1 | #include "libbb.h"
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2 |
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3 | /* uncompress for busybox -- (c) 2002 Robert Griebl
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4 | *
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5 | * based on the original compress42.c source
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6 | * (see disclaimer below)
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7 | */
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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 | #include <stdio.h>
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29 | #include <string.h>
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30 | #include <unistd.h>
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31 |
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32 | /* Default input buffer size */
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33 | #define IBUFSIZ 2048
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34 |
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35 | /* Default output buffer size */
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36 | #define OBUFSIZ 2048
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37 |
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38 | /* Defines for third byte of header */
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39 | #define MAGIC_1 (char_type)'\037' /* First byte of compressed file */
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40 | #define MAGIC_2 (char_type)'\235' /* Second byte of compressed file */
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41 | #define BIT_MASK 0x1f /* Mask for 'number of compresssion bits' */
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42 | /* Masks 0x20 and 0x40 are free. */
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43 | /* I think 0x20 should mean that there is */
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44 | /* a fourth header byte (for expansion). */
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45 | #define BLOCK_MODE 0x80 /* Block compresssion if table is full and */
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46 | /* compression rate is dropping flush tables */
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47 | /* the next two codes should not be changed lightly, as they must not */
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48 | /* lie within the contiguous general code space. */
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49 | #define FIRST 257 /* first free entry */
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50 | #define CLEAR 256 /* table clear output code */
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51 |
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52 | #define INIT_BITS 9 /* initial number of bits/code */
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53 |
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54 |
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55 | /* machine variants which require cc -Dmachine: pdp11, z8000, DOS */
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56 | #define FAST
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57 |
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58 | #define HBITS 17 /* 50% occupancy */
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59 | #define HSIZE (1<<HBITS)
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60 | #define HMASK (HSIZE-1)
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61 | #define HPRIME 9941
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62 | #define BITS 16
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63 | #undef MAXSEG_64K
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64 | #define MAXCODE(n) (1L << (n))
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65 |
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66 | /* Block compress mode -C compatible with 2.0 */
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67 | static int block_mode = BLOCK_MODE;
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68 |
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69 | /* user settable max # bits/code */
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70 | static int maxbits = BITS;
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71 |
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72 | /* Input buffer */
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73 | static unsigned char inbuf[IBUFSIZ + 64];
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74 |
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75 | /* Output buffer */
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76 | static unsigned char outbuf[OBUFSIZ + 2048];
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77 |
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78 |
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79 | static unsigned char htab[HSIZE];
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80 | static unsigned short codetab[HSIZE];
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81 |
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82 | #define htabof(i) htab[i]
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83 | #define codetabof(i) codetab[i]
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84 | #define tab_prefixof(i) codetabof(i)
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85 | #define tab_suffixof(i) ((unsigned char *)(htab))[i]
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86 | #define de_stack ((unsigned char *)&(htab[HSIZE-1]))
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87 | #define clear_htab() memset(htab, -1, sizeof(htab))
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88 | #define clear_tab_prefixof() memset(codetab, 0, 256);
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89 |
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90 |
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91 | /*
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92 | * Decompress stdin to stdout. This routine adapts to the codes in the
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93 | * file building the "string" table on-the-fly; requiring no table to
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94 | * be stored in the compressed file. The tables used herein are shared
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95 | * with those of the compress() routine. See the definitions above.
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96 | */
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97 |
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98 | int uncompress(int fd_in, int fd_out)
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99 | {
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100 | unsigned char *stackp;
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101 | long int code;
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102 | int finchar;
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103 | long int oldcode;
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104 | long int incode;
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105 | int inbits;
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106 | int posbits;
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107 | int outpos;
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108 | int insize;
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109 | int bitmask;
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110 | long int free_ent;
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111 | long int maxcode;
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112 | long int maxmaxcode;
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113 | int n_bits;
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114 | int rsize = 0;
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115 |
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116 | insize = 0;
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117 |
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118 | inbuf[0] = bb_xread_char(fd_in);
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119 |
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120 | maxbits = inbuf[0] & BIT_MASK;
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121 | block_mode = inbuf[0] & BLOCK_MODE;
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122 | maxmaxcode = MAXCODE(maxbits);
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123 |
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124 | if (maxbits > BITS) {
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125 | bb_error_msg("compressed with %d bits, can only handle %d bits", maxbits,
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126 | BITS);
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127 | return -1;
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128 | }
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129 |
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130 | maxcode = MAXCODE(n_bits = INIT_BITS) - 1;
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131 | bitmask = (1 << n_bits) - 1;
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132 | oldcode = -1;
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133 | finchar = 0;
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134 | outpos = 0;
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135 | posbits = 0 << 3;
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136 |
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137 | free_ent = ((block_mode) ? FIRST : 256);
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138 |
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139 | /* As above, initialize the first 256 entries in the table. */
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140 | clear_tab_prefixof();
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141 |
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142 | for (code = 255; code >= 0; --code) {
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143 | tab_suffixof(code) = (unsigned char) code;
