVutf8> macro for compilers
which can't cope with complex macro expressions. Always use the macro
instead.

    char*    sv_pvutf8n(SV *sv, STRLEN *len)

=for hackers
Found in file sv.c

=item sv_pvutf8n_force

A private implementation of the C<SvPVutf8_force> macro for compilers
which can't cope with complex macro expressions. Always use the macro
instead.

    char*    sv_pvutf8n_force(SV* sv, STRLEN* lp)

=for hackers
Found in file sv.c

=item sv_reftype

Returns a string describing what the SV is a reference to.

    char*    sv_reftype(SV* sv, int ob)

=for hackers
Found in file sv.c

=item sv_replace

Make the first argument a copy of the second, then delete the original.
The target SV physically takes over ownership of the body of the source SV
and inherits its flags; however, the target keeps any magic it owns,
and any magic in the source is discarded.
Note that this is a rather specialist SV copying operation; most of the
time you'll want to use C<sv_setsv> or one of its many macro front-ends.

    void    sv_replace(SV* sv, SV* nsv)

=for hackers
Found in file sv.c

=item sv_report_used

Dump the contents of all SVs not yet freed. (Debugging aid).

    void    sv_report_used()

=for hackers
Found in file sv.c

=item sv_reset

Underlying implementation for the C<reset> Perl function.
Note that the perl-level function is vaguely deprecated.

    void    sv_reset(char* s, HV* stash)

=for hackers
Found in file sv.c

=item sv_rvweaken

Weaken a reference: set the C<SvWEAKREF> flag on this RV; give the
referred-to SV C<PERL_MAGIC_backref> magic if it hasn't already; and
push a back-reference to this RV onto the array of backreferences
associated with that magic.

    SV*    sv_rvweaken(SV *sv)

=for hackers
Found in file sv.c

=item sv_setiv

Copies an integer into the given SV, upgrading first if necessary.
Does not handle 'set' magic.  See also C<sv_setiv_mg>.

    void    sv_setiv(SV* sv, IV num)

=for hackers
Found in file sv.c

=item sv_setiv_mg

Like C<sv_setiv>, but also handles 'set' magic.

    void    sv_setiv_mg(SV *sv, IV i)

=for hackers
Found in file sv.c

=item sv_setnv

Copies a double into the given SV, upgrading first if necessary.
Does not handle 'set' magic.  See also C<sv_setnv_mg>.

    void    sv_setnv(SV* sv, NV num)

=for hackers
Found in file sv.c

=item sv_setnv_mg

Like C<sv_setnv>, but also handles 'set' magic.

    void    sv_setnv_mg(SV *sv, NV num)

=for hackers
Found in file sv.c

=item sv_setpv

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

    void    sv_setpv(SV* sv, const char* ptr)

=for hackers
Found in file sv.c

=item sv_setpvf

Works like C<sv_catpvf> but copies the text into the SV instead of
appending it.  Does not handle 'set' magic.  See C<sv_setpvf_mg>.

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

=for hackers
Found in file sv.c

=item sv_setpvf_mg

Like C<sv_setpvf>, but also handles 'set' magic.

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

=for hackers
Found in file sv.c

=item sv_setpviv

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

    void    sv_setpviv(SV* sv, IV num)

=for hackers
Found in file sv.c

=item sv_setpviv_mg

Like C<sv_setpviv>, but also handles 'set' magic.

    void    sv_setpviv_mg(SV *sv, IV iv)

=for hackers
Found in file sv.c

=item sv_setpvn

Copies a string into an SV.  The C<len> parameter indicates the number of
bytes to be copied.  If the C<ptr> argument is NULL the SV will become
undefined.  Does not handle 'set' magic.  See C<sv_setpvn_mg>.

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

=for hackers
Found in file sv.c

=item sv_setpvn_mg

Like C<sv_setpvn>, but also handles 'set' magic.

