src/jpeg/jmemdos.c

   1 /*
   2  * jmemdos.c
   3  *
   4  * Copyright (C) 1992-1997, 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 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.
  11  *
  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
  17  * 2-byte boundaries.
  18  *
  19  * Based on code contributed by Ge' Weijers.
  20  */
  21
  22 /*
  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? :-).
  29  *
  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).
  32  */
  33
  34 #ifndef XMS_SUPPORTED
  35 #define XMS_SUPPORTED  1
  36 #endif
  37 #ifndef EMS_SUPPORTED
  38 #define EMS_SUPPORTED  1
  39 #endif
  40
  41
  42 #define JPEG_INTERNALS
  43 #include "jinclude.h"
  44 #include "jpeglib.h"
  45 #include "jmemsys.h"            /* import the system-dependent declarations */
  46
  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));
  51 #endif
  52
  53 #ifdef NEED_FAR_POINTERS
  54
  55 #ifdef __TURBOC__
  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)
  60 #else
  61 /* These definitions work for Microsoft C and compatible compilers */
  62 #include <malloc.h>             /* need _fmalloc(), _ffree() */
  63 #define far_malloc(x)   _fmalloc(x)
  64 #define far_free(x)     _ffree(x)
  65 #endif
  66
  67 #else /* not NEED_FAR_POINTERS */
  68
  69 #define far_malloc(x)   malloc(x)
  70 #define far_free(x)     free(x)
  71
  72 #endif /* NEED_FAR_POINTERS */
  73
  74 #ifdef DONT_USE_B_MODE          /* define mode parameters for fopen() */
  75 #define READ_BINARY     "r"
  76 #else
  77 #define READ_BINARY     "rb"
  78 #endif
  79
  80 #ifndef USE_MSDOS_MEMMGR        /* make sure user got configuration right */
  81   You forgot to define USE_MSDOS_MEMMGR in jconfig.h. /* deliberate syntax error */
  82 #endif
  83
  84 #if MAX_ALLOC_CHUNK >= 65535L   /* make sure jconfig.h got this right */
  85   MAX_ALLOC_CHUNK should be less than 64K. /* deliberate syntax error */
  86 #endif
  87
  88
  89 /*
  90  * Declarations for assembly-language support routines (see jmemdosa.asm).
  91  *
  92  * The functions are declared "far" as are all their pointer arguments;
  93  * this ensures the assembly source code will work regardless of the
  94  * compiler memory model.  We assume "short" is 16 bits, "long" is 32.
  95  */
  96
  97 typedef void far * XMSDRIVER;   /* actually a pointer to code */
  98 typedef struct {                /* registers for calling XMS driver */
  99         unsigned short ax, dx, bx;
 100         void far * ds_si;
 101       } XMScontext;
 102 typedef struct {                /* registers for calling EMS driver */
 103         unsigned short ax, dx, bx;
 104         void far * ds_si;
 105       } EMScontext;
 106
 107 extern short far jdos_open JPP((short far * handle, char far * filename));
 108 extern short far jdos_close JPP((short handle));
 109 extern short far jdos_seek JPP((short handle, long offset));
 110 extern short far jdos_read JPP((short handle, void far * buffer,
 111                                 unsigned short count));
 112 extern short far jdos_write JPP((short handle, void far * buffer,
 113                                  unsigned short count));
 114 extern void far jxms_getdriver JPP((XMSDRIVER far *));
 115 extern void far jxms_calldriver JPP((XMSDRIVER, XMScontext far *));
 116 extern short far jems_available JPP((void));
 117 extern void far jems_calldriver JPP((EMScontext far *));
 118
 119
 120 /*
 121  * Selection of a file name for a temporary file.
 122  * This is highly system-dependent, and you may want to customize it.
 123  */
 124
 125 static int next_file_num;       /* to distinguish among several temp files */
 126
 127 LOCAL(void)
 128 select_file_name (char * fname)
 129 {
 130   const char * env;
 131   char * ptr;
 132   FILE * tfile;
 133
 134   /* Keep generating file names till we find one that's not in use */
 135   for (;;) {
 136     /* Get temp directory name from environment TMP or TEMP variable;
 137      * if none, use "."
