Thomas G. Lane | 4a6b730 | 1992-03-17 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * jmemdos.c (jmemsys.c) |
| 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 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 | * |
| 17 | * Based on code contributed by Ge' Weijers. |
| 18 | */ |
| 19 | |
| 20 | /* |
| 21 | * If you have both extended and expanded memory, you may want to change the |
| 22 | * order in which they are tried in jopen_backing_store. On a 286 machine |
| 23 | * expanded memory is usually faster, since extended memory access involves |
| 24 | * an expensive protected-mode-and-back switch. On 386 and better, extended |
| 25 | * memory is usually faster. As distributed, the code tries extended memory |
| 26 | * first (what? not everyone has a 386? :-). |
| 27 | * |
| 28 | * You can disable use of extended/expanded memory entirely by altering these |
| 29 | * definitions or overriding them from the Makefile (eg, -DEMS_SUPPORTED=0). |
| 30 | */ |
| 31 | |
| 32 | #ifndef XMS_SUPPORTED |
| 33 | #define XMS_SUPPORTED 1 |
| 34 | #endif |
| 35 | #ifndef EMS_SUPPORTED |
| 36 | #define EMS_SUPPORTED 1 |
| 37 | #endif |
| 38 | |
| 39 | |
| 40 | #include "jinclude.h" |
| 41 | #include "jmemsys.h" |
| 42 | |
| 43 | #ifdef INCLUDES_ARE_ANSI |
| 44 | #include <stdlib.h> /* to declare malloc(), free() */ |
| 45 | #else |
| 46 | extern void * malloc PP((size_t size)); |
| 47 | extern void free PP((void *ptr)); |
| 48 | #endif |
| 49 | |
| 50 | #ifdef NEED_FAR_POINTERS |
| 51 | |
| 52 | #ifdef __TURBOC__ |
| 53 | /* These definitions work for Borland C (Turbo C) */ |
| 54 | #include <alloc.h> /* need farmalloc(), farfree() */ |
| 55 | #define far_malloc(x) farmalloc(x) |
| 56 | #define far_free(x) farfree(x) |
| 57 | #else |
| 58 | /* These definitions work for Microsoft C and compatible compilers */ |
| 59 | #include <malloc.h> /* need _fmalloc(), _ffree() */ |
| 60 | #define far_malloc(x) _fmalloc(x) |
| 61 | #define far_free(x) _ffree(x) |
| 62 | #endif |
| 63 | |
| 64 | #endif |
| 65 | |
| 66 | #ifdef DONT_USE_B_MODE /* define mode parameters for fopen() */ |
| 67 | #define READ_BINARY "r" |
| 68 | #else |
| 69 | #define READ_BINARY "rb" |
| 70 | #endif |
| 71 | |
| 72 | |
| 73 | /* |
| 74 | * Declarations for assembly-language support routines (see jmemdosa.asm). |
| 75 | * |
| 76 | * The functions are declared "far" as are all pointer arguments; |
| 77 | * this ensures the assembly source code will work regardless of the |
| 78 | * compiler memory model. We assume "short" is 16 bits, "long" is 32. |
| 79 | */ |
| 80 | |
| 81 | typedef void far * XMSDRIVER; /* actually a pointer to code */ |
| 82 | typedef struct { /* registers for calling XMS driver */ |
| 83 | unsigned short ax, dx, bx; |
| 84 | void far * ds_si; |
| 85 | } XMScontext; |
| 86 | typedef struct { /* registers for calling EMS driver */ |
| 87 | unsigned short ax, dx, bx; |
| 88 | void far * ds_si; |
| 89 | } EMScontext; |
| 90 | |
| 91 | EXTERN short far jdos_open PP((short far * handle, char far * filename)); |
| 92 | EXTERN short far jdos_close PP((short handle)); |
