Programmer 7500/MAX_PROGRAMMERS.iso/INFO/BBS/PUP.ZIP/MS-ASM.ASM

Assembly Source File | 1987-10-18 | 10.8 KB | 540 lines

title MSDOS dependent functions
name msasm

comment %

    T. Jennings
    13 Oct 87

    (k) all rights reversed


These are support routines for Puppy that are
currently implemented in MSDOS MASM.EXE assembler.
Most of them are pretty simple; some are annoying.

Some, such as time & date, you can dummy for systems
that dont support those functions, like CP/M; best to
return a 0 or something rather than remove the code;
if you ever get a clock/calendar you can add it later.

Some are arbitrary 8086isms; byte order in longs. Motorola
people will just have to shut up and implement! :-)

And some are just because when you invoke some supposedly
simple thing like read() or open() the stupid library
drags a whole bag of shit with it. There is a very simple
but effective Level 1 File I/O set of calls here.


handle= open(pathname,access);
int handle,access;
char *pathname;

    Open a file. handle returns either
the DOS handle, or -1 if error (file not
found). Access is: 0 == read only, 1 == write
only, 2 == read/write.

handle= creat(pathname,access);

    Create a new file, delete any existing
copy. Access is not used: use 0. Returns the
handle or -1 if error.

v= read(handle,buffer,count);
v= write(handle,buffer,count);
int v,handle,count;
char *buffer;

    File read or write to an opened or
created file. reads or writes 'count' bytes
to the file 'handle', to or from 'buffer'.
Returns the number of bytes processed: equal
to 'count' if sucessful.

error= close(handle)
int error;

    Close an open file. Returns -1 if
error. Any buffers are flushed at this point.

pos= lseek(handle,distance,flag);
long pos;    new position, else -1
int handle;
long distance;    displacement
int flag;    0 == from BOF,
        1 == from current,
        2 == from EOF,

    Seek to a position within a file.


Get the time & date from the system, store
in the provided array. Unsupported items
should be returned as 0's.

See PUPPY.H for the definition of 'time';
its just 6 bytes to hold it.

gtod(time);
struct _time *time;



GET and SET MSDOS file creation times of the open
file handle. If not supported, GET a 0 and
make SET do nothing.

SET is done just before the file is closed.

    _ftime(1,handle,timedate) set time/date
    _ftime(0,handle,timedate) get time/date
    char *timedate;
    int handle;



    val= _ioctl(func,handle,data,dummy)
    val= _ioctl(func,handle,buff,count)
    int val;    ret value or flag
    int func,handle,dummy,count;
    char *buff;

This is the MSDOS ioctl() function, used only
to support the function badname(), in MS-C.C. The
description below is only for informational
purposes; if not MSDOS, just dont implement any
of it. Refer to badname().


RETURN:    See below
    VAL returns as -1 if any error.

DESCRIPTION:
    IOCTL get/set device information. The
    args and return values depend on the
    function:

func == 0    get
func == 1    set
    Get or set device info on (handle).
    0x80 Is a device (else file)
    0x01    Console input
    0x02    Console out
    0x04    Null device
    0x08    Clock device
    0x10    Special (fast) device
    0x20    Raw mode
    0x40    EOF on input
    0x4000    Accepts control strings

func == 2    read
func == 3    write
    Read or write (count) bytes from
    the control channel.

func == 4    read
func == 5    write
    Same as 2,3, except (handle) is drive
    number; 0 == default, 1 == A:, etc.

func == 6    input status
func == 7    output status
    if (handle) is a device, returns 0 if
    not ready, else non-zero if device is
    ready. For files, output always ready,
    input always ready until EOF hit.



Search for file first/next function.

found= _find(pathname,n,&xfbuf);
int n;
char *pathname;
struct _xfbuf *xfbuf;

The structure xfbuf holds search information
inbetween calls to _find(); MSDOS, unlike CP/M,
allows other file operations between successive
_find() calls. It is absolutely necessary to
support this. The CP/M implementation of a
Unix level 1 file system (CPMFILES.C) supports
this.

This function returns 0 if there is no (more)
matching filenames.

pathname is the pathname to search for; it may
contain wildcards and drive specs.

