4
* Copyright (C) 1992-1994, 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.
8
* This file provides an MS-DOS-compatible implementation of the system-
9
* dependent portion of the JPEG memory manager. Temporary data can be
10
* stored in extended or expanded memory as well as in regular DOS files.
12
* If you use this file, you must be sure that NEED_FAR_POINTERS is defined
13
* if you compile in a small-data memory model; it should NOT be defined if
14
* you use a large-data memory model. This file is not recommended if you
15
* are using a flat-memory-space 386 environment such as DJGCC or Watcom C.
16
* Also, this code will NOT work if struct fields are aligned on greater than
19
* Based on code contributed by Ge' Weijers.
23
* If you have both extended and expanded memory, you may want to change the
24
* order in which they are tried in jopen_backing_store. On a 286 machine
25
* expanded memory is usually faster, since extended memory access involves
26
* an expensive protected-mode-and-back switch. On 386 and better, extended
27
* memory is usually faster. As distributed, the code tries extended memory
28
* first (what? not everyone has a 386? :-).
30
* You can disable use of extended/expanded memory entirely by altering these
31
* definitions or overriding them from the Makefile (eg, -DEMS_SUPPORTED=0).
35
#define XMS_SUPPORTED 1
38
#define EMS_SUPPORTED 1
42
#define JPEG_INTERNALS
45
#include "jmemsys.h" /* import the system-dependent declarations */
47
#ifndef HAVE_STDLIB_H /* <stdlib.h> should declare these */
48
extern void * malloc JPP((size_t size));
49
extern void free JPP((void *ptr));
50
extern char * getenv JPP((const char * name));
53
#ifdef NEED_FAR_POINTERS
56
/* These definitions work for Borland C (Turbo C) */
57
#include <alloc.h> /* need farmalloc(), farfree() */
58
#define far_malloc(x) farmalloc(x)
59
#define far_free(x) farfree(x)
61
/* These definitions work for Microsoft C and compatible compilers */
62
#include <malloc.h> /* need _fmalloc(), _ffree() */
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#define far_malloc(x) _fmalloc(x)
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#define far_free(x) _ffree(x)
67
#else /* not NEED_FAR_POINTERS */
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#define far_malloc(x) malloc(x)
70
#define far_free(x) free(x)
72
#endif /* NEED_FAR_POINTERS */
74
#ifdef DONT_USE_B_MODE /* define mode parameters for fopen() */
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#define READ_BINARY "r"
77
#define READ_BINARY "rb"
80
#if MAX_ALLOC_CHUNK >= 65535L /* make sure jconfig.h got this right */
81
MAX_ALLOC_CHUNK should be less than 64K. /* deliberate syntax error */
86
* Declarations for assembly-language support routines (see jmemdosa.asm).
88
* The functions are declared "far" as are all pointer arguments;
89
* this ensures the assembly source code will work regardless of the
90
* compiler memory model. We assume "short" is 16 bits, "long" is 32.
93
typedef void far * XMSDRIVER; /* actually a pointer to code */
94
typedef struct { /* registers for calling XMS driver */
95
unsigned short ax, dx, bx;
98
typedef struct { /* registers for calling EMS driver */
99
unsigned short ax, dx, bx;
103
EXTERN short far jdos_open JPP((short far * handle, char far * filename));
104
EXTERN short far jdos_close JPP((short handle));
105
EXTERN short far jdos_seek JPP((short handle, long offset));
106
EXTERN short far jdos_read JPP((short handle, void far * buffer,
107
unsigned short count));
108
EXTERN short far jdos_write JPP((short handle, void far * buffer,
109
unsigned short count));
110
EXTERN void far jxms_getdriver JPP((XMSDRIVER far *));
111
EXTERN void far jxms_calldriver JPP((XMSDRIVER, XMScontext far *));
112
EXTERN short far jems_available JPP((void));
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EXTERN void far jems_calldriver JPP((EMScontext far *));
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* Selection of a file name for a temporary file.
