1 | /* vi: set sw=4 ts=4: */
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2 | #include "libbb.h"
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3 |
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4 | /* uncompress for busybox -- (c) 2002 Robert Griebl
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5 | *
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6 | * based on the original compress42.c source
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7 | * (see disclaimer below)
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8 | */
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9 |
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10 | /* (N)compress42.c - File compression ala IEEE Computer, Mar 1992.
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11 | *
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12 | * Authors:
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13 | * Spencer W. Thomas (decvax!harpo!utah-cs!utah-gr!thomas)
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14 | * Jim McKie (decvax!mcvax!jim)
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15 | * Steve Davies (decvax!vax135!petsd!peora!srd)
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16 | * Ken Turkowski (decvax!decwrl!turtlevax!ken)
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17 | * James A. Woods (decvax!ihnp4!ames!jaw)
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18 | * Joe Orost (decvax!vax135!petsd!joe)
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19 | * Dave Mack (csu@alembic.acs.com)
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20 | * Peter Jannesen, Network Communication Systems
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21 | * (peter@ncs.nl)
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22 | *
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23 | * marc@suse.de : a small security fix for a buffer overflow
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24 | *
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25 | * [... History snipped ...]
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26 | *
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27 | */
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28 |
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29 | /* Default input buffer size */
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30 | #define IBUFSIZ 2048
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31 |
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32 | /* Default output buffer size */
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33 | #define OBUFSIZ 2048
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34 |
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35 | /* Defines for third byte of header */
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36 | #define BIT_MASK 0x1f /* Mask for 'number of compresssion bits' */
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37 | /* Masks 0x20 and 0x40 are free. */
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38 | /* I think 0x20 should mean that there is */
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39 | /* a fourth header byte (for expansion). */
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40 | #define BLOCK_MODE 0x80 /* Block compression if table is full and */
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41 | /* compression rate is dropping flush tables */
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42 | /* the next two codes should not be changed lightly, as they must not */
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43 | /* lie within the contiguous general code space. */
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44 | #define FIRST 257 /* first free entry */
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45 | #define CLEAR 256 /* table clear output code */
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46 |
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47 | #define INIT_BITS 9 /* initial number of bits/code */
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48 |
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49 |
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50 | /* machine variants which require cc -Dmachine: pdp11, z8000, DOS */
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51 | #define HBITS 17 /* 50% occupancy */
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52 | #define HSIZE (1<<HBITS)
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53 | #define HMASK (HSIZE-1) /* unused */
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54 | #define HPRIME 9941 /* unused */
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55 | #define BITS 16
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56 | #define BITS_STR "16"
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57 | #undef MAXSEG_64K /* unused */
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58 | #define MAXCODE(n) (1L << (n))
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59 |
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60 | #define htabof(i) htab[i]
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61 | #define codetabof(i) codetab[i]
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62 | #define tab_prefixof(i) codetabof(i)
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63 | #define tab_suffixof(i) ((unsigned char *)(htab))[i]
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64 | #define de_stack ((unsigned char *)&(htab[HSIZE-1]))
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65 | #define clear_tab_prefixof() memset(codetab, 0, 256)
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66 |
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67 | /*
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68 | * Decompress stdin to stdout. This routine adapts to the codes in the
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69 | * file building the "string" table on-the-fly; requiring no table to
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70 | * be stored in the compressed file.
