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1 /* |
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2 * jdphuff.c |
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3 * |
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4 * Copyright (C) 1995-1997, 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 Huffman entropy decoding routines for progressive JPEG. |
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9 * |
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10 * Much of the complexity here has to do with supporting input suspension. |
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11 * If the data source module demands suspension, we want to be able to back |
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12 * up to the start of the current MCU. To do this, we copy state variables |
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13 * into local working storage, and update them back to the permanent |
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14 * storage only upon successful completion of an MCU. |
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15 */ |
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16 |
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17 #define JPEG_INTERNALS |
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18 #include "jinclude.h" |
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19 #include "jpeglib.h" |
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20 #include "jdhuff.h" /* Declarations shared with jdhuff.c */ |
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21 |
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22 |
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23 #ifdef D_PROGRESSIVE_SUPPORTED |
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24 |
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25 /* |
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26 * Expanded entropy decoder object for progressive Huffman decoding. |
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27 * |
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28 * The savable_state subrecord contains fields that change within an MCU, |
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29 * but must not be updated permanently until we complete the MCU. |
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30 */ |
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31 |
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32 typedef struct { |
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33 unsigned int EOBRUN; /* remaining EOBs in EOBRUN */ |
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34 int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */ |
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35 } savable_state; |
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36 |
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37 /* This macro is to work around compilers with missing or broken |
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38 * structure assignment. You'll need to fix this code if you have |
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39 * such a compiler and you change MAX_COMPS_IN_SCAN. |
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40 */ |
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41 |
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42 #ifndef NO_STRUCT_ASSIGN |
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43 #define ASSIGN_STATE(dest,src) ((dest) = (src)) |
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44 #else |
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45 #if MAX_COMPS_IN_SCAN == 4 |
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46 #define ASSIGN_STATE(dest,src) \ |
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47 ((dest).EOBRUN = (src).EOBRUN, \ |
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48 (dest).last_dc_val[0] = (src).last_dc_val[0], \ |
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49 (dest).last_dc_val[1] = (src).last_dc_val[1], \ |
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50 (dest).last_dc_val[2] = (src).last_dc_val[2], \ |
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51 (dest).last_dc_val[3] = (src).last_dc_val[3]) |
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52 #endif |
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53 #endif |
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54 |
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55 |
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56 typedef struct { |
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57 struct jpeg_entropy_decoder pub; /* public fields */ |
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58 |
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59 /* These fields are loaded into local variables at start of each MCU. |
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60 * In case of suspension, we exit WITHOUT updating them. |
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61 */ |
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62 bitread_perm_state bitstate; /* Bit buffer at start of MCU */ |
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63 savable_state saved; /* Other state at start of MCU */ |
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64 |
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65 /* These fields are NOT loaded into local working state. */ |
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66 unsigned int restarts_to_go; /* MCUs left in this restart interval */ |
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67 |
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68 /* Pointers to derived tables (these workspaces have image lifespan) */ |
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69 d_derived_tbl * derived_tbls[NUM_HUFF_TBLS]; |
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70 |
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71 d_derived_tbl * ac_derived_tbl; /* active table during an AC scan */ |
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72 } phuff_entropy_decoder; |
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73 |
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74 typedef phuff_entropy_decoder * phuff_entropy_ptr; |
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75 |
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76 /* Forward declarations */ |
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77 METHODDEF(boolean) decode_mcu_DC_first JPP((j_decompress_ptr cinfo, |
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78 JBLOCKROW *MCU_data)); |
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79 METHODDEF(boolean) decode_mcu_AC_first JPP((j_decompress_ptr cinfo, |
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80 JBLOCKROW *MCU_data)); |
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81 METHODDEF(boolean) decode_mcu_DC_refine JPP((j_decompress_ptr cinfo, |
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82 JBLOCKROW *MCU_data)); |
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83 METHODDEF(boolean) decode_mcu_AC_refine JPP((j_decompress_ptr cinfo, |
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84 JBLOCKROW *MCU_data)); |
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85 |
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86 |
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87 /* |
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88 * Initialize for a Huffman-compressed scan. |
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89 */ |
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90 |
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91 METHODDEF(void) |
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92 start_pass_phuff_decoder (j_decompress_ptr cinfo) |
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93 { |
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94 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; |
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95 boolean is_DC_band, bad; |
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96 int ci, coefi, tbl; |
