/*

* jmemdos.c

*

* Copyright (C) 1992-1997, 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.

* Also, this code will NOT work if struct fields are aligned on greater than

* 2-byte boundaries.

*

* 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

#define JPEG_INTERNALS

#include "jinclude.h"

#include "jpeglib.h"

#include "jmemsys.h" /* import the system-dependent declarations */

#ifndef HAVE_STDLIB_H /* <stdlib.h> should declare these */

extern void * malloc JPP((size_t size));

extern void free JPP((void *ptr));

extern char * getenv JPP((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

#else /* not NEED_FAR_POINTERS */

#define far_malloc(x) malloc(x)

#define far_free(x) free(x)

#endif /* NEED_FAR_POINTERS */

#ifdef DONT_USE_B_MODE /* define mode parameters for fopen() */

#define READ_BINARY "r"

#else

#define READ_BINARY "rb"

#endif

#ifndef USE_MSDOS_MEMMGR /* make sure user got configuration right */

You forgot to define USE_MSDOS_MEMMGR in jconfig.h. /* deliberate syntax error */

#endif

#if MAX_ALLOC_CHUNK >= 65535L /* make sure jconfig.h got this right */

MAX_ALLOC_CHUNK should be less than 64K. /* deliberate syntax error */

#endif

/*

* Declarations for assembly-language support routines (see jmemdosa.asm).

*

* The functions are declared "far" as are all their 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 JPP((short far * handle, char far * filename));

extern short far jdos_close JPP((short handle));

extern short far jdos_seek JPP((short handle, long offset));

extern short far jdos_read JPP((short handle, void far * buffer,

unsigned short count));

extern short far jdos_write JPP((short handle, void far * buffer,

unsigned short count));

extern void far jxms_getdriver JPP((XMSDRIVER far *));

extern void far jxms_calldriver JPP((XMSDRIVER, XMScontext far *));

extern short far jems_available JPP((void));

extern void far jems_calldriver JPP((EMScontext 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 *)

jpeg_get_small (j_common_ptr cinfo, size_t sizeofobject)

{

return (void *) malloc(sizeofobject);

}

GLOBAL(void)

jpeg_free_small (j_common_ptr cinfo, void * object, size_t sizeofobject)

{

free(object);

}

/*

* "Large" objects are allocated in far memory, if possible

*/

GLOBAL(void FAR *)

jpeg_get_large (j_common_ptr cinfo, size_t sizeofobject)

{

return (void FAR *) far_malloc(sizeofobject);

}

GLOBAL(void)

jpeg_free_large (j_common_ptr cinfo, void FAR * object, size_t sizeofobject)

{

far_free(object);

}

/*

* 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)

jpeg_mem_available (j_common_ptr cinfo, long min_bytes_needed,

long max_bytes_needed, long already_allocated)

{

return cinfo->mem->max_memory_to_use - already_allocated;

}

/*

* Backing store (temporary file) management.

* Backing store objects are only used when the value returned by

* jpeg_mem_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 the SIMTEL archives

* (oak.oakland.edu and its various mirror sites). See files

* pub/msdos/microsoft/xms20.arc and pub/msdos/info/limems41.zip.

*/

/*

* Access methods for a DOS file.

*/

METHODDEF(void)

read_file_store (j_common_ptr cinfo, backing_store_ptr info,

void FAR * buffer_address,

long file_offset, long byte_count)

{

if (jdos_seek(info->handle.file_handle, file_offset))

ERREXIT(cinfo, JERR_TFILE_SEEK);

/* Since MAX_ALLOC_CHUNK is less than 64K, byte_count will be too. */

if (byte_count > 65535L) /* safety check */

ERREXIT(cinfo, JERR_BAD_ALLOC_CHUNK);

if (jdos_read(info->handle.file_handle, buffer_address,

(unsigned short) byte_count))

ERREXIT(cinfo, JERR_TFILE_READ);

}

METHODDEF(void)

write_file_store (j_common_ptr cinfo, backing_store_ptr info,

void FAR * buffer_address,

long file_offset, long byte_count)

