1 /* |
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2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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3 * |
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4 * This code is free software; you can redistribute it and/or modify it |
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5 * under the terms of the GNU General Public License version 2 only, as |
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6 * published by the Free Software Foundation. Oracle designates this |
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7 * particular file as subject to the "Classpath" exception as provided |
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8 * by Oracle in the LICENSE file that accompanied this code. |
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9 * |
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10 * This code is distributed in the hope that it will be useful, but WITHOUT |
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11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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13 * version 2 for more details (a copy is included in the LICENSE file that |
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14 * accompanied this code). |
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15 * |
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16 * You should have received a copy of the GNU General Public License version |
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17 * 2 along with this work; if not, write to the Free Software Foundation, |
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18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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19 * |
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20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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21 * or visit www.oracle.com if you need additional information or have any |
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22 * questions. |
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23 */ |
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24 |
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25 /* inffast.c -- fast decoding |
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26 * Copyright (C) 1995-2004 Mark Adler |
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27 * For conditions of distribution and use, see copyright notice in zlib.h |
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28 */ |
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29 |
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30 #include "zutil.h" |
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31 #include "inftrees.h" |
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32 #include "inflate.h" |
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33 #include "inffast.h" |
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34 |
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35 #ifndef ASMINF |
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36 |
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37 /* Allow machine dependent optimization for post-increment or pre-increment. |
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38 Based on testing to date, |
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39 Pre-increment preferred for: |
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40 - PowerPC G3 (Adler) |
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41 - MIPS R5000 (Randers-Pehrson) |
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42 Post-increment preferred for: |
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43 - none |
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44 No measurable difference: |
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45 - Pentium III (Anderson) |
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46 - M68060 (Nikl) |
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47 */ |
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48 #ifdef POSTINC |
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49 # define OFF 0 |
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50 # define PUP(a) *(a)++ |
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51 #else |
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52 # define OFF 1 |
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53 # define PUP(a) *++(a) |
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54 #endif |
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55 |
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56 /* |
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57 Decode literal, length, and distance codes and write out the resulting |
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58 literal and match bytes until either not enough input or output is |
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59 available, an end-of-block is encountered, or a data error is encountered. |
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60 When large enough input and output buffers are supplied to inflate(), for |
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61 example, a 16K input buffer and a 64K output buffer, more than 95% of the |
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62 inflate execution time is spent in this routine. |
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63 |
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64 Entry assumptions: |
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65 |
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66 state->mode == LEN |
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67 strm->avail_in >= 6 |
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68 strm->avail_out >= 258 |
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69 start >= strm->avail_out |
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70 state->bits < 8 |
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71 |
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72 On return, state->mode is one of: |
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73 |
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74 LEN -- ran out of enough output space or enough available input |
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75 TYPE -- reached end of block code, inflate() to interpret next block |
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76 BAD -- error in block data |
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77 |
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78 Notes: |
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79 |
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80 - The maximum input bits used by a length/distance pair is 15 bits for the |
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81 length code, 5 bits for the length extra, 15 bits for the distance code, |
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82 and 13 bits for the distance extra. This totals 48 bits, or six bytes. |
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83 Therefore if strm->avail_in >= 6, then there is enough input to avoid |
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84 checking for available input while decoding. |
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85 |
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86 - The maximum bytes that a single length/distance pair can output is 258 |
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87 bytes, which is the maximum length that can be coded. inflate_fast() |
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88 requires strm->avail_out >= 258 for each loop to avoid checking for |
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89 output space. |
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90 */ |
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91 void inflate_fast(strm, start) |
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92 z_streamp strm; |
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93 unsigned start; /* inflate()'s starting value for strm->avail_out */ |
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94 { |
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95 struct inflate_state FAR *state; |
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96 unsigned char FAR *in; /* local strm->next_in */ |
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97 unsigned char FAR *last; /* while in < last, enough input available */ |
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98 unsigned char FAR *out; /* local strm->next_out */ |
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99 unsigned char FAR *beg; /* inflate()'s initial strm->next_out */ |
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100 unsigned char FAR *end; /* while out < end, enough space available */ |
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101 #ifdef INFLATE_STRICT |
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102 unsigned dmax; /* maximum distance from zlib header */ |
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103 #endif |
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104 unsigned wsize; /* window size or zero if not using window */ |
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105 unsigned whave; /* valid bytes in the window */ |
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106 unsigned write; /* window write index */ |
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107 unsigned char FAR *window; /* allocated sliding window, if wsize != 0 */ |
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108 unsigned long hold; /* local strm->hold */ |
