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annotate libs/libjpeg/jutils.c @ 33:33e9eedad390

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ah.. blunder
author John Tsiombikas <nuclear@mutantstargoat.com>
date Fri, 09 Sep 2011 00:03:37 +0300
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nuclear@26 1 /*
nuclear@26 2 * jutils.c
nuclear@26 3 *
nuclear@26 4 * Copyright (C) 1991-1996, Thomas G. Lane.
nuclear@26 5 * This file is part of the Independent JPEG Group's software.
nuclear@26 6 * For conditions of distribution and use, see the accompanying README file.
nuclear@26 7 *
nuclear@26 8 * This file contains tables and miscellaneous utility routines needed
nuclear@26 9 * for both compression and decompression.
nuclear@26 10 * Note we prefix all global names with "j" to minimize conflicts with
nuclear@26 11 * a surrounding application.
nuclear@26 12 */
nuclear@26 13
nuclear@26 14 #define JPEG_INTERNALS
nuclear@26 15 #include "jinclude.h"
nuclear@26 16 #include "jpeglib.h"
nuclear@26 17
nuclear@26 18
nuclear@26 19 /*
nuclear@26 20 * jpeg_zigzag_order[i] is the zigzag-order position of the i'th element
nuclear@26 21 * of a DCT block read in natural order (left to right, top to bottom).
nuclear@26 22 */
nuclear@26 23
nuclear@26 24 #if 0 /* This table is not actually needed in v6a */
nuclear@26 25
nuclear@26 26 const int jpeg_zigzag_order[DCTSIZE2] = {
nuclear@26 27 0, 1, 5, 6, 14, 15, 27, 28,
nuclear@26 28 2, 4, 7, 13, 16, 26, 29, 42,
nuclear@26 29 3, 8, 12, 17, 25, 30, 41, 43,
nuclear@26 30 9, 11, 18, 24, 31, 40, 44, 53,
nuclear@26 31 10, 19, 23, 32, 39, 45, 52, 54,
nuclear@26 32 20, 22, 33, 38, 46, 51, 55, 60,
nuclear@26 33 21, 34, 37, 47, 50, 56, 59, 61,
nuclear@26 34 35, 36, 48, 49, 57, 58, 62, 63
nuclear@26 35 };
nuclear@26 36
nuclear@26 37 #endif
nuclear@26 38
nuclear@26 39 /*
nuclear@26 40 * jpeg_natural_order[i] is the natural-order position of the i'th element
nuclear@26 41 * of zigzag order.
nuclear@26 42 *
nuclear@26 43 * When reading corrupted data, the Huffman decoders could attempt
nuclear@26 44 * to reference an entry beyond the end of this array (if the decoded
nuclear@26 45 * zero run length reaches past the end of the block). To prevent
nuclear@26 46 * wild stores without adding an inner-loop test, we put some extra
nuclear@26 47 * "63"s after the real entries. This will cause the extra coefficient
nuclear@26 48 * to be stored in location 63 of the block, not somewhere random.
nuclear@26 49 * The worst case would be a run-length of 15, which means we need 16
nuclear@26 50 * fake entries.
nuclear@26 51 */
nuclear@26 52
nuclear@26 53 const int jpeg_natural_order[DCTSIZE2+16] = {
nuclear@26 54 0, 1, 8, 16, 9, 2, 3, 10,
nuclear@26 55 17, 24, 32, 25, 18, 11, 4, 5,
nuclear@26 56 12, 19, 26, 33, 40, 48, 41, 34,
nuclear@26 57 27, 20, 13, 6, 7, 14, 21, 28,
nuclear@26 58 35, 42, 49, 56, 57, 50, 43, 36,
nuclear@26 59 29, 22, 15, 23, 30, 37, 44, 51,
nuclear@26 60 58, 59, 52, 45, 38, 31, 39, 46,
nuclear@26 61 53, 60, 61, 54, 47, 55, 62, 63,
nuclear@26 62 63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */
nuclear@26 63 63, 63, 63, 63, 63, 63, 63, 63
nuclear@26 64 };
nuclear@26 65
nuclear@26 66
nuclear@26 67 /*
nuclear@26 68 * Arithmetic utilities
nuclear@26 69 */
nuclear@26 70
nuclear@26 71 GLOBAL(long)
nuclear@26 72 jdiv_round_up (long a, long b)
nuclear@26 73 /* Compute a/b rounded up to next integer, ie, ceil(a/b) */
nuclear@26 74 /* Assumes a >= 0, b > 0 */
nuclear@26 75 {
nuclear@26 76 return (a + b - 1L) / b;
nuclear@26 77 }
nuclear@26 78
nuclear@26 79
nuclear@26 80 GLOBAL(long)
nuclear@26 81 jround_up (long a, long b)
nuclear@26 82 /* Compute a rounded up to next multiple of b, ie, ceil(a/b)*b */
nuclear@26 83 /* Assumes a >= 0, b > 0 */
nuclear@26 84 {
nuclear@26 85 a += b - 1L;
nuclear@26 86 return a - (a % b);
nuclear@26 87 }
nuclear@26 88
nuclear@26 89
nuclear@26 90 /* On normal machines we can apply MEMCOPY() and MEMZERO() to sample arrays
nuclear@26 91 * and coefficient-block arrays. This won't work on 80x86 because the arrays
nuclear@26 92 * are FAR and we're assuming a small-pointer memory model. However, some
nuclear@26 93 * DOS compilers provide far-pointer versions of memcpy() and memset() even
nuclear@26 94 * in the small-model libraries. These will be used if USE_FMEM is defined.
