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