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(long) 81 jround_up (long a, long 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 GLOBAL(long) 90 jmin (long a, long b) 91 { 92 return a < b ? a : b; 93 } 94 95 96 /* On normal machines we can apply MEMCOPY() and MEMZERO() to sample arrays 97 * and coefficient-block arrays. This won't work on 80x86 because the arrays 98 * are FAR and we're assuming a small-pointer memory model. However, some 99 * DOS compilers provide far-pointer versions of memcpy() and memset() even 100 * in the small-model libraries. These will be used if USE_FMEM is defined. 101 * Otherwise, the routines below do it the hard way. (The performance cost 102 * is not all that great, because these routines aren't very heavily used.) 103 */ 104 105 #ifndef NEED_FAR_POINTERS /* normal case, same as regular macros */ 106 #define FMEMCOPY(dest,src,size) MEMCOPY(dest,src,size) 107 #define FMEMZERO(target,size) MEMZERO(target,size) 108 #else /* 80x86 case, define if we can */ 109 #ifdef USE_FMEM 110 #define FMEMCOPY(dest,src,size) _fmemcpy((void FAR *)(dest), (const void FAR *)(src), (size_t)(size)) 111 #define FMEMZERO(target,size) _fmemset((void FAR *)(target), 0, (size_t)(size)) 112 #endif 113 #endif 114 115 116 GLOBAL(void) 117 jcopy_sample_rows (JSAMPARRAY input_array, int source_row, 118 JSAMPARRAY output_array, int dest_row, 119 int num_rows, JDIMENSION num_cols) 120 /* Copy some rows of samples from one place to another. 121 * num_rows rows are copied from input_array[source_row++] 122 * to output_array[dest_row++]; these areas may overlap for duplication. 123 * The source and destination arrays must be at least as wide as num_cols. 124 */ 125 { 126 register JSAMPROW inptr, outptr; 127 #ifdef FMEMCOPY 128 register size_t count = (size_t) (num_cols * SIZEOF(JSAMPLE)); 129 #else 130 register JDIMENSION count; 131 #endif 132 register int row; 133 134 input_array += source_row; 135 output_array += dest_row; 136 137 for (row = num_rows; row > 0; row--) { 138 inptr = *input_array++; 139 outptr = *output_array++; 140 #ifdef FMEMCOPY 141 FMEMCOPY(outptr, inptr, count); 142 #else 143 for (count = num_cols; count > 0; count--) 144 *outptr++ = *inptr++; /* needn't bother with GETJSAMPLE() here */ 145 #endif 146 } 147 } 148 149 150 GLOBAL(void) 151 jcopy_block_row (JBLOCKROW input_row, JBLOCKROW output_row, 152 JDIMENSION num_blocks) 153 /* Copy a row of coefficient blocks from one place to another. */ 154 { 155 #ifdef FMEMCOPY 156 FMEMCOPY(output_row, input_row, num_blocks * (DCTSIZE2 * SIZEOF(JCOEF))); 157 #else 158 register JCOEFPTR inptr, outptr; 159 register long count; 160 161 inptr = (JCOEFPTR) input_row; 162 outptr = (JCOEFPTR) output_row; 163 for (count = (long) num_blocks * DCTSIZE2; count > 0; count--) { 164 *outptr++ = *inptr++; 165 } 166 #endif 167 } 168 169 170 GLOBAL(void) 171 jzero_far (void FAR * target, size_t bytestozero) 172 /* Zero out a chunk of FAR memory. */ 173 /* This might be sample-array data, block-array data, or alloc_large data. */ 174 { 175 #ifdef FMEMZERO 176 FMEMZERO(target, bytestozero); 177 #else 178 register char FAR * ptr = (char FAR *) target; 179 register size_t count; 180 181 for (count = bytestozero; count > 0; count--) { 182 *ptr++ = 0; 183 } 184 #endif 185 } 186