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97 int *coef_bit_ptr; |
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98 jpeg_component_info * compptr; |
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99 |
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100 is_DC_band = (cinfo->Ss == 0); |
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101 |
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102 /* Validate scan parameters */ |
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103 bad = FALSE; |
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104 if (is_DC_band) { |
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105 if (cinfo->Se != 0) |
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106 bad = TRUE; |
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107 } else { |
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108 /* need not check Ss/Se < 0 since they came from unsigned bytes */ |
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109 if (cinfo->Ss > cinfo->Se || cinfo->Se >= DCTSIZE2) |
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110 bad = TRUE; |
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111 /* AC scans may have only one component */ |
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112 if (cinfo->comps_in_scan != 1) |
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113 bad = TRUE; |
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114 } |
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115 if (cinfo->Ah != 0) { |
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116 /* Successive approximation refinement scan: must have Al = Ah-1. */ |
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117 if (cinfo->Al != cinfo->Ah-1) |
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118 bad = TRUE; |
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119 } |
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120 if (cinfo->Al > 13) /* need not check for < 0 */ |
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121 bad = TRUE; |
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122 /* Arguably the maximum Al value should be less than 13 for 8-bit precision, |
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123 * but the spec doesn't say so, and we try to be liberal about what we |
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124 * accept. Note: large Al values could result in out-of-range DC |
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125 * coefficients during early scans, leading to bizarre displays due to |
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126 * overflows in the IDCT math. But we won't crash. |
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127 */ |
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128 if (bad) |
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129 ERREXIT4(cinfo, JERR_BAD_PROGRESSION, |
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130 cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al); |
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131 /* Update progression status, and verify that scan order is legal. |
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132 * Note that inter-scan inconsistencies are treated as warnings |
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133 * not fatal errors ... not clear if this is right way to behave. |
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134 */ |
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135 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { |
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136 int cindex = cinfo->cur_comp_info[ci]->component_index; |
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137 coef_bit_ptr = & cinfo->coef_bits[cindex][0]; |
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138 if (!is_DC_band && coef_bit_ptr[0] < 0) /* AC without prior DC scan */ |
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139 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0); |
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140 for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) { |
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141 int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi]; |
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142 if (cinfo->Ah != expected) |
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143 WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi); |
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144 coef_bit_ptr[coefi] = cinfo->Al; |
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145 } |
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146 } |
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147 |
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148 /* Select MCU decoding routine */ |
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149 if (cinfo->Ah == 0) { |
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150 if (is_DC_band) |
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151 entropy->pub.decode_mcu = decode_mcu_DC_first; |
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152 else |
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153 entropy->pub.decode_mcu = decode_mcu_AC_first; |
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154 } else { |
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155 if (is_DC_band) |
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156 entropy->pub.decode_mcu = decode_mcu_DC_refine; |
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157 else |
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158 entropy->pub.decode_mcu = decode_mcu_AC_refine; |
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159 } |
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160 |
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161 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { |
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162 compptr = cinfo->cur_comp_info[ci]; |
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163 /* Make sure requested tables are present, and compute derived tables. |
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164 * We may build same derived table more than once, but it's not expensive. |
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165 */ |
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166 if (is_DC_band) { |
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167 if (cinfo->Ah == 0) { /* DC refinement needs no table */ |
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168 tbl = compptr->dc_tbl_no; |
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169 jpeg_make_d_derived_tbl(cinfo, TRUE, tbl, |
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170 & entropy->derived_tbls[tbl]); |
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171 } |
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172 } else { |
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173 tbl = compptr->ac_tbl_no; |
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174 jpeg_make_d_derived_tbl(cinfo, FALSE, tbl, |
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175 & entropy->derived_tbls[tbl]); |
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176 /* remember the single active table */ |
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177 entropy->ac_derived_tbl = entropy->derived_tbls[tbl]; |
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178 } |
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179 /* Initialize DC predictions to 0 */ |
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180 entropy->saved.last_dc_val[ci] = 0; |
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181 } |
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182 |
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183 /* Initialize bitread state variables */ |
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184 entropy->bitstate.bits_left = 0; |
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185 entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */ |
