src/jpeg/jmemdosa.asm

;
; jmemdosa.asm
;
; Copyright (C) 1992, Thomas G. Lane.
; This file is part of the Independent JPEG Group's software.
; For conditions of distribution and use, see the accompanying README file.
;
; This file contains low-level interface routines to support the MS-DOS
; backing store manager (jmemdos.c).  Routines are provided to access disk
; files through direct DOS calls, and to access XMS and EMS drivers.
;
; This file should assemble with Microsoft's MASM or any compatible
; assembler (including Borland's Turbo Assembler).  If you haven't got
; a compatible assembler, better fall back to jmemansi.c or jmemname.c.
;
; To minimize dependence on the C compiler's register usage conventions,
; we save and restore all 8086 registers, even though most compilers only
; require SI,DI,DS to be preserved.  Also, we use only 16-bit-wide return
; values, which everybody returns in AX.
;
; Based on code contributed by Ge' Weijers.
;

JMEMDOSA_TXT	segment byte public 'CODE'

		assume	cs:JMEMDOSA_TXT

		public	_jdos_open
		public	_jdos_close
		public	_jdos_seek
		public	_jdos_read
		public	_jdos_write
		public	_jxms_getdriver
		public	_jxms_calldriver
		public	_jems_available
		public	_jems_calldriver

;
; short far jdos_open (short far * handle, char far * filename)
;
; Create and open a temporary file
;
_jdos_open	proc	far
		push	bp			; linkage
		mov 	bp,sp
		push	si			; save all registers for safety
		push	di
		push	bx
		push	cx
		push	dx
		push	es
		push	ds
		mov	cx,0			; normal file attributes
		lds	dx,dword ptr [bp+10]	; get filename pointer
		mov	ah,3ch			; create file
		int	21h
		jc	open_err		; if failed, return error code
		lds	bx,dword ptr [bp+6]	; get handle pointer
		mov	word ptr [bx],ax	; save the handle
		xor	ax,ax			; return zero for OK
open_err:	pop	ds			; restore registers and exit
		pop	es
		pop	dx
		pop	cx
		pop	bx
		pop	di
		pop	si
		pop 	bp
		ret
_jdos_open	endp


;
; short far jdos_close (short handle)
;
; Close the file handle
;
_jdos_close	proc	far
		push	bp			; linkage
		mov 	bp,sp
		push	si			; save all registers for safety
		push	di
		push	bx
		push	cx
		push	dx
		push	es
		push	ds
		mov	bx,word ptr [bp+6]	; file handle
		mov	ah,3eh			; close file
		int	21h
		jc	close_err		; if failed, return error code
		xor	ax,ax			; return zero for OK
close_err:	pop	ds			; restore registers and exit
		pop	es
		pop	dx
		pop	cx
		pop	bx
		pop	di
		pop	si
		pop 	bp
		ret
_jdos_close	endp


;
; short far jdos_seek (short handle, long offset)
;
; Set file position
;
_jdos_seek	proc	far
		push	bp			; linkage
		mov 	bp,sp
		push	si			; save all registers for safety
		push	di
		push	bx
		push	cx
		push	dx
		push	es
		push	ds
		mov	bx,word ptr [bp+6]	; file handle
		mov	dx,word ptr [bp+8]	; LS offset
		mov	cx,word ptr [bp+10]	; MS offset
		mov	ax,4200h		; absolute seek
		int	21h
		jc	seek_err		; if failed, return error code
		xor	ax,ax			; return zero for OK
seek_err:	pop	ds			; restore registers and exit
		pop	es
		pop	dx
		pop	cx
		pop	bx
		pop	di
		pop	si
		pop 	bp
		ret
_jdos_seek	endp


;
; short far jdos_read (short handle, void far * buffer, unsigned short count)
;
; Read from file
;
_jdos_read	proc	far
		push	bp			; linkage
		mov 	bp,sp
		push	si			; save all registers for safety
		push	di
		push	bx
		push	cx
		push	dx
		push	es
		push	ds
		mov	bx,word ptr [bp+6]	; file handle
		lds	dx,dword ptr [bp+8]	; buffer address
		mov	cx,word ptr [bp+12]	; number of bytes
		mov	ah,3fh			; read file
		int	21h
		jc	read_err		; if failed, return error code
		cmp	ax,word ptr [bp+12]	; make sure all bytes were read
		je	read_ok
		mov	ax,1			; else return 1 for not OK
		jmp	short read_err
read_ok:	xor	ax,ax			; return zero for OK
read_err:	pop	ds			; restore registers and exit
		pop	es
		pop	dx
		pop	cx
		pop	bx
		pop	di
		pop	si
		pop 	bp
		ret
_jdos_read	endp


