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6417 | ashmew2 | 1 | /* |
2 | * jutils.c |
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3 | * |
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4 | * Copyright (C) 1991-1996, Thomas G. Lane. |
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5 | * This file is part of the Independent JPEG Group's software. |
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6 | * For conditions of distribution and use, see the accompanying README file. |
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7 | * |
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8 | * This file contains tables and miscellaneous utility routines needed |
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9 | * for both compression and decompression. |
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10 | * Note we prefix all global names with "j" to minimize conflicts with |
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11 | * a surrounding application. |
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12 | */ |
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13 | |||
14 | #define JPEG_INTERNALS |
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15 | #include "jinclude.h" |
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16 | #include "jpeglib.h" |
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17 | |||
18 | |||
19 | /* |
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20 | * jpeg_zigzag_order[i] is the zigzag-order position of the i'th element |
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21 | * of a DCT block read in natural order (left to right, top to bottom). |
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22 | */ |
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23 | |||
24 | #if 0 /* This table is not actually needed in v6a */ |
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25 | |||
26 | const int jpeg_zigzag_order[DCTSIZE2] = { |
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27 | 0, 1, 5, 6, 14, 15, 27, 28, |
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28 | 2, 4, 7, 13, 16, 26, 29, 42, |
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29 | 3, 8, 12, 17, 25, 30, 41, 43, |
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30 | 9, 11, 18, 24, 31, 40, 44, 53, |
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31 | 10, 19, 23, 32, 39, 45, 52, 54, |
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32 | 20, 22, 33, 38, 46, 51, 55, 60, |
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33 | 21, 34, 37, 47, 50, 56, 59, 61, |
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34 | 35, 36, 48, 49, 57, 58, 62, 63 |
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35 | }; |
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36 | |||
37 | #endif |
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38 | |||
39 | /* |
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40 | * jpeg_natural_order[i] is the natural-order position of the i'th element |
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41 | * of zigzag order. |
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42 | * |
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43 | * When reading corrupted data, the Huffman decoders could attempt |
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44 | * to reference an entry beyond the end of this array (if the decoded |
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45 | * zero run length reaches past the end of the block). To prevent |
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46 | * wild stores without adding an inner-loop test, we put some extra |
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47 | * "63"s after the real entries. This will cause the extra coefficient |
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48 | * to be stored in location 63 of the block, not somewhere random. |
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49 | * The worst case would be a run-length of 15, which means we need 16 |
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50 | * fake entries. |
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51 | */ |
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52 | |||
53 | const int jpeg_natural_order[DCTSIZE2+16] = { |
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54 | 0, 1, 8, 16, 9, 2, 3, 10, |
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55 | 17, 24, 32, 25, 18, 11, 4, 5, |
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56 | 12, 19, 26, 33, 40, 48, 41, 34, |
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57 | 27, 20, 13, 6, 7, 14, 21, 28, |
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58 | 35, 42, 49, 56, 57, 50, 43, 36, |
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59 | 29, 22, 15, 23, 30, 37, 44, 51, |
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60 | 58, 59, 52, 45, 38, 31, 39, 46, |
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61 | 53, 60, 61, 54, 47, 55, 62, 63, |
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62 | 63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */ |
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63 | 63, 63, 63, 63, 63, 63, 63, 63 |
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64 | }; |
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65 | |||
66 | |||
67 | /* |
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68 | * Arithmetic utilities |
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69 | */ |
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70 | |||
71 | GLOBAL(long) |
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72 | jdiv_round_up (long a, long b) |
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73 | /* Compute a/b rounded up to next integer, ie, ceil(a/b) */ |
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74 | /* Assumes a >= 0, b > 0 */ |
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75 | { |
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76 | return (a + b - 1L) / b; |
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77 | } |
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78 | |||
79 | |||
80 | GLOBAL(long) |
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81 | jround_up (long a, long b) |
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82 | /* Compute a rounded up to next multiple of b, ie, ceil(a/b)*b */ |
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83 | /* Assumes a >= 0, b > 0 */ |
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84 | { |
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85 | a += b - 1L; |
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86 | return a - (a % b); |
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87 | } |
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88 | |||
89 | |||
90 | /* On normal machines we can apply MEMCOPY() and MEMZERO() to sample arrays |
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91 | * and coefficient-block arrays. This won't work on 80x86 because the arrays |
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92 | * are FAR and we're assuming a small-pointer memory model. However, some |