 138      */
 139     if ((env = (const char *) getenv("TMP")) == NULL)
 140       if ((env = (const char *) getenv("TEMP")) == NULL)
 141         env = ".";
 142     if (*env == '\0')           /* null string means "." */
 143       env = ".";
 144     ptr = fname;                /* copy name to fname */
 145     while (*env != '\0')
 146       *ptr++ = *env++;
 147     if (ptr[-1] != '\\' && ptr[-1] != '/')
 148       *ptr++ = '\\';            /* append backslash if not in env variable */
 149     /* Append a suitable file name */
 150     next_file_num++;            /* advance counter */
 151     sprintf(ptr, "JPG%03d.TMP", next_file_num);
 152     /* Probe to see if file name is already in use */
 153     if ((tfile = fopen(fname, READ_BINARY)) == NULL)
 154       break;
 155     fclose(tfile);              /* oops, it's there; close tfile & try again */
 156   }
 157 }
 158
 159
 160 /*
 161  * Near-memory allocation and freeing are controlled by the regular library
 162  * routines malloc() and free().
 163  */
 164
 165 GLOBAL(void *)
 166 jpeg_get_small (j_common_ptr cinfo, size_t sizeofobject)
 167 {
 168   return (void *) malloc(sizeofobject);
 169 }
 170
 171 GLOBAL(void)
 172 jpeg_free_small (j_common_ptr cinfo, void * object, size_t sizeofobject)
 173 {
 174   free(object);
 175 }
 176
 177
 178 /*
 179  * "Large" objects are allocated in far memory, if possible
 180  */
 181
 182 GLOBAL(void FAR *)
 183 jpeg_get_large (j_common_ptr cinfo, size_t sizeofobject)
 184 {
 185   return (void FAR *) far_malloc(sizeofobject);
 186 }
 187
 188 GLOBAL(void)
 189 jpeg_free_large (j_common_ptr cinfo, void FAR * object, size_t sizeofobject)
 190 {
 191   far_free(object);
 192 }
 193
 194
 195 /*
 196  * This routine computes the total memory space available for allocation.
 197  * It's impossible to do this in a portable way; our current solution is
 198  * to make the user tell us (with a default value set at compile time).
 199  * If you can actually get the available space, it's a good idea to subtract
 200  * a slop factor of 5% or so.
 201  */
 202
 203 #ifndef DEFAULT_MAX_MEM         /* so can override from makefile */
 204 #define DEFAULT_MAX_MEM         300000L /* for total usage about 450K */
 205 #endif
 206
 207 GLOBAL(long)
 208 jpeg_mem_available (j_common_ptr cinfo, long min_bytes_needed,
 209                     long max_bytes_needed, long already_allocated)
 210 {
 211   return cinfo->mem->max_memory_to_use - already_allocated;
 212 }
 213
 214
 215 /*
 216  * Backing store (temporary file) management.
 217  * Backing store objects are only used when the value returned by
 218  * jpeg_mem_available is less than the total space needed.  You can dispense
 219  * with these routines if you have plenty of virtual memory; see jmemnobs.c.
 220  */
 221
 222 /*
 223  * For MS-DOS we support three types of backing storage:
 224  *   1. Conventional DOS files.  We access these by direct DOS calls rather
 225  *      than via the stdio package.  This provides a bit better performance,
 226  *      but the real reason is that the buffers to be read or written are FAR.
 227  *      The stdio library for small-data memory models can't cope with that.
 228  *   2. Extended memory, accessed per the XMS V2.0 specification.
 229  *   3. Expanded memory, accessed per the LIM/EMS 4.0 specification.
 230  * You'll need copies of those specs to make sense of the related code.
 231  * The specs are available by Internet FTP from the SIMTEL archives
 232  * (oak.oakland.edu and its various mirror sites).  See files
 233  * pub/msdos/microsoft/xms20.arc and pub/msdos/info/limems41.zip.
 234  */
 235
 236
 237 /*
 238  * Access methods for a DOS file.