;
; short far jdos_write (short handle, void far * buffer, unsigned short count)
;
; Write to file
;
_jdos_write	proc	far
		push	bp			; linkage
		mov 	bp,sp
		push	si			; save all registers for safety
		push	di
		push	bx
		push	cx
		push	dx
		push	es
		push	ds
		mov	bx,word ptr [bp+6]	; file handle
		lds	dx,dword ptr [bp+8]	; buffer address
		mov	cx,word ptr [bp+12]	; number of bytes
		mov	ah,40h			; write file
		int	21h
		jc	write_err		; if failed, return error code
		cmp	ax,word ptr [bp+12]	; make sure all bytes written
		je	write_ok
		mov	ax,1			; else return 1 for not OK
		jmp	short write_err
write_ok:	xor	ax,ax			; return zero for OK
write_err:	pop	ds			; restore registers and exit
		pop	es
		pop	dx
		pop	cx
		pop	bx
		pop	di
		pop	si
		pop 	bp
		ret
_jdos_write	endp


;
; void far jxms_getdriver (XMSDRIVER far *)
;
; Get the address of the XMS driver, or NULL if not available
;
_jxms_getdriver	proc	far
		push	bp			; linkage
		mov 	bp,sp
		push	si			; save all registers for safety
		push	di
		push	bx
		push	cx
		push	dx
		push	es
		push	ds
		mov 	ax,4300h		; call multiplex interrupt with
		int	2fh			; a magic cookie, hex 4300
		cmp 	al,80h			; AL should contain hex 80
		je	xmsavail
		xor 	dx,dx			; no XMS driver available
		xor 	ax,ax			; return a nil pointer
		jmp	short xmsavail_done
xmsavail:	mov 	ax,4310h		; fetch driver address with
		int	2fh			; another magic cookie
		mov 	dx,es			; copy address to dx:ax
		mov 	ax,bx
xmsavail_done:	les 	bx,dword ptr [bp+6]	; get pointer to return value
		mov	word ptr es:[bx],ax
		mov	word ptr es:[bx+2],dx
		pop	ds			; restore registers and exit
		pop	es
		pop	dx
		pop	cx
		pop	bx
		pop	di
		pop	si
		pop	bp
		ret
_jxms_getdriver	endp


;
; void far jxms_calldriver (XMSDRIVER, XMScontext far *)
;
; The XMScontext structure contains values for the AX,DX,BX,SI,DS registers.
; These are loaded, the XMS call is performed, and the new values of the
; AX,DX,BX registers are written back to the context structure.
;
_jxms_calldriver 	proc	far
		push	bp			; linkage
		mov 	bp,sp
		push	si			; save all registers for safety
		push	di
		push	bx
		push	cx
		push	dx
		push	es
		push	ds
		les 	bx,dword ptr [bp+10]	; get XMScontext pointer
		mov 	ax,word ptr es:[bx]	; load registers
		mov 	dx,word ptr es:[bx+2]
		mov 	si,word ptr es:[bx+6]
		mov 	ds,word ptr es:[bx+8]
		mov 	bx,word ptr es:[bx+4]
		call	dword ptr [bp+6]	; call the driver
		mov	cx,bx			; save returned BX for a sec
		les 	bx,dword ptr [bp+10]	; get XMScontext pointer
		mov 	word ptr es:[bx],ax	; put back ax,dx,bx
		mov 	word ptr es:[bx+2],dx
		mov 	word ptr es:[bx+4],cx
		pop	ds			; restore registers and exit
		pop	es
		pop	dx
		pop	cx
		pop	bx
		pop	di
		pop	si
		pop 	bp
		ret
_jxms_calldriver 	endp


;
; short far jems_available (void)
;
; Have we got an EMS driver? (this comes straight from the EMS 4.0 specs)
;
_jems_available	proc	far
		push	si			; save all registers for safety
		push	di
		push	bx
		push	cx
		push	dx
		push	es
		push	ds
		mov	ax,3567h		; get interrupt vector 67h
		int	21h
		push	cs
		pop	ds
		mov	di,000ah		; check offs 10 in returned seg
		lea	si,ASCII_device_name	; against literal string
		mov	cx,8
		cld
		repe cmpsb
		jne	no_ems
		mov	ax,1			; match, it's there
		jmp	short avail_done
no_ems:		xor	ax,ax			; it's not there
avail_done:	pop	ds			; restore registers and exit
		pop	es
		pop	dx
		pop	cx
		pop	bx
		pop	di
		pop	si
		ret