118
* This is highly system-dependent, and you may want to customize it.
121
static int next_file_num; /* to distinguish among several temp files */
124
select_file_name (char * fname)
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/* Keep generating file names till we find one that's not in use */
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/* Get temp directory name from environment TMP or TEMP variable;
135
if ((env = (const char *) getenv("TMP")) == NULL)
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if ((env = (const char *) getenv("TEMP")) == NULL)
138
if (*env == '\0') /* null string means "." */
140
ptr = fname; /* copy name to fname */
143
if (ptr[-1] != '\\' && ptr[-1] != '/')
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*ptr++ = '\\'; /* append backslash if not in env variable */
145
/* Append a suitable file name */
146
next_file_num++; /* advance counter */
147
sprintf(ptr, "JPG%03d.TMP", next_file_num);
148
/* Probe to see if file name is already in use */
149
if ((tfile = fopen(fname, READ_BINARY)) == NULL)
151
fclose(tfile); /* oops, it's there; close tfile & try again */
157
* Near-memory allocation and freeing are controlled by the regular library
158
* routines malloc() and free().
162
jpeg_get_small (j_common_ptr cinfo, size_t sizeofobject)
164
return (void *) malloc(sizeofobject);
168
jpeg_free_small (j_common_ptr cinfo, void * object, size_t sizeofobject)
175
* "Large" objects are allocated in far memory, if possible
179
jpeg_get_large (j_common_ptr cinfo, size_t sizeofobject)
181
return (void FAR *) far_malloc(sizeofobject);
185
jpeg_free_large (j_common_ptr cinfo, void FAR * object, size_t sizeofobject)
192
* This routine computes the total memory space available for allocation.
193
* It's impossible to do this in a portable way; our current solution is
194
* to make the user tell us (with a default value set at compile time).
195
* If you can actually get the available space, it's a good idea to subtract
196
* a slop factor of 5% or so.
199
#ifndef DEFAULT_MAX_MEM /* so can override from makefile */
200
#define DEFAULT_MAX_MEM 300000L /* for total usage about 450K */
204
jpeg_mem_available (j_common_ptr cinfo, long min_bytes_needed,
205
long max_bytes_needed, long already_allocated)
207
return cinfo->mem->max_memory_to_use - already_allocated;
212
* Backing store (temporary file) management.
213
* Backing store objects are only used when the value returned by
214
* jpeg_mem_available is less than the total space needed. You can dispense
215
* with these routines if you have plenty of virtual memory; see jmemnobs.c.
219
* For MS-DOS we support three types of backing storage:
220
* 1. Conventional DOS files. We access these by direct DOS calls rather
221
* than via the stdio package. This provides a bit better performance,
222
* but the real reason is that the buffers to be read or written are FAR.
223
* The stdio library for small-data memory models can't cope with that.
224
* 2. Extended memory, accessed per the XMS V2.0 specification.
225
* 3. Expanded memory, accessed per the LIM/EMS 4.0 specification.
226
* You'll need copies of those specs to make sense of the related code.
227
* The specs are available by Internet FTP from the SIMTEL archives
228
* (oak.oakland.edu and its various mirror sites). See files
229
* pub/msdos/microsoft/xms20.arc and pub/msdos/info/limems41.zip.
234
* Access methods for a DOS file.