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186 entropy->pub.insufficient_data = FALSE; |
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187 |
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188 /* Initialize private state variables */ |
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189 entropy->saved.EOBRUN = 0; |
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190 |
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191 /* Initialize restart counter */ |
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192 entropy->restarts_to_go = cinfo->restart_interval; |
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193 } |
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194 |
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195 |
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196 /* |
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197 * Figure F.12: extend sign bit. |
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198 * On some machines, a shift and add will be faster than a table lookup. |
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199 */ |
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200 |
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201 #ifdef AVOID_TABLES |
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202 |
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203 #define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x)) |
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204 |
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205 #else |
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206 |
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207 #define HUFF_EXTEND(x,s) ((x) < extend_test[s] ? (x) + extend_offset[s] : (x)) |
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208 |
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209 static const int extend_test[16] = /* entry n is 2**(n-1) */ |
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210 { 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080, |
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211 0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 }; |
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212 |
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213 static const int extend_offset[16] = /* entry n is (-1 << n) + 1 */ |
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214 { 0, ((-1)<<1) + 1, ((-1)<<2) + 1, ((-1)<<3) + 1, ((-1)<<4) + 1, |
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215 ((-1)<<5) + 1, ((-1)<<6) + 1, ((-1)<<7) + 1, ((-1)<<8) + 1, |
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216 ((-1)<<9) + 1, ((-1)<<10) + 1, ((-1)<<11) + 1, ((-1)<<12) + 1, |
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217 ((-1)<<13) + 1, ((-1)<<14) + 1, ((-1)<<15) + 1 }; |
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218 |
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219 #endif /* AVOID_TABLES */ |
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220 |
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221 |
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222 /* |
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223 * Check for a restart marker & resynchronize decoder. |
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224 * Returns FALSE if must suspend. |
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225 */ |
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226 |
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227 LOCAL(boolean) |
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228 process_restart (j_decompress_ptr cinfo) |
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229 { |
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230 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; |
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231 int ci; |
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232 |
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233 /* Throw away any unused bits remaining in bit buffer; */ |
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234 /* include any full bytes in next_marker's count of discarded bytes */ |
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235 cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8; |
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236 entropy->bitstate.bits_left = 0; |
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237 |
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238 /* Advance past the RSTn marker */ |
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239 if (! (*cinfo->marker->read_restart_marker) (cinfo)) |
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240 return FALSE; |
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241 |
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242 /* Re-initialize DC predictions to 0 */ |
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243 for (ci = 0; ci < cinfo->comps_in_scan; ci++) |
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244 entropy->saved.last_dc_val[ci] = 0; |
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245 /* Re-init EOB run count, too */ |
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246 entropy->saved.EOBRUN = 0; |
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247 |
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248 /* Reset restart counter */ |
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249 entropy->restarts_to_go = cinfo->restart_interval; |
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250 |
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251 /* Reset out-of-data flag, unless read_restart_marker left us smack up |
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252 * against a marker. In that case we will end up treating the next data |
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253 * segment as empty, and we can avoid producing bogus output pixels by |
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254 * leaving the flag set. |
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255 */ |
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256 if (cinfo->unread_marker == 0) |
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257 entropy->pub.insufficient_data = FALSE; |
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258 |
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259 return TRUE; |
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260 } |
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261 |
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262 |
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263 /* |
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264 * Huffman MCU decoding. |
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265 * Each of these routines decodes and returns one MCU's worth of |
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266 * Huffman-compressed coefficients. |
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267 * The coefficients are reordered from zigzag order into natural array order, |
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268 * but are not dequantized. |
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269 * |
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270 * The i'th block of the MCU is stored into the block pointed to by |
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271 * MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER. |
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272 * |
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273 * We return FALSE if data source requested suspension. In that case no |
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274 * changes have been made to permanent state. (Exception: some output |
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275 * coefficients may already have been assigned. This is harmless for |
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276 * spectral selection, since we'll just re-assign them on the next call. |
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277 * Successive approximation AC refinement has to be more careful, however.) |