ASCII_device_name	db	"EMMXXXX0"

_jems_available	endp


;
; void far jems_calldriver (EMScontext far *)
;
; The EMScontext structure contains values for the AX,DX,BX,SI,DS registers.
; These are loaded, the EMS trap is performed, and the new values of the
; AX,DX,BX registers are written back to the context structure.
;
_jems_calldriver	proc far
		push	bp			; linkage
		mov 	bp,sp
		push	si			; save all registers for safety
		push	di
		push	bx
		push	cx
		push	dx
		push	es
		push	ds
		les 	bx,dword ptr [bp+6]	; get EMScontext pointer
		mov 	ax,word ptr es:[bx]	; load registers
		mov 	dx,word ptr es:[bx+2]
		mov 	si,word ptr es:[bx+6]
		mov 	ds,word ptr es:[bx+8]
		mov 	bx,word ptr es:[bx+4]
		int	67h			; call the EMS driver
		mov	cx,bx			; save returned BX for a sec
		les 	bx,dword ptr [bp+6]	; get EMScontext pointer
		mov 	word ptr es:[bx],ax	; put back ax,dx,bx
		mov 	word ptr es:[bx+2],dx
		mov 	word ptr es:[bx+4],cx
		pop	ds			; restore registers and exit
		pop	es
		pop	dx
		pop	cx
		pop	bx
		pop	di
		pop	si
		pop 	bp
		ret
_jems_calldriver	endp