| 93 | EXTERN short far jdos_seek PP((short handle, long offset)); |
| 94 | EXTERN short far jdos_read PP((short handle, void far * buffer, |
| 95 | unsigned short count)); |
| 96 | EXTERN short far jdos_write PP((short handle, void far * buffer, |
| 97 | unsigned short count)); |
| 98 | EXTERN void far jxms_getdriver PP((XMSDRIVER far *)); |
| 99 | EXTERN void far jxms_calldriver PP((XMSDRIVER, XMScontext far *)); |
| 100 | EXTERN short far jems_available PP((void)); |
| 101 | EXTERN void far jems_calldriver PP((EMScontext far *)); |
| 102 | |
| 103 | |
| 104 | static external_methods_ptr methods; /* saved for access to error_exit */ |
| 105 | |
| 106 | static long total_used; /* total FAR memory requested so far */ |
| 107 | |
| 108 | |
| 109 | /* |
| 110 | * Selection of a file name for a temporary file. |
| 111 | * This is highly system-dependent, and you may want to customize it. |
| 112 | */ |
| 113 | |
| 114 | static int next_file_num; /* to distinguish among several temp files */ |
| 115 | |
| 116 | LOCAL void |
| 117 | select_file_name (char * fname) |
| 118 | { |
| 119 | const char * env; |
| 120 | char * ptr; |
| 121 | FILE * tfile; |
| 122 | |
| 123 | /* Keep generating file names till we find one that's not in use */ |
| 124 | for (;;) { |
| 125 | /* Get temp directory name from environment TMP or TEMP variable; |
| 126 | * if none, use "." |
| 127 | */ |
| 128 | if ((env = (const char *) getenv("TMP")) == NULL) |
| 129 | if ((env = (const char *) getenv("TEMP")) == NULL) |
| 130 | env = "."; |
| 131 | if (*env == '\0') /* null string means "." */ |
| 132 | env = "."; |
| 133 | ptr = fname; /* copy name to fname */ |
| 134 | while (*env != '\0') |
| 135 | *ptr++ = *env++; |
| 136 | if (ptr[-1] != '\\' && ptr[-1] != '/') |
| 137 | *ptr++ = '\\'; /* append backslash if not in env variable */ |
| 138 | /* Append a suitable file name */ |
| 139 | next_file_num++; /* advance counter */ |
| 140 | sprintf(ptr, "JPG%03d.TMP", next_file_num); |
| 141 | /* Probe to see if file name is already in use */ |
| 142 | if ((tfile = fopen(fname, READ_BINARY)) == NULL) |
| 143 | break; |
| 144 | fclose(tfile); /* oops, it's there; close tfile & try again */ |
| 145 | } |
| 146 | } |
| 147 | |
| 148 | |
| 149 | /* |
| 150 | * Near-memory allocation and freeing are controlled by the regular library |
| 151 | * routines malloc() and free(). |
| 152 | */ |
| 153 | |
| 154 | GLOBAL void * |
| 155 | jget_small (size_t sizeofobject) |
| 156 | { |
| 157 | /* near data space is NOT counted in total_used */ |
| 158 | #ifndef NEED_FAR_POINTERS |
| 159 | total_used += sizeofobject; |
| 160 | #endif |
| 161 | return (void *) malloc(sizeofobject); |
| 162 | } |
| 163 | |
| 164 | GLOBAL void |
| 165 | jfree_small (void * object) |
| 166 | { |
| 167 | free(object); |
| 168 | } |
| 169 | |
| 170 | |
| 171 | /* |
| 172 | * Far-memory allocation and freeing |
| 173 | */ |
| 174 | |
| 175 | #ifdef NEED_FAR_POINTERS |
| 176 | |
| 177 | GLOBAL void FAR * |
| 178 | jget_large (size_t sizeofobject) |
| 179 | { |
| 180 | total_used += sizeofobject; |