239
read_file_store (j_common_ptr cinfo, backing_store_ptr info,
240
void FAR * buffer_address,
241
long file_offset, long byte_count)
243
if (jdos_seek(info->handle.file_handle, file_offset))
244
ERREXIT(cinfo, JERR_TFILE_SEEK);
245
/* Since MAX_ALLOC_CHUNK is less than 64K, byte_count will be too. */
246
if (byte_count > 65535L) /* safety check */
247
ERREXIT(cinfo, JERR_BAD_ALLOC_CHUNK);
248
if (jdos_read(info->handle.file_handle, buffer_address,
249
(unsigned short) byte_count))
250
ERREXIT(cinfo, JERR_TFILE_READ);
255
write_file_store (j_common_ptr cinfo, backing_store_ptr info,
256
void FAR * buffer_address,
257
long file_offset, long byte_count)
259
if (jdos_seek(info->handle.file_handle, file_offset))
260
ERREXIT(cinfo, JERR_TFILE_SEEK);
261
/* Since MAX_ALLOC_CHUNK is less than 64K, byte_count will be too. */
262
if (byte_count > 65535L) /* safety check */
263
ERREXIT(cinfo, JERR_BAD_ALLOC_CHUNK);
264
if (jdos_write(info->handle.file_handle, buffer_address,
265
(unsigned short) byte_count))
266
ERREXIT(cinfo, JERR_TFILE_WRITE);
271
close_file_store (j_common_ptr cinfo, backing_store_ptr info)
273
jdos_close(info->handle.file_handle); /* close the file */
274
remove(info->temp_name); /* delete the file */
275
/* If your system doesn't have remove(), try unlink() instead.
276
* remove() is the ANSI-standard name for this function, but
277
* unlink() was more common in pre-ANSI systems.
279
TRACEMSS(cinfo, 1, JTRC_TFILE_CLOSE, info->temp_name);
284
open_file_store (j_common_ptr cinfo, backing_store_ptr info,
285
long total_bytes_needed)
289
select_file_name(info->temp_name);
290
if (jdos_open((short far *) & handle, (char far *) info->temp_name)) {
291
/* might as well exit since jpeg_open_backing_store will fail anyway */
292
ERREXITS(cinfo, JERR_TFILE_CREATE, info->temp_name);
295
info->handle.file_handle = handle;
296
info->read_backing_store = read_file_store;
297
info->write_backing_store = write_file_store;
298
info->close_backing_store = close_file_store;
299
TRACEMSS(cinfo, 1, JTRC_TFILE_OPEN, info->temp_name);
300
return TRUE; /* succeeded */
305
* Access methods for extended memory.
310
static XMSDRIVER xms_driver; /* saved address of XMS driver */
312
typedef union { /* either long offset or real-mode pointer */
317
typedef struct { /* XMS move specification structure */
325
#define ODD(X) (((X) & 1L) != 0)
329
read_xms_store (j_common_ptr cinfo, backing_store_ptr info,
330
void FAR * buffer_address,
331
long file_offset, long byte_count)
337
/* The XMS driver can't cope with an odd length, so handle the last byte
338
* specially if byte_count is odd. We don't expect this to be common.
341
spec.length = byte_count & (~ 1L);
342
spec.src_handle = info->handle.xms_handle;
343
spec.src.offset = file_offset;
345
spec.dst.ptr = buffer_address;
347
ctx.ds_si = (void far *) & spec;
348
ctx.ax = 0x0b00; /* EMB move */
349
jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
351
ERREXIT(cinfo, JERR_XMS_READ);
353
if (ODD(byte_count)) {
354
read_xms_store(cinfo, info, (void FAR *) endbuffer,
355
file_offset + byte_count - 1L, 2L);
356
((char FAR *) buffer_address)[byte_count - 1L] = endbuffer[0];
362
write_xms_store (j_common_ptr cinfo, backing_store_ptr info,
363
void FAR * buffer_address,
364
long file_offset, long byte_count)
370
/* The XMS driver can't cope with an odd length, so handle the last byte
371
* specially if byte_count is odd. We don't expect this to be common.