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

=for hackers
Found in file sv.c

=item sv_setpv_mg

Like C<sv_setpv>, but also handles 'set' magic.

    void    sv_setpv_mg(SV *sv, const char *ptr)

=for hackers
Found in file sv.c

=item sv_setref_iv

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

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

=for hackers
Found in file sv.c

=item sv_setref_nv

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

    SV*    sv_setref_nv(SV* rv, const char* classname, NV nv)

=for hackers
Found in file sv.c

=item sv_setref_pv

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

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

Note that C<sv_setref_pvn> copies the string while this copies the pointer.

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

=for hackers
Found in file sv.c

=item sv_setref_pvn

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

Note that C<sv_setref_pv> copies the pointer while this copies the string.

    SV*    sv_setref_pvn(SV* rv, const char* classname, char* pv, STRLEN n)

=for hackers
Found in file sv.c

=item sv_setref_uv

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

    SV*    sv_setref_uv(SV* rv, const char* classname, UV uv)

=for hackers
Found in file sv.c

=item sv_setsv

Copies the contents of the source SV C<ssv> into the destination SV
C<dsv>.  The source SV may be destroyed if it is mortal, so don't use this
function if the source SV needs to be reused. Does not handle 'set' magic.
Loosely speaking, it performs a copy-by-value, obliterating any previous
content of the destination.

You probably want to use one of the assortment of wrappers, such as
C<SvSetSV>, C<SvSetSV_nosteal>, C<SvSetMagicSV> and
C<SvSetMagicSV_nosteal>.

    void    sv_setsv(SV* dsv, SV* ssv)

=for hackers
Found in file sv.c

=item sv_setsv_flags

Copies the contents of the source SV C<ssv> into the destination SV
C<dsv>.  The source SV may be destroyed if it is mortal, so don't use this
function if the source SV needs to be reused. Does not handle 'set' magic.
Loosely speaking, it performs a copy-by-value, obliterating any previous
content of the destination.
If the C<flags> parameter has the C<SV_GMAGIC> bit set, will C<mg_get> on
C<ssv> if appropriate, else not. If the C<flags> parameter has the
C<NOSTEAL> bit set then the buffers of temps will not be stolen. <sv_setsv>
and C<sv_setsv_nomg> are implemented in terms of this function.

You probably want to use one of the assortment of wrappers, such as
C<SvSetSV>, C<SvSetSV_nosteal>, C<SvSetMagicSV> and
C<SvSetMagicSV_nosteal>.

This is the primary function for copying scalars, and most other
copy-ish functions and macros use this underneath.

    void    sv_setsv_flags(SV* dsv, SV* ssv, I32 flags)

=for hackers
Found in file sv.c

=item sv_setsv_mg

Like C<sv_setsv>, but also handles 'set' magic.

    void    sv_setsv_mg(SV *dstr, SV *sstr)

=for hackers
Found in file sv.c

=item sv_setsv_nomg

Like C<sv_setsv> but doesn't process magic.

    void    sv_setsv_nomg(SV* dsv, SV* ssv)

=for hackers
Found in file sv.h

=item sv_setuv

Copies an unsigned integer into the given SV, upgrading first if necessary.
Does not handle 'set' magic.  See also C<sv_setuv_mg>.

    void    sv_setuv(SV* sv, UV num)

=for hackers
Found in file sv.c

=item sv_setuv_mg

Like C<sv_setuv>, but also handles 'set' magic.

    void    sv_setuv_mg(SV *sv, UV u)

=for hackers
Found in file sv.c

=item sv_taint

Taint an SV. Use C<SvTAINTED_on> instead.
    void    sv_taint(SV* sv)

=for hackers
Found in file sv.c

=item sv_tainted

Test an SV for taintedness. Use C<SvTAINTED> instead.
    bool    sv_tainted(SV* sv)

=for hackers
Found in file sv.c

=item sv_true

Returns true if the SV has a true value by Perl's rules.
Use the C<SvTRUE> macro instead, which may call C<sv_true()> or may
instead use an in-line version.

