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annotate libs/libjpeg/jdatadst.c @ 13:ea928c313344

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author John Tsiombikas <nuclear@member.fsf.org>
date Mon, 28 Sep 2015 19:04:50 +0300
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nuclear@2 1 /*
nuclear@2 2 * jdatadst.c
nuclear@2 3 *
nuclear@2 4 * Copyright (C) 1994-1996, Thomas G. Lane.
nuclear@2 5 * This file is part of the Independent JPEG Group's software.
nuclear@2 6 * For conditions of distribution and use, see the accompanying README file.
nuclear@2 7 *
nuclear@2 8 * This file contains compression data destination routines for the case of
nuclear@2 9 * emitting JPEG data to a file (or any stdio stream). While these routines
nuclear@2 10 * are sufficient for most applications, some will want to use a different
nuclear@2 11 * destination manager.
nuclear@2 12 * IMPORTANT: we assume that fwrite() will correctly transcribe an array of
nuclear@2 13 * JOCTETs into 8-bit-wide elements on external storage. If char is wider
nuclear@2 14 * than 8 bits on your machine, you may need to do some tweaking.
nuclear@2 15 */
nuclear@2 16
nuclear@2 17 /* this is not a core library module, so it doesn't define JPEG_INTERNALS */
nuclear@2 18 #include "jinclude.h"
nuclear@2 19 #include "jpeglib.h"
nuclear@2 20 #include "jerror.h"
nuclear@2 21
nuclear@2 22
nuclear@2 23 /* Expanded data destination object for stdio output */
nuclear@2 24
nuclear@2 25 typedef struct {
nuclear@2 26 struct jpeg_destination_mgr pub; /* public fields */
nuclear@2 27
nuclear@2 28 FILE * outfile; /* target stream */
nuclear@2 29 JOCTET * buffer; /* start of buffer */
nuclear@2 30 } my_destination_mgr;
nuclear@2 31
nuclear@2 32 typedef my_destination_mgr * my_dest_ptr;
nuclear@2 33
nuclear@2 34 #define OUTPUT_BUF_SIZE 4096 /* choose an efficiently fwrite'able size */
nuclear@2 35
nuclear@2 36
nuclear@2 37 /*
nuclear@2 38 * Initialize destination --- called by jpeg_start_compress
nuclear@2 39 * before any data is actually written.
nuclear@2 40 */
nuclear@2 41
nuclear@2 42 METHODDEF(void)
nuclear@2 43 init_destination (j_compress_ptr cinfo)
nuclear@2 44 {
nuclear@2 45 my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
nuclear@2 46
nuclear@2 47 /* Allocate the output buffer --- it will be released when done with image */
nuclear@2 48 dest->buffer = (JOCTET *)
nuclear@2 49 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@2 50 OUTPUT_BUF_SIZE * SIZEOF(JOCTET));
nuclear@2 51
nuclear@2 52 dest->pub.next_output_byte = dest->buffer;
nuclear@2 53 dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;
nuclear@2 54 }
nuclear@2 55
nuclear@2 56
nuclear@2 57 /*
nuclear@2 58 * Empty the output buffer --- called whenever buffer fills up.
nuclear@2 59 *
nuclear@2 60 * In typical applications, this should write the entire output buffer
nuclear@2 61 * (ignoring the current state of next_output_byte & free_in_buffer),
nuclear@2 62 * reset the pointer & count to the start of the buffer, and return TRUE
nuclear@2 63 * indicating that the buffer has been dumped.
nuclear@2 64 *
nuclear@2 65 * In applications that need to be able to suspend compression due to output
nuclear@2 66 * overrun, a FALSE return indicates that the buffer cannot be emptied now.
nuclear@2 67 * In this situation, the compressor will return to its caller (possibly with
nuclear@2 68 * an indication that it has not accepted all the supplied scanlines). The
nuclear@2 69 * application should resume compression after it has made more room in the
nuclear@2 70 * output buffer. Note that there are substantial restrictions on the use of
nuclear@2 71 * suspension --- see the documentation.