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278 */ |
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279 |
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280 /* |
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281 * MCU decoding for DC initial scan (either spectral selection, |
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282 * or first pass of successive approximation). |
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283 */ |
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284 |
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285 METHODDEF(boolean) |
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286 decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) |
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287 { |
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288 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; |
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289 int Al = cinfo->Al; |
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290 register int s, r; |
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291 int blkn, ci; |
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292 JBLOCKROW block; |
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293 BITREAD_STATE_VARS; |
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294 savable_state state; |
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295 d_derived_tbl * tbl; |
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296 jpeg_component_info * compptr; |
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297 |
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298 /* Process restart marker if needed; may have to suspend */ |
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299 if (cinfo->restart_interval) { |
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300 if (entropy->restarts_to_go == 0) |
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301 if (! process_restart(cinfo)) |
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302 return FALSE; |
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303 } |
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304 |
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305 /* If we've run out of data, just leave the MCU set to zeroes. |
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306 * This way, we return uniform gray for the remainder of the segment. |
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307 */ |
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308 if (! entropy->pub.insufficient_data) { |
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309 |
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310 /* Load up working state */ |
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311 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); |
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312 ASSIGN_STATE(state, entropy->saved); |
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313 |
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314 /* Outer loop handles each block in the MCU */ |
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315 |
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316 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { |
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317 block = MCU_data[blkn]; |
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318 ci = cinfo->MCU_membership[blkn]; |
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319 compptr = cinfo->cur_comp_info[ci]; |
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320 tbl = entropy->derived_tbls[compptr->dc_tbl_no]; |
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321 |
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322 /* Decode a single block's worth of coefficients */ |
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323 |
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324 /* Section F.2.2.1: decode the DC coefficient difference */ |
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325 HUFF_DECODE(s, br_state, tbl, return FALSE, label1); |
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326 if (s) { |
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327 CHECK_BIT_BUFFER(br_state, s, return FALSE); |
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328 r = GET_BITS(s); |
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329 s = HUFF_EXTEND(r, s); |
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330 } |
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331 |
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332 /* Convert DC difference to actual value, update last_dc_val */ |
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333 s += state.last_dc_val[ci]; |
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334 state.last_dc_val[ci] = s; |
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335 /* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */ |
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336 (*block)[0] = (JCOEF) (s << Al); |
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337 } |
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338 |
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339 /* Completed MCU, so update state */ |
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340 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); |
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341 ASSIGN_STATE(entropy->saved, state); |
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342 } |
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343 |
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344 /* Account for restart interval (no-op if not using restarts) */ |
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345 entropy->restarts_to_go--; |
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346 |
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347 return TRUE; |
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348 } |
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349 |
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350 |
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351 /* |
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352 * MCU decoding for AC initial scan (either spectral selection, |
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353 * or first pass of successive approximation). |
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354 */ |
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355 |
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356 METHODDEF(boolean) |
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357 decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) |
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358 { |
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359 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; |
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360 int Se = cinfo->Se; |
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361 int Al = cinfo->Al; |
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362 register int s, k, r; |
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363 unsigned int EOBRUN; |
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364 JBLOCKROW block; |
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365 BITREAD_STATE_VARS; |
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366 d_derived_tbl * tbl; |
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367 |
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368 /* Process restart marker if needed; may have to suspend */ |
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369 if (cinfo->restart_interval) { |
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370 if (entropy->restarts_to_go == 0) |
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371 if (! process_restart(cinfo)) |
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372 return FALSE; |
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373 } |
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374 |
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375 /* If we've run out of data, just leave the MCU set to zeroes. |