    I32    sv_true(SV *sv)

=for hackers
Found in file sv.c

=item sv_unmagic

Removes all magic of type C<type> from an SV.

    int    sv_unmagic(SV* sv, int type)

=for hackers
Found in file sv.c

=item 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 C<newSVrv>.  This is C<sv_unref_flags> with the C<flag>
being zero.  See C<SvROK_off>.

    void    sv_unref(SV* sv)

=for hackers
Found in file sv.c

=item sv_unref_flags

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 C<newSVrv>.  The C<cflags> argument can contain
C<SV_IMMEDIATE_UNREF> to force the reference count to be decremented
(otherwise the decrementing is conditional on the reference count being
different from one or the reference being a readonly SV).
See C<SvROK_off>.

    void    sv_unref_flags(SV* sv, U32 flags)

=for hackers
Found in file sv.c

=item sv_untaint

Untaint an SV. Use C<SvTAINTED_off> instead.
    void    sv_untaint(SV* sv)

=for hackers
Found in file sv.c

=item sv_upgrade

Upgrade an SV to a more complex form.  Generally adds a new body type to the
SV, then copies across as much information as possible from the old body.
You generally want to use the C<SvUPGRADE> macro wrapper. See also C<svtype>.

    bool    sv_upgrade(SV* sv, U32 mt)

=for hackers
Found in file sv.c

=item sv_usepvn

Tells an SV to use C<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 C<ptr> should point to memory that was allocated by C<malloc>.  The
string length, C<len>, must be supplied.  This function will realloc the
memory pointed to by C<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 C<sv_usepvn_mg>.

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

=for hackers
Found in file sv.c

=item sv_usepvn_mg

Like C<sv_usepvn>, but also handles 'set' magic.

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

=for hackers
Found in file sv.c

=item sv_utf8_decode

If the PV of the SV is an octet sequence in UTF-8
and contains a multiple-byte character, the C<SvUTF8> flag is turned on
so that it looks like a character. If the PV contains only single-byte
characters, the C<SvUTF8> flag stays being off.
Scans PV for validity and returns false if the PV is invalid UTF-8.

NOTE: this function is experimental and may change or be
removed without notice.

    bool    sv_utf8_decode(SV *sv)

=for hackers
Found in file sv.c

=item sv_utf8_downgrade

Attempts to convert the PV of an SV from characters to bytes.
If the PV contains a character beyond byte, this conversion will fail;
in this case, either returns false or, if C<fail_ok> is not
true, croaks.

This is not as a general purpose Unicode to byte encoding interface:
use the Encode extension for that.

NOTE: this function is experimental and may change or be
removed without notice.

    bool    sv_utf8_downgrade(SV *sv, bool fail_ok)

=for hackers
Found in file sv.c

=item sv_utf8_encode

Converts the PV of an SV to UTF-8, but then turns the C<SvUTF8>
flag off so that it looks like octets again.

    void    sv_utf8_encode(SV *sv)

=for hackers
Found in file sv.c

=item sv_utf8_upgrade

Converts the PV of an SV to its UTF-8-encoded form.
Forces the SV to string form if it is not already.
Always sets the SvUTF8 flag to avoid future validity checks even
if all the bytes have hibit clear.

This is not as a general purpose byte encoding to Unicode interface:
use the Encode extension for that.

    STRLEN    sv_utf8_upgrade(SV *sv)

=for hackers
Found in file sv.c

=item sv_utf8_upgrade_flags

Converts the PV of an SV to its UTF-8-encoded form.
Forces the SV to string form if it is not already.
Always sets the SvUTF8 flag to avoid future validity checks even
if all the bytes have hibit clear. If C<flags> has C<SV_GMAGIC> bit set,
will C<mg_get> on C<sv> if appropriate, else not. C<sv_utf8_upgrade> and
C<sv_utf8_upgrade_nomg> are implemented in terms of this function.

This is not as a general purpose byte encoding to Unicode interface:
use the Encode extension for that.

    STRLEN    sv_utf8_upgrade_flags(SV *sv, I32 flags)

=for hackers
Found in file sv.c

=item sv_uv

A private implementation of the C<SvUVx> macro for compilers which can't
cope with complex macro expressions. Always use the macro instead.

    UV    sv_uv(SV* sv)

=for hackers
Found in file sv.c

=item sv_vcatpvf

Processes its arguments like C<vsprintf> and appends the formatted output
to an SV.  Does not handle 'set' magic.  See C<sv_vcatpvf_mg>.

