4 * Copyright (C) 1991-1995, 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.
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.
14 #define JPEG_INTERNALS
16 #include "radiant_jpeglib.h"
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).
24 const int jpeg_zigzag_order[DCTSIZE2] = {
25 0, 1, 5, 6, 14, 15, 27, 28,
26 2, 4, 7, 13, 16, 26, 29, 42,
27 3, 8, 12, 17, 25, 30, 41, 43,
28 9, 11, 18, 24, 31, 40, 44, 53,
29 10, 19, 23, 32, 39, 45, 52, 54,
30 20, 22, 33, 38, 46, 51, 55, 60,
31 21, 34, 37, 47, 50, 56, 59, 61,
32 35, 36, 48, 49, 57, 58, 62, 63
36 * jpeg_natural_order[i] is the natural-order position of the i'th element
39 * When reading corrupted data, the Huffman decoders could attempt
40 * to reference an entry beyond the end of this array (if the decoded
41 * zero run length reaches past the end of the block). To prevent
42 * wild stores without adding an inner-loop test, we put some extra
43 * "63"s after the real entries. This will cause the extra coefficient
44 * to be stored in location 63 of the block, not somewhere random.
45 * The worst case would be a run-length of 15, which means we need 16
49 const int jpeg_natural_order[DCTSIZE2+16] = {
50 0, 1, 8, 16, 9, 2, 3, 10,
51 17, 24, 32, 25, 18, 11, 4, 5,
52 12, 19, 26, 33, 40, 48, 41, 34,
53 27, 20, 13, 6, 7, 14, 21, 28,
54 35, 42, 49, 56, 57, 50, 43, 36,
55 29, 22, 15, 23, 30, 37, 44, 51,
56 58, 59, 52, 45, 38, 31, 39, 46,
57 53, 60, 61, 54, 47, 55, 62, 63,
58 63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */
59 63, 63, 63, 63, 63, 63, 63, 63
64 * Arithmetic utilities
68 jdiv_round_up (long a, long b)
69 /* Compute a/b rounded up to next integer, ie, ceil(a/b) */
70 /* Assumes a >= 0, b > 0 */
72 return (a + b - 1L) / b;
77 jround_up (long a, long b)
78 /* Compute a rounded up to next multiple of b, ie, ceil(a/b)*b */
79 /* Assumes a >= 0, b > 0 */
86 /* On normal machines we can apply MEMCOPY() and MEMZERO() to sample arrays
87 * and coefficient-block arrays. This won't work on 80x86 because the arrays
88 * are FAR and we're assuming a small-pointer memory model. However, some
89 * DOS compilers provide far-pointer versions of memcpy() and memset() even
90 * in the small-model libraries. These will be used if USE_FMEM is defined.
91 * Otherwise, the routines below do it the hard way. (The performance cost
92 * is not all that great, because these routines aren't very heavily used.)
95 #ifndef NEED_FAR_POINTERS /* normal case, same as regular macros */
96 #define FMEMCOPY(dest,src,size) MEMCOPY(dest,src,size)
97 #define FMEMZERO(target,size) MEMZERO(target,size)
98 #else /* 80x86 case, define if we can */
100 #define FMEMCOPY(dest,src,size) _fmemcpy((void FAR *)(dest), (const void FAR *)(src), (size_t)(size))
101 #define FMEMZERO(target,size) _fmemset((void FAR *)(target), 0, (size_t)(size))
107 jcopy_sample_rows (JSAMPARRAY input_array, int source_row,
108 JSAMPARRAY output_array, int dest_row,
109 int num_rows, JDIMENSION num_cols)
110 /* Copy some rows of samples from one place to another.
111 * num_rows rows are copied from input_array[source_row++]
112 * to output_array[dest_row++]; these areas may overlap for duplication.
113 * The source and destination arrays must be at least as wide as num_cols.
116 register JSAMPROW inptr, outptr;
118 register size_t count = (size_t) (num_cols * SIZEOF(JSAMPLE));
120 register JDIMENSION count;
124 input_array += source_row;
125 output_array += dest_row;
127 for (row = num_rows; row > 0; row--) {
128 inptr = *input_array++;
129 outptr = *output_array++;
131 FMEMCOPY(outptr, inptr, count);
133 for (count = num_cols; count > 0; count--)
134 *outptr++ = *inptr++; /* needn't bother with GETJSAMPLE() here */
141 jcopy_block_row (JBLOCKROW input_row, JBLOCKROW output_row,
142 JDIMENSION num_blocks)
143 /* Copy a row of coefficient blocks from one place to another. */
146 FMEMCOPY(output_row, input_row, num_blocks * (DCTSIZE2 * SIZEOF(JCOEF)));
148 register JCOEFPTR inptr, outptr;
151 inptr = (JCOEFPTR) input_row;
152 outptr = (JCOEFPTR) output_row;
153 for (count = (long) num_blocks * DCTSIZE2; count > 0; count--) {
154 *outptr++ = *inptr++;
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. */
166 FMEMZERO(target, bytestozero);
168 register char FAR * ptr = (char FAR *) target;
169 register size_t count;
171 for (count = bytestozero; count > 0; count--) {