    /*
     * 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 */
    }