1 | /* |
2 | * jutils.c |
3 | * |
4 | * Copyright (C) 1991-1996, Thomas G. Lane. |
5 | * Modified 2009-2011 by Guido Vollbeding. |
6 | * This file is part of the Independent JPEG Group's software. |
7 | * For conditions of distribution and use, see the accompanying README file. |
8 | * |
9 | * This file contains tables and miscellaneous utility routines needed |
10 | * for both compression and decompression. |
11 | * Note we prefix all global names with "j" to minimize conflicts with |
12 | * a surrounding application. |
13 | */ |
14 | |
15 | #define JPEG_INTERNALS |
16 | #include "jinclude.h" |
17 | #include "jpeglib.h" |
18 | |
19 | |
20 | /* |
21 | * jpeg_zigzag_order[i] is the zigzag-order position of the i'th element |
22 | * of a DCT block read in natural order (left to right, top to bottom). |
23 | */ |
24 | |
25 | #if 0 /* This table is not actually needed in v6a */ |
26 | |
27 | const int jpeg_zigzag_order[DCTSIZE2] = { |
28 | 0, 1, 5, 6, 14, 15, 27, 28, |
29 | 2, 4, 7, 13, 16, 26, 29, 42, |
30 | 3, 8, 12, 17, 25, 30, 41, 43, |
31 | 9, 11, 18, 24, 31, 40, 44, 53, |
32 | 10, 19, 23, 32, 39, 45, 52, 54, |
33 | 20, 22, 33, 38, 46, 51, 55, 60, |
34 | 21, 34, 37, 47, 50, 56, 59, 61, |
35 | 35, 36, 48, 49, 57, 58, 62, 63 |
36 | }; |
37 | |
38 | #endif |
39 | |
40 | /* |
41 | * jpeg_natural_order[i] is the natural-order position of the i'th element |
42 | * of zigzag order. |
43 | * |
44 | * When reading corrupted data, the Huffman decoders could attempt |
45 | * to reference an entry beyond the end of this array (if the decoded |
46 | * zero run length reaches past the end of the block). To prevent |
47 | * wild stores without adding an inner-loop test, we put some extra |
48 | * "63"s after the real entries. This will cause the extra coefficient |
49 | * to be stored in location 63 of the block, not somewhere random. |
50 | * The worst case would be a run-length of 15, which means we need 16 |
51 | * fake entries. |
52 | */ |
53 | |
54 | const int jpeg_natural_order[DCTSIZE2+16] = { |
55 | 0, 1, 8, 16, 9, 2, 3, 10, |
56 | 17, 24, 32, 25, 18, 11, 4, 5, |
57 | 12, 19, 26, 33, 40, 48, 41, 34, |
58 | 27, 20, 13, 6, 7, 14, 21, 28, |
59 | 35, 42, 49, 56, 57, 50, 43, 36, |
60 | 29, 22, 15, 23, 30, 37, 44, 51, |
61 | 58, 59, 52, 45, 38, 31, 39, 46, |
62 | 53, 60, 61, 54, 47, 55, 62, 63, |
63 | 63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */ |
64 | 63, 63, 63, 63, 63, 63, 63, 63 |
65 | }; |
66 | |
67 | const int jpeg_natural_order7[7*7+16] = { |
68 | 0, 1, 8, 16, 9, 2, 3, 10, |
69 | 17, 24, 32, 25, 18, 11, 4, 5, |
70 | 12, 19, 26, 33, 40, 48, 41, 34, |
71 | 27, 20, 13, 6, 14, 21, 28, 35, |
72 | 42, 49, 50, 43, 36, 29, 22, 30, |
73 | 37, 44, 51, 52, 45, 38, 46, 53, |
74 | 54, |
75 | 63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */ |
76 | 63, 63, 63, 63, 63, 63, 63, 63 |
77 | }; |
78 | |
79 | const int jpeg_natural_order6[6*6+16] = { |
80 | 0, 1, 8, 16, 9, 2, 3, 10, |
81 | 17, 24, 32, 25, 18, 11, 4, 5, |
82 | 12, 19, 26, 33, 40, 41, 34, 27, |
83 | 20, 13, 21, 28, 35, 42, 43, 36, |
84 | 29, 37, 44, 45, |
85 | 63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */ |
86 | 63, 63, 63, 63, 63, 63, 63, 63 |
87 | }; |
88 | |
89 | const int jpeg_natural_order5[5*5+16] = { |
90 | 0, 1, 8, 16, 9, 2, 3, 10, |
91 | 17, 24, 32, 25, 18, 11, 4, 12, |
92 | 19, 26, 33, 34, 27, 20, 28, 35, |
93 | 36, |
94 | 63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */ |
95 | 63, 63, 63, 63, 63, 63, 63, 63 |
96 | }; |
97 | |
98 | const int jpeg_natural_order4[4*4+16] = { |
99 | 0, 1, 8, 16, 9, 2, 3, 10, |
100 | 17, 24, 25, 18, 11, 19, 26, 27, |
101 | 63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */ |
102 | 63, 63, 63, 63, 63, 63, 63, 63 |
103 | }; |
104 | |
105 | const int jpeg_natural_order3[3*3+16] = { |
106 | 0, 1, 8, 16, 9, 2, 10, 17, |
107 | 18, |
108 | 63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */ |
109 | 63, 63, 63, 63, 63, 63, 63, 63 |
110 | }; |
111 | |
112 | const int jpeg_natural_order2[2*2+16] = { |
113 | 0, 1, 8, 9, |