nuclear@2 72 *
nuclear@2 73 * When suspending, the compressor will back up to a convenient restart point
nuclear@2 74 * (typically the start of the current MCU). next_output_byte & free_in_buffer
nuclear@2 75 * indicate where the restart point will be if the current call returns FALSE.
nuclear@2 76 * Data beyond this point will be regenerated after resumption, so do not
nuclear@2 77 * write it out when emptying the buffer externally.
nuclear@2 78 */
nuclear@2 79
nuclear@2 80 METHODDEF(boolean)
nuclear@2 81 empty_output_buffer (j_compress_ptr cinfo)
nuclear@2 82 {
nuclear@2 83 my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
nuclear@2 84
nuclear@2 85 if (JFWRITE(dest->outfile, dest->buffer, OUTPUT_BUF_SIZE) !=
nuclear@2 86 (size_t) OUTPUT_BUF_SIZE)
nuclear@2 87 ERREXIT(cinfo, JERR_FILE_WRITE);
nuclear@2 88
nuclear@2 89 dest->pub.next_output_byte = dest->buffer;
nuclear@2 90 dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;
nuclear@2 91
nuclear@2 92 return TRUE;
nuclear@2 93 }
nuclear@2 94
nuclear@2 95
nuclear@2 96 /*
nuclear@2 97 * Terminate destination --- called by jpeg_finish_compress
nuclear@2 98 * after all data has been written. Usually needs to flush buffer.
nuclear@2 99 *
nuclear@2 100 * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
nuclear@2 101 * application must deal with any cleanup that should happen even
nuclear@2 102 * for error exit.
nuclear@2 103 */
nuclear@2 104
nuclear@2 105 METHODDEF(void)
nuclear@2 106 term_destination (j_compress_ptr cinfo)
nuclear@2 107 {
nuclear@2 108 my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
nuclear@2 109 size_t datacount = OUTPUT_BUF_SIZE - dest->pub.free_in_buffer;
nuclear@2 110
nuclear@2 111 /* Write any data remaining in the buffer */
nuclear@2 112 if (datacount > 0) {
nuclear@2 113 if (JFWRITE(dest->outfile, dest->buffer, datacount) != datacount)
nuclear@2 114 ERREXIT(cinfo, JERR_FILE_WRITE);
nuclear@2 115 }
nuclear@2 116 fflush(dest->outfile);
nuclear@2 117 /* Make sure we wrote the output file OK */
nuclear@2 118 if (ferror(dest->outfile))
nuclear@2 119 ERREXIT(cinfo, JERR_FILE_WRITE);
nuclear@2 120 }
nuclear@2 121
nuclear@2 122
nuclear@2 123 /*
nuclear@2 124 * Prepare for output to a stdio stream.
nuclear@2 125 * The caller must have already opened the stream, and is responsible
nuclear@2 126 * for closing it after finishing compression.
nuclear@2 127 */
nuclear@2 128
nuclear@2 129 GLOBAL(void)
nuclear@2 130 jpeg_stdio_dest (j_compress_ptr cinfo, FILE * outfile)
nuclear@2 131 {
nuclear@2 132 my_dest_ptr dest;
nuclear@2 133
nuclear@2 134 /* The destination object is made permanent so that multiple JPEG images
nuclear@2 135 * can be written to the same file without re-executing jpeg_stdio_dest.
nuclear@2 136 * This makes it dangerous to use this manager and a different destination
nuclear@2 137 * manager serially with the same JPEG object, because their private object
nuclear@2 138 * sizes may be different. Caveat programmer.
nuclear@2 139 */
nuclear@2 140 if (cinfo->dest == NULL) { /* first time for this JPEG object? */
nuclear@2 141 cinfo->dest = (struct jpeg_destination_mgr *)
nuclear@2 142 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
nuclear@2 143 SIZEOF(my_destination_mgr));
nuclear@2 144 }
nuclear@2 145
nuclear@2 146 dest = (my_dest_ptr) cinfo->dest;
nuclear@2 147 dest->pub.init_destination = init_destination;
nuclear@2 148 dest->pub.empty_output_buffer = empty_output_buffer;
nuclear@2 149 dest->pub.term_destination = term_destination;
nuclear@2 150 dest->outfile = outfile;
nuclear@2 151 }