{

if (jdos_seek(info->handle.file_handle, file_offset))

ERREXIT(cinfo, JERR_TFILE_SEEK);

/* Since MAX_ALLOC_CHUNK is less than 64K, byte_count will be too. */

if (byte_count > 65535L) /* safety check */

ERREXIT(cinfo, JERR_BAD_ALLOC_CHUNK);

if (jdos_write(info->handle.file_handle, buffer_address,

(unsigned short) byte_count))

ERREXIT(cinfo, JERR_TFILE_WRITE);

}

METHODDEF(void)

close_file_store (j_common_ptr cinfo, 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.

*/

TRACEMSS(cinfo, 1, JTRC_TFILE_CLOSE, info->temp_name);

}

LOCAL(boolean)

open_file_store (j_common_ptr cinfo, backing_store_ptr info,

long total_bytes_needed)

{

short handle;

select_file_name(info->temp_name);

if (jdos_open((short far *) & handle, (char far *) info->temp_name)) {

/* might as well exit since jpeg_open_backing_store will fail anyway */

ERREXITS(cinfo, JERR_TFILE_CREATE, 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;

TRACEMSS(cinfo, 1, JTRC_TFILE_OPEN, info->temp_name);

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 (j_common_ptr cinfo, 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(cinfo, JERR_XMS_READ);

if (ODD(byte_count)) {

read_xms_store(cinfo, info, (void FAR *) endbuffer,

file_offset + byte_count - 1L, 2L);

((char FAR *) buffer_address)[byte_count - 1L] = endbuffer[0];

}

}

METHODDEF(void)

write_xms_store (j_common_ptr cinfo, 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(cinfo, JERR_XMS_WRITE);

if (ODD(byte_count)) {

read_xms_store(cinfo, info, (void FAR *) endbuffer,

file_offset + byte_count - 1L, 2L);

endbuffer[0] = ((char FAR *) buffer_address)[byte_count - 1L];

write_xms_store(cinfo, info, (void FAR *) endbuffer,

file_offset + byte_count - 1L, 2L);

}

}

METHODDEF(void)

close_xms_store (j_common_ptr cinfo, backing_store_ptr info)

{

XMScontext ctx;

ctx.dx = info->handle.xms_handle;

ctx.ax = 0x0a00;

jxms_calldriver(xms_driver, (XMScontext far *) & ctx);

TRACEMS1(cinfo, 1, JTRC_XMS_CLOSE, info->handle.xms_handle);

/* we ignore any error return from the driver */

}

LOCAL(boolean)

open_xms_store (j_common_ptr cinfo, 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(cinfo, 1, JTRC_XMS_OPEN, ctx.dx);

return TRUE; /* succeeded */

}

#endif /* XMS_SUPPORTED */

/*

* Access methods for expanded memory.

*/

#if EMS_SUPPORTED

/* The EMS move specification structure requires word and long fields aligned

* at odd byte boundaries. Some compilers will align struct fields at even

* byte boundaries. While it's usually possible to force byte alignment,

* that causes an overall performance penalty and may pose problems in merging

* JPEG into a larger application. Instead we accept some rather dirty code

* here. Note this code would fail if the hardware did not allow odd-byte

* word & long accesses, but all 80x86 CPUs do.

*/

typedef void far * EMSPTR;

typedef union { /* EMS move specification structure */

long length; /* It's easy to access first 4 bytes */

char bytes[18]; /* Misaligned fields in here! */

} EMSspec;

/* Macros for accessing misaligned fields */

#define FIELD_AT(spec,offset,type) (*((type *) &(spec.bytes[offset])))

#define SRC_TYPE(spec) FIELD_AT(spec,4,char)

#define SRC_HANDLE(spec) FIELD_AT(spec,5,EMSH)

#define SRC_OFFSET(spec) FIELD_AT(spec,7,unsigned short)

#define SRC_PAGE(spec) FIELD_AT(spec,9,unsigned short)