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93 | * DOS compilers provide far-pointer versions of memcpy() and memset() even |
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94 | * in the small-model libraries. These will be used if USE_FMEM is defined. |
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95 | * Otherwise, the routines below do it the hard way. (The performance cost |
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96 | * is not all that great, because these routines aren't very heavily used.) |
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97 | */ |
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98 | |||
99 | #ifndef NEED_FAR_POINTERS /* normal case, same as regular macros */ |
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100 | #define FMEMCOPY(dest,src,size) MEMCOPY(dest,src,size) |
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101 | #define FMEMZERO(target,size) MEMZERO(target,size) |
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102 | #else /* 80x86 case, define if we can */ |
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103 | #ifdef USE_FMEM |
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104 | #define FMEMCOPY(dest,src,size) _fmemcpy((void FAR *)(dest), (const void FAR *)(src), (size_t)(size)) |
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105 | #define FMEMZERO(target,size) _fmemset((void FAR *)(target), 0, (size_t)(size)) |
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106 | #endif |
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107 | #endif |
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108 | |||
109 | |||
110 | GLOBAL(void) |
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111 | jcopy_sample_rows (JSAMPARRAY input_array, int source_row, |
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112 | JSAMPARRAY output_array, int dest_row, |
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113 | int num_rows, JDIMENSION num_cols) |
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114 | /* Copy some rows of samples from one place to another. |
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115 | * num_rows rows are copied from input_array[source_row++] |
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116 | * to output_array[dest_row++]; these areas may overlap for duplication. |
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117 | * The source and destination arrays must be at least as wide as num_cols. |
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118 | */ |
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119 | { |
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120 | register JSAMPROW inptr, outptr; |
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121 | #ifdef FMEMCOPY |
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122 | register size_t count = (size_t) (num_cols * SIZEOF(JSAMPLE)); |
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123 | #else |
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124 | register JDIMENSION count; |
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125 | #endif |
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126 | register int row; |
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127 | |||
128 | input_array += source_row; |
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129 | output_array += dest_row; |
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130 | |||
131 | for (row = num_rows; row > 0; row--) { |
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132 | inptr = *input_array++; |
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133 | outptr = *output_array++; |
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134 | #ifdef FMEMCOPY |
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135 | FMEMCOPY(outptr, inptr, count); |
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136 | #else |
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137 | for (count = num_cols; count > 0; count--) |
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138 | *outptr++ = *inptr++; /* needn't bother with GETJSAMPLE() here */ |
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139 | #endif |
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140 | } |
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141 | } |
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142 | |||
143 | |||
144 | GLOBAL(void) |
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145 | jcopy_block_row (JBLOCKROW input_row, JBLOCKROW output_row, |
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146 | JDIMENSION num_blocks) |
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147 | /* Copy a row of coefficient blocks from one place to another. */ |
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148 | { |
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149 | #ifdef FMEMCOPY |
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150 | FMEMCOPY(output_row, input_row, num_blocks * (DCTSIZE2 * SIZEOF(JCOEF))); |
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151 | #else |
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152 | register JCOEFPTR inptr, outptr; |
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153 | register long count; |
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154 | |||
155 | inptr = (JCOEFPTR) input_row; |
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156 | outptr = (JCOEFPTR) output_row; |
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157 | for (count = (long) num_blocks * DCTSIZE2; count > 0; count--) { |
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158 | *outptr++ = *inptr++; |
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159 | } |
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160 | #endif |
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161 | } |
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162 | |||
163 | |||
164 | GLOBAL(void) |
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165 | jzero_far (void FAR * target, size_t bytestozero) |
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166 | /* Zero out a chunk of FAR memory. */ |
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167 | /* This might be sample-array data, block-array data, or alloc_large data. */ |
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168 | { |
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169 | #ifdef FMEMZERO |
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170 | FMEMZERO(target, bytestozero); |
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171 | #else |
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172 | register char FAR * ptr = (char FAR *) target; |
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173 | register size_t count; |
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174 | |||
175 | for (count = bytestozero; count > 0; count--) { |
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176 | *ptr++ = 0; |
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177 | } |
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178 | #endif |
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179 | } |