1 /*- 2 * Copyright (c) 2009 Xin LI <delphij@FreeBSD.org> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 * 26 * $FreeBSD: head/usr.bin/gzip/unpack.c 194579 2009-06-21 09:39:43Z delphij $ 27 */ 28 29 /* This file is #included by gzip.c */ 30 31 /* 32 * pack(1) file format: 33 * 34 * The first 7 bytes is the header: 35 * 00, 01 - Signature (US, RS), we already validated it earlier. 36 * 02..05 - Uncompressed size 37 * 06 - Level for the huffman tree (<=24) 38 * 39 * pack(1) will then store symbols (leaf) nodes count in each huffman 40 * tree levels, each level would consume 1 byte (See [1]). 41 * 42 * After the symbol count table, there is the symbol table, storing 43 * symbols represented by coresponding leaf node. EOB is not being 44 * explicitly transmitted (not necessary anyway) in the symbol table. 45 * 46 * Compressed data goes after the symbol table. 47 * 48 * NOTES 49 * 50 * [1] If we count EOB into the symbols, that would mean that we will 51 * have at most 256 symbols in the huffman tree. pack(1) rejects empty 52 * file and files that just repeats one character, which means that we 53 * will have at least 2 symbols. Therefore, pack(1) would reduce the 54 * last level symbol count by 2 which makes it a number in 55 * range [0..254], so all levels' symbol count would fit into 1 byte. 56 */ 57 58 #define PACK_HEADER_LENGTH 7 59 #define HTREE_MAXLEVEL 24 60 61 /* 62 * unpack descriptor 63 * 64 * Represent the huffman tree in a similiar way that pack(1) would 65 * store in a packed file. We store all symbols in a linear table, 66 * and store pointers to each level's first symbol. In addition to 67 * that, maintain two counts for each level: inner nodes count and 68 * leaf nodes count. 69 */ 70 typedef struct { 71 int symbol_size; /* Size of the symbol table */ 72 int treelevels; /* Levels for the huffman tree */ 73 74 int *symbolsin; /* Table of leaf symbols count in 75 each level */ 76 int *inodesin; /* Table of internal nodes count in 77 each level */ 78 79 char *symbol; /* The symbol table */ 80 char *symbol_eob; /* Pointer to the EOB symbol */ 81 char **tree; /* Decoding huffman tree (pointers to 82 first symbol of each tree level */ 83 84 off_t uncompressed_size; /* Uncompressed size */ 85 FILE *fpIn; /* Input stream */ 86 FILE *fpOut; /* Output stream */ 87 } unpack_descriptor_t; 88 89 /* 90 * Release resource allocated to an unpack descriptor. 91 * 92 * Caller is responsible to make sure that all of these pointers are 93 * initialized (in our case, they all point to valid memory block). 94 * We don't zero out pointers here because nobody else would ever 95 * reference the memory block without scrubing them. 96 */ 97 static void 98 unpack_descriptor_fini(unpack_descriptor_t *unpackd) 99 { 100 101 free(unpackd->symbolsin); 102 free(unpackd->inodesin); 103 free(unpackd->symbol); 104 free(unpackd->tree); 105 106 fclose(unpackd->fpIn); 107 fclose(unpackd->fpOut); 108 } 109 110 /* 111 * Recursively fill the internal node count table 112 */ 113 static void 114 unpackd_fill_inodesin(const unpack_descriptor_t *unpackd, int level) 115 { 116 117 /* 118 * The internal nodes would be 1/2 of total internal nodes and 119 * leaf nodes in the next level. For the last level there 120 * would be no internal node by defination. 