Usually used via its frontend C<sv_catpvf>.

    void    sv_vcatpvf(SV* sv, const char* pat, va_list* args)

=for hackers
Found in file sv.c

=item sv_vcatpvfn

Processes its arguments like C<vsprintf> and appends the formatted output
to an SV.  Uses an array of SVs if the C style variable argument list is
missing (NULL).  When running with taint checks enabled, indicates via
C<maybe_tainted> if results are untrustworthy (often due to the use of
locales).

Usually used via one of its frontends C<sv_vcatpvf> and C<sv_vcatpvf_mg>.

    void    sv_vcatpvfn(SV* sv, const char* pat, STRLEN patlen, va_list* args, SV** svargs, I32 svmax, bool *maybe_tainted)

=for hackers
Found in file sv.c

=item sv_vcatpvf_mg

Like C<sv_vcatpvf>, but also handles 'set' magic.

Usually used via its frontend C<sv_catpvf_mg>.

    void    sv_vcatpvf_mg(SV* sv, const char* pat, va_list* args)

=for hackers
Found in file sv.c

=item sv_vsetpvf

Works like C<sv_vcatpvf> but copies the text into the SV instead of
appending it.  Does not handle 'set' magic.  See C<sv_vsetpvf_mg>.

Usually used via its frontend C<sv_setpvf>.

    void    sv_vsetpvf(SV* sv, const char* pat, va_list* args)

=for hackers
Found in file sv.c

=item sv_vsetpvfn

Works like C<sv_vcatpvfn> but copies the text into the SV instead of
appending it.

Usually used via one of its frontends C<sv_vsetpvf> and C<sv_vsetpvf_mg>.

    void    sv_vsetpvfn(SV* sv, const char* pat, STRLEN patlen, va_list* args, SV** svargs, I32 svmax, bool *maybe_tainted)

=for hackers
Found in file sv.c

=item sv_vsetpvf_mg

Like C<sv_vsetpvf>, but also handles 'set' magic.

Usually used via its frontend C<sv_setpvf_mg>.

    void    sv_vsetpvf_mg(SV* sv, const char* pat, va_list* args)

=for hackers
Found in file sv.c


=back

=head1 Unicode Support

=over 8

=item bytes_from_utf8

Converts a string C<s> of length C<len> from UTF-8 into byte encoding.
Unlike <utf8_to_bytes> but like C<bytes_to_utf8>, returns a pointer to
the newly-created string, and updates C<len> to contain the new
length.  Returns the original string if no conversion occurs, C<len>
is unchanged. Do nothing if C<is_utf8> points to 0. Sets C<is_utf8> to
0 if C<s> is converted or contains all 7bit characters.

NOTE: this function is experimental and may change or be
removed without notice.

    U8*    bytes_from_utf8(U8 *s, STRLEN *len, bool *is_utf8)

=for hackers
Found in file utf8.c

=item bytes_to_utf8

Converts a string C<s> of length C<len> from ASCII into UTF-8 encoding.
Returns a pointer to the newly-created string, and sets C<len> to
reflect the new length.

If you want to convert to UTF-8 from other encodings than ASCII,
see sv_recode_to_utf8().

NOTE: this function is experimental and may change or be
removed without notice.

    U8*    bytes_to_utf8(U8 *s, STRLEN *len)

=for hackers
Found in file utf8.c

=item ibcmp_utf8

Return true if the strings s1 and s2 differ case-insensitively, false
if not (if they are equal case-insensitively).  If u1 is true, the
string s1 is assumed to be in UTF-8-encoded Unicode.  If u2 is true,
the string s2 is assumed to be in UTF-8-encoded Unicode.  If u1 or u2
are false, the respective string is assumed to be in native 8-bit
encoding.

If the pe1 and pe2 are non-NULL, the scanning pointers will be copied
in there (they will point at the beginning of the I<next> character).
If the pointers behind pe1 or pe2 are non-NULL, they are the end
pointers beyond which scanning will not continue under any
circumstances.  If the byte lengths l1 and l2 are non-zero, s1+l1 and
s2+l2 will be used as goal end pointers that will also stop the scan,
and which qualify towards defining a successful match: all the scans
that define an explicit length must reach their goal pointers for
a match to succeed).

