/*

 * jmemname.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 a generic implementation of the system-dependent

 * portion of the JPEG memory manager.  This implementation assumes that

 * you must explicitly construct a name for each temp file.

 * Also, the problem of determining the amount of memory available

 * is shoved onto the user.

 */



#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 malloc(),free() */

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

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

#endif



#ifndef SEEK_SET		/* pre-ANSI systems may not define this; */

#define SEEK_SET  0		/* if not, assume 0 is correct */

#endif



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

#define READ_BINARY	"r"

#define RW_BINARY	"w+"

#else

#ifdef VMS			/* VMS is very nonstandard */

#define READ_BINARY	"rb", "ctx=stm"

#define RW_BINARY	"w+b", "ctx=stm"

#else				/* standard ANSI-compliant case */

#define READ_BINARY	"rb"

#define RW_BINARY	"w+b"

#endif

#endif





/*

 * Selection of a file name for a temporary file.

 * This is system-dependent!

 *

 * The code as given is suitable for most Unix systems, and it is easily

 * modified for most non-Unix systems.  Some notes:

 *  1.  The temp file is created in the directory named by TEMP_DIRECTORY.

 *      The default value is /usr/tmp, which is the conventional place for

 *      creating large temp files on Unix.  On other systems you'll probably

 *      want to change the file location.  You can do this by editing the

 *      #define, or (preferred) by defining TEMP_DIRECTORY in jconfig.h.

 *

 *  2.  If you need to change the file name as well as its location,

 *      you can override the TEMP_FILE_NAME macro.  (Note that this is

 *      actually a printf format string; it must contain %s and %d.)

 *      Few people should need to do this.

 *

 *  3.  mktemp() is used to ensure that multiple processes running

 *      simultaneously won't select the same file names.  If your system

 *      doesn't have mktemp(), define NO_MKTEMP to do it the hard way.

 *      (If you don't have <errno.h>, also define NO_ERRNO_H.)

 *

 *  4.  You probably want to define NEED_SIGNAL_CATCHER so that cjpeg.c/djpeg.c

 *      will cause the temp files to be removed if you stop the program early.

 */



#ifndef TEMP_DIRECTORY		/* can override from jconfig.h or Makefile */

#define TEMP_DIRECTORY  "/usr/tmp/" /* recommended setting for Unix */

#endif



static int next_file_num;	/* to distinguish among several temp files */



#ifdef NO_MKTEMP



#ifndef TEMP_FILE_NAME		/* can override from jconfig.h or Makefile */

#define TEMP_FILE_NAME  "%sJPG%03d.TMP"

#endif



#ifndef NO_ERRNO_H

#include <errno.h>		/* to define ENOENT */

#endif



/* ANSI C specifies that errno is a macro, but on older systems it's more

 * likely to be a plain int variable.  And not all versions of errno.h

 * bother to declare it, so we have to in order to be most portable.  Thus:

 */

#ifndef errno

extern int errno;

#endif





LOCAL(void)

select_file_name (char * fname)

{

  FILE * tfile;



  /* Keep generating file names till we find one that's not in use */

  for (;;) {

    next_file_num++;		/* advance counter */

    sprintf(fname, TEMP_FILE_NAME, TEMP_DIRECTORY, next_file_num);

    if ((tfile = fopen(fname, READ_BINARY)) == NULL) {

      /* fopen could have failed for a reason other than the file not

       * being there; for example, file there but unreadable.

       * If <errno.h> isn't available, then we cannot test the cause.

       */

#ifdef ENOENT

      if (errno != ENOENT)

	continue;

#endif

      break;

    }

    fclose(tfile);		/* oops, it's there; close tfile & try again */

  }

}



#else /* ! NO_MKTEMP */



/* Note that mktemp() requires the initial filename to end in six X's */

#ifndef TEMP_FILE_NAME		/* can override from jconfig.h or Makefile */

#define TEMP_FILE_NAME  "%sJPG%dXXXXXX"

#endif



LOCAL(void)

select_file_name (char * fname)

{

  next_file_num++;		/* advance counter */

  sprintf(fname, TEMP_FILE_NAME, TEMP_DIRECTORY, next_file_num);

  mktemp(fname);		/* make sure file name is unique */

  /* mktemp replaces the trailing XXXXXX with a unique string of characters */

}



#endif /* NO_MKTEMP */





/*

 * 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 treated the same as "small" ones.

 * NB: although we include FAR keywords in the routine declarations,

 * this file won't actually work in 80x86 small/medium model; at least,

 * you probably won't be able to process useful-size images in only 64KB.

 */



GLOBAL(void FAR *)

jpeg_get_large (j_common_ptr cinfo, size_t sizeofobject)

{

  return (void FAR *) malloc(sizeofobject);

}



GLOBAL(void)

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

{

  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		1000000L /* default: one megabyte */

#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.

 */





METHODDEF(void)

read_backing_store (j_common_ptr cinfo, backing_store_ptr info,

		    void FAR * buffer_address,

		    long file_offset, long byte_count)

{

  if (fseek(info->temp_file, file_offset, SEEK_SET))

    ERREXIT(cinfo, JERR_TFILE_SEEK);

  if (JFREAD(info->temp_file, buffer_address, byte_count)

      != (size_t) byte_count)

    ERREXIT(cinfo, JERR_TFILE_READ);

}





METHODDEF(void)

write_backing_store (j_common_ptr cinfo, backing_store_ptr info,

		     void FAR * buffer_address,

		     long file_offset, long byte_count)

{

  if (fseek(info->temp_file, file_offset, SEEK_SET))

    ERREXIT(cinfo, JERR_TFILE_SEEK);

  if (JFWRITE(info->temp_file, buffer_address, byte_count)

      != (size_t) byte_count)

    ERREXIT(cinfo, JERR_TFILE_WRITE);

}





METHODDEF(void)

close_backing_store (j_common_ptr cinfo, backing_store_ptr info)

{

  fclose(info->temp_file);	/* close the file */

  unlink(info->temp_name);	/* delete the file */

/* If your system doesn't have unlink(), use remove() instead.

 * remove() is the ANSI-standard name for this function, but if

 * your system was ANSI you'd be using jmemansi.c, right?

 */

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

}





/*

 * 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)

{

  select_file_name(info->temp_name);

  if ((info->temp_file = fopen(info->temp_name, RW_BINARY)) == NULL)

    ERREXITS(cinfo, JERR_TFILE_CREATE, info->temp_name);

  info->read_backing_store = read_backing_store;

  info->write_backing_store = write_backing_store;

  info->close_backing_store = close_backing_store;

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

}





/*

 * 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)

{

  /* no work */

}