N indicates first or "next" searches; it is
0 for the first time. For systems like CP/M you
should build a list of all matching files and
return the first, if any. Each successive call
will return N + 1, ie. 1 2 3 ... N. You
can use this to index the table built when N
was 0.

xfbuf is the address of the structure used to
hold information to perform the search. The
contents are preserved in between calls, so
you can store anything you want in it. It is
completely uninitialized space, so you should
init it during the N == 0 pass.


title XMODEM CRC Algorithm 8086 / Lattice C Compiler

I did not write this. I dont know who did. I munged an 8080
M80 source into 8086 MASM.

clrcrc();
CLRCRC - A call to this entry resets the CRC accumulator.
 It must be called at the start of each message.

 Entry Parameters:    None.
 Exit Conditions:     CRC accumulator cleared.

udcrc(c);
char c;
UPDCRC - A call to this entry updates the CRC accumulator.
 It must be called once for each byte in the
 message for which the CRC is being calculated.

 Entry Parameters:    a byte to be included
             in the CRC calculation.
 Exit Conditions:    CRC accumulator updated.

crc= fincrc();
unsigned crc;
FINCRC - A call to this entry finishes the CRC calculation
 for a message which is to be TRANSMITTED. It must
 be called after the last byte of the message has
 been passed thru UPDCRC. It returns the calculated
 CRC bytes, which must be transmitted as the final
 two bytes of the message.

Note that this returns a single 16 bit value;
if transmitting bytes, it must be transmitted
upper half first then lower half:

    output (crc >> 8);
    output (crc);

 Entry Parameters: None.
 Exit Conditions:  calculated CRC bytes.


error= chkcrc();
int error;
CHKCRC - A call to this routine checks the CRC bytes of
 a RECEIVED message and returns a code to indicate
 whether the message was received correctly. It must
 be called after the message AND the two CRC bytes
 have been received AND passed thru UPDCRC.

 Entry Parameters: None.
 Exit Conditions:  0 if message ok.
           non-zero if message garbled.

end of comment ------> %

;
;Define a (paranoid) near function.
;
 func macro procname
  public procname
  procname proc near
    push    bp
    mov    bp,sp
    push    ds
    push    es
    mov    ax,ds
    mov    es,ax
 endm
;
;Close a function declaration.
;
 endf macro procname
    pop    es
    pop    ds
    pop    bp
    ret
  procname endp
 endm
;
;Define the args on the stack.
;
arg0    equ    [bp+4]
arg1    equ    [bp+6]
arg2    equ    [bp+8]
arg3    equ    [bp+10]
arg4    equ    [bp+12]
arg5    equ    [bp+14]
arg6    equ    [bp+16]
arg7    equ    [bp+18]
arg8    equ    [bp+20]
;
;dgroup just generates a runtime accessible
;constant 'dataseg' so that drivers and other
;such oddities can set DS: to access data
;during interrupt service routines.
;
dgroup group data
data segment byte public 'data'
assume ds:dgroup

public dataseg
dataseg dw dgroup    ;so drivers can find it

data ends

pgroup group prog        ;MASM mumbo jumbo
prog segment byte public 'prog'
assume cs:pgroup
page
;
;Return one of the time or date components.
;Returns -1 if bad arg.
;
func gtod
    mov    ah,2ah
    int    21h        ;get date
    mov    bx,arg0
    sub    cx,1900        ;remove offset
    mov    [bx],cl        ;year
    mov    [bx + 1],dh    ;month
    mov    [bx + 2],dl    ;day
    push    bx
    mov    ah,2ch
    int    21h        ;get time
    pop    bx
    mov    [bx + 3],ch    ;hour
    mov    [bx + 4],cl    ;minute
    mov    [bx + 5],dh    ;second
endf gtod
page
;
;Convert a long to a character array.
;
func _ltoc
    cld
    mov    di,arg2
    mov    ax,arg0        ;LSW,
    stosw
    mov    ax,arg1        ;MSW
    stosw
endf _ltoc
;
;Convert a character array to a long.
;
func _ctol
    cld
    mov    si,arg0
    lodsw        ;get LSW,
    mov    bx,ax    ;MSW to AX,
    lodsw        ;return AX:BX.
endf _ctol
page
;
;Get and set File times.
;
func _ftime
    mov    al,arg0        ;1=set, 0=get,
    and    al,1
    mov    bx,arg1        ;file handle,
    mov    si,arg2        ;ptr to array,
    mov    cx,[si]        ;CX= time,
    mov    dx,[si+2]    ;DX= date,
    push    si
    mov    ah,87
    int    33
    pop    si
    test byte ptr arg0,1    ;if get time,
    jnz    _ft1
    mov    [si],cx        ;return time,
    mov    [si+2],dx    ;return date,
_ft1:
endf _ftime
page
;
;Perform IOCTL() functions.
;
func _ioctl
    mov    al,arg0        ;func
    mov    bx,arg1        ;handle
    mov    dx,arg2        ;data/buff
    mov    cx,arg3        ;dummy/count
    mov    ah,68
    int    33

    jnc    _io1        ;if error,
    mov    ax,-1        ;return -1
    jmp    short _ioz

