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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() */
#else
extern void * malloc PP((size_t size));
extern void free PP((void *ptr));
#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))
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 */
}
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