| 181 | return (void FAR *) far_malloc(sizeofobject); |
| 182 | } |
| 183 | |
| 184 | GLOBAL void |
| 185 | jfree_large (void FAR * object) |
| 186 | { |
| 187 | far_free(object); |
| 188 | } |
| 189 | |
| 190 | #endif |
| 191 | |
| 192 | |
| 193 | /* |
| 194 | * This routine computes the total memory space available for allocation. |
| 195 | * It's impossible to do this in a portable way; our current solution is |
| 196 | * to make the user tell us (with a default value set at compile time). |
| 197 | * If you can actually get the available space, it's a good idea to subtract |
| 198 | * a slop factor of 5% or so. |
| 199 | */ |
| 200 | |
| 201 | #ifndef DEFAULT_MAX_MEM /* so can override from makefile */ |
| 202 | #define DEFAULT_MAX_MEM 300000L /* for total usage about 450K */ |
| 203 | #endif |
| 204 | |
| 205 | GLOBAL long |
| 206 | jmem_available (long min_bytes_needed, long max_bytes_needed) |
| 207 | { |
| 208 | return methods->max_memory_to_use - total_used; |
| 209 | } |
| 210 | |
| 211 | |
| 212 | /* |
| 213 | * Backing store (temporary file) management. |
| 214 | * Backing store objects are only used when the value returned by |
| 215 | * jmem_available is less than the total space needed. You can dispense |
| 216 | * with these routines if you have plenty of virtual memory; see jmemnobs.c. |
| 217 | */ |
| 218 | |
| 219 | /* |
| 220 | * For MS-DOS we support three types of backing storage: |
| 221 | * 1. Conventional DOS files. We access these by direct DOS calls rather |
| 222 | * than via the stdio package. This provides a bit better performance, |
| 223 | * but the real reason is that the buffers to be read or written are FAR. |
| 224 | * The stdio library for small-data memory models can't cope with that. |
| 225 | * 2. Extended memory, accessed per the XMS V2.0 specification. |
| 226 | * 3. Expanded memory, accessed per the LIM/EMS 4.0 specification. |
| 227 | * You'll need copies of those specs to make sense of the related code. |
| 228 | * The specs are available by Internet FTP from SIMTEL20 and its various |
| 229 | * mirror sites; see microsoft/xms20.arc and info/limems41.zip. |
| 230 | */ |
| 231 | |
| 232 | |
| 233 | /* |
| 234 | * Access methods for a DOS file. |
| 235 | */ |
| 236 | |
| 237 | |
| 238 | METHODDEF void |
| 239 | read_file_store (backing_store_ptr info, void FAR * buffer_address, |
| 240 | long file_offset, long byte_count) |
| 241 | { |
| 242 | if (jdos_seek(info->handle.file_handle, file_offset)) |
| 243 | ERREXIT(methods, "seek failed on temporary file"); |
| 244 | /* Since MAX_ALLOC_CHUNK is less than 64K, byte_count will be too. */ |
| 245 | if (byte_count > 65535L) /* safety check */ |
| 246 | ERREXIT(methods, "MAX_ALLOC_CHUNK should be less than 64K"); |
| 247 | if (jdos_read(info->handle.file_handle, buffer_address, |
| 248 | (unsigned short) byte_count)) |
| 249 | ERREXIT(methods, "read failed on temporary file"); |
| 250 | } |
| 251 | |
| 252 | |
| 253 | METHODDEF void |
| 254 | write_file_store (backing_store_ptr info, void FAR * buffer_address, |
| 255 | long file_offset, long byte_count) |
| 256 | { |
