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