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376 * This way, we return uniform gray for the remainder of the segment. |
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377 */ |
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378 if (! entropy->pub.insufficient_data) { |
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379 |
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380 /* Load up working state. |
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381 * We can avoid loading/saving bitread state if in an EOB run. |
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382 */ |
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383 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */ |
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384 |
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385 /* There is always only one block per MCU */ |
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386 |
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387 if (EOBRUN > 0) /* if it's a band of zeroes... */ |
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388 EOBRUN--; /* ...process it now (we do nothing) */ |
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389 else { |
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390 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); |
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391 block = MCU_data[0]; |
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392 tbl = entropy->ac_derived_tbl; |
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393 |
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394 for (k = cinfo->Ss; k <= Se; k++) { |
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395 HUFF_DECODE(s, br_state, tbl, return FALSE, label2); |
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396 r = s >> 4; |
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397 s &= 15; |
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398 if (s) { |
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399 k += r; |
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400 CHECK_BIT_BUFFER(br_state, s, return FALSE); |
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401 r = GET_BITS(s); |
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402 s = HUFF_EXTEND(r, s); |
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403 /* Scale and output coefficient in natural (dezigzagged) order */ |
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404 (*block)[jpeg_natural_order[k]] = (JCOEF) (s << Al); |
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405 } else { |
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406 if (r == 15) { /* ZRL */ |
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407 k += 15; /* skip 15 zeroes in band */ |
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408 } else { /* EOBr, run length is 2^r + appended bits */ |
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409 EOBRUN = 1 << r; |
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410 if (r) { /* EOBr, r > 0 */ |
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411 CHECK_BIT_BUFFER(br_state, r, return FALSE); |
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412 r = GET_BITS(r); |
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413 EOBRUN += r; |
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414 } |
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415 EOBRUN--; /* this band is processed at this moment */ |
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416 break; /* force end-of-band */ |
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417 } |
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418 } |
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419 } |
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420 |
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421 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); |
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422 } |
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423 |
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424 /* Completed MCU, so update state */ |
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425 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */ |
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426 } |
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427 |
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428 /* Account for restart interval (no-op if not using restarts) */ |
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429 entropy->restarts_to_go--; |
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430 |
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431 return TRUE; |
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432 } |
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433 |
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434 |
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435 /* |
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436 * MCU decoding for DC successive approximation refinement scan. |
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437 * Note: we assume such scans can be multi-component, although the spec |
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438 * is not very clear on the point. |
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439 */ |
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440 |
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441 METHODDEF(boolean) |
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442 decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) |
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443 { |
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444 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; |
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445 int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ |
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446 int blkn; |
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447 JBLOCKROW block; |
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448 BITREAD_STATE_VARS; |
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449 |
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450 /* Process restart marker if needed; may have to suspend */ |
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451 if (cinfo->restart_interval) { |
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452 if (entropy->restarts_to_go == 0) |
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453 if (! process_restart(cinfo)) |
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454 return FALSE; |
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455 } |
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456 |
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457 /* Not worth the cycles to check insufficient_data here, |
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458 * since we will not change the data anyway if we read zeroes. |
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459 */ |
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460 |
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461 /* Load up working state */ |
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462 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); |
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463 |
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464 /* Outer loop handles each block in the MCU */ |
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465 |
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466 for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { |
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467 block = MCU_data[blkn]; |
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468 |
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469 /* Encoded data is simply the next bit of the two's-complement DC value */ |
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470 CHECK_BIT_BUFFER(br_state, 1, return FALSE); |
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471 if (GET_BITS(1)) |