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144 | }
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145 |
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146 | do {
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147 | resetbuf:;
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148 | {
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149 | int i;
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150 | int e;
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151 | int o;
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152 |
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153 | e = insize - (o = (posbits >> 3));
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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) sizeof(inbuf) - IBUFSIZ) {
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163 | rsize = safe_read(fd_in, inbuf + insize, IBUFSIZ);
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164 | insize += rsize;
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165 | }
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166 |
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167 | inbits = ((rsize > 0) ? (insize - insize % n_bits) << 3 :
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168 | (insize << 3) - (n_bits - 1));
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169 |
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170 | while (inbits > posbits) {
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171 | if (free_ent > maxcode) {
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172 | posbits =
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173 | ((posbits - 1) +
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174 | ((n_bits << 3) -
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175 | (posbits - 1 + (n_bits << 3)) % (n_bits << 3)));
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176 | ++n_bits;
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177 | if (n_bits == maxbits) {
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178 | maxcode = maxmaxcode;
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179 | } else {
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180 | maxcode = MAXCODE(n_bits) - 1;
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181 | }
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182 | bitmask = (1 << n_bits) - 1;
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183 | goto resetbuf;
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184 | }
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185 | {
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186 | unsigned char *p = &inbuf[posbits >> 3];
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187 |
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188 | code =
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189 | ((((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 | outbuf[outpos++] = (unsigned char) (finchar =
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197 | (int) (oldcode = code));
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198 | continue;
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199 | }
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200 |
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201 | if (code == CLEAR && block_mode) {
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202 | clear_tab_prefixof();
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203 | free_ent = FIRST - 1;
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204 | posbits =
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205 | ((posbits - 1) +
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206 | ((n_bits << 3) -
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207 | (posbits - 1 + (n_bits << 3)) % (n_bits << 3)));
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208 | maxcode = MAXCODE(n_bits = INIT_BITS) - 1;
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209 | bitmask = (1 << n_bits) - 1;
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210 | goto resetbuf;
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211 | }
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212 |
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213 | incode = code;
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214 | stackp = de_stack;
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215 |
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216 | /* Special case for KwKwK string. */
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217 | if (code >= free_ent) {
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218 | if (code > free_ent) {
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219 | unsigned char *p;
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220 |
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221 | posbits -= n_bits;
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222 | p = &inbuf[posbits >> 3];
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223 |
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224 | bb_error_msg
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225 | ("insize:%d posbits:%d inbuf:%02X %02X %02X %02X %02X (%d)",
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226 | insize, posbits, p[-1], p[0], p[1], p[2], p[3],
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227 | (posbits & 07));
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228 | bb_error_msg("uncompress: corrupt input");
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229 | return -1;
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230 | }
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231 |
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232 | *--stackp = (unsigned char) finchar;
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233 | code = oldcode;
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234 | }
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235 |
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236 | /* Generate output characters in reverse order */
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237 | while ((long int) code >= (long int) 256) {
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238 | *--stackp = tab_suffixof(code);
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239 | code = tab_prefixof(code);
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240 | }
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241 |
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242 | *--stackp = (unsigned char) (finchar = tab_suffixof(code));
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243 |
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244 | /* And put them out in forward order */
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245 | {
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246 | int i;
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247 |
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248 | if (outpos + (i = (de_stack - stackp)) >= OBUFSIZ) {
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249 | do {
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250 | if (i > OBUFSIZ - outpos) {
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251 | i = OBUFSIZ - outpos;
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252 | }
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253 |
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254 | if (i > 0) {
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255 | memcpy(outbuf + outpos, stackp, i);
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256 | outpos += i;
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257 | }
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258 |
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259 | if (outpos >= OBUFSIZ) {
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260 | write(fd_out, outbuf, outpos);
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261 | outpos = 0;
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262 | }
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263 | stackp += i;
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264 | } while ((i = (de_stack - stackp)) > 0);
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265 | } else {
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266 | memcpy(outbuf + outpos, stackp, i);
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267 | outpos += i;
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268 | }
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269 | }
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270 |
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271 | /* Generate the new entry. */
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272 | if ((code = free_ent) < maxmaxcode) {
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273 | tab_prefixof(code) = (unsigned short) oldcode;
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274 | tab_suffixof(code) = (unsigned char) finchar;
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275 | free_ent = code + 1;
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276 | }
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277 |
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278 | /* Remember previous code. */
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279 | oldcode = incode;
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280 | }
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281 |
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282 | } while (rsize > 0);
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283 |
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284 | if (outpos > 0) {
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285 | write(fd_out, outbuf, outpos);
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286 | }
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287 |
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288 | return 0;
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289 | }
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