 239  */
 240
 241
 242 METHODDEF(void)
 243 read_file_store (j_common_ptr cinfo, backing_store_ptr info,
 244                  void FAR * buffer_address,
 245                  long file_offset, long byte_count)
 246 {
 247   if (jdos_seek(info->handle.file_handle, file_offset))
 248     ERREXIT(cinfo, JERR_TFILE_SEEK);
 249   /* Since MAX_ALLOC_CHUNK is less than 64K, byte_count will be too. */
 250   if (byte_count > 65535L)      /* safety check */
 251     ERREXIT(cinfo, JERR_BAD_ALLOC_CHUNK);
 252   if (jdos_read(info->handle.file_handle, buffer_address,
 253                 (unsigned short) byte_count))
 254     ERREXIT(cinfo, JERR_TFILE_READ);
 255 }
 256
 257
 258 METHODDEF(void)
 259 write_file_store (j_common_ptr cinfo, backing_store_ptr info,
 260                   void FAR * buffer_address,
 261                   long file_offset, long byte_count)
 262 {
 263   if (jdos_seek(info->handle.file_handle, file_offset))
 264     ERREXIT(cinfo, JERR_TFILE_SEEK);
 265   /* Since MAX_ALLOC_CHUNK is less than 64K, byte_count will be too. */
 266   if (byte_count > 65535L)      /* safety check */
 267     ERREXIT(cinfo, JERR_BAD_ALLOC_CHUNK);
 268   if (jdos_write(info->handle.file_handle, buffer_address,
 269                  (unsigned short) byte_count))
 270     ERREXIT(cinfo, JERR_TFILE_WRITE);
 271 }
 272
 273
 274 METHODDEF(void)
 275 close_file_store (j_common_ptr cinfo, backing_store_ptr info)
 276 {
 277   jdos_close(info->handle.file_handle); /* close the file */
 278   remove(info->temp_name);      /* delete the file */
 279 /* If your system doesn't have remove(), try unlink() instead.
 280  * remove() is the ANSI-standard name for this function, but
 281  * unlink() was more common in pre-ANSI systems.
 282  */
 283   TRACEMSS(cinfo, 1, JTRC_TFILE_CLOSE, info->temp_name);
 284 }
 285
 286
 287 LOCAL(wxjpeg_boolean)
 288 open_file_store (j_common_ptr cinfo, backing_store_ptr info,
 289                  long total_bytes_needed)
 290 {
 291   short handle;
 292
 293   select_file_name(info->temp_name);
 294   if (jdos_open((short far *) & handle, (char far *) info->temp_name)) {
 295     /* might as well exit since jpeg_open_backing_store will fail anyway */
 296     ERREXITS(cinfo, JERR_TFILE_CREATE, info->temp_name);
 297     return FALSE;
 298   }
 299   info->handle.file_handle = handle;
 300   info->read_backing_store = read_file_store;
 301   info->write_backing_store = write_file_store;
 302   info->close_backing_store = close_file_store;
 303   TRACEMSS(cinfo, 1, JTRC_TFILE_OPEN, info->temp_name);
 304   return TRUE;                  /* succeeded */
 305 }
 306
 307
 308 /*
 309  * Access methods for extended memory.
 310  */
 311
 312 #if XMS_SUPPORTED
 313
 314 static XMSDRIVER xms_driver;    /* saved address of XMS driver */
 315
 316 typedef union {                 /* either long offset or real-mode pointer */
 317         long offset;
 318         void far * ptr;
 319       } XMSPTR;
 320
 321 typedef struct {                /* XMS move specification structure */
 322         long length;
 323         XMSH src_handle;
 324         XMSPTR src;
 325         XMSH dst_handle;
 326         XMSPTR dst;
 327       } XMSspec;
 328
 329 #define ODD(X)  (((X) & 1L) != 0)
 330
 331
 332 METHODDEF(void)
 333 read_xms_store (j_common_ptr cinfo, backing_store_ptr info,
 334                 void FAR * buffer_address,
 335                 long file_offset, long byte_count)
 336 {
 337   XMScontext ctx;
 338   XMSspec spec;
 339   char endbuffer[2];
 340
 341   /* The XMS driver can't cope with an odd length, so handle the last byte
 342    * specially if byte_count is odd.  We don't expect this to be common.