nuclear@26 95 * Otherwise, the routines below do it the hard way. (The performance cost
nuclear@26 96 * is not all that great, because these routines aren't very heavily used.)
nuclear@26 97 */
nuclear@26 98
nuclear@26 99 #ifndef NEED_FAR_POINTERS /* normal case, same as regular macros */
nuclear@26 100 #define FMEMCOPY(dest,src,size) MEMCOPY(dest,src,size)
nuclear@26 101 #define FMEMZERO(target,size) MEMZERO(target,size)
nuclear@26 102 #else /* 80x86 case, define if we can */
nuclear@26 103 #ifdef USE_FMEM
nuclear@26 104 #define FMEMCOPY(dest,src,size) _fmemcpy((void FAR *)(dest), (const void FAR *)(src), (size_t)(size))
nuclear@26 105 #define FMEMZERO(target,size) _fmemset((void FAR *)(target), 0, (size_t)(size))
nuclear@26 106 #endif
nuclear@26 107 #endif
nuclear@26 108
nuclear@26 109
nuclear@26 110 GLOBAL(void)
nuclear@26 111 jcopy_sample_rows (JSAMPARRAY input_array, int source_row,
nuclear@26 112 JSAMPARRAY output_array, int dest_row,
nuclear@26 113 int num_rows, JDIMENSION num_cols)
nuclear@26 114 /* Copy some rows of samples from one place to another.
nuclear@26 115 * num_rows rows are copied from input_array[source_row++]
nuclear@26 116 * to output_array[dest_row++]; these areas may overlap for duplication.
nuclear@26 117 * The source and destination arrays must be at least as wide as num_cols.
nuclear@26 118 */
nuclear@26 119 {
nuclear@26 120 register JSAMPROW inptr, outptr;
nuclear@26 121 #ifdef FMEMCOPY
nuclear@26 122 register size_t count = (size_t) (num_cols * SIZEOF(JSAMPLE));
nuclear@26 123 #else
nuclear@26 124 register JDIMENSION count;
nuclear@26 125 #endif
nuclear@26 126 register int row;
nuclear@26 127
nuclear@26 128 input_array += source_row;
nuclear@26 129 output_array += dest_row;
nuclear@26 130
nuclear@26 131 for (row = num_rows; row > 0; row--) {
nuclear@26 132 inptr = *input_array++;
nuclear@26 133 outptr = *output_array++;
nuclear@26 134 #ifdef FMEMCOPY
nuclear@26 135 FMEMCOPY(outptr, inptr, count);
nuclear@26 136 #else
nuclear@26 137 for (count = num_cols; count > 0; count--)
nuclear@26 138 *outptr++ = *inptr++; /* needn't bother with GETJSAMPLE() here */
nuclear@26 139 #endif
nuclear@26 140 }
nuclear@26 141 }
nuclear@26 142
nuclear@26 143
nuclear@26 144 GLOBAL(void)
nuclear@26 145 jcopy_block_row (JBLOCKROW input_row, JBLOCKROW output_row,
nuclear@26 146 JDIMENSION num_blocks)
nuclear@26 147 /* Copy a row of coefficient blocks from one place to another. */
nuclear@26 148 {
nuclear@26 149 #ifdef FMEMCOPY
nuclear@26 150 FMEMCOPY(output_row, input_row, num_blocks * (DCTSIZE2 * SIZEOF(JCOEF)));
nuclear@26 151 #else
nuclear@26 152 register JCOEFPTR inptr, outptr;
nuclear@26 153 register long count;
nuclear@26 154
nuclear@26 155 inptr = (JCOEFPTR) input_row;
nuclear@26 156 outptr = (JCOEFPTR) output_row;
nuclear@26 157 for (count = (long) num_blocks * DCTSIZE2; count > 0; count--) {
nuclear@26 158 *outptr++ = *inptr++;
nuclear@26 159 }
nuclear@26 160 #endif
nuclear@26 161 }
nuclear@26 162
nuclear@26 163
nuclear@26 164 GLOBAL(void)
nuclear@26 165 jzero_far (void FAR * target, size_t bytestozero)
nuclear@26 166 /* Zero out a chunk of FAR memory. */
nuclear@26 167 /* This might be sample-array data, block-array data, or alloc_large data. */
nuclear@26 168 {
nuclear@26 169 #ifdef FMEMZERO
nuclear@26 170 FMEMZERO(target, bytestozero);
nuclear@26 171 #else
nuclear@26 172 register char FAR * ptr = (char FAR *) target;
nuclear@26 173 register size_t count;
nuclear@26 174
nuclear@26 175 for (count = bytestozero; count > 0; count--) {
nuclear@26 176 *ptr++ = 0;
nuclear@26 177 }
nuclear@26 178 #endif
nuclear@26 179 }