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472 (*block)[0] |= p1; |
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473 /* Note: since we use |=, repeating the assignment later is safe */ |
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474 } |
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475 |
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476 /* Completed MCU, so update state */ |
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477 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); |
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478 |
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479 /* Account for restart interval (no-op if not using restarts) */ |
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480 entropy->restarts_to_go--; |
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481 |
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482 return TRUE; |
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483 } |
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484 |
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485 |
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486 /* |
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487 * MCU decoding for AC successive approximation refinement scan. |
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488 */ |
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489 |
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490 METHODDEF(boolean) |
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491 decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data) |
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492 { |
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493 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy; |
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494 int Se = cinfo->Se; |
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495 int p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */ |
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496 int m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */ |
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497 register int s, k, r; |
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498 unsigned int EOBRUN; |
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499 JBLOCKROW block; |
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500 JCOEFPTR thiscoef; |
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501 BITREAD_STATE_VARS; |
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502 d_derived_tbl * tbl; |
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503 int num_newnz; |
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504 int newnz_pos[DCTSIZE2]; |
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505 |
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506 /* Process restart marker if needed; may have to suspend */ |
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507 if (cinfo->restart_interval) { |
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508 if (entropy->restarts_to_go == 0) |
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509 if (! process_restart(cinfo)) |
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510 return FALSE; |
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511 } |
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512 |
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513 /* If we've run out of data, don't modify the MCU. |
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514 */ |
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515 if (! entropy->pub.insufficient_data) { |
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516 |
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517 /* Load up working state */ |
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518 BITREAD_LOAD_STATE(cinfo,entropy->bitstate); |
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519 EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */ |
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520 |
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521 /* There is always only one block per MCU */ |
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522 block = MCU_data[0]; |
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523 tbl = entropy->ac_derived_tbl; |
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524 |
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525 /* If we are forced to suspend, we must undo the assignments to any newly |
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526 * nonzero coefficients in the block, because otherwise we'd get confused |
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527 * next time about which coefficients were already nonzero. |
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528 * But we need not undo addition of bits to already-nonzero coefficients; |
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529 * instead, we can test the current bit to see if we already did it. |
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530 */ |
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531 num_newnz = 0; |
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532 |
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533 /* initialize coefficient loop counter to start of band */ |
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534 k = cinfo->Ss; |
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535 |
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536 if (EOBRUN == 0) { |
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537 for (; k <= Se; k++) { |
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538 HUFF_DECODE(s, br_state, tbl, goto undoit, label3); |
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539 r = s >> 4; |
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540 s &= 15; |
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541 if (s) { |
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542 if (s != 1) /* size of new coef should always be 1 */ |
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543 WARNMS(cinfo, JWRN_HUFF_BAD_CODE); |
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544 CHECK_BIT_BUFFER(br_state, 1, goto undoit); |
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545 if (GET_BITS(1)) |
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546 s = p1; /* newly nonzero coef is positive */ |
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547 else |
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548 s = m1; /* newly nonzero coef is negative */ |
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549 } else { |
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550 if (r != 15) { |
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551 EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */ |
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552 if (r) { |
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553 CHECK_BIT_BUFFER(br_state, r, goto undoit); |
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554 r = GET_BITS(r); |
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555 EOBRUN += r; |
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556 } |
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557 break; /* rest of block is handled by EOB logic */ |
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558 } |
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559 /* note s = 0 for processing ZRL */ |
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560 } |
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561 /* Advance over already-nonzero coefs and r still-zero coefs, |
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562 * appending correction bits to the nonzeroes. A correction bit is 1 |
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563 * if the absolute value of the coefficient must be increased. |
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564 */ |
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565 do { |
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566 thiscoef = *block + jpeg_natural_order[k]; |