114 | 63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */ |
115 | 63, 63, 63, 63, 63, 63, 63, 63 |
116 | }; |
117 | |
118 | |
119 | /* |
120 | * Arithmetic utilities |
121 | */ |
122 | |
123 | GLOBAL(long) |
124 | jdiv_round_up (long a, long b) |
125 | /* Compute a/b rounded up to next integer, ie, ceil(a/b) */ |
126 | /* Assumes a >= 0, b > 0 */ |
127 | { |
128 | return (a + b - 1L) / b; |
129 | } |
130 | |
131 | |
132 | GLOBAL(long) |
133 | jround_up (long a, long b) |
134 | /* Compute a rounded up to next multiple of b, ie, ceil(a/b)*b */ |
135 | /* Assumes a >= 0, b > 0 */ |
136 | { |
137 | a += b - 1L; |
138 | return a - (a % b); |
139 | } |
140 | |
141 | |
142 | /* On normal machines we can apply MEMCOPY() and MEMZERO() to sample arrays |
143 | * and coefficient-block arrays. This won't work on 80x86 because the arrays |
144 | * are FAR and we're assuming a small-pointer memory model. However, some |
145 | * DOS compilers provide far-pointer versions of memcpy() and memset() even |
146 | * in the small-model libraries. These will be used if USE_FMEM is defined. |
147 | * Otherwise, the routines below do it the hard way. (The performance cost |
148 | * is not all that great, because these routines aren't very heavily used.) |
149 | */ |
150 | |
151 | #ifndef NEED_FAR_POINTERS /* normal case, same as regular macro */ |
152 | #define FMEMCOPY(dest,src,size) MEMCOPY(dest,src,size) |
153 | #else /* 80x86 case, define if we can */ |
154 | #ifdef USE_FMEM |
155 | #define FMEMCOPY(dest,src,size) _fmemcpy((void FAR *)(dest), (const void FAR *)(src), (size_t)(size)) |
156 | #else |
157 | /* This function is for use by the FMEMZERO macro defined in jpegint.h. |
158 | * Do not call this function directly, use the FMEMZERO macro instead. |
159 | */ |
160 | GLOBAL(void) |
161 | jzero_far (void FAR * target, size_t bytestozero) |
162 | /* Zero out a chunk of FAR memory. */ |
163 | /* This might be sample-array data, block-array data, or alloc_large data. */ |
164 | { |
165 | register char FAR * ptr = (char FAR *) target; |
166 | register size_t count; |
167 | |
168 | for (count = bytestozero; count > 0; count--) { |
169 | *ptr++ = 0; |
170 | } |
171 | } |
172 | #endif |
173 | #endif |
174 | |
175 | |
176 | GLOBAL(void) |
177 | jcopy_sample_rows (JSAMPARRAY input_array, int source_row, |
178 | JSAMPARRAY output_array, int dest_row, |
179 | int num_rows, JDIMENSION num_cols) |
180 | /* Copy some rows of samples from one place to another. |
181 | * num_rows rows are copied from input_array[source_row++] |
182 | * to output_array[dest_row++]; these areas may overlap for duplication. |
183 | * The source and destination arrays must be at least as wide as num_cols. |
184 | */ |
185 | { |
186 | register JSAMPROW inptr, outptr; |
187 | #ifdef FMEMCOPY |
188 | register size_t count = (size_t) (num_cols * SIZEOF(JSAMPLE)); |
189 | #else |
190 | register JDIMENSION count; |
191 | #endif |
192 | register int row; |
193 | |
194 | input_array += source_row; |
195 | output_array += dest_row; |
196 | |
197 | for (row = num_rows; row > 0; row--) { |
198 | inptr = *input_array++; |
199 | outptr = *output_array++; |
200 | #ifdef FMEMCOPY |
201 | FMEMCOPY(outptr, inptr, count); |
202 | #else |
203 | for (count = num_cols; count > 0; count--) |
204 | *outptr++ = *inptr++; /* needn't bother with GETJSAMPLE() here */ |
205 | #endif |
206 | } |
207 | } |
208 | |
209 | |
210 | GLOBAL(void) |
211 | jcopy_block_row (JBLOCKROW input_row, JBLOCKROW output_row, |
212 | JDIMENSION num_blocks) |
213 | /* Copy a row of coefficient blocks from one place to another. */ |
214 | { |
215 | #ifdef FMEMCOPY |
216 | FMEMCOPY(output_row, input_row, num_blocks * (DCTSIZE2 * SIZEOF(JCOEF))); |
217 | #else |
218 | register JCOEFPTR inptr, outptr; |
219 | register long count; |
220 | |
221 | inptr = (JCOEFPTR) input_row; |
222 | outptr = (JCOEFPTR) output_row; |
223 | for (count = (long) num_blocks * DCTSIZE2; count > 0; count--) { |
224 | *outptr++ = *inptr++; |
225 | } |
226 | #endif |
227 | } |
228 | |