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.ijg 9 * file. 10 * 11 * This file contains tables and miscellaneous utility routines needed 12 * for both compression and decompression. 13 * Note we prefix all global names with "j" to minimize conflicts with 14 * a surrounding application. 15 */ 16 17 #define JPEG_INTERNALS 18 #include "jinclude.h" 19 #include "jpeglib.h" 20 21 22 /* 23 * jpeg_zigzag_order[i] is the zigzag-order position of the i'th element 24 * of a DCT block read in natural order (left to right, top to bottom). 25 */ 26 27 #if 0 /* This table is not actually needed in v6a */ 28 29 const int jpeg_zigzag_order[DCTSIZE2] = { 30 0, 1, 5, 6, 14, 15, 27, 28, 31 2, 4, 7, 13, 16, 26, 29, 42, 32 3, 8, 12, 17, 25, 30, 41, 43, 33 9, 11, 18, 24, 31, 40, 44, 53, 34 10, 19, 23, 32, 39, 45, 52, 54, 35 20, 22, 33, 38, 46, 51, 55, 60, 36 21, 34, 37, 47, 50, 56, 59, 61, 37 35, 36, 48, 49, 57, 58, 62, 63 38 }; 39 40 #endif 41 42 /* 43 * jpeg_natural_order[i] is the natural-order position of the i'th element 44 * of zigzag order. 45 * 46 * When reading corrupted data, the Huffman decoders could attempt 47 * to reference an entry beyond the end of this array (if the decoded 48 * zero run length reaches past the end of the block). To prevent 49 * wild stores without adding an inner-loop test, we put some extra 50 * "63"s after the real entries. This will cause the extra coefficient 51 * to be stored in location 63 of the block, not somewhere random. 52 * The worst case would be a run-length of 15, which means we need 16 53 * fake entries. 54 */ 55 56 const int jpeg_natural_order[DCTSIZE2+16] = { 57 0, 1, 8, 16, 9, 2, 3, 10, 58 17, 24, 32, 25, 18, 11, 4, 5, 59 12, 19, 26, 33, 40, 48, 41, 34, 60 27, 20, 13, 6, 7, 14, 21, 28, 61 35, 42, 49, 56, 57, 50, 43, 36, 62 29, 22, 15, 23, 30, 37, 44, 51, 63 58, 59, 52, 45, 38, 31, 39, 46, 64 53, 60, 61, 54, 47, 55, 62, 63, 65 63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */ 66 63, 63, 63, 63, 63, 63, 63, 63 67 }; 68 69 70 /* 71 * Arithmetic utilities 72 */ 73 74 GLOBAL(long) 75 jdiv_round_up (long a, long b) 76 /* Compute a/b rounded up to next integer, ie, ceil(a/b) */ 77 /* Assumes a >= 0, b > 0 */ 78 { 79 return (a + b - 1L) / b; 80 } 81 82 83 GLOBAL(long) 84 jround_up (long a, long b) 85 /* Compute a rounded up to next multiple of b, ie, ceil(a/b)*b */ 86 /* Assumes a >= 0, b > 0 */ 87 { 88 a += b - 1L; 89 return a - (a % b); 90 } 91 92 93 GLOBAL(void) 94 jcopy_sample_rows (JSAMPARRAY input_array, int source_row, 95 JSAMPARRAY output_array, int dest_row, 96 int num_rows, JDIMENSION num_cols) 97 /* Copy some rows of samples from one place to another. 98 * num_rows rows are copied from input_array[source_row++] 99 * to output_array[dest_row++]; these areas may overlap for duplication. 100 * The source and destination arrays must be at least as wide as num_cols. 101 */ 102 { 103 register JSAMPROW inptr, outptr; 104 register size_t count = (size_t) (num_cols * sizeof(JSAMPLE)); 105 register int row; 106 107 input_array += source_row; 108 output_array += dest_row; 109 110 for (row = num_rows; row > 0; row--) { 111 inptr = *input_array++; 112 outptr = *output_array++; 113 MEMCOPY(outptr, inptr, count); 114 } 115 } 116 117 118 GLOBAL(void) 119 jcopy_block_row (JBLOCKROW input_row, JBLOCKROW output_row, 120 JDIMENSION num_blocks) 121 /* Copy a row of coefficient blocks from one place to another. */ 122 { 123 MEMCOPY(output_row, input_row, num_blocks * (DCTSIZE2 * sizeof(JCOEF))); 124 } 125 126 127 GLOBAL(void) 128 jzero_far (void *target, size_t bytestozero) 129 /* Zero out a chunk of memory. */ 130 /* This might be sample-array data, block-array data, or alloc_large data. */ 131 { 132 MEMZERO(target, bytestozero); 133 } 134