| 257 | if (jdos_seek(info->handle.file_handle, file_offset)) |
| 258 | ERREXIT(methods, "seek failed on temporary file"); |
| 259 | /* Since MAX_ALLOC_CHUNK is less than 64K, byte_count will be too. */ |
| 260 | if (byte_count > 65535L) /* safety check */ |
| 261 | ERREXIT(methods, "MAX_ALLOC_CHUNK should be less than 64K"); |
| 262 | if (jdos_write(info->handle.file_handle, buffer_address, |
| 263 | (unsigned short) byte_count)) |
| 264 | ERREXIT(methods, "write failed on temporary file --- out of disk space?"); |
| 265 | } |
| 266 | |
| 267 | |
| 268 | METHODDEF void |
| 269 | close_file_store (backing_store_ptr info) |
| 270 | { |
| 271 | jdos_close(info->handle.file_handle); /* close the file */ |
| 272 | remove(info->temp_name); /* delete the file */ |
| 273 | /* If your system doesn't have remove(), try unlink() instead. |
| 274 | * remove() is the ANSI-standard name for this function, but |
| 275 | * unlink() was more common in pre-ANSI systems. |
| 276 | */ |
| 277 | TRACEMS1(methods, 1, "Closed DOS file %d", info->handle.file_handle); |
| 278 | } |
| 279 | |
| 280 | |
| 281 | LOCAL boolean |
| 282 | open_file_store (backing_store_ptr info, long total_bytes_needed) |
| 283 | { |
| 284 | short handle; |
| 285 | char tracemsg[TEMP_NAME_LENGTH+40]; |
| 286 | |
| 287 | select_file_name(info->temp_name); |
| 288 | if (jdos_open((short far *) & handle, (char far *) info->temp_name)) |
| 289 | return FALSE; |
| 290 | info->handle.file_handle = handle; |
| 291 | info->read_backing_store = read_file_store; |
| 292 | info->write_backing_store = write_file_store; |
| 293 | info->close_backing_store = close_file_store; |
| 294 | /* hack to get around TRACEMS' inability to handle string parameters */ |
| 295 | sprintf(tracemsg, "Opened DOS file %d %s", handle, info->temp_name); |
| 296 | TRACEMS(methods, 1, tracemsg); |
| 297 | return TRUE; /* succeeded */ |
| 298 | } |
| 299 | |
| 300 | |
| 301 | /* |
| 302 | * Access methods for extended memory. |
| 303 | */ |
| 304 | |
| 305 | #if XMS_SUPPORTED |
| 306 | |
| 307 | static XMSDRIVER xms_driver; /* saved address of XMS driver */ |
| 308 | |
| 309 | typedef union { /* either long offset or real-mode pointer */ |
| 310 | long offset; |
| 311 | void far * ptr; |
| 312 | } XMSPTR; |
| 313 | |
| 314 | typedef struct { /* XMS move specification structure */ |
| 315 | long length; |
| 316 | XMSH src_handle; |
| 317 | XMSPTR src; |
| 318 | XMSH dst_handle; |
| 319 | XMSPTR dst; |
| 320 | } XMSspec; |
| 321 | |
| 322 | #define ODD(X) (((X) & 1L) != 0) |
| 323 | |
| 324 | |
| 325 | METHODDEF void |
| 326 | read_xms_store (backing_store_ptr info, void FAR * buffer_address, |
| 327 | long file_offset, long byte_count) |
| 328 | { |
| 329 | XMScontext ctx; |
| 330 | XMSspec spec; |
| 331 | char endbuffer[2]; |
| 332 | |
| 333 | /* The XMS driver can't cope with an odd length, so handle the last byte |
| 334 | * specially if byte_count is odd. We don't expect this to be common. |
| 335 | */ |
| 336 | |
| 337 | spec.length = byte_count & (~ 1L); |
| 338 | spec.src_handle = info->handle.xms_handle; |
| 339 | spec.src.offset = file_offset; |