For case-insensitiveness, the "casefolding" of Unicode is used
instead of upper/lowercasing both the characters, see
http://www.unicode.org/unicode/reports/tr21/ (Case Mappings).

    I32    ibcmp_utf8(const char* a, char **pe1, UV l1, bool u1, const char* b, char **pe2, UV l2, bool u2)

=for hackers
Found in file utf8.c

=item is_utf8_char

Tests if some arbitrary number of bytes begins in a valid UTF-8
character.  Note that an INVARIANT (i.e. ASCII) character is a valid
UTF-8 character.  The actual number of bytes in the UTF-8 character
will be returned if it is valid, otherwise 0.

    STRLEN    is_utf8_char(U8 *p)

=for hackers
Found in file utf8.c

=item is_utf8_string

Returns true if first C<len> bytes of the given string form a valid
UTF-8 string, false otherwise.  Note that 'a valid UTF-8 string' does
not mean 'a string that contains code points above 0x7F encoded in UTF-8'
because a valid ASCII string is a valid UTF-8 string.

    bool    is_utf8_string(U8 *s, STRLEN len)

=for hackers
Found in file utf8.c

=item is_utf8_string_loc

Like is_ut8_string but store the location of the failure in
the last argument.

    bool    is_utf8_string_loc(U8 *s, STRLEN len, U8 **p)

=for hackers
Found in file utf8.c

=item pv_uni_display

Build to the scalar dsv a displayable version of the string spv,
length len, the displayable version being at most pvlim bytes long
(if longer, the rest is truncated and "..." will be appended).

The flags argument can have UNI_DISPLAY_ISPRINT set to display
isPRINT()able characters as themselves, UNI_DISPLAY_BACKSLASH
to display the \\[nrfta\\] as the backslashed versions (like '\n')
(UNI_DISPLAY_BACKSLASH is preferred over UNI_DISPLAY_ISPRINT for \\).
UNI_DISPLAY_QQ (and its alias UNI_DISPLAY_REGEX) have both
UNI_DISPLAY_BACKSLASH and UNI_DISPLAY_ISPRINT turned on.

The pointer to the PV of the dsv is returned.

    char*    pv_uni_display(SV *dsv, U8 *spv, STRLEN len, STRLEN pvlim, UV flags)

=for hackers
Found in file utf8.c

=item sv_cat_decode

The encoding is assumed to be an Encode object, the PV of the ssv is
assumed to be octets in that encoding and decoding the input starts
from the position which (PV + *offset) pointed to.  The dsv will be
concatenated the decoded UTF-8 string from ssv.  Decoding will terminate
when the string tstr appears in decoding output or the input ends on
the PV of the ssv. The value which the offset points will be modified
to the last input position on the ssv.

Returns TRUE if the terminator was found, else returns FALSE.

    bool    sv_cat_decode(SV* dsv, SV *encoding, SV *ssv, int *offset, char* tstr, int tlen)

=for hackers
Found in file sv.c

=item sv_recode_to_utf8

The encoding is assumed to be an Encode object, on entry the PV
of the sv is assumed to be octets in that encoding, and the sv
will be converted into Unicode (and UTF-8).

If the sv already is UTF-8 (or if it is not POK), or if the encoding
is not a reference, nothing is done to the sv.  If the encoding is not
an C<Encode::XS> Encoding object, bad things will happen.
(See F<lib/encoding.pm> and L<Encode>).

The PV of the sv is returned.

    char*    sv_recode_to_utf8(SV* sv, SV *encoding)

=for hackers
Found in file sv.c

=item sv_uni_display

Build to the scalar dsv a displayable version of the scalar sv,
the displayable version being at most pvlim bytes long
(if longer, the rest is truncated and "..." will be appended).

The flags argument is as in pv_uni_display().

