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- /*
- * jmemdos.c (jmemsys.c)
- *
- * 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 provides an MS-DOS-compatible implementation of the system-
- * dependent portion of the JPEG memory manager. Temporary data can be
- * stored in extended or expanded memory as well as in regular DOS files.
- *
- * If you use this file, you must be sure that NEED_FAR_POINTERS is defined
- * if you compile in a small-data memory model; it should NOT be defined if
- * you use a large-data memory model. This file is not recommended if you
- * are using a flat-memory-space 386 environment such as DJGCC or Watcom C.
- *
- * Based on code contributed by Ge' Weijers.
- */
-
- /*
- * If you have both extended and expanded memory, you may want to change the
- * order in which they are tried in jopen_backing_store. On a 286 machine
- * expanded memory is usually faster, since extended memory access involves
- * an expensive protected-mode-and-back switch. On 386 and better, extended
- * memory is usually faster. As distributed, the code tries extended memory
- * first (what? not everyone has a 386? :-).
- *
- * You can disable use of extended/expanded memory entirely by altering these
- * definitions or overriding them from the Makefile (eg, -DEMS_SUPPORTED=0).
- */
-
- #ifndef XMS_SUPPORTED
- #define XMS_SUPPORTED 1
- #endif
- #ifndef EMS_SUPPORTED
- #define EMS_SUPPORTED 1
- #endif
-
-
- #include "jinclude.h"
- #include "jmemsys.h"
-
- #ifdef INCLUDES_ARE_ANSI
- #include <stdlib.h> /* to declare malloc(), free(), getenv() */
- #else
- extern void * malloc PP((size_t size));
- extern void free PP((void *ptr));
- extern char * getenv PP((const char * name));
- #endif
-
- #ifdef NEED_FAR_POINTERS
-
- #ifdef __TURBOC__
- /* These definitions work for Borland C (Turbo C) */
- #include <alloc.h> /* need farmalloc(), farfree() */
- #define far_malloc(x) farmalloc(x)
- #define far_free(x) farfree(x)
- #else
- /* These definitions work for Microsoft C and compatible compilers */
- #include <malloc.h> /* need _fmalloc(), _ffree() */
- #define far_malloc(x) _fmalloc(x)
- #define far_free(x) _ffree(x)
- #endif
-
- #endif
-
- #ifdef DONT_USE_B_MODE /* define mode parameters for fopen() */
- #define READ_BINARY "r"
- #else
- #define READ_BINARY "rb"
- #endif
-
-
- /*
- * Declarations for assembly-language support routines (see jmemdosa.asm).
- *
- * The functions are declared "far" as are all pointer arguments;
- * this ensures the assembly source code will work regardless of the
- * compiler memory model. We assume "short" is 16 bits, "long" is 32.
- */
-
- typedef void far * XMSDRIVER; /* actually a pointer to code */
- typedef struct { /* registers for calling XMS driver */
- unsigned short ax, dx, bx;
- void far * ds_si;
- } XMScontext;
- typedef struct { /* registers for calling EMS driver */
- unsigned short ax, dx, bx;
- void far * ds_si;
- } EMScontext;
-
- EXTERN short far jdos_open PP((short far * handle, char far * filename));
- EXTERN short far jdos_close PP((short handle));
- EXTERN short far jdos_seek PP((short handle, long offset));
- EXTERN short far jdos_read PP((short handle, void far * buffer,
- unsigned short count));
- EXTERN short far jdos_write PP((short handle, void far * buffer,
- unsigned short count));
- EXTERN void far jxms_getdriver PP((XMSDRIVER far *));
- EXTERN void far jxms_calldriver PP((XMSDRIVER, XMScontext far *));
- EXTERN short far jems_available PP((void));
- EXTERN void far jems_calldriver PP((EMScontext far *));
-
-
- static external_methods_ptr methods; /* saved for access to error_exit */
-
- static long total_used; /* total FAR memory requested so far */
-
-
- /*
- * Selection of a file name for a temporary file.
- * This is highly system-dependent, and you may want to customize it.
