168 lines
4.5 KiB
C
168 lines
4.5 KiB
C
/*
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* jmemansi.c
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*
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* Copyright (C) 1992-1996, Thomas G. Lane.
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* This file is part of the Independent JPEG Group's software.
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* For conditions of distribution and use, see the accompanying README file.
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*
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* This file provides a simple generic implementation of the system-
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* dependent portion of the JPEG memory manager. This implementation
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* assumes that you have the ANSI-standard library routine tmpfile().
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* Also, the problem of determining the amount of memory available
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* is shoved onto the user.
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*/
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#define JPEG_INTERNALS
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#include "jinclude.h"
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#include "jpeglib.h"
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#include "jmemsys.h" /* import the system-dependent declarations */
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#ifndef HAVE_STDLIB_H /* <stdlib.h> should declare malloc(),free() */
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extern void * malloc JPP((size_t size));
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extern void free JPP((void *ptr));
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#endif
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#ifndef SEEK_SET /* pre-ANSI systems may not define this; */
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#define SEEK_SET 0 /* if not, assume 0 is correct */
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#endif
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/*
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* Memory allocation and freeing are controlled by the regular library
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* routines malloc() and free().
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*/
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GLOBAL(void *)
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jpeg_get_small (j_common_ptr cinfo, size_t sizeofobject)
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{
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return (void *) malloc(sizeofobject);
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}
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GLOBAL(void)
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jpeg_free_small (j_common_ptr cinfo, void * object, size_t sizeofobject)
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{
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free(object);
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}
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/*
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* "Large" objects are treated the same as "small" ones.
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* NB: although we include FAR keywords in the routine declarations,
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* this file won't actually work in 80x86 small/medium model; at least,
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* you probably won't be able to process useful-size images in only 64KB.
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*/
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GLOBAL(void FAR *)
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jpeg_get_large (j_common_ptr cinfo, size_t sizeofobject)
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{
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return (void FAR *) malloc(sizeofobject);
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}
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GLOBAL(void)
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jpeg_free_large (j_common_ptr cinfo, void FAR * object, size_t sizeofobject)
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{
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free(object);
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}
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/*
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* This routine computes the total memory space available for allocation.
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* It's impossible to do this in a portable way; our current solution is
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* to make the user tell us (with a default value set at compile time).
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* If you can actually get the available space, it's a good idea to subtract
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* a slop factor of 5% or so.
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*/
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#ifndef DEFAULT_MAX_MEM /* so can override from makefile */
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#define DEFAULT_MAX_MEM 1000000L /* default: one megabyte */
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#endif
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GLOBAL(long)
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jpeg_mem_available (j_common_ptr cinfo, long min_bytes_needed,
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long max_bytes_needed, long already_allocated)
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{
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return cinfo->mem->max_memory_to_use - already_allocated;
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}
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/*
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* Backing store (temporary file) management.
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* Backing store objects are only used when the value returned by
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* jpeg_mem_available is less than the total space needed. You can dispense
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* with these routines if you have plenty of virtual memory; see jmemnobs.c.
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*/
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METHODDEF(void)
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read_backing_store (j_common_ptr cinfo, backing_store_ptr info,
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void FAR * buffer_address,
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long file_offset, long byte_count)
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{
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if (fseek(info->temp_file, file_offset, SEEK_SET))
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ERREXIT(cinfo, JERR_TFILE_SEEK);
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if (JFREAD(info->temp_file, buffer_address, byte_count)
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!= (size_t) byte_count)
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ERREXIT(cinfo, JERR_TFILE_READ);
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}
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METHODDEF(void)
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write_backing_store (j_common_ptr cinfo, backing_store_ptr info,
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void FAR * buffer_address,
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long file_offset, long byte_count)
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{
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if (fseek(info->temp_file, file_offset, SEEK_SET))
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ERREXIT(cinfo, JERR_TFILE_SEEK);
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if (JFWRITE(info->temp_file, buffer_address, byte_count)
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!= (size_t) byte_count)
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ERREXIT(cinfo, JERR_TFILE_WRITE);
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}
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METHODDEF(void)
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close_backing_store (j_common_ptr cinfo, backing_store_ptr info)
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{
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fclose(info->temp_file);
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/* Since this implementation uses tmpfile() to create the file,
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* no explicit file deletion is needed.
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*/
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}
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/*
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* Initial opening of a backing-store object.
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*
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* This version uses tmpfile(), which constructs a suitable file name
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* behind the scenes. We don't have to use info->temp_name[] at all;
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* indeed, we can't even find out the actual name of the temp file.
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*/
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GLOBAL(void)
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jpeg_open_backing_store (j_common_ptr cinfo, backing_store_ptr info,
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long total_bytes_needed)
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{
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if ((info->temp_file = tmpfile()) == NULL)
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ERREXITS(cinfo, JERR_TFILE_CREATE, "");
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info->read_backing_store = read_backing_store;
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info->write_backing_store = write_backing_store;
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info->close_backing_store = close_backing_store;
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}
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/*
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* These routines take care of any system-dependent initialization and
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* cleanup required.
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*/
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GLOBAL(long)
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jpeg_mem_init (j_common_ptr cinfo)
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{
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return DEFAULT_MAX_MEM; /* default for max_memory_to_use */
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}
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GLOBAL(void)
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jpeg_mem_term (j_common_ptr cinfo)
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{
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/* no work */
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}
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