The pointer to the PV of the dsv is returned.

    char*    sv_uni_display(SV *dsv, SV *ssv, STRLEN pvlim, UV flags)

=for hackers
Found in file utf8.c

=item to_utf8_case

The "p" contains the pointer to the UTF-8 string encoding
the character that is being converted.

The "ustrp" is a pointer to the character buffer to put the
conversion result to.  The "lenp" is a pointer to the length
of the result.

The "swashp" is a pointer to the swash to use.

Both the special and normal mappings are stored lib/unicore/To/Foo.pl,
and loaded by SWASHGET, using lib/utf8_heavy.pl.  The special (usually,
but not always, a multicharacter mapping), is tried first.

The "special" is a string like "utf8::ToSpecLower", which means the
hash %utf8::ToSpecLower.  The access to the hash is through
Perl_to_utf8_case().

The "normal" is a string like "ToLower" which means the swash
%utf8::ToLower.

    UV    to_utf8_case(U8 *p, U8* ustrp, STRLEN *lenp, SV **swash, char *normal, char *special)

=for hackers
Found in file utf8.c

=item to_utf8_fold

Convert the UTF-8 encoded character at p to its foldcase version and
store that in UTF-8 in ustrp and its length in bytes in lenp.  Note
that the ustrp needs to be at least UTF8_MAXBYTES_CASE+1 bytes since the
foldcase version may be longer than the original character (up to
three characters).

The first character of the foldcased version is returned
(but note, as explained above, that there may be more.)

    UV    to_utf8_fold(U8 *p, U8* ustrp, STRLEN *lenp)

=for hackers
Found in file utf8.c

=item to_utf8_lower

Convert the UTF-8 encoded character at p to its lowercase version and
store that in UTF-8 in ustrp and its length in bytes in lenp.  Note
that the ustrp needs to be at least UTF8_MAXBYTES_CASE+1 bytes since the
lowercase version may be longer than the original character.

The first character of the lowercased version is returned
(but note, as explained above, that there may be more.)

    UV    to_utf8_lower(U8 *p, U8* ustrp, STRLEN *lenp)

=for hackers
Found in file utf8.c

=item to_utf8_title

Convert the UTF-8 encoded character at p to its titlecase version and
store that in UTF-8 in ustrp and its length in bytes in lenp.  Note
that the ustrp needs to be at least UTF8_MAXBYTES_CASE+1 bytes since the
titlecase version may be longer than the original character.

The first character of the titlecased version is returned
(but note, as explained above, that there may be more.)

    UV    to_utf8_title(U8 *p, U8* ustrp, STRLEN *lenp)

=for hackers
Found in file utf8.c

=item to_utf8_upper

Convert the UTF-8 encoded character at p to its uppercase version and
store that in UTF-8 in ustrp and its length in bytes in lenp.  Note
that the ustrp needs to be at least UTF8_MAXBYTES_CASE+1 bytes since
the uppercase version may be longer than the original character.

The first character of the uppercased version is returned
(but note, as explained above, that there may be more.)

    UV    to_utf8_upper(U8 *p, U8* ustrp, STRLEN *lenp)

=for hackers
Found in file utf8.c

=item utf8n_to_uvchr

Returns the native character value of the first character in the string C<s>
which is assumed to be in UTF-8 encoding; C<retlen> will be set to the
length, in bytes, of that character.

Allows length and flags to be passed to low level routine.

    UV    utf8n_to_uvchr(U8 *s, STRLEN curlen, STRLEN* retlen, U32 flags)

=for hackers
Found in file utf8.c

=item utf8n_to_uvuni

Bottom level UTF-8 decode routine.
Returns the unicode code point value of the first character in the string C<s>
which is assumed to be in UTF-8 encoding and no longer than C<curlen>;
C<retlen> will be set to the length, in bytes, of that character.

If C<s> does not point to a well-formed UTF-8 character, the behaviour
is dependent on the value of C<flags>: if it contains UTF8_CHECK_ONLY,
it is assumed that the caller will raise a warning, and this function
will silently just set C<retlen> to C<-1> and return zero.  If the
C<flags> does not contain UTF8_CHECK_ONLY, warnings about
malformations will be given, C<retlen> will be set to the expected
length of the UTF-8 character in bytes, and zero will be returned.