JMEMDOSA_TXT	ends

		end
Commit	Line	Data
	1	;
	2	; jmemdosa.asm
	3	;
	4	; Copyright (C) 1992, Thomas G. Lane.
	5	; This file is part of the Independent JPEG Group's software.
	6	; For conditions of distribution and use, see the accompanying README file.
	7	;
	8	; This file contains low-level interface routines to support the MS-DOS
	9	; backing store manager (jmemdos.c). Routines are provided to access disk
	10	; files through direct DOS calls, and to access XMS and EMS drivers.
	11	;
	12	; This file should assemble with Microsoft's MASM or any compatible
	13	; assembler (including Borland's Turbo Assembler). If you haven't got
	14	; a compatible assembler, better fall back to jmemansi.c or jmemname.c.
	15	;
	16	; To minimize dependence on the C compiler's register usage conventions,
	17	; we save and restore all 8086 registers, even though most compilers only
	18	; require SI,DI,DS to be preserved. Also, we use only 16-bit-wide return
	19	; values, which everybody returns in AX.
	20	;
	21	; Based on code contributed by Ge' Weijers.
	22	;
	23
	24	JMEMDOSA_TXT segment byte public 'CODE'
	25
	26	assume cs:JMEMDOSA_TXT
	27
	28	public _jdos_open
	29	public _jdos_close
	30	public _jdos_seek
	31	public _jdos_read
	32	public _jdos_write
	33	public _jxms_getdriver
	34	public _jxms_calldriver
	35	public _jems_available
	36	public _jems_calldriver
	37
	38	;
	39	; short far jdos_open (short far * handle, char far * filename)
	40	;
	41	; Create and open a temporary file
	42	;
	43	_jdos_open proc far
	44	push bp ; linkage
	45	mov bp,sp
	46	push si ; save all registers for safety
	47	push di
	48	push bx
	49	push cx
	50	push dx
	51	push es
	52	push ds
	53	mov cx,0 ; normal file attributes
	54	lds dx,dword ptr [bp+10] ; get filename pointer
	55	mov ah,3ch ; create file
	56	int 21h
	57	jc open_err ; if failed, return error code
	58	lds bx,dword ptr [bp+6] ; get handle pointer
	59	mov word ptr [bx],ax ; save the handle
	60	xor ax,ax ; return zero for OK
	61	open_err: pop ds ; restore registers and exit
	62	pop es
	63	pop dx
	64	pop cx
	65	pop bx
	66	pop di
	67	pop si
	68	pop bp
	69	ret
	70	_jdos_open endp
	71
	72
	73	;
	74	; short far jdos_close (short handle)
	75	;
	76	; Close the file handle
	77	;
	78	_jdos_close proc far
	79	push bp ; linkage
	80	mov bp,sp
	81	push si ; save all registers for safety
	82	push di
	83	push bx
	84	push cx
	85	push dx
	86	push es
	87	push ds
	88	mov bx,word ptr [bp+6] ; file handle
	89	mov ah,3eh ; close file
	90	int 21h
	91	jc close_err ; if failed, return error code
	92	xor ax,ax ; return zero for OK
	93	close_err: pop ds ; restore registers and exit
	94	pop es
	95	pop dx
	96	pop cx
	97	pop bx
	98	pop di
	99	pop si
	100	pop bp
	101	ret
	102	_jdos_close endp
	103
	104
	105	;
	106	; short far jdos_seek (short handle, long offset)
	107	;
	108	; Set file position
	109	;
	110	_jdos_seek proc far
	111	push bp ; linkage
	112	mov bp,sp
	113	push si ; save all registers for safety
	114	push di
	115	push bx
	116	push cx
	117	push dx
	118	push es
	119	push ds
	120	mov bx,word ptr [bp+6] ; file handle
	121	mov dx,word ptr [bp+8] ; LS offset
	122	mov cx,word ptr [bp+10] ; MS offset
	123	mov ax,4200h ; absolute seek
	124	int 21h
	125	jc seek_err ; if failed, return error code
	126	xor ax,ax ; return zero for OK
	127	seek_err: pop ds ; restore registers and exit
	128	pop es
	129	pop dx
	130	pop cx
	131	pop bx
	132	pop di
	133	pop si
	134	pop bp
	135	ret
	136	_jdos_seek endp
	137
	138
	139	;
	140	; short far jdos_read (short handle, void far * buffer, unsigned short count)
	141	;
	142	; Read from file
	143	;
	144	_jdos_read proc far
	145	push bp ; linkage
	146	mov bp,sp
	147	push si ; save all registers for safety
	148	push di
	149	push bx
	150	push cx
	151	push dx
	152	push es
	153	push ds
	154	mov bx,word ptr [bp+6] ; file handle
	155	lds dx,dword ptr [bp+8] ; buffer address
	156	mov cx,word ptr [bp+12] ; number of bytes
	157	mov ah,3fh ; read file
	158	int 21h
	159	jc read_err ; if failed, return error code
	160	cmp ax,word ptr [bp+12] ; make sure all bytes were read
	161	je read_ok
	162	mov ax,1 ; else return 1 for not OK
	163	jmp short read_err
	164	read_ok: xor ax,ax ; return zero for OK
	165	read_err: pop ds ; restore registers and exit
	166	pop es
	167	pop dx
	168	pop cx
	169	pop bx
	170	pop di
	171	pop si
	172	pop bp
	173	ret
	174	_jdos_read endp
	175
	176
	177	;
	178	; short far jdos_write (short handle, void far * buffer, unsigned short count)
	179	;
	180	; Write to file
	181	;
	182	_jdos_write proc far
	183	push bp ; linkage
	184	mov bp,sp
	185	push si ; save all registers for safety
	186	push di
	187	push bx
	188	push cx
	189	push dx
	190	push es
	191	push ds
	192	mov bx,word ptr [bp+6] ; file handle
	193	lds dx,dword ptr [bp+8] ; buffer address