- */
-
- static int next_file_num; /* to distinguish among several temp files */
-
- LOCAL void
- select_file_name (char * fname)
- {
- const char * env;
- char * ptr;
- FILE * tfile;
-
- /* Keep generating file names till we find one that's not in use */
- for (;;) {
- /* Get temp directory name from environment TMP or TEMP variable;
- * if none, use "."
- */
- if ((env = (const char *) getenv("TMP")) == NULL)
- if ((env = (const char *) getenv("TEMP")) == NULL)
- env = ".";
- if (*env == '\0') /* null string means "." */
- env = ".";
- ptr = fname; /* copy name to fname */
- while (*env != '\0')
- *ptr++ = *env++;
- if (ptr[-1] != '\\' && ptr[-1] != '/')
- *ptr++ = '\\'; /* append backslash if not in env variable */
- /* Append a suitable file name */
- next_file_num++; /* advance counter */
- sprintf(ptr, "JPG%03d.TMP", next_file_num);
- /* Probe to see if file name is already in use */
- if ((tfile = fopen(fname, READ_BINARY)) == NULL)
- break;
- fclose(tfile); /* oops, it's there; close tfile & try again */
- }
- }
-
-
- /*
- * Near-memory allocation and freeing are controlled by the regular library
- * routines malloc() and free().
- */
-
- GLOBAL void *
- jget_small (size_t sizeofobject)
- {
- /* near data space is NOT counted in total_used */
- #ifndef NEED_FAR_POINTERS
- total_used += sizeofobject;
- #endif
- return (void *) malloc(sizeofobject);
- }
-
- GLOBAL void
- jfree_small (void * object)
- {
- free(object);
- }
-
-
- /*
- * Far-memory allocation and freeing
- */
-
- #ifdef NEED_FAR_POINTERS
-
- GLOBAL void FAR *
- jget_large (size_t sizeofobject)
- {
- total_used += sizeofobject;
- return (void FAR *) far_malloc(sizeofobject);
- }
-
- GLOBAL void
- jfree_large (void FAR * object)
- {
- far_free(object);
- }
-
- #endif
-
-
- /*
- * This routine computes the total memory space available for allocation.
- * It's impossible to do this in a portable way; our current solution is
- * to make the user tell us (with a default value set at compile time).
- * If you can actually get the available space, it's a good idea to subtract
- * a slop factor of 5% or so.
- */
-
- #ifndef DEFAULT_MAX_MEM /* so can override from makefile */
- #define DEFAULT_MAX_MEM 300000L /* for total usage about 450K */
- #endif
-
- GLOBAL long
- jmem_available (long min_bytes_needed, long max_bytes_needed)
- {
- return methods->max_memory_to_use - total_used;
- }
-
-
- /*
- * Backing store (temporary file) management.
- * Backing store objects are only used when the value returned by
- * jmem_available is less than the total space needed. You can dispense
- * with these routines if you have plenty of virtual memory; see jmemnobs.c.
- */
-
- /*
- * For MS-DOS we support three types of backing storage:
- * 1. Conventional DOS files. We access these by direct DOS calls rather
- * than via the stdio package. This provides a bit better performance,
- * but the real reason is that the buffers to be read or written are FAR.
- * The stdio library for small-data memory models can't cope with that.
- * 2. Extended memory, accessed per the XMS V2.0 specification.
- * 3. Expanded memory, accessed per the LIM/EMS 4.0 specification.
- * You'll need copies of those specs to make sense of the related code.
- * The specs are available by Internet FTP from SIMTEL20 and its various
- * mirror sites; see microsoft/xms20.arc and info/limems41.zip.
- */
-
-
- /*
- * Access methods for a DOS file.