 343    */
 344
 345   spec.length = byte_count & (~ 1L);
 346   spec.src_handle = info->handle.xms_handle;
 347   spec.src.offset = file_offset;
 348   spec.dst_handle = 0;
 349   spec.dst.ptr = buffer_address;
 350
 351   ctx.ds_si = (void far *) & spec;
 352   ctx.ax = 0x0b00;              /* EMB move */
 353   jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
 354   if (ctx.ax != 1)
 355     ERREXIT(cinfo, JERR_XMS_READ);
 356
 357   if (ODD(byte_count)) {
 358     read_xms_store(cinfo, info, (void FAR *) endbuffer,
 359                    file_offset + byte_count - 1L, 2L);
 360     ((char FAR *) buffer_address)[byte_count - 1L] = endbuffer[0];
 361   }
 362 }
 363
 364
 365 METHODDEF(void)
 366 write_xms_store (j_common_ptr cinfo, backing_store_ptr info,
 367                  void FAR * buffer_address,
 368                  long file_offset, long byte_count)
 369 {
 370   XMScontext ctx;
 371   XMSspec spec;
 372   char endbuffer[2];
 373
 374   /* The XMS driver can't cope with an odd length, so handle the last byte
 375    * specially if byte_count is odd.  We don't expect this to be common.
 376    */
 377
 378   spec.length = byte_count & (~ 1L);
 379   spec.src_handle = 0;
 380   spec.src.ptr = buffer_address;
 381   spec.dst_handle = info->handle.xms_handle;
 382   spec.dst.offset = file_offset;
 383
 384   ctx.ds_si = (void far *) & spec;
 385   ctx.ax = 0x0b00;              /* EMB move */
 386   jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
 387   if (ctx.ax != 1)
 388     ERREXIT(cinfo, JERR_XMS_WRITE);
 389
 390   if (ODD(byte_count)) {
 391     read_xms_store(cinfo, info, (void FAR *) endbuffer,
 392                    file_offset + byte_count - 1L, 2L);
 393     endbuffer[0] = ((char FAR *) buffer_address)[byte_count - 1L];
 394     write_xms_store(cinfo, info, (void FAR *) endbuffer,
 395                     file_offset + byte_count - 1L, 2L);
 396   }
 397 }
 398
 399
 400 METHODDEF(void)
 401 close_xms_store (j_common_ptr cinfo, backing_store_ptr info)
 402 {
 403   XMScontext ctx;
 404
 405   ctx.dx = info->handle.xms_handle;
 406   ctx.ax = 0x0a00;
 407   jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
 408   TRACEMS1(cinfo, 1, JTRC_XMS_CLOSE, info->handle.xms_handle);
 409   /* we ignore any error return from the driver */
 410 }
 411
 412
 413 LOCAL(wxjpeg_boolean)
 414 open_xms_store (j_common_ptr cinfo, backing_store_ptr info,
 415                 long total_bytes_needed)
 416 {
 417   XMScontext ctx;
 418
 419   /* Get address of XMS driver */
 420   jxms_getdriver((XMSDRIVER far *) & xms_driver);
 421   if (xms_driver == NULL)
 422     return FALSE;               /* no driver to be had */
 423
 424   /* Get version number, must be >= 2.00 */
 425   ctx.ax = 0x0000;
 426   jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
 427   if (ctx.ax < (unsigned short) 0x0200)
 428     return FALSE;
 429
 430   /* Try to get space (expressed in kilobytes) */
 431   ctx.dx = (unsigned short) ((total_bytes_needed + 1023L) >> 10);
 432   ctx.ax = 0x0900;
 433   jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
 434   if (ctx.ax != 1)
 435     return FALSE;
 436
 437   /* Succeeded, save the handle and away we go */
 438   info->handle.xms_handle = ctx.dx;
 439   info->read_backing_store = read_xms_store;
 440   info->write_backing_store = write_xms_store;
 441   info->close_backing_store = close_xms_store;
 442   TRACEMS1(cinfo, 1, JTRC_XMS_OPEN, ctx.dx);
 443   return TRUE;                  /* succeeded */
 444 }
 445
 446 #endif /* XMS_SUPPORTED */
 447
 448
 449 /*
 450  * Access methods for expanded memory.