374
spec.length = byte_count & (~ 1L);
376
spec.src.ptr = buffer_address;
377
spec.dst_handle = info->handle.xms_handle;
378
spec.dst.offset = file_offset;
380
ctx.ds_si = (void far *) & spec;
381
ctx.ax = 0x0b00; /* EMB move */
382
jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
384
ERREXIT(cinfo, JERR_XMS_WRITE);
386
if (ODD(byte_count)) {
387
read_xms_store(cinfo, info, (void FAR *) endbuffer,
388
file_offset + byte_count - 1L, 2L);
389
endbuffer[0] = ((char FAR *) buffer_address)[byte_count - 1L];
390
write_xms_store(cinfo, info, (void FAR *) endbuffer,
391
file_offset + byte_count - 1L, 2L);
397
close_xms_store (j_common_ptr cinfo, backing_store_ptr info)
401
ctx.dx = info->handle.xms_handle;
403
jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
404
TRACEMS1(cinfo, 1, JTRC_XMS_CLOSE, info->handle.xms_handle);
405
/* we ignore any error return from the driver */
410
open_xms_store (j_common_ptr cinfo, backing_store_ptr info,
411
long total_bytes_needed)
415
/* Get address of XMS driver */
416
jxms_getdriver((XMSDRIVER far *) & xms_driver);
417
if (xms_driver == NULL)
418
return FALSE; /* no driver to be had */
420
/* Get version number, must be >= 2.00 */
422
jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
423
if (ctx.ax < (unsigned short) 0x0200)
426
/* Try to get space (expressed in kilobytes) */
427
ctx.dx = (unsigned short) ((total_bytes_needed + 1023L) >> 10);
429
jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
433
/* Succeeded, save the handle and away we go */
434
info->handle.xms_handle = ctx.dx;
435
info->read_backing_store = read_xms_store;
436
info->write_backing_store = write_xms_store;
437
info->close_backing_store = close_xms_store;
438
TRACEMS1(cinfo, 1, JTRC_XMS_OPEN, ctx.dx);
439
return TRUE; /* succeeded */
442
#endif /* XMS_SUPPORTED */
446
* Access methods for expanded memory.
451
/* The EMS move specification structure requires word and long fields aligned
452
* at odd byte boundaries. Some compilers will align struct fields at even
453
* byte boundaries. While it's usually possible to force byte alignment,
454
* that causes an overall performance penalty and may pose problems in merging
455
* JPEG into a larger application. Instead we accept some rather dirty code
456
* here. Note this code would fail if the hardware did not allow odd-byte
457
* word & long accesses, but all 80x86 CPUs do.
460
typedef void far * EMSPTR;
462
typedef union { /* EMS move specification structure */
463
long length; /* It's easy to access first 4 bytes */
464
char bytes[18]; /* Misaligned fields in here! */
467
/* Macros for accessing misaligned fields */
468
#define FIELD_AT(spec,offset,type) (*((type *) &(spec.bytes[offset])))
469
#define SRC_TYPE(spec) FIELD_AT(spec,4,char)
470
#define SRC_HANDLE(spec) FIELD_AT(spec,5,EMSH)
471
#define SRC_OFFSET(spec) FIELD_AT(spec,7,unsigned short)
472
#define SRC_PAGE(spec) FIELD_AT(spec,9,unsigned short)
473
#define SRC_PTR(spec) FIELD_AT(spec,7,EMSPTR)
474
#define DST_TYPE(spec) FIELD_AT(spec,11,char)
475
#define DST_HANDLE(spec) FIELD_AT(spec,12,EMSH)
476
#define DST_OFFSET(spec) FIELD_AT(spec,14,unsigned short)
477
#define DST_PAGE(spec) FIELD_AT(spec,16,unsigned short)
478
#define DST_PTR(spec) FIELD_AT(spec,14,EMSPTR)
480
#define EMSPAGESIZE 16384L /* gospel, see the EMS specs */
482
#define HIBYTE(W) (((W) >> 8) & 0xFF)
483