121 */ 122 if (level < unpackd->treelevels) { 123 unpackd_fill_inodesin(unpackd, level + 1); 124 unpackd->inodesin[level] = (unpackd->inodesin[level + 1] + 125 unpackd->symbolsin[level + 1]) / 2; 126 } else 127 unpackd->inodesin[level] = 0; 128 } 129 130 /* 131 * Update counter for accepted bytes 132 */ 133 static void 134 accepted_bytes(off_t *bytes_in, off_t newbytes) 135 { 136 137 if (bytes_in != NULL) 138 (*bytes_in) += newbytes; 139 } 140 141 /* 142 * Read file header and construct the tree. Also, prepare the buffered I/O 143 * for decode rountine. 144 * 145 * Return value is uncompressed size. 146 */ 147 static void 148 unpack_parse_header(int in, int out, char *pre, size_t prelen, off_t *bytes_in, 149 unpack_descriptor_t *unpackd) 150 { 151 unsigned char hdr[PACK_HEADER_LENGTH]; /* buffer for header */ 152 ssize_t bytesread; /* Bytes read from the file */ 153 int i, j, thisbyte; 154 155 /* Prepend the header buffer if we already read some data */ 156 if (prelen != 0) 157 memcpy(hdr, pre, prelen); 158 159 /* Read in and fill the rest bytes of header */ 160 bytesread = read(in, hdr + prelen, PACK_HEADER_LENGTH - prelen); 161 if (bytesread < 0) 162 maybe_err("Error reading pack header"); 163 164 accepted_bytes(bytes_in, PACK_HEADER_LENGTH); 165 166 /* Obtain uncompressed length (bytes 2,3,4,5)*/ 167 unpackd->uncompressed_size = 0; 168 for (i = 2; i <= 5; i++) { 169 unpackd->uncompressed_size <<= 8; 170 unpackd->uncompressed_size |= hdr[i]; 171 } 172 173 /* Get the levels of the tree */ 174 unpackd->treelevels = hdr[6]; 175 if (unpackd->treelevels > HTREE_MAXLEVEL || unpackd->treelevels < 1) 176 maybe_errx("Huffman tree has insane levels"); 177 178 /* Let libc take care for buffering from now on */ 179 if ((unpackd->fpIn = fdopen(in, "r")) == NULL) 180 maybe_err("Can not fdopen() input stream"); 181 if ((unpackd->fpOut = fdopen(out, "w")) == NULL) 182 maybe_err("Can not fdopen() output stream"); 183 184 /* Allocate for the tables of bounds and the tree itself */ 185 unpackd->inodesin = 186 calloc(unpackd->treelevels, sizeof(*(unpackd->inodesin))); 187 unpackd->symbolsin = 188 calloc(unpackd->treelevels, sizeof(*(unpackd->symbolsin))); 189 unpackd->tree = 190 calloc(unpackd->treelevels, (sizeof (*(unpackd->tree)))); 191 if (unpackd->inodesin == NULL || unpackd->symbolsin == NULL || 192 unpackd->tree == NULL) 193 maybe_err("calloc"); 194 195 /* We count from 0 so adjust to match array upper bound */ 196 unpackd->treelevels--; 197 198 /* Read the levels symbol count table and caculate total */ 199 unpackd->symbol_size = 1; /* EOB */ 200 for (i = 0; i <= unpackd->treelevels; i++) { 201 if ((thisbyte = fgetc(unpackd->fpIn)) == EOF) 202 maybe_err("File appears to be truncated"); 203 unpackd->symbolsin[i] = (unsigned char)thisbyte; 204 unpackd->symbol_size += unpackd->symbolsin[i]; 205 } 206 accepted_bytes(bytes_in, unpackd->treelevels); 207 if (unpackd->symbol_size > 256) 208 maybe_errx("Bad symbol table"); 209 210 /* Allocate for the symbol table, point symbol_eob at the beginning */ 211 unpackd->symbol_eob = unpackd->symbol = calloc(1, unpackd->symbol_size); 212 if (unpackd->symbol == NULL) 213 maybe_err("calloc"); 214 215 /* 216 * Read in the symbol table, which contain [2, 256] symbols. 