 451  */
 452
 453 #if EMS_SUPPORTED
 454
 455 /* The EMS move specification structure requires word and long fields aligned
 456  * at odd byte boundaries.  Some compilers will align struct fields at even
 457  * byte boundaries.  While it's usually possible to force byte alignment,
 458  * that causes an overall performance penalty and may pose problems in merging
 459  * JPEG into a larger application.  Instead we accept some rather dirty code
 460  * here.  Note this code would fail if the hardware did not allow odd-byte
 461  * word & long accesses, but all 80x86 CPUs do.
 462  */
 463
 464 typedef void far * EMSPTR;
 465
 466 typedef union {                 /* EMS move specification structure */
 467         long length;            /* It's easy to access first 4 bytes */
 468         char bytes[18];         /* Misaligned fields in here! */
 469       } EMSspec;
 470
 471 /* Macros for accessing misaligned fields */
 472 #define FIELD_AT(spec,offset,type)  (*((type *) &(spec.bytes[offset])))
 473 #define SRC_TYPE(spec)          FIELD_AT(spec,4,char)
 474 #define SRC_HANDLE(spec)        FIELD_AT(spec,5,EMSH)
 475 #define SRC_OFFSET(spec)        FIELD_AT(spec,7,unsigned short)
 476 #define SRC_PAGE(spec)          FIELD_AT(spec,9,unsigned short)
 477 #define SRC_PTR(spec)           FIELD_AT(spec,7,EMSPTR)
 478 #define DST_TYPE(spec)          FIELD_AT(spec,11,char)
 479 #define DST_HANDLE(spec)        FIELD_AT(spec,12,EMSH)
 480 #define DST_OFFSET(spec)        FIELD_AT(spec,14,unsigned short)
 481 #define DST_PAGE(spec)          FIELD_AT(spec,16,unsigned short)
 482 #define DST_PTR(spec)           FIELD_AT(spec,14,EMSPTR)
 483
 484 #define EMSPAGESIZE     16384L  /* gospel, see the EMS specs */
 485
 486 #define HIBYTE(W)  (((W) >> 8) & 0xFF)
 487 #define LOBYTE(W)  ((W) & 0xFF)
 488
 489
 490 METHODDEF(void)
 491 read_ems_store (j_common_ptr cinfo, backing_store_ptr info,
 492                 void FAR * buffer_address,
 493                 long file_offset, long byte_count)
 494 {
 495   EMScontext ctx;
 496   EMSspec spec;
 497
 498   spec.length = byte_count;
 499   SRC_TYPE(spec) = 1;
 500   SRC_HANDLE(spec) = info->handle.ems_handle;
 501   SRC_PAGE(spec)   = (unsigned short) (file_offset / EMSPAGESIZE);
 502   SRC_OFFSET(spec) = (unsigned short) (file_offset % EMSPAGESIZE);
 503   DST_TYPE(spec) = 0;
 504   DST_HANDLE(spec) = 0;
 505   DST_PTR(spec)    = buffer_address;
 506
 507   ctx.ds_si = (void far *) & spec;
 508   ctx.ax = 0x5700;              /* move memory region */
 509   jems_calldriver((EMScontext far *) & ctx);
 510   if (HIBYTE(ctx.ax) != 0)
 511     ERREXIT(cinfo, JERR_EMS_READ);
 512 }
 513
 514
 515 METHODDEF(void)
 516 write_ems_store (j_common_ptr cinfo, backing_store_ptr info,
 517                  void FAR * buffer_address,
 518                  long file_offset, long byte_count)
 519 {
 520   EMScontext ctx;
 521   EMSspec spec;
 522
 523   spec.length = byte_count;
 524   SRC_TYPE(spec) = 0;
 525   SRC_HANDLE(spec) = 0;
 526   SRC_PTR(spec)    = buffer_address;
 527   DST_TYPE(spec) = 1;
 528   DST_HANDLE(spec) = info->handle.ems_handle;
 529   DST_PAGE(spec)   = (unsigned short) (file_offset / EMSPAGESIZE);
 530   DST_OFFSET(spec) = (unsigned short) (file_offset % EMSPAGESIZE);
