/*

 * 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;