217 * In order to fit the count in one byte, pack(1) would offset 218 * it by reducing 2 from the actual number from the last level. 219 * 220 * We adjust the last level's symbol count by 1 here, because 221 * the EOB symbol is not being transmitted explicitly. Another 222 * adjustment would be done later afterward. 223 */ 224 unpackd->symbolsin[unpackd->treelevels]++; 225 for (i = 0; i <= unpackd->treelevels; i++) { 226 unpackd->tree[i] = unpackd->symbol_eob; 227 for (j = 0; j < unpackd->symbolsin[i]; j++) { 228 if ((thisbyte = fgetc(unpackd->fpIn)) == EOF) 229 maybe_errx("Symbol table truncated"); 230 *unpackd->symbol_eob++ = (char)thisbyte; 231 } 232 accepted_bytes(bytes_in, unpackd->symbolsin[i]); 233 } 234 235 /* Now, take account for the EOB symbol as well */ 236 unpackd->symbolsin[unpackd->treelevels]++; 237 238 /* 239 * The symbolsin table has been constructed now. 240 * Caculate the internal nodes count table based on it. 241 */ 242 unpackd_fill_inodesin(unpackd, 0); 243 } 244 245 /* 246 * Decode huffman stream, based on the huffman tree. 247 */ 248 static void 249 unpack_decode(const unpack_descriptor_t *unpackd, off_t *bytes_in) 250 { 251 int thislevel, thiscode, thisbyte, inlevelindex; 252 int i; 253 off_t bytes_out = 0; 254 const char *thissymbol; /* The symbol pointer decoded from stream */ 255 256 /* 257 * Decode huffman. Fetch every bytes from the file, get it 258 * into 'thiscode' bit-by-bit, then output the symbol we got 259 * when one has been found. 260 * 261 * Assumption: sizeof(int) > ((max tree levels + 1) / 8). 262 * bad things could happen if not. 263 */ 264 thislevel = 0; 265 thiscode = thisbyte = 0; 266 267 while ((thisbyte = fgetc(unpackd->fpIn)) != EOF) { 268 accepted_bytes(bytes_in, 1); 269 270 /* 271 * Split one bit from thisbyte, from highest to lowest, 272 * feed the bit into thiscode, until we got a symbol from 273 * the tree. 274 */ 275 for (i = 7; i >= 0; i--) { 276 thiscode = (thiscode << 1) | ((thisbyte >> i) & 1); 277 278 /* Did we got a symbol? (referencing leaf node) */ 279 if (thiscode >= unpackd->inodesin[thislevel]) { 280 inlevelindex = 281 thiscode - unpackd->inodesin[thislevel]; 282 if (inlevelindex > unpackd->symbolsin[thislevel]) 283 maybe_errx("File corrupt"); 284 285 thissymbol = 286 &(unpackd->tree[thislevel][inlevelindex]); 287 if ((thissymbol == unpackd->symbol_eob) && 288 (bytes_out == unpackd->uncompressed_size)) 289 goto finished; 290 291 fputc((*thissymbol), unpackd->fpOut); 292 bytes_out++; 293 294 /* Prepare for next input */ 295 thislevel = 0; thiscode = 0; 296 } else { 297 thislevel++; 298 if (thislevel > unpackd->treelevels) 299 maybe_errx("File corrupt"); 300 } 301 } 302 } 303 304 finished: 305 if (bytes_out != unpackd->uncompressed_size) 306 maybe_errx("Premature EOF"); 307 } 308 309 /* Handler for pack(1)'ed file */ 310 static off_t 311 unpack(int in, int out, char *pre, size_t prelen, off_t *bytes_in) 312 { 313 unpack_descriptor_t unpackd; 314 315 unpack_parse_header(dup(in), dup(out), pre, prelen, bytes_in, &unpackd); 316 unpack_decode(&unpackd, bytes_in); 317 unpack_descriptor_fini(&unpackd); 318 319 /* If we reached here, the unpack was successful */ 320 return (unpackd.uncompressed_size); 321 } 322