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109 unsigned bits; /* local strm->bits */ |
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110 code const FAR *lcode; /* local strm->lencode */ |
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111 code const FAR *dcode; /* local strm->distcode */ |
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112 unsigned lmask; /* mask for first level of length codes */ |
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113 unsigned dmask; /* mask for first level of distance codes */ |
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114 code this; /* retrieved table entry */ |
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115 unsigned op; /* code bits, operation, extra bits, or */ |
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116 /* window position, window bytes to copy */ |
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117 unsigned len; /* match length, unused bytes */ |
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118 unsigned dist; /* match distance */ |
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119 unsigned char FAR *from; /* where to copy match from */ |
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120 |
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121 /* copy state to local variables */ |
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122 state = (struct inflate_state FAR *)strm->state; |
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123 in = strm->next_in - OFF; |
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124 last = in + (strm->avail_in - 5); |
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125 out = strm->next_out - OFF; |
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126 beg = out - (start - strm->avail_out); |
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127 end = out + (strm->avail_out - 257); |
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128 #ifdef INFLATE_STRICT |
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129 dmax = state->dmax; |
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130 #endif |
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131 wsize = state->wsize; |
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132 whave = state->whave; |
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133 write = state->write; |
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134 window = state->window; |
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135 hold = state->hold; |
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136 bits = state->bits; |
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137 lcode = state->lencode; |
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138 dcode = state->distcode; |
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139 lmask = (1U << state->lenbits) - 1; |
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140 dmask = (1U << state->distbits) - 1; |
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141 |
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142 /* decode literals and length/distances until end-of-block or not enough |
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143 input data or output space */ |
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144 do { |
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145 if (bits < 15) { |
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146 hold += (unsigned long)(PUP(in)) << bits; |
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147 bits += 8; |
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148 hold += (unsigned long)(PUP(in)) << bits; |
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149 bits += 8; |
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150 } |
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151 this = lcode[hold & lmask]; |
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152 dolen: |
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153 op = (unsigned)(this.bits); |
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154 hold >>= op; |
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155 bits -= op; |
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156 op = (unsigned)(this.op); |
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157 if (op == 0) { /* literal */ |
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158 Tracevv((stderr, this.val >= 0x20 && this.val < 0x7f ? |
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159 "inflate: literal '%c'\n" : |
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160 "inflate: literal 0x%02x\n", this.val)); |
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161 PUP(out) = (unsigned char)(this.val); |
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162 } |
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163 else if (op & 16) { /* length base */ |
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164 len = (unsigned)(this.val); |
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165 op &= 15; /* number of extra bits */ |
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166 if (op) { |
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167 if (bits < op) { |
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168 hold += (unsigned long)(PUP(in)) << bits; |
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169 bits += 8; |
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170 } |
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171 len += (unsigned)hold & ((1U << op) - 1); |
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172 hold >>= op; |
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173 bits -= op; |
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174 } |
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175 Tracevv((stderr, "inflate: length %u\n", len)); |
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176 if (bits < 15) { |
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177 hold += (unsigned long)(PUP(in)) << bits; |
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178 bits += 8; |
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179 hold += (unsigned long)(PUP(in)) << bits; |
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180 bits += 8; |
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181 } |
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182 this = dcode[hold & dmask]; |
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183 dodist: |
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184 op = (unsigned)(this.bits); |
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185 hold >>= op; |
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186 bits -= op; |
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187 op = (unsigned)(this.op); |
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188 if (op & 16) { /* distance base */ |
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189 dist = (unsigned)(this.val); |
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190 op &= 15; /* number of extra bits */ |
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191 if (bits < op) { |
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192 hold += (unsigned long)(PUP(in)) << bits; |
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193 bits += 8; |
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194 if (bits < op) { |
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195 hold += (unsigned long)(PUP(in)) << bits; |
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196 bits += 8; |
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197 } |
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198 } |
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199 dist += (unsigned)hold & ((1U << op) - 1); |
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200 #ifdef INFLATE_STRICT |
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201 if (dist > dmax) { |
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202 strm->msg = (char *)"invalid distance too far back"; |
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203 state->mode = BAD; |
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204 break; |
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205 } |
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206 #endif |
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207 hold >>= op; |
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208 bits -= op; |
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209 Tracevv((stderr, "inflate: distance %u\n", dist)); |
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210 op = (unsigned)(out - beg); /* max distance in output */ |
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211 if (dist > op) { /* see if copy from window */ |
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212 op = dist - op; /* distance back in window */ |
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213 if (op > whave) { |
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214 strm->msg = (char *)"invalid distance too far back"; |
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215 state->mode = BAD; |
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216 break; |
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217 } |
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218 from = window - OFF; |
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219 if (write == 0) { /* very common case */ |
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220 from += wsize - op; |
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221 if (op < len) { /* some from window */ |
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222 len -= op; |
