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