 531
 532   ctx.ds_si = (void far *) & spec;
 533   ctx.ax = 0x5700;              /* move memory region */
 534   jems_calldriver((EMScontext far *) & ctx);
 535   if (HIBYTE(ctx.ax) != 0)
 536     ERREXIT(cinfo, JERR_EMS_WRITE);
 537 }
 538
 539
 540 METHODDEF(void)
 541 close_ems_store (j_common_ptr cinfo, backing_store_ptr info)
 542 {
 543   EMScontext ctx;
 544
 545   ctx.ax = 0x4500;
 546   ctx.dx = info->handle.ems_handle;
 547   jems_calldriver((EMScontext far *) & ctx);
 548   TRACEMS1(cinfo, 1, JTRC_EMS_CLOSE, info->handle.ems_handle);
 549   /* we ignore any error return from the driver */
 550 }
 551
 552
 553 LOCAL(wxjpeg_boolean)
 554 open_ems_store (j_common_ptr cinfo, backing_store_ptr info,
 555                 long total_bytes_needed)
 556 {
 557   EMScontext ctx;
 558
 559   /* Is EMS driver there? */
 560   if (! jems_available())
 561     return FALSE;
 562
 563   /* Get status, make sure EMS is OK */
 564   ctx.ax = 0x4000;
 565   jems_calldriver((EMScontext far *) & ctx);
 566   if (HIBYTE(ctx.ax) != 0)
 567     return FALSE;
 568
 569   /* Get version, must be >= 4.0 */
 570   ctx.ax = 0x4600;
 571   jems_calldriver((EMScontext far *) & ctx);
 572   if (HIBYTE(ctx.ax) != 0 || LOBYTE(ctx.ax) < 0x40)
 573     return FALSE;
 574
 575   /* Try to allocate requested space */
 576   ctx.ax = 0x4300;
 577   ctx.bx = (unsigned short) ((total_bytes_needed + EMSPAGESIZE-1L) / EMSPAGESIZE);
 578   jems_calldriver((EMScontext far *) & ctx);
 579   if (HIBYTE(ctx.ax) != 0)
 580     return FALSE;
 581
 582   /* Succeeded, save the handle and away we go */
 583   info->handle.ems_handle = ctx.dx;
 584   info->read_backing_store = read_ems_store;
 585   info->write_backing_store = write_ems_store;
 586   info->close_backing_store = close_ems_store;
 587   TRACEMS1(cinfo, 1, JTRC_EMS_OPEN, ctx.dx);
 588   return TRUE;                  /* succeeded */
 589 }
 590
 591 #endif /* EMS_SUPPORTED */
 592
 593
 594 /*
 595  * Initial opening of a backing-store object.
 596  */
 597
 598 GLOBAL(void)
 599 jpeg_open_backing_store (j_common_ptr cinfo, backing_store_ptr info,
 600                          long total_bytes_needed)
 601 {
 602   /* Try extended memory, then expanded memory, then regular file. */
 603 #if XMS_SUPPORTED
 604   if (open_xms_store(cinfo, info, total_bytes_needed))
 605     return;
 606 #endif
 607 #if EMS_SUPPORTED
 608   if (open_ems_store(cinfo, info, total_bytes_needed))
 609     return;
 610 #endif
 611   if (open_file_store(cinfo, info, total_bytes_needed))
 612     return;
 613   ERREXITS(cinfo, JERR_TFILE_CREATE, "");
 614 }
 615
 616
 617 /*
 618  * These routines take care of any system-dependent initialization and
 619  * cleanup required.
 620  */
 621
 622 GLOBAL(long)
 623 jpeg_mem_init (j_common_ptr cinfo)
 624 {
 625   next_file_num = 0;            /* initialize temp file name generator */
 626   return DEFAULT_MAX_MEM;       /* default for max_memory_to_use */
 627 }
 628
 629 GLOBAL(void)
 630 jpeg_mem_term (j_common_ptr cinfo)
 631 {
 632   /* Microsoft C, at least in v6.00A, will not successfully reclaim freed
 633    * blocks of size > 32Kbytes unless we give it a kick in the rear, like so:
 634    */
 635 #ifdef NEED_FHEAPMIN
 636   _fheapmin();
 637 #endif
 638 }