| 340 | spec.dst_handle = 0; |
| 341 | spec.dst.ptr = buffer_address; |
| 342 | |
| 343 | ctx.ds_si = (void far *) & spec; |
| 344 | ctx.ax = 0x0b00; /* EMB move */ |
| 345 | jxms_calldriver(xms_driver, (XMScontext far *) & ctx); |
| 346 | if (ctx.ax != 1) |
| 347 | ERREXIT(methods, "read from extended memory failed"); |
| 348 | |
| 349 | if (ODD(byte_count)) { |
| 350 | read_xms_store(info, (void FAR *) endbuffer, |
| 351 | file_offset + byte_count - 1L, 2L); |
| 352 | ((char FAR *) buffer_address)[byte_count - 1L] = endbuffer[0]; |
| 353 | } |
| 354 | } |
| 355 | |
| 356 | |
| 357 | METHODDEF void |
| 358 | write_xms_store (backing_store_ptr info, void FAR * buffer_address, |
| 359 | long file_offset, long byte_count) |
| 360 | { |
| 361 | XMScontext ctx; |
| 362 | XMSspec spec; |
| 363 | char endbuffer[2]; |
| 364 | |
| 365 | /* The XMS driver can't cope with an odd length, so handle the last byte |
| 366 | * specially if byte_count is odd. We don't expect this to be common. |
| 367 | */ |
| 368 | |
| 369 | spec.length = byte_count & (~ 1L); |
| 370 | spec.src_handle = 0; |
| 371 | spec.src.ptr = buffer_address; |
| 372 | spec.dst_handle = info->handle.xms_handle; |
| 373 | spec.dst.offset = file_offset; |
| 374 | |
| 375 | ctx.ds_si = (void far *) & spec; |
| 376 | ctx.ax = 0x0b00; /* EMB move */ |
| 377 | jxms_calldriver(xms_driver, (XMScontext far *) & ctx); |
| 378 | if (ctx.ax != 1) |
| 379 | ERREXIT(methods, "write to extended memory failed"); |
| 380 | |
| 381 | if (ODD(byte_count)) { |
| 382 | read_xms_store(info, (void FAR *) endbuffer, |
| 383 | file_offset + byte_count - 1L, 2L); |
| 384 | endbuffer[0] = ((char FAR *) buffer_address)[byte_count - 1L]; |
| 385 | write_xms_store(info, (void FAR *) endbuffer, |
| 386 | file_offset + byte_count - 1L, 2L); |
| 387 | } |
| 388 | } |
| 389 | |
| 390 | |
| 391 | METHODDEF void |
| 392 | close_xms_store (backing_store_ptr info) |
| 393 | { |
| 394 | XMScontext ctx; |
| 395 | |
| 396 | ctx.dx = info->handle.xms_handle; |
| 397 | ctx.ax = 0x0a00; |
| 398 | jxms_calldriver(xms_driver, (XMScontext far *) & ctx); |
| 399 | TRACEMS1(methods, 1, "Freed XMS handle %u", info->handle.xms_handle); |
| 400 | /* we ignore any error return from the driver */ |
| 401 | } |
| 402 | |
| 403 | |
| 404 | LOCAL boolean |
| 405 | open_xms_store (backing_store_ptr info, long total_bytes_needed) |
| 406 | { |
| 407 | XMScontext ctx; |
| 408 | |
| 409 | /* Get address of XMS driver */ |
| 410 | jxms_getdriver((XMSDRIVER far *) & xms_driver); |
| 411 | if (xms_driver == NULL) |
| 412 | return FALSE; /* no driver to be had */ |
| 413 | |
| 414 | /* Get version number, must be >= 2.00 */ |
| 415 | ctx.ax = 0x0000; |
| 416 | jxms_calldriver(xms_driver, (XMScontext far *) & ctx); |
| 417 | if (ctx.ax < (unsigned short) 0x0200) |
| 418 | return FALSE; |
| 419 | |
| 420 | /* Try to get space (expressed in kilobytes) */ |
| 421 | ctx.dx = (unsigned short) ((total_bytes_needed + 1023L) >> 10); |
| 422 | ctx.ax = 0x0900; |
| 423 | jxms_calldriver(xms_driver, (XMScontext far *) & ctx); |
| 424 | if (ctx.ax != 1) |
