1 /* 2 * jutils.c 3 * 4 * This file was part of the Independent JPEG Group's software: 5 * Copyright (C) 1991-1996, Thomas G. Lane. 6 * It was modified by The libjpeg-turbo Project to include only code 7 * relevant to libjpeg-turbo. 8 * For conditions of distribution and use, see the accompanying README file. 9 * 10 * This file contains tables and miscellaneous utility routines needed 11 * for both compression and decompression. 12 * Note we prefix all global names with "j" to minimize conflicts with 13 * a surrounding application. 14 */ 15 16 #define JPEG_INTERNALS 17 #include "jinclude.h" 18 #include "jpeglib.h" 19 20 21 /* 22 * jpeg_zigzag_order[i] is the zigzag-order position of the i'th element 23 * of a DCT block read in natural order (left to right, top to bottom). 24 */ 25 26 #if 0 /* This table is not actually needed in v6a */ 27 28 const int jpeg_zigzag_order[DCTSIZE2] = { 29 0, 1, 5, 6, 14, 15, 27, 28, 30 2, 4, 7, 13, 16, 26, 29, 42, 31 3, 8, 12, 17, 25, 30, 41, 43, 32 9, 11, 18, 24, 31, 40, 44, 53, 33 10, 19, 23, 32, 39, 45, 52, 54, 34 20, 22, 33, 38, 46, 51, 55, 60, 35 21, 34, 37, 47, 50, 56, 59, 61, 36 35, 36, 48, 49, 57, 58, 62, 63 37 }; 38 39 #endif 40 41 /* 42 * jpeg_natural_order[i] is the natural-order position of the i'th element 43 * of zigzag order. 44 * 45 * When reading corrupted data, the Huffman decoders could attempt 46 * to reference an entry beyond the end of this array (if the decoded 47 * zero run length reaches past the end of the block). To prevent 48 * wild stores without adding an inner-loop test, we put some extra 49 * "63"s after the real entries. This will cause the extra coefficient 50 * to be stored in location 63 of the block, not somewhere random. 51 * The worst case would be a run-length of 15, which means we need 16 52 * fake entries. 53 */ 54 55 const int jpeg_natural_order[DCTSIZE2+16] = { 56 0, 1, 8, 16, 9, 2, 3, 10, 57 17, 24, 32, 25, 18, 11, 4, 5, 58 12, 19, 26, 33, 40, 48, 41, 34, 59 27, 20, 13, 6, 7, 14, 21, 28, 60 35, 42, 49, 56, 57, 50, 43, 36, 61 29, 22, 15, 23, 30, 37, 44, 51, 62 58, 59, 52, 45, 38, 31, 39, 46, 63 53, 60, 61, 54, 47, 55, 62, 63, 64 63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */ 65 63, 63, 63, 63, 63, 63, 63, 63 66 }; 67 68 69 /* 70 * Arithmetic utilities 71 */ 72 73 GLOBAL(long) 74 jdiv_round_up (long a, long b) 75 /* Compute a/b rounded up to next integer, ie, ceil(a/b) */ 76 /* Assumes a >= 0, b > 0 */ 77 { 78 return (a + b - 1L) / b; 79 } 80 81 82 GLOBAL(long) 83 jround_up (long a, long b) 84 /* Compute a rounded up to next multiple of b, ie, ceil(a/b)*b */ 85 /* Assumes a >= 0, b > 0 */ 86 { 87 a += b - 1L; 88 return a - (a % b); 89 } 90 91 92 GLOBAL(void) 93 jcopy_sample_rows (JSAMPARRAY input_array, int source_row, 94 JSAMPARRAY output_array, int dest_row, 95 int num_rows, JDIMENSION num_cols) 96 /* Copy some rows of samples from one place to another. 97 * num_rows rows are copied from input_array[source_row++] 98 * to output_array[dest_row++]; these areas may overlap for duplication. 99 * The source and destination arrays must be at least as wide as num_cols. 100 */ 101 { 102 register JSAMPROW inptr, outptr; 103 register size_t count = (size_t) (num_cols * sizeof(JSAMPLE)); 104 register int row; 105 106 input_array += source_row; 107 output_array += dest_row; 108 109 for (row = num_rows; row > 0; row--) { 110 inptr = *input_array++; 111 outptr = *output_array++; 112 MEMCOPY(outptr, inptr, count); 113 } 114 } 115 116 117 GLOBAL(void) 118 jcopy_block_row (JBLOCKROW input_row, JBLOCKROW output_row, 119 JDIMENSION num_blocks) 120 /* Copy a row of coefficient blocks from one place to another. */ 121 { 122 MEMCOPY(output_row, input_row, num_blocks * (DCTSIZE2 * sizeof(JCOEF))); 123 } 124 125 126 GLOBAL(void) 127 jzero_far (void * target, size_t bytestozero) 128 /* Zero out a chunk of memory. */ 129 /* This might be sample-array data, block-array data, or alloc_large data. */ 130 { 131 MEMZERO(target, bytestozero); 132 } 133