_io1:    cmp    word ptr arg0,2    ;functions 0,1
    jae    _io2        ;return from DX
    mov    ax,dx
    jmp    short _ioz

_io2:    cmp    word ptr arg0,6    ;functions 2-5
    jb    _ioz        ;return from AX
    mov    ah,0        ;6,7 from AL
_ioz:
endf _ioctl
page
;
;Do search first/next.
;
func _find
    mov    dx,arg2        ;XFBUF ptr,
    mov    bx,dx
    mov    ah,26        ;set DMA addr
    int    21h        ;to buffer,
    mov    cx,0        ;CX == attrib
    mov    dx,arg0        ;pathname
    mov    ax,arg1        ;iteration flag
    or    ax,ax
    jz    f0
    mov    al,1        ;make 0,1

f0:    mov    ah,78        ;search first
    cmp    al,0        ;if AL == 0,
    je    f1
    mov    ah,79        ;else search next
f1:    int    21h        ;DOS call,
    mov    ax,-1        ;make 0 == not found
    adc    ax,0
endf _find
page
;
;Our very own little bit of data space.
;
crc    dw    0    ;in CS space

;
;Initialize the CRC.
;
func clrcrc
    mov    cs:crc,0
endf clrcrc

;
;Update the CRC with the new byte. The method used is
;the CCITT polynomial:
;
;    x^16 + x^12 + x^5 + 1
;
;An alternate method often used in synchronous
;protocols is:
;
;    x^16 + x^15 + x^2 + 1
;
;Which can be generated by changing the XOR pattern
;from 1021 hex to 8005 hex.
;
func updcrc
    mov    bx,cs:crc    ;BX == CRC a reg for speed,
    mov    cx,8        ;CX == bits in a byte,
    mov    ax,arg0        ;AL == msg byte,

u1:    rcl    al,1        ;MSB -> carry,
    rcl    bx,1        ;    -> CRC LSB,
    jnc    u2
    xor    bx,1021h
u2:    loop    u1

    mov    cs:crc,bx
endf updcrc

;
;Finish off the CRC.
;
func fincrc
    xor    ax,ax        ;do two zeros
    push    ax
    call    updcrc
    call    updcrc
    pop    ax
    mov    ax,cs:crc    ;return finished CRC
endf fincrc

;
;Check the calculated CRC. Return 0 if OK.
;
func chkcrc
    mov    ax,cs:crc
endf chkcrc
page
;
;File functions
;
func open
    mov    ah,61
    call    opncrt
endf open

func creat
    mov    ah,60
    call    opncrt
endf creat

opncrt:
    mov    dx,arg0        ;pathname,
    mov    al,arg1        ;access,
    xor    bx,bx
    xor    cx,cx
    int    21h        ;do it,
    jnc    opncrt1
    mov    ax,-1        ;error!
opncrt1:ret
;
;Close a file
;
func close
    mov    ah,62
    mov    bx,arg0        ;handle,
    int    21h
endf close
;
;File read & write
;
func read
    mov    ah,63
    call    rdwrt
endf read

func write
    mov    ah,64
    call    rdwrt
endf write

rdwrt:    mov    bx,arg0        ;handle,
    mov    dx,arg1        ;buffer,
    mov    cx,arg2        ;count,
    int    21h
    ret
;
;File seek
;
func lseek
    mov    bx,arg0        ;BX == handle,
    mov    dx,arg1        ;CX:DX == disp,
    mov    cx,arg2
    mov    ah,42h
    mov    al,arg3        ;unless error,
    int    21h        ;DX:AX == pos,
    mov    bx,ax
    mov    ax,dx
    jnc    _x1
    mov    ax,-1
    mov    bx,-1
_x1:
endf lseek

prog ends

end