1/* 2 * reserved comment block 3 * DO NOT REMOVE OR ALTER! 4 */ 5/* 6 * jutils.c 7 * 8 * Copyright (C) 1991-1996, Thomas G. Lane. 9 * This file is part of the Independent JPEG Group's software. 10 * For conditions of distribution and use, see the accompanying README file. 11 * 12 * This file contains tables and miscellaneous utility routines needed 13 * for both compression and decompression. 14 * Note we prefix all global names with "j" to minimize conflicts with 15 * a surrounding application. 16 */ 17 18#define JPEG_INTERNALS 19#include "jinclude.h" 20#include "jpeglib.h" 21 22 23/* 24 * jpeg_zigzag_order[i] is the zigzag-order position of the i'th element 25 * of a DCT block read in natural order (left to right, top to bottom). 26 */ 27 28#if 0 /* This table is not actually needed in v6a */ 29 30const int jpeg_zigzag_order[DCTSIZE2] = { 31 0, 1, 5, 6, 14, 15, 27, 28, 32 2, 4, 7, 13, 16, 26, 29, 42, 33 3, 8, 12, 17, 25, 30, 41, 43, 34 9, 11, 18, 24, 31, 40, 44, 53, 35 10, 19, 23, 32, 39, 45, 52, 54, 36 20, 22, 33, 38, 46, 51, 55, 60, 37 21, 34, 37, 47, 50, 56, 59, 61, 38 35, 36, 48, 49, 57, 58, 62, 63 39}; 40 41#endif 42 43/* 44 * jpeg_natural_order[i] is the natural-order position of the i'th element 45 * of zigzag order. 46 * 47 * When reading corrupted data, the Huffman decoders could attempt 48 * to reference an entry beyond the end of this array (if the decoded 49 * zero run length reaches past the end of the block). To prevent 50 * wild stores without adding an inner-loop test, we put some extra 51 * "63"s after the real entries. This will cause the extra coefficient 52 * to be stored in location 63 of the block, not somewhere random. 53 * The worst case would be a run-length of 15, which means we need 16 54 * fake entries. 55 */ 56 57const int jpeg_natural_order[DCTSIZE2+16] = { 58 0, 1, 8, 16, 9, 2, 3, 10, 59 17, 24, 32, 25, 18, 11, 4, 5, 60 12, 19, 26, 33, 40, 48, 41, 34, 61 27, 20, 13, 6, 7, 14, 21, 28, 62 35, 42, 49, 56, 57, 50, 43, 36, 63 29, 22, 15, 23, 30, 37, 44, 51, 64 58, 59, 52, 45, 38, 31, 39, 46, 65 53, 60, 61, 54, 47, 55, 62, 63, 66 63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */ 67 63, 63, 63, 63, 63, 63, 63, 63 68}; 69 70 71/* 72 * Arithmetic utilities 73 */ 74 75GLOBAL(long) 76jdiv_round_up (long a, long b) 77/* Compute a/b rounded up to next integer, ie, ceil(a/b) */ 78/* Assumes a >= 0, b > 0 */ 79{ 80 return (a + b - 1L) / b; 81} 82 83 84GLOBAL(long) 85jround_up (long a, long b) 86/* Compute a rounded up to next multiple of b, ie, ceil(a/b)*b */ 87/* Assumes a >= 0, b > 0 */ 88{ 89 a += b - 1L; 90 return a - (a % b); 91} 92 93 94/* On normal machines we can apply MEMCOPY() and MEMZERO() to sample arrays 95 * and coefficient-block arrays. This won't work on 80x86 because the arrays 96 * are FAR and we're assuming a small-pointer memory model. However, some 97 * DOS compilers provide far-pointer versions of memcpy() and memset() even 98 * in the small-model libraries. These will be used if USE_FMEM is defined. 99 * Otherwise, the routines below do it the hard way. (The performance cost 100 * is not all that great, because these routines aren't very heavily used.) 101 */ 102 103#ifndef NEED_FAR_POINTERS /* normal case, same as regular macros */ 104#define FMEMCOPY(dest,src,size) MEMCOPY(dest,src,size) 105#define FMEMZERO(target,size) MEMZERO(target,size) 106#else /* 80x86 case, define if we can */ 107#ifdef USE_FMEM 108#define FMEMCOPY(dest,src,size) _fmemcpy((void FAR *)(dest), (const void FAR *)(src), (size_t)(size)) 109#define FMEMZERO(target,size) _fmemset((void FAR *)(target), 0, (size_t)(size)) 110#endif 111#endif 112 113 114GLOBAL(void) 115jcopy_sample_rows (JSAMPARRAY input_array, int source_row, 116 JSAMPARRAY output_array, int dest_row, 117 int num_rows, JDIMENSION num_cols) 118/* Copy some rows of samples from one place to another. 119 * num_rows rows are copied from input_array[source_row++] 120 * to output_array[dest_row++]; these areas may overlap for duplication. 121 * The source and destination arrays must be at least as wide as num_cols. 122 */ 123{ 124 register JSAMPROW inptr, outptr; 125#ifdef FMEMCOPY 126 register size_t count = (size_t) (num_cols * SIZEOF(JSAMPLE)); 127#else 128 register JDIMENSION count; 129#endif 130 register int row; 131 132 input_array += source_row; 133 output_array += dest_row; 134 135 for (row = num_rows; row > 0; row--) { 136 inptr = *input_array++; 137 outptr = *output_array++; 138#ifdef FMEMCOPY 139 FMEMCOPY(outptr, inptr, count); 140#else 141 for (count = num_cols; count > 0; count--) 142 *outptr++ = *inptr++; /* needn't bother with GETJSAMPLE() here */ 143#endif 144 } 145} 146 147 148GLOBAL(void) 149jcopy_block_row (JBLOCKROW input_row, JBLOCKROW output_row, 150 JDIMENSION num_blocks) 151/* Copy a row of coefficient blocks from one place to another. */ 152{ 153#ifdef FMEMCOPY 154 FMEMCOPY(output_row, input_row, num_blocks * (DCTSIZE2 * SIZEOF(JCOEF))); 155#else 156 register JCOEFPTR inptr, outptr; 157 register long count; 158 159 inptr = (JCOEFPTR) input_row; 160 outptr = (JCOEFPTR) output_row; 161 for (count = (long) num_blocks * DCTSIZE2; count > 0; count--) { 162 *outptr++ = *inptr++; 163 } 164#endif 165} 166 167 168GLOBAL(void) 169jzero_far (void FAR * target, size_t bytestozero) 170/* Zero out a chunk of FAR memory. */ 171/* This might be sample-array data, block-array data, or alloc_large data. */ 172{ 173#ifdef FMEMZERO 174 FMEMZERO(target, bytestozero); 175#else 176 register char FAR * ptr = (char FAR *) target; 177 register size_t count; 178 179 for (count = bytestozero; count > 0; count--) { 180 *ptr++ = 0; 181 } 182#endif 183} 184