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71 | */
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72 |
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73 | USE_DESKTOP(long long) int
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74 | uncompress(int fd_in, int fd_out)
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75 | {
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76 | USE_DESKTOP(long long total_written = 0;)
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77 | USE_DESKTOP(long long) int retval = -1;
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78 | unsigned char *stackp;
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79 | long code;
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80 | int finchar;
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81 | long oldcode;
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82 | long incode;
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83 | int inbits;
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84 | int posbits;
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85 | int outpos;
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86 | int insize;
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87 | int bitmask;
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88 | long free_ent;
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89 | long maxcode;
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90 | long maxmaxcode;
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91 | int n_bits;
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92 | int rsize = 0;
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93 | unsigned char *inbuf; /* were eating insane amounts of stack - */
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94 | unsigned char *outbuf; /* bad for some embedded targets */
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95 | unsigned char *htab;
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96 | unsigned short *codetab;
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97 |
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98 | /* Hmm, these were statics - why?! */
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99 | /* user settable max # bits/code */
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100 | int maxbits; /* = BITS; */
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101 | /* block compress mode -C compatible with 2.0 */
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102 | int block_mode; /* = BLOCK_MODE; */
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103 |
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104 | inbuf = xzalloc(IBUFSIZ + 64);
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105 | outbuf = xzalloc(OBUFSIZ + 2048);
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106 | htab = xzalloc(HSIZE); /* wsn't zeroed out before, maybe can xmalloc? */
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107 | codetab = xzalloc(HSIZE * sizeof(codetab[0]));
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108 |
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109 | insize = 0;
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110 |
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111 | /* xread isn't good here, we have to return - caller may want
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112 | * to do some cleanup (e.g. delete incomplete unpacked file etc) */
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113 | if (full_read(fd_in, inbuf, 1) != 1) {
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114 | bb_error_msg("short read");
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115 | goto err;
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116 | }
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117 |
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118 | maxbits = inbuf[0] & BIT_MASK;
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119 | block_mode = inbuf[0] & BLOCK_MODE;
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120 | maxmaxcode = MAXCODE(maxbits);
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121 |
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122 | if (maxbits > BITS) {
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123 | bb_error_msg("compressed with %d bits, can only handle "
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124 | BITS_STR" bits", maxbits);
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125 | goto err;
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126 | }
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127 |
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128 | n_bits = INIT_BITS;
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129 | maxcode = MAXCODE(INIT_BITS) - 1;
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130 | bitmask = (1 << INIT_BITS) - 1;
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131 | oldcode = -1;
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132 | finchar = 0;
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133 | outpos = 0;
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134 | posbits = 0 << 3;
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135 |
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136 | free_ent = ((block_mode) ? FIRST : 256);
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137 |
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138 | /* As above, initialize the first 256 entries in the table. */
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139 | /*clear_tab_prefixof(); - done by xzalloc */
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140 |
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141 | for (code = 255; code >= 0; --code) {
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142 | tab_suffixof(code) = (unsigned char) code;
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143 | }
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144 |
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145 | do {
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146 | resetbuf:
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147 | {
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148 | int i;
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149 | int e;
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150 | int o;
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151 |
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152 | o = posbits >> 3;
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153 | e = insize - o;
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154 |
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155 | for (i = 0; i < e; ++i)
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156 | inbuf[i] = inbuf[i + o];
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157 |
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158 | insize = e;
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159 | posbits = 0;
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160 | }
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161 |
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162 | if (insize < (int) (IBUFSIZ + 64) - IBUFSIZ) {
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163 | rsize = safe_read(fd_in, inbuf + insize, IBUFSIZ);
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164 | //error check??