#define LOBYTE(W) ((W) & 0xFF)
487
read_ems_store (j_common_ptr cinfo, backing_store_ptr info,
488
void FAR * buffer_address,
489
long file_offset, long byte_count)
494
spec.length = byte_count;
496
SRC_HANDLE(spec) = info->handle.ems_handle;
497
SRC_PAGE(spec) = (unsigned short) (file_offset / EMSPAGESIZE);
498
SRC_OFFSET(spec) = (unsigned short) (file_offset % EMSPAGESIZE);
500
DST_HANDLE(spec) = 0;
501
DST_PTR(spec) = buffer_address;
503
ctx.ds_si = (void far *) & spec;
504
ctx.ax = 0x5700; /* move memory region */
505
jems_calldriver((EMScontext far *) & ctx);
506
if (HIBYTE(ctx.ax) != 0)
507
ERREXIT(cinfo, JERR_EMS_READ);
512
write_ems_store (j_common_ptr cinfo, backing_store_ptr info,
513
void FAR * buffer_address,
514
long file_offset, long byte_count)
519
spec.length = byte_count;
521
SRC_HANDLE(spec) = 0;
522
SRC_PTR(spec) = buffer_address;
524
DST_HANDLE(spec) = info->handle.ems_handle;
525
DST_PAGE(spec) = (unsigned short) (file_offset / EMSPAGESIZE);
526
DST_OFFSET(spec) = (unsigned short) (file_offset % EMSPAGESIZE);
528
ctx.ds_si = (void far *) & spec;
529
ctx.ax = 0x5700; /* move memory region */
530
jems_calldriver((EMScontext far *) & ctx);
531
if (HIBYTE(ctx.ax) != 0)
532
ERREXIT(cinfo, JERR_EMS_WRITE);
537
close_ems_store (j_common_ptr cinfo, backing_store_ptr info)
542
ctx.dx = info->handle.ems_handle;
543
jems_calldriver((EMScontext far *) & ctx);
544
TRACEMS1(cinfo, 1, JTRC_EMS_CLOSE, info->handle.ems_handle);
545
/* we ignore any error return from the driver */
550
open_ems_store (j_common_ptr cinfo, backing_store_ptr info,
551
long total_bytes_needed)
555
/* Is EMS driver there? */
556
if (! jems_available())
559
/* Get status, make sure EMS is OK */
561
jems_calldriver((EMScontext far *) & ctx);
562
if (HIBYTE(ctx.ax) != 0)
565
/* Get version, must be >= 4.0 */
567
jems_calldriver((EMScontext far *) & ctx);
568
if (HIBYTE(ctx.ax) != 0 || LOBYTE(ctx.ax) < 0x40)
571
/* Try to allocate requested space */
573
ctx.bx = (unsigned short) ((total_bytes_needed + EMSPAGESIZE-1L) / EMSPAGESIZE);
574
jems_calldriver((EMScontext far *) & ctx);
575
if (HIBYTE(ctx.ax) != 0)
578
/* Succeeded, save the handle and away we go */
579
info->handle.ems_handle = ctx.dx;
580
info->read_backing_store = read_ems_store;
581
info->write_backing_store = write_ems_store;
582
info->close_backing_store = close_ems_store;
583
TRACEMS1(cinfo, 1, JTRC_EMS_OPEN, ctx.dx);
584
return TRUE; /* succeeded */
587
#endif /* EMS_SUPPORTED */
591
* Initial opening of a backing-store object.
595
jpeg_open_backing_store (j_common_ptr cinfo, backing_store_ptr info,
596
long total_bytes_needed)
598
/* Try extended memory, then expanded memory, then regular file. */
600
if (open_xms_store(cinfo, info, total_bytes_needed))
604
if (open_ems_store(cinfo, info, total_bytes_needed))
607
if (open_file_store(cinfo, info, total_bytes_needed))
609
ERREXITS(cinfo, JERR_TFILE_CREATE, "");
614
* These routines take care of any system-dependent initialization and
619
jpeg_mem_init (j_common_ptr cinfo)
621
next_file_num = 0; /* initialize temp file name generator */
622
return DEFAULT_MAX_MEM; /* default for max_memory_to_use */
626
jpeg_mem_term (j_common_ptr cinfo)
628
/* Microsoft C, at least in v6.00A, will not successfully reclaim freed
629
* blocks of size > 32Kbytes unless we give it a kick in the rear, like so:
added
removed
code/jpeg-6/jmemdos.c
