jutils.c (5240B)
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 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 }