- */
-
-
- METHODDEF void
- read_file_store (backing_store_ptr info, void FAR * buffer_address,
- long file_offset, long byte_count)
- {
- if (jdos_seek(info->handle.file_handle, file_offset))
- ERREXIT(methods, "seek failed on temporary file");
- /* Since MAX_ALLOC_CHUNK is less than 64K, byte_count will be too. */
- if (byte_count > 65535L) /* safety check */
- ERREXIT(methods, "MAX_ALLOC_CHUNK should be less than 64K");
- if (jdos_read(info->handle.file_handle, buffer_address,
- (unsigned short) byte_count))
- ERREXIT(methods, "read failed on temporary file");
- }
-
-
- METHODDEF void
- write_file_store (backing_store_ptr info, void FAR * buffer_address,
- long file_offset, long byte_count)
- {
- if (jdos_seek(info->handle.file_handle, file_offset))
- ERREXIT(methods, "seek failed on temporary file");
- /* Since MAX_ALLOC_CHUNK is less than 64K, byte_count will be too. */
- if (byte_count > 65535L) /* safety check */
- ERREXIT(methods, "MAX_ALLOC_CHUNK should be less than 64K");
- if (jdos_write(info->handle.file_handle, buffer_address,
- (unsigned short) byte_count))
- ERREXIT(methods, "write failed on temporary file --- out of disk space?");
- }
-
-
- METHODDEF void
- close_file_store (backing_store_ptr info)
- {
- jdos_close(info->handle.file_handle); /* close the file */
- remove(info->temp_name); /* delete the file */
- /* If your system doesn't have remove(), try unlink() instead.
- * remove() is the ANSI-standard name for this function, but
- * unlink() was more common in pre-ANSI systems.
- */
- TRACEMS1(methods, 1, "Closed DOS file %d", info->handle.file_handle);
- }
-
-
- LOCAL boolean
- open_file_store (backing_store_ptr info, long total_bytes_needed)
- {
- short handle;
- char tracemsg[TEMP_NAME_LENGTH+40];
-
- select_file_name(info->temp_name);
- if (jdos_open((short far *) & handle, (char far *) info->temp_name)) {
- /* hack to get around TRACEMS' inability to handle string parameters */
- sprintf(tracemsg, "Failed to create temporary file %s", info->temp_name);
- ERREXIT(methods, tracemsg); /* jopen_backing_store will fail anyway */
- return FALSE;
- }
- info->handle.file_handle = handle;
- info->read_backing_store = read_file_store;
- info->write_backing_store = write_file_store;
- info->close_backing_store = close_file_store;
- /* hack to get around TRACEMS' inability to handle string parameters */
- sprintf(tracemsg, "Opened DOS file %d %s", handle, info->temp_name);
- TRACEMS(methods, 1, tracemsg);
- return TRUE; /* succeeded */
- }
-
-
- /*
- * Access methods for extended memory.
- */
-
- #if XMS_SUPPORTED
-
- static XMSDRIVER xms_driver; /* saved address of XMS driver */
-
- typedef union { /* either long offset or real-mode pointer */
- long offset;
- void far * ptr;
- } XMSPTR;
-
- typedef struct { /* XMS move specification structure */
- long length;
- XMSH src_handle;
- XMSPTR src;
- XMSH dst_handle;
- XMSPTR dst;
- } XMSspec;
-
- #define ODD(X) (((X) & 1L) != 0)
-
-
- METHODDEF void
- read_xms_store (backing_store_ptr info, void FAR * buffer_address,
- long file_offset, long byte_count)
- {
- XMScontext ctx;
- XMSspec spec;
- char endbuffer[2];
-
- /* The XMS driver can't cope with an odd length, so handle the last byte
- * specially if byte_count is odd. We don't expect this to be common.
- */
-
- spec.length = byte_count & (~ 1L);
- spec.src_handle = info->handle.xms_handle;
- spec.src.offset = file_offset;
- spec.dst_handle = 0;
- spec.dst.ptr = buffer_address;
-
- ctx.ds_si = (void far *) & spec;
- ctx.ax = 0x0b00; /* EMB move */
- jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
- if (ctx.ax != 1)
- ERREXIT(methods, "read from extended memory failed");
-
- if (ODD(byte_count)) {
- read_xms_store(info, (void FAR *) endbuffer,
- file_offset + byte_count - 1L, 2L);
- ((char FAR *) buffer_address)[byte_count - 1L] = endbuffer[0];
- }
- }
-
-
- METHODDEF void
- write_xms_store (backing_store_ptr info, void FAR * buffer_address,
- long file_offset, long byte_count)
- {
- XMScontext ctx;
- XMSspec spec;
- char endbuffer[2];
-
- /* The XMS driver can't cope with an odd length, so handle the last byte
- * specially if byte_count is odd. We don't expect this to be common.