| 425 | return FALSE; |
| 426 | |
| 427 | /* Succeeded, save the handle and away we go */ |
| 428 | info->handle.xms_handle = ctx.dx; |
| 429 | info->read_backing_store = read_xms_store; |
| 430 | info->write_backing_store = write_xms_store; |
| 431 | info->close_backing_store = close_xms_store; |
| 432 | TRACEMS1(methods, 1, "Obtained XMS handle %u", ctx.dx); |
| 433 | return TRUE; /* succeeded */ |
| 434 | } |
| 435 | |
| 436 | #endif /* XMS_SUPPORTED */ |
| 437 | |
| 438 | |
| 439 | /* |
| 440 | * Access methods for expanded memory. |
| 441 | */ |
| 442 | |
| 443 | #if EMS_SUPPORTED |
| 444 | |
| 445 | typedef union { /* either offset/page or real-mode pointer */ |
| 446 | struct { unsigned short offset, page; } ems; |
| 447 | void far * ptr; |
| 448 | } EMSPTR; |
| 449 | |
| 450 | typedef struct { /* EMS move specification structure */ |
| 451 | long length; |
| 452 | char src_type; /* 1 = EMS, 0 = conventional memory */ |
| 453 | EMSH src_handle; /* use 0 if conventional memory */ |
| 454 | EMSPTR src; |
| 455 | char dst_type; |
| 456 | EMSH dst_handle; |
| 457 | EMSPTR dst; |
| 458 | } EMSspec; |
| 459 | |
| 460 | #define EMSPAGESIZE 16384L /* gospel, see the EMS specs */ |
| 461 | |
| 462 | #define HIBYTE(W) (((W) >> 8) & 0xFF) |
| 463 | #define LOBYTE(W) ((W) & 0xFF) |
| 464 | |
| 465 | |
| 466 | METHODDEF void |
| 467 | read_ems_store (backing_store_ptr info, void FAR * buffer_address, |
| 468 | long file_offset, long byte_count) |
| 469 | { |
| 470 | EMScontext ctx; |
| 471 | EMSspec spec; |
| 472 | |
| 473 | spec.length = byte_count; |
| 474 | spec.src_type = 1; |
| 475 | spec.src_handle = info->handle.ems_handle; |
| 476 | spec.src.ems.page = (unsigned short) (file_offset / EMSPAGESIZE); |
| 477 | spec.src.ems.offset = (unsigned short) (file_offset % EMSPAGESIZE); |
| 478 | spec.dst_type = 0; |
| 479 | spec.dst_handle = 0; |
| 480 | spec.dst.ptr = buffer_address; |
| 481 | |
| 482 | ctx.ds_si = (void far *) & spec; |
| 483 | ctx.ax = 0x5700; /* move memory region */ |
| 484 | jems_calldriver((EMScontext far *) & ctx); |
| 485 | if (HIBYTE(ctx.ax) != 0) |
| 486 | ERREXIT(methods, "read from expanded memory failed"); |
| 487 | } |
| 488 | |
| 489 | |
| 490 | METHODDEF void |
| 491 | write_ems_store (backing_store_ptr info, void FAR * buffer_address, |
| 492 | long file_offset, long byte_count) |
| 493 | { |
| 494 | EMScontext ctx; |
| 495 | EMSspec spec; |
| 496 | |
| 497 | spec.length = byte_count; |
| 498 | spec.src_type = 0; |
| 499 | spec.src_handle = 0; |
| 500 | spec.src.ptr = buffer_address; |
| 501 | spec.dst_type = 1; |
| 502 | spec.dst_handle = info->handle.ems_handle; |
| 503 | spec.dst.ems.page = (unsigned short) (file_offset / EMSPAGESIZE); |
| 504 | spec.dst.ems.offset = (unsigned short) (file_offset % EMSPAGESIZE); |
| 505 | |
| 506 | ctx.ds_si = (void far *) & spec; |
| 507 | ctx.ax = 0x5700; /* move memory region */ |
| 508 | jems_calldriver((EMScontext far *) & ctx); |
| 509 | if (HIBYTE(ctx.ax) != 0) |
| 510 | ERREXIT(methods, "write to expanded memory failed"); |
| 511 | } |
| 512 | |
| 513 | |
| 514 | METHODDEF void |