	194	mov cx,word ptr [bp+12] ; number of bytes
	195	mov ah,40h ; write file
	196	int 21h
	197	jc write_err ; if failed, return error code
	198	cmp ax,word ptr [bp+12] ; make sure all bytes written
	199	je write_ok
	200	mov ax,1 ; else return 1 for not OK
	201	jmp short write_err
	202	write_ok: xor ax,ax ; return zero for OK
	203	write_err: pop ds ; restore registers and exit
	204	pop es
	205	pop dx
	206	pop cx
	207	pop bx
	208	pop di
	209	pop si
	210	pop bp
	211	ret
	212	_jdos_write endp
	213
	214
	215	;
	216	; void far jxms_getdriver (XMSDRIVER far *)
	217	;
	218	; Get the address of the XMS driver, or NULL if not available
	219	;
	220	_jxms_getdriver proc far
	221	push bp ; linkage
	222	mov bp,sp
	223	push si ; save all registers for safety
	224	push di
	225	push bx
	226	push cx
	227	push dx
	228	push es
	229	push ds
	230	mov ax,4300h ; call multiplex interrupt with
	231	int 2fh ; a magic cookie, hex 4300
	232	cmp al,80h ; AL should contain hex 80
	233	je xmsavail
	234	xor dx,dx ; no XMS driver available
	235	xor ax,ax ; return a nil pointer
	236	jmp short xmsavail_done
	237	xmsavail: mov ax,4310h ; fetch driver address with
	238	int 2fh ; another magic cookie
	239	mov dx,es ; copy address to dx:ax
	240	mov ax,bx
	241	xmsavail_done: les bx,dword ptr [bp+6] ; get pointer to return value
	242	mov word ptr es:[bx],ax
	243	mov word ptr es:[bx+2],dx
	244	pop ds ; restore registers and exit
	245	pop es
	246	pop dx
	247	pop cx
	248	pop bx
	249	pop di
	250	pop si
	251	pop bp
	252	ret
	253	_jxms_getdriver endp
	254
	255
	256	;
	257	; void far jxms_calldriver (XMSDRIVER, XMScontext far *)
	258	;
	259	; The XMScontext structure contains values for the AX,DX,BX,SI,DS registers.
	260	; These are loaded, the XMS call is performed, and the new values of the
	261	; AX,DX,BX registers are written back to the context structure.
	262	;
	263	_jxms_calldriver proc far
	264	push bp ; linkage
	265	mov bp,sp
	266	push si ; save all registers for safety
	267	push di
	268	push bx
	269	push cx
	270	push dx
	271	push es
	272	push ds
	273	les bx,dword ptr [bp+10] ; get XMScontext pointer
	274	mov ax,word ptr es:[bx] ; load registers
	275	mov dx,word ptr es:[bx+2]
	276	mov si,word ptr es:[bx+6]
	277	mov ds,word ptr es:[bx+8]
	278	mov bx,word ptr es:[bx+4]
	279	call dword ptr [bp+6] ; call the driver
	280	mov cx,bx ; save returned BX for a sec
	281	les bx,dword ptr [bp+10] ; get XMScontext pointer
	282	mov word ptr es:[bx],ax ; put back ax,dx,bx
	283	mov word ptr es:[bx+2],dx
	284	mov word ptr es:[bx+4],cx
	285	pop ds ; restore registers and exit
	286	pop es
	287	pop dx
	288	pop cx
	289	pop bx
	290	pop di
	291	pop si
	292	pop bp
	293	ret
	294	_jxms_calldriver endp
	295
	296
	297	;
	298	; short far jems_available (void)
	299	;
	300	; Have we got an EMS driver? (this comes straight from the EMS 4.0 specs)
	301	;
	302	_jems_available proc far
	303	push si ; save all registers for safety
	304	push di
	305	push bx
	306	push cx
	307	push dx
	308	push es
	309	push ds
	310	mov ax,3567h ; get interrupt vector 67h
	311	int 21h
	312	push cs
	313	pop ds
	314	mov di,000ah ; check offs 10 in returned seg
	315	lea si,ASCII_device_name ; against literal string
	316	mov cx,8
	317	cld
	318	repe cmpsb
	319	jne no_ems
	320	mov ax,1 ; match, it's there
	321	jmp short avail_done
	322	no_ems: xor ax,ax ; it's not there
	323	avail_done: pop ds ; restore registers and exit
	324	pop es
	325	pop dx
	326	pop cx
	327	pop bx
	328	pop di
	329	pop si
	330	ret
	331
	332	ASCII_device_name db "EMMXXXX0"
	333
	334	_jems_available endp
	335
	336
	337	;
	338	; void far jems_calldriver (EMScontext far *)
	339	;
	340	; The EMScontext structure contains values for the AX,DX,BX,SI,DS registers.
	341	; These are loaded, the EMS trap is performed, and the new values of the
	342	; AX,DX,BX registers are written back to the context structure.
	343	;
	344	_jems_calldriver proc far
	345	push bp ; linkage
	346	mov bp,sp
	347	push si ; save all registers for safety
	348	push di
	349	push bx
	350	push cx
	351	push dx
	352	push es
	353	push ds
	354	les bx,dword ptr [bp+6] ; get EMScontext pointer
	355	mov ax,word ptr es:[bx] ; load registers
	356	mov dx,word ptr es:[bx+2]
	357	mov si,word ptr es:[bx+6]
	358	mov ds,word ptr es:[bx+8]
	359	mov bx,word ptr es:[bx+4]
	360	int 67h ; call the EMS driver
	361	mov cx,bx ; save returned BX for a sec
	362	les bx,dword ptr [bp+6] ; get EMScontext pointer
	363	mov word ptr es:[bx],ax ; put back ax,dx,bx
	364	mov word ptr es:[bx+2],dx
	365	mov word ptr es:[bx+4],cx
	366	pop ds ; restore registers and exit
	367	pop es
	368	pop dx
	369	pop cx
	370	pop bx
	371	pop di
	372	pop si
	373	pop bp
	374	ret
	375	_jems_calldriver endp
	376
	377	JMEMDOSA_TXT ends
	378
	379	end