- */
-
- spec.length = byte_count & (~ 1L);
- spec.src_handle = 0;
- spec.src.ptr = buffer_address;
- spec.dst_handle = info->handle.xms_handle;
- spec.dst.offset = file_offset;
-
- ctx.ds_si = (void far *) & spec;
- ctx.ax = 0x0b00; /* EMB move */
- jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
- if (ctx.ax != 1)
- ERREXIT(methods, "write to extended memory failed");
-
- if (ODD(byte_count)) {
- read_xms_store(info, (void FAR *) endbuffer,
- file_offset + byte_count - 1L, 2L);
- endbuffer[0] = ((char FAR *) buffer_address)[byte_count - 1L];
- write_xms_store(info, (void FAR *) endbuffer,
- file_offset + byte_count - 1L, 2L);
- }
- }
-
-
- METHODDEF void
- close_xms_store (backing_store_ptr info)
- {
- XMScontext ctx;
-
- ctx.dx = info->handle.xms_handle;
- ctx.ax = 0x0a00;
- jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
- TRACEMS1(methods, 1, "Freed XMS handle %u", info->handle.xms_handle);
- /* we ignore any error return from the driver */
- }
-
-
- LOCAL boolean
- open_xms_store (backing_store_ptr info, long total_bytes_needed)
- {
- XMScontext ctx;
-
- /* Get address of XMS driver */
- jxms_getdriver((XMSDRIVER far *) & xms_driver);
- if (xms_driver == NULL)
- return FALSE; /* no driver to be had */
-
- /* Get version number, must be >= 2.00 */
- ctx.ax = 0x0000;
- jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
- if (ctx.ax < (unsigned short) 0x0200)
- return FALSE;
-
- /* Try to get space (expressed in kilobytes) */
- ctx.dx = (unsigned short) ((total_bytes_needed + 1023L) >> 10);
- ctx.ax = 0x0900;
- jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
- if (ctx.ax != 1)
- return FALSE;
-
- /* Succeeded, save the handle and away we go */
- info->handle.xms_handle = ctx.dx;
- info->read_backing_store = read_xms_store;
- info->write_backing_store = write_xms_store;
- info->close_backing_store = close_xms_store;
- TRACEMS1(methods, 1, "Obtained XMS handle %u", ctx.dx);
- return TRUE; /* succeeded */
- }
-
- #endif /* XMS_SUPPORTED */
-
-
- /*
- * Access methods for expanded memory.
- */
-
- #if EMS_SUPPORTED
-
- typedef union { /* either offset/page or real-mode pointer */
- struct { unsigned short offset, page; } ems;
- void far * ptr;
- } EMSPTR;
-
- typedef struct { /* EMS move specification structure */
- long length;
- char src_type; /* 1 = EMS, 0 = conventional memory */
- EMSH src_handle; /* use 0 if conventional memory */
- EMSPTR src;
- char dst_type;
- EMSH dst_handle;
- EMSPTR dst;
- } EMSspec;
-
- #define EMSPAGESIZE 16384L /* gospel, see the EMS specs */
-
- #define HIBYTE(W) (((W) >> 8) & 0xFF)
- #define LOBYTE(W) ((W) & 0xFF)
-
-
- METHODDEF void
- read_ems_store (backing_store_ptr info, void FAR * buffer_address,
- long file_offset, long byte_count)
- {
- EMScontext ctx;
- EMSspec spec;
-
- spec.length = byte_count;
- spec.src_type = 1;
- spec.src_handle = info->handle.ems_handle;
- spec.src.ems.page = (unsigned short) (file_offset / EMSPAGESIZE);
- spec.src.ems.offset = (unsigned short) (file_offset % EMSPAGESIZE);
- spec.dst_type = 0;
- spec.dst_handle = 0;
- spec.dst.ptr = buffer_address;
-
- ctx.ds_si = (void far *) & spec;
- ctx.ax = 0x5700; /* move memory region */