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567 if (*thiscoef != 0) { |
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568 CHECK_BIT_BUFFER(br_state, 1, goto undoit); |
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569 if (GET_BITS(1)) { |
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570 if ((*thiscoef & p1) == 0) { /* do nothing if already set it */ |
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571 if (*thiscoef >= 0) |
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572 *thiscoef += p1; |
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573 else |
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574 *thiscoef += m1; |
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575 } |
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576 } |
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577 } else { |
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578 if (--r < 0) |
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579 break; /* reached target zero coefficient */ |
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580 } |
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581 k++; |
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582 } while (k <= Se); |
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583 if (s) { |
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584 int pos = jpeg_natural_order[k]; |
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585 /* Output newly nonzero coefficient */ |
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586 (*block)[pos] = (JCOEF) s; |
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587 /* Remember its position in case we have to suspend */ |
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588 newnz_pos[num_newnz++] = pos; |
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589 } |
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590 } |
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591 } |
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592 |
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593 if (EOBRUN > 0) { |
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594 /* Scan any remaining coefficient positions after the end-of-band |
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595 * (the last newly nonzero coefficient, if any). Append a correction |
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596 * bit to each already-nonzero coefficient. A correction bit is 1 |
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597 * if the absolute value of the coefficient must be increased. |
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598 */ |
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599 for (; k <= Se; k++) { |
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600 thiscoef = *block + jpeg_natural_order[k]; |
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601 if (*thiscoef != 0) { |
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602 CHECK_BIT_BUFFER(br_state, 1, goto undoit); |
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603 if (GET_BITS(1)) { |
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604 if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */ |
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605 if (*thiscoef >= 0) |
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606 *thiscoef += p1; |
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607 else |
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608 *thiscoef += m1; |
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609 } |
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610 } |
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611 } |
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612 } |
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613 /* Count one block completed in EOB run */ |
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614 EOBRUN--; |
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615 } |
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616 |
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617 /* Completed MCU, so update state */ |
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618 BITREAD_SAVE_STATE(cinfo,entropy->bitstate); |
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619 entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */ |
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620 } |
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621 |
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622 /* Account for restart interval (no-op if not using restarts) */ |
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623 entropy->restarts_to_go--; |
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624 |
|
625 return TRUE; |
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626 |
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627 undoit: |
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628 /* Re-zero any output coefficients that we made newly nonzero */ |
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629 while (num_newnz > 0) |
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630 (*block)[newnz_pos[--num_newnz]] = 0; |
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631 |
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632 return FALSE; |
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633 } |
|
634 |
|
635 |
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636 /* |
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637 * Module initialization routine for progressive Huffman entropy decoding. |
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638 */ |
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639 |
|
640 GLOBAL(void) |
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641 jinit_phuff_decoder (j_decompress_ptr cinfo) |
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642 { |
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643 phuff_entropy_ptr entropy; |
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644 int *coef_bit_ptr; |
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645 int ci, i; |
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646 |
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647 entropy = (phuff_entropy_ptr) |
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648 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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649 SIZEOF(phuff_entropy_decoder)); |
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650 cinfo->entropy = (struct jpeg_entropy_decoder *) entropy; |
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651 entropy->pub.start_pass = start_pass_phuff_decoder; |
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652 |
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653 /* Mark derived tables unallocated */ |
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654 for (i = 0; i < NUM_HUFF_TBLS; i++) { |
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655 entropy->derived_tbls[i] = NULL; |
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656 } |
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657 |
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658 /* Create progression status table */ |
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659 cinfo->coef_bits = (int (*)[DCTSIZE2]) |
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660 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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661 cinfo->num_components*DCTSIZE2*SIZEOF(int)); |
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662 coef_bit_ptr = & cinfo->coef_bits[0][0]; |
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663 for (ci = 0; ci < cinfo->num_components; ci++) |
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664 for (i = 0; i < DCTSIZE2; i++) |
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665 *coef_bit_ptr++ = -1; |
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666 } |
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667 |
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668 #endif /* D_PROGRESSIVE_SUPPORTED */ |