| 515 | close_ems_store (backing_store_ptr info) |
| 516 | { |
| 517 | EMScontext ctx; |
| 518 | |
| 519 | ctx.ax = 0x4500; |
| 520 | ctx.dx = info->handle.ems_handle; |
| 521 | jems_calldriver((EMScontext far *) & ctx); |
| 522 | TRACEMS1(methods, 1, "Freed EMS handle %u", info->handle.ems_handle); |
| 523 | /* we ignore any error return from the driver */ |
| 524 | } |
| 525 | |
| 526 | |
| 527 | LOCAL boolean |
| 528 | open_ems_store (backing_store_ptr info, long total_bytes_needed) |
| 529 | { |
| 530 | EMScontext ctx; |
| 531 | |
| 532 | /* Is EMS driver there? */ |
| 533 | if (! jems_available()) |
| 534 | return FALSE; |
| 535 | |
| 536 | /* Get status, make sure EMS is OK */ |
| 537 | ctx.ax = 0x4000; |
| 538 | jems_calldriver((EMScontext far *) & ctx); |
| 539 | if (HIBYTE(ctx.ax) != 0) |
| 540 | return FALSE; |
| 541 | |
| 542 | /* Get version, must be >= 4.0 */ |
| 543 | ctx.ax = 0x4600; |
| 544 | jems_calldriver((EMScontext far *) & ctx); |
| 545 | if (HIBYTE(ctx.ax) != 0 || LOBYTE(ctx.ax) < 0x40) |
| 546 | return FALSE; |
| 547 | |
| 548 | /* Try to allocate requested space */ |
| 549 | ctx.ax = 0x4300; |
| 550 | ctx.bx = (unsigned short) ((total_bytes_needed + EMSPAGESIZE-1L) / EMSPAGESIZE); |
| 551 | jems_calldriver((EMScontext far *) & ctx); |
| 552 | if (HIBYTE(ctx.ax) != 0) |
| 553 | return FALSE; |
| 554 | |
| 555 | /* Succeeded, save the handle and away we go */ |
| 556 | info->handle.ems_handle = ctx.dx; |
| 557 | info->read_backing_store = read_ems_store; |
| 558 | info->write_backing_store = write_ems_store; |
| 559 | info->close_backing_store = close_ems_store; |
| 560 | TRACEMS1(methods, 1, "Obtained EMS handle %u", ctx.dx); |
| 561 | return TRUE; /* succeeded */ |
| 562 | } |
| 563 | |
| 564 | #endif /* EMS_SUPPORTED */ |
| 565 | |
| 566 | |
| 567 | /* |
| 568 | * Initial opening of a backing-store object. |
| 569 | */ |
| 570 | |
| 571 | GLOBAL void |
| 572 | jopen_backing_store (backing_store_ptr info, long total_bytes_needed) |
| 573 | { |
| 574 | /* Try extended memory, then expanded memory, then regular file. */ |
| 575 | #if XMS_SUPPORTED |
| 576 | if (open_xms_store(info, total_bytes_needed)) |
| 577 | return; |
| 578 | #endif |
| 579 | #if EMS_SUPPORTED |
| 580 | if (open_ems_store(info, total_bytes_needed)) |
| 581 | return; |
| 582 | #endif |
| 583 | if (open_file_store(info, total_bytes_needed)) |
| 584 | return; |
| 585 | ERREXIT(methods, "Failed to create temporary file"); |
| 586 | } |
| 587 | |
| 588 | |
| 589 | /* |
| 590 | * These routines take care of any system-dependent initialization and |
| 591 | * cleanup required. Keep in mind that jmem_term may be called more than |
| 592 | * once. |
| 593 | */ |
| 594 | |
| 595 | GLOBAL void |
| 596 | jmem_init (external_methods_ptr emethods) |
| 597 | { |
| 598 | methods = emethods; /* save struct addr for error exit access */ |
| 599 | emethods->max_memory_to_use = DEFAULT_MAX_MEM; |
| 600 | total_used = 0; |
| 601 | next_file_num = 0; |
| 602 | } |
| 603 | |
| 604 | GLOBAL void |
| 605 | jmem_term (void) |
| 606 | { |
| 607 | /* no work */ |
| 608 | } |