The C<flags> can also contain various flags to allow deviations from
the strict UTF-8 encoding (see F<utf8.h>).

Most code should use utf8_to_uvchr() rather than call this directly.

    UV    utf8n_to_uvuni(U8 *s, STRLEN curlen, STRLEN* retlen, U32 flags)

=for hackers
Found in file utf8.c

=item utf8_distance

Returns the number of UTF-8 characters between the UTF-8 pointers C<a>
and C<b>.

WARNING: use only if you *know* that the pointers point inside the
same UTF-8 buffer.

    IV    utf8_distance(U8 *a, U8 *b)

=for hackers
Found in file utf8.c

=item utf8_hop

Return the UTF-8 pointer C<s> displaced by C<off> characters, either
forward or backward.

WARNING: do not use the following unless you *know* C<off> is within
the UTF-8 data pointed to by C<s> *and* that on entry C<s> is aligned
on the first byte of character or just after the last byte of a character.

    U8*    utf8_hop(U8 *s, I32 off)

=for hackers
Found in file utf8.c

=item utf8_length

Return the length of the UTF-8 char encoded string C<s> in characters.
Stops at C<e> (inclusive).  If C<e E<lt> s> or if the scan would end
up past C<e>, croaks.

    STRLEN    utf8_length(U8* s, U8 *e)

=for hackers
Found in file utf8.c

=item utf8_to_bytes

Converts a string C<s> of length C<len> from UTF-8 into byte encoding.
Unlike C<bytes_to_utf8>, this over-writes the original string, and
updates len to contain the new length.
Returns zero on failure, setting C<len> to -1.

NOTE: this function is experimental and may change or be
removed without notice.

    U8*    utf8_to_bytes(U8 *s, STRLEN *len)

=for hackers
Found in file utf8.c

=item utf8_to_uvchr

Returns the native character value of the first character in the string C<s>
which is assumed to be in UTF-8 encoding; C<retlen> will be set to the
length, in bytes, of that character.

If C<s> does not point to a well-formed UTF-8 character, zero is
returned and retlen is set, if possible, to -1.

    UV    utf8_to_uvchr(U8 *s, STRLEN* retlen)

=for hackers
Found in file utf8.c

=item utf8_to_uvuni

Returns the Unicode code point of the first character in the string C<s>
which is assumed to be in UTF-8 encoding; C<retlen> will be set to the
length, in bytes, of that character.

This function should only be used when returned UV is considered
an index into the Unicode semantic tables (e.g. swashes).

If C<s> does not point to a well-formed UTF-8 character, zero is
returned and retlen is set, if possible, to -1.

    UV    utf8_to_uvuni(U8 *s, STRLEN* retlen)

=for hackers
Found in file utf8.c

=item uvchr_to_utf8

Adds the UTF-8 representation of the Native codepoint C<uv> to the end
of the string C<d>; C<d> should be have at least C<UTF8_MAXBYTES+1> free
bytes available. The return value is the pointer to the byte after the
end of the new character. In other words,

    d = uvchr_to_utf8(d, uv);

is the recommended wide native character-aware way of saying

    *(d++) = uv;

    U8*    uvchr_to_utf8(U8 *d, UV uv)

=for hackers
Found in file utf8.c

=item uvuni_to_utf8_flags

Adds the UTF-8 representation of the Unicode codepoint C<uv> to the end
of the string C<d>; C<d> should be have at least C<UTF8_MAXBYTES+1> free
bytes available. The return value is the pointer to the byte after the
end of the new character. In other words,

    d = uvuni_to_utf8_flags(d, uv, flags);

or, in most cases,

    d = uvuni_to_utf8(d, uv);

(which is equivalent to)

    d = uvuni_to_utf8_flags(d, uv, 0);

is the recommended Unicode-aware way of saying

    *(d++) = uv;

    U8*    uvuni_to_utf8_flags(U8 *d, UV uv, UV flags)

=for hackers
Found in file utf8.c


=back

=head1 Variables created by C<xsubpp> and C<xsubpp> internal functions

=over 8

=item ax

Variable which is setup by C<xsubpp> to indicate the stack base offset,
used by the C<ST>, C<XSprePUSH> and C<XSRETURN> macros.  The C<dMARK> macro
must be called prior to setup the C<MARK> variable.

