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)
jdiv_round_up(long a,long b)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)
jround_up(long a,long b)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)
jcopy_sample_rows(JSAMPARRAY input_array,int source_row,JSAMPARRAY output_array,int dest_row,int num_rows,JDIMENSION num_cols)94 jcopy_sample_rows(JSAMPARRAY input_array, int source_row,
95 JSAMPARRAY output_array, int dest_row, int num_rows,
96 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)
jcopy_block_row(JBLOCKROW input_row,JBLOCKROW output_row,JDIMENSION num_blocks)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)
jzero_far(void * target,size_t bytestozero)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