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223 do { |
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224 PUP(out) = PUP(from); |
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225 } while (--op); |
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226 from = out - dist; /* rest from output */ |
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227 } |
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228 } |
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229 else if (write < op) { /* wrap around window */ |
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230 from += wsize + write - op; |
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231 op -= write; |
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232 if (op < len) { /* some from end of window */ |
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233 len -= op; |
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234 do { |
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235 PUP(out) = PUP(from); |
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236 } while (--op); |
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237 from = window - OFF; |
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238 if (write < len) { /* some from start of window */ |
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239 op = write; |
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240 len -= op; |
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241 do { |
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242 PUP(out) = PUP(from); |
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243 } while (--op); |
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244 from = out - dist; /* rest from output */ |
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245 } |
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246 } |
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247 } |
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248 else { /* contiguous in window */ |
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249 from += write - op; |
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250 if (op < len) { /* some from window */ |
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251 len -= op; |
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252 do { |
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253 PUP(out) = PUP(from); |
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254 } while (--op); |
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255 from = out - dist; /* rest from output */ |
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256 } |
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257 } |
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258 while (len > 2) { |
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259 PUP(out) = PUP(from); |
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260 PUP(out) = PUP(from); |
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261 PUP(out) = PUP(from); |
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262 len -= 3; |
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263 } |
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264 if (len) { |
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265 PUP(out) = PUP(from); |
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266 if (len > 1) |
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267 PUP(out) = PUP(from); |
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268 } |
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269 } |
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270 else { |
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271 from = out - dist; /* copy direct from output */ |
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272 do { /* minimum length is three */ |
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273 PUP(out) = PUP(from); |
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274 PUP(out) = PUP(from); |
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275 PUP(out) = PUP(from); |
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276 len -= 3; |
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277 } while (len > 2); |
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278 if (len) { |
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279 PUP(out) = PUP(from); |
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280 if (len > 1) |
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281 PUP(out) = PUP(from); |
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282 } |
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283 } |
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284 } |
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285 else if ((op & 64) == 0) { /* 2nd level distance code */ |
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286 this = dcode[this.val + (hold & ((1U << op) - 1))]; |
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287 goto dodist; |
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288 } |
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289 else { |
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290 strm->msg = (char *)"invalid distance code"; |
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291 state->mode = BAD; |
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292 break; |
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293 } |
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294 } |
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295 else if ((op & 64) == 0) { /* 2nd level length code */ |
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296 this = lcode[this.val + (hold & ((1U << op) - 1))]; |
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297 goto dolen; |
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298 } |
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299 else if (op & 32) { /* end-of-block */ |
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300 Tracevv((stderr, "inflate: end of block\n")); |
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301 state->mode = TYPE; |
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302 break; |
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303 } |
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304 else { |
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305 strm->msg = (char *)"invalid literal/length code"; |
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306 state->mode = BAD; |
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307 break; |
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308 } |
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309 } while (in < last && out < end); |
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310 |
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311 /* return unused bytes (on entry, bits < 8, so in won't go too far back) */ |
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312 len = bits >> 3; |
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313 in -= len; |
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314 bits -= len << 3; |
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315 hold &= (1U << bits) - 1; |
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316 |
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317 /* update state and return */ |
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318 strm->next_in = in + OFF; |
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319 strm->next_out = out + OFF; |
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320 strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last)); |
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321 strm->avail_out = (unsigned)(out < end ? |
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322 257 + (end - out) : 257 - (out - end)); |
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323 state->hold = hold; |
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324 state->bits = bits; |
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325 return; |
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326 } |
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327 |
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328 /* |
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329 inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe): |
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330 - Using bit fields for code structure |
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331 - Different op definition to avoid & for extra bits (do & for table bits) |
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332 - Three separate decoding do-loops for direct, window, and write == 0 |
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333 - Special case for distance > 1 copies to do overlapped load and store copy |
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334 - Explicit branch predictions (based on measured branch probabilities) |
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335 - Deferring match copy and interspersed it with decoding subsequent codes |
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336 - Swapping literal/length else |
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337 - Swapping window/direct else |
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338 - Larger unrolled copy loops (three is about right) |
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339 - Moving len -= 3 statement into middle of loop |
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340 */ |
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341 |
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342 #endif /* !ASMINF */ |
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