    I32    ax

=for hackers
Found in file XSUB.h

=item CLASS

Variable which is setup by C<xsubpp> to indicate the
class name for a C++ XS constructor.  This is always a C<char*>.  See C<THIS>.

    char*    CLASS

=for hackers
Found in file XSUB.h

=item dAX

Sets up the C<ax> variable.
This is usually handled automatically by C<xsubpp> by calling C<dXSARGS>.

        dAX;

=for hackers
Found in file XSUB.h

=item dITEMS

Sets up the C<items> variable.
This is usually handled automatically by C<xsubpp> by calling C<dXSARGS>.

        dITEMS;

=for hackers
Found in file XSUB.h

=item dXSARGS

Sets up stack and mark pointers for an XSUB, calling dSP and dMARK.
Sets up the C<ax> and C<items> variables by calling C<dAX> and C<dITEMS>.
This is usually handled automatically by C<xsubpp>.

        dXSARGS;

=for hackers
Found in file XSUB.h

=item dXSI32

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

        dXSI32;

=for hackers
Found in file XSUB.h

=item items

Variable which is setup by C<xsubpp> to indicate the number of
items on the stack.  See L<perlxs/"Variable-length Parameter Lists">.

    I32    items

=for hackers
Found in file XSUB.h

=item ix

Variable which is setup by C<xsubpp> to indicate which of an
XSUB's aliases was used to invoke it.  See L<perlxs/"The ALIAS: Keyword">.

    I32    ix

=for hackers
Found in file XSUB.h

=item newXSproto

Used by C<xsubpp> to hook up XSUBs as Perl subs.  Adds Perl prototypes to
the subs.

=for hackers
Found in file XSUB.h

=item RETVAL

Variable which is setup by C<xsubpp> to hold the return value for an
XSUB. This is always the proper type for the XSUB. See
L<perlxs/"The RETVAL Variable">.

    (whatever)    RETVAL

=for hackers
Found in file XSUB.h

=item ST

Used to access elements on the XSUB's stack.

    SV*    ST(int ix)

=for hackers
Found in file XSUB.h

=item THIS

Variable which is setup by C<xsubpp> to designate the object in a C++
XSUB.  This is always the proper type for the C++ object.  See C<CLASS> and
L<perlxs/"Using XS With C++">.

    (whatever)    THIS

=for hackers
Found in file XSUB.h

=item XS

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

=for hackers
Found in file XSUB.h

=item XS_VERSION

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

=for hackers
Found in file XSUB.h

=item XS_VERSION_BOOTCHECK

Macro to verify that a PM module's $VERSION variable matches the XS
module's C<XS_VERSION> variable.  This is usually handled automatically by
C<xsubpp>.  See L<perlxs/"The VERSIONCHECK: Keyword">.

        XS_VERSION_BOOTCHECK;

=for hackers
Found in file XSUB.h


=back

=head1 Warning and Dieing

=over 8

=item croak

This is the XSUB-writer's interface to Perl's C<die> function.
Normally call this function the same way you call the C C<printf>
function.  Calling C<croak> returns control directly to Perl,
sidestepping the normal C order of execution. See C<warn>.

If you want to throw an exception object, assign the object to
C<$@> and then pass C<Nullch> to croak():

   errsv = get_sv("@", TRUE);
   sv_setsv(errsv, exception_object);
   croak(Nullch);

    void    croak(const char* pat, ...)

=for hackers
Found in file util.c

=item warn

This is the XSUB-writer's interface to Perl's C<warn> function.  Call this
function the same way you call the C C<printf> function.  See C<croak>.

    void    warn(const char* pat, ...)

=for hackers
Found in file util.c


=back

=head1 AUTHORS

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]>.

Updated to be autogenerated from comments in the source by Benjamin Stuhl.

=head1 SEE ALSO

perlguts(1), perlxs(1), perlxstut(1), perlintern(1)