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165 | insize += rsize;
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166 | }
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167 |
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168 | inbits = ((rsize > 0) ? (insize - insize % n_bits) << 3 :
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169 | (insize << 3) - (n_bits - 1));
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170 |
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171 | while (inbits > posbits) {
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172 | if (free_ent > maxcode) {
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173 | posbits =
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174 | ((posbits - 1) +
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175 | ((n_bits << 3) -
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176 | (posbits - 1 + (n_bits << 3)) % (n_bits << 3)));
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177 | ++n_bits;
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178 | if (n_bits == maxbits) {
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179 | maxcode = maxmaxcode;
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180 | } else {
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181 | maxcode = MAXCODE(n_bits) - 1;
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182 | }
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183 | bitmask = (1 << n_bits) - 1;
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184 | goto resetbuf;
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185 | }
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186 | {
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187 | unsigned char *p = &inbuf[posbits >> 3];
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188 |
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189 | code = ((((long) (p[0])) | ((long) (p[1]) << 8) |
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190 | ((long) (p[2]) << 16)) >> (posbits & 0x7)) & bitmask;
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191 | }
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192 | posbits += n_bits;
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193 |
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194 |
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195 | if (oldcode == -1) {
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196 | oldcode = code;
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197 | finchar = (int) oldcode;
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198 | outbuf[outpos++] = (unsigned char) finchar;
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199 | continue;
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200 | }
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201 |
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202 | if (code == CLEAR && block_mode) {
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203 | clear_tab_prefixof();
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204 | free_ent = FIRST - 1;
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205 | posbits =
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206 | ((posbits - 1) +
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207 | ((n_bits << 3) -
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208 | (posbits - 1 + (n_bits << 3)) % (n_bits << 3)));
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209 | n_bits = INIT_BITS;
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210 | maxcode = MAXCODE(INIT_BITS) - 1;
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211 | bitmask = (1 << INIT_BITS) - 1;
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212 | goto resetbuf;
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213 | }
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214 |
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215 | incode = code;
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216 | stackp = de_stack;
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217 |
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218 | /* Special case for KwKwK string. */
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219 | if (code >= free_ent) {
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220 | if (code > free_ent) {
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221 | unsigned char *p;
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222 |
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223 | posbits -= n_bits;
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224 | p = &inbuf[posbits >> 3];
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225 |
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226 | bb_error_msg
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227 | ("insize:%d posbits:%d inbuf:%02X %02X %02X %02X %02X (%d)",
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228 | insize, posbits, p[-1], p[0], p[1], p[2], p[3],
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229 | (posbits & 07));
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230 | bb_error_msg("uncompress: corrupt input");
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231 | goto err;
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232 | }
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233 |
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234 | *--stackp = (unsigned char) finchar;
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235 | code = oldcode;
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236 | }
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237 |
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238 | /* Generate output characters in reverse order */
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239 | while ((long) code >= (long) 256) {
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240 | *--stackp = tab_suffixof(code);
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241 | code = tab_prefixof(code);
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242 | }
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243 |
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244 | finchar = tab_suffixof(code);
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245 | *--stackp = (unsigned char) finchar;
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246 |
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247 | /* And put them out in forward order */
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248 | {
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249 | int i;
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250 |
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251 | i = de_stack - stackp;
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252 | if (outpos + i >= OBUFSIZ) {
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253 | do {
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254 | if (i > OBUFSIZ - outpos) {
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255 | i = OBUFSIZ - outpos;
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256 | }
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257 |
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258 | if (i > 0) {
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259 | memcpy(outbuf + outpos, stackp, i);
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260 | outpos += i;
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261 | }
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262 |
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263 | if (outpos >= OBUFSIZ) {
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264 | full_write(fd_out, outbuf, outpos);
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265 | //error check??
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266 | USE_DESKTOP(total_written += outpos;)
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267 | outpos = 0;
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268 | }
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269 | stackp += i;
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270 | i = de_stack - stackp;
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271 | } while (i > 0);
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272 | } else {
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273 | memcpy(outbuf + outpos, stackp, i);
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274 | outpos += i;
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275 | }
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276 | }
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277 |
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278 | /* Generate the new entry. */
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279 | code = free_ent;
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280 | if (code < maxmaxcode) {
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281 | tab_prefixof(code) = (unsigned short) oldcode;
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282 | tab_suffixof(code) = (unsigned char) finchar;
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283 | free_ent = code + 1;
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284 | }
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285 |
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286 | /* Remember previous code. */
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287 | oldcode = incode;
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288 | }
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289 |
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290 | } while (rsize > 0);
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291 |
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292 | if (outpos > 0) {
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293 | full_write(fd_out, outbuf, outpos);
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294 | //error check??
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295 | USE_DESKTOP(total_written += outpos;)
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296 | }
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297 |
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298 | retval = USE_DESKTOP(total_written) + 0;
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299 | err:
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300 | free(inbuf);
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301 | free(outbuf);
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302 | free(htab);
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303 | free(codetab);
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304 | return retval;
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305 | }
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