- jems_calldriver((EMScontext far *) & ctx);
- if (HIBYTE(ctx.ax) != 0)
- ERREXIT(methods, "read from expanded memory failed");
- }
-
-
- METHODDEF void
- write_ems_store (backing_store_ptr info, void FAR * buffer_address,
- long file_offset, long byte_count)
- {
- EMScontext ctx;
- EMSspec spec;
-
- spec.length = byte_count;
- spec.src_type = 0;
- spec.src_handle = 0;
- spec.src.ptr = buffer_address;
- spec.dst_type = 1;
- spec.dst_handle = info->handle.ems_handle;
- spec.dst.ems.page = (unsigned short) (file_offset / EMSPAGESIZE);
- spec.dst.ems.offset = (unsigned short) (file_offset % EMSPAGESIZE);
-
- ctx.ds_si = (void far *) & spec;
- ctx.ax = 0x5700; /* move memory region */
- jems_calldriver((EMScontext far *) & ctx);
- if (HIBYTE(ctx.ax) != 0)
- ERREXIT(methods, "write to expanded memory failed");
- }
-
-
- METHODDEF void
- close_ems_store (backing_store_ptr info)
- {
- EMScontext ctx;
-
- ctx.ax = 0x4500;
- ctx.dx = info->handle.ems_handle;
- jems_calldriver((EMScontext far *) & ctx);
- TRACEMS1(methods, 1, "Freed EMS handle %u", info->handle.ems_handle);
- /* we ignore any error return from the driver */
- }
-
-
- LOCAL boolean
- open_ems_store (backing_store_ptr info, long total_bytes_needed)
- {
- EMScontext ctx;
-
- /* Is EMS driver there? */
- if (! jems_available())
- return FALSE;
-
- /* Get status, make sure EMS is OK */
- ctx.ax = 0x4000;
- jems_calldriver((EMScontext far *) & ctx);
- if (HIBYTE(ctx.ax) != 0)
- return FALSE;
-
- /* Get version, must be >= 4.0 */
- ctx.ax = 0x4600;
- jems_calldriver((EMScontext far *) & ctx);
- if (HIBYTE(ctx.ax) != 0 || LOBYTE(ctx.ax) < 0x40)
- return FALSE;
-
- /* Try to allocate requested space */
- ctx.ax = 0x4300;
- ctx.bx = (unsigned short) ((total_bytes_needed + EMSPAGESIZE-1L) / EMSPAGESIZE);
- jems_calldriver((EMScontext far *) & ctx);
- if (HIBYTE(ctx.ax) != 0)
- return FALSE;
-
- /* Succeeded, save the handle and away we go */
- info->handle.ems_handle = ctx.dx;
- info->read_backing_store = read_ems_store;
- info->write_backing_store = write_ems_store;
- info->close_backing_store = close_ems_store;
- TRACEMS1(methods, 1, "Obtained EMS handle %u", ctx.dx);
- return TRUE; /* succeeded */
- }
-
- #endif /* EMS_SUPPORTED */
-
-
- /*
- * Initial opening of a backing-store object.
- */
-
- GLOBAL void
- jopen_backing_store (backing_store_ptr info, long total_bytes_needed)
- {
- /* Try extended memory, then expanded memory, then regular file. */
- #if XMS_SUPPORTED
- if (open_xms_store(info, total_bytes_needed))
- return;
- #endif
- #if EMS_SUPPORTED
- if (open_ems_store(info, total_bytes_needed))
- return;
- #endif
- if (open_file_store(info, total_bytes_needed))
- return;
- ERREXIT(methods, "Failed to create temporary file");
- }
-
-
- /*
- * These routines take care of any system-dependent initialization and
- * cleanup required. Keep in mind that jmem_term may be called more than
- * once.
- */
-
- GLOBAL void
- jmem_init (external_methods_ptr emethods)
- {
- methods = emethods; /* save struct addr for error exit access */
- emethods->max_memory_to_use = DEFAULT_MAX_MEM;
- total_used = 0;
- next_file_num = 0;
- }
-
- GLOBAL void
- jmem_term (void)
- {
- /* no work */
- }
-