#define SRC_PTR(spec) FIELD_AT(spec,7,EMSPTR)

#define DST_TYPE(spec) FIELD_AT(spec,11,char)

#define DST_HANDLE(spec) FIELD_AT(spec,12,EMSH)

#define DST_OFFSET(spec) FIELD_AT(spec,14,unsigned short)

#define DST_PAGE(spec) FIELD_AT(spec,16,unsigned short)

#define DST_PTR(spec) FIELD_AT(spec,14,EMSPTR)

#define EMSPAGESIZE 16384L /* gospel, see the EMS specs */

#define HIBYTE(W) (((W) >> 8) & 0xFF)

#define LOBYTE(W) ((W) & 0xFF)

METHODDEF(void)

read_ems_store (j_common_ptr cinfo, backing_store_ptr info,

void FAR * buffer_address,

long file_offset, long byte_count)

{

EMScontext ctx;

EMSspec spec;

spec.length = byte_count;

SRC_TYPE(spec) = 1;

SRC_HANDLE(spec) = info->handle.ems_handle;

SRC_PAGE(spec) = (unsigned short) (file_offset / EMSPAGESIZE);

SRC_OFFSET(spec) = (unsigned short) (file_offset % EMSPAGESIZE);

DST_TYPE(spec) = 0;

DST_HANDLE(spec) = 0;

DST_PTR(spec) = 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(cinfo, JERR_EMS_READ);

}

METHODDEF(void)

write_ems_store (j_common_ptr cinfo, backing_store_ptr info,

void FAR * buffer_address,

long file_offset, long byte_count)

{

EMScontext ctx;

EMSspec spec;

spec.length = byte_count;

SRC_TYPE(spec) = 0;

SRC_HANDLE(spec) = 0;

SRC_PTR(spec) = buffer_address;

DST_TYPE(spec) = 1;

DST_HANDLE(spec) = info->handle.ems_handle;

DST_PAGE(spec) = (unsigned short) (file_offset / EMSPAGESIZE);

DST_OFFSET(spec) = (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(cinfo, JERR_EMS_WRITE);

}

METHODDEF(void)

close_ems_store (j_common_ptr cinfo, backing_store_ptr info)

{

EMScontext ctx;

ctx.ax = 0x4500;

ctx.dx = info->handle.ems_handle;

jems_calldriver((EMScontext far *) & ctx);

TRACEMS1(cinfo, 1, JTRC_EMS_CLOSE, info->handle.ems_handle);

/* we ignore any error return from the driver */

}

LOCAL(boolean)

open_ems_store (j_common_ptr cinfo, 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(cinfo, 1, JTRC_EMS_OPEN, ctx.dx);

return TRUE; /* succeeded */

}

#endif /* EMS_SUPPORTED */

/*

* Initial opening of a backing-store object.

*/

GLOBAL(void)

jpeg_open_backing_store (j_common_ptr cinfo, backing_store_ptr info,

long total_bytes_needed)

{

/* Try extended memory, then expanded memory, then regular file. */

#if XMS_SUPPORTED

if (open_xms_store(cinfo, info, total_bytes_needed))

return;

#endif

#if EMS_SUPPORTED

if (open_ems_store(cinfo, info, total_bytes_needed))

return;

#endif

if (open_file_store(cinfo, info, total_bytes_needed))

return;

ERREXITS(cinfo, JERR_TFILE_CREATE, "");

}

/*

* These routines take care of any system-dependent initialization and

* cleanup required.

*/

GLOBAL(long)

jpeg_mem_init (j_common_ptr cinfo)

{

next_file_num = 0; /* initialize temp file name generator */

return DEFAULT_MAX_MEM; /* default for max_memory_to_use */

}

GLOBAL(void)

jpeg_mem_term (j_common_ptr cinfo)

{

/* Microsoft C, at least in v6.00A, will not successfully reclaim freed

* blocks of size > 32Kbytes unless we give it a kick in the rear, like so:

*/

#ifdef NEED_FHEAPMIN

_fheapmin();

#endif

}