1/* $FreeBSD: head/usr.bin/gzip/unpack.c 194579 2009-06-21 09:39:43Z delphij $ */ 2/* $NetBSD: unpack.c,v 1.1 2009/10/11 07:07:54 mrg Exp $ */ 3 4/*- 5 * Copyright (c) 2009 Xin LI <delphij@FreeBSD.org> 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 30/* This file is #included by gzip.c */ 31 32/* 33 * pack(1) file format: 34 * 35 * The first 7 bytes is the header: 36 * 00, 01 - Signature (US, RS), we already validated it earlier. 37 * 02..05 - Uncompressed size 38 * 06 - Level for the huffman tree (<=24) 39 * 40 * pack(1) will then store symbols (leaf) nodes count in each huffman 41 * tree levels, each level would consume 1 byte (See [1]). 42 * 43 * After the symbol count table, there is the symbol table, storing 44 * symbols represented by corresponding leaf node. EOB is not being 45 * explicitly transmitted (not necessary anyway) in the symbol table. 46 * 47 * Compressed data goes after the symbol table. 48 * 49 * NOTES 50 * 51 * [1] If we count EOB into the symbols, that would mean that we will 52 * have at most 256 symbols in the huffman tree. pack(1) rejects empty 53 * file and files that just repeats one character, which means that we 54 * will have at least 2 symbols. Therefore, pack(1) would reduce the 55 * last level symbol count by 2 which makes it a number in 56 * range [0..254], so all levels' symbol count would fit into 1 byte. 57 */ 58 59#define PACK_HEADER_LENGTH 7 60#define HTREE_MAXLEVEL 24 61 62/* 63 * unpack descriptor 64 * 65 * Represent the huffman tree in a similar way that pack(1) would 66 * store in a packed file. We store all symbols in a linear table, 67 * and store pointers to each level's first symbol. In addition to 68 * that, maintain two counts for each level: inner nodes count and 69 * leaf nodes count. 70 */ 71typedef struct { 72 int symbol_size; /* Size of the symbol table */ 73 int treelevels; /* Levels for the huffman tree */ 74 75 int *symbolsin; /* Table of leaf symbols count in 76 each level */ 77 int *inodesin; /* Table of internal nodes count in 78 each level */ 79 80 char *symbol; /* The symbol table */ 81 char *symbol_eob; /* Pointer to the EOB symbol */ 82 char **tree; /* Decoding huffman tree (pointers to 83 first symbol of each tree level */ 84 85 off_t uncompressed_size; /* Uncompressed size */ 86 FILE *fpIn; /* Input stream */ 87 FILE *fpOut; /* Output stream */ 88} unpack_descriptor_t; 89 90/* 91 * Release resource allocated to an unpack descriptor. 92 * 93 * Caller is responsible to make sure that all of these pointers are 94 * initialized (in our case, they all point to valid memory block). 95 * We don't zero out pointers here because nobody else would ever 96 * reference the memory block without scrubbing them. 97 */ 98static void 99unpack_descriptor_fini(unpack_descriptor_t *unpackd) 100{ 101 102 free(unpackd->symbolsin); 103 free(unpackd->inodesin); 104 free(unpackd->symbol); 105 free(unpackd->tree); 106 107 fclose(unpackd->fpIn); 108 fclose(unpackd->fpOut); 109} 110 111/* 112 * Recursively fill the internal node count table 113 */ 114static void 115unpackd_fill_inodesin(const unpack_descriptor_t *unpackd, int level) 116{ 117 118 /* 119 * The internal nodes would be 1/2 of total internal nodes and 120 * leaf nodes in the next level. For the last level there 121 * would be no internal node by definition. 122 */ 123 if (level < unpackd->treelevels) { 124 unpackd_fill_inodesin(unpackd, level + 1); 125 unpackd->inodesin[level] = (unpackd->inodesin[level + 1] + 126 unpackd->symbolsin[level + 1]) / 2; 127 } else 128 unpackd->inodesin[level] = 0; 129} 130 131/* 132 * Update counter for accepted bytes 133 */ 134static void 135accepted_bytes(off_t *bytes_in, off_t newbytes) 136{ 137 138 if (bytes_in != NULL) 139 (*bytes_in) += newbytes; 140} 141 142/* 143 * Read file header and construct the tree. Also, prepare the buffered I/O 144 * for decode routine. 145 * 146 * Return value is uncompressed size. 147 */ 148static void 149unpack_parse_header(int in, int out, char *pre, size_t prelen, off_t *bytes_in, 150 unpack_descriptor_t *unpackd) 151{ 152 unsigned char hdr[PACK_HEADER_LENGTH]; /* buffer for header */ 153 ssize_t bytesread; /* Bytes read from the file */ 154 int i, j, thisbyte; 155 156 /* Prepend the header buffer if we already read some data */ 157 if (prelen != 0) 158 memcpy(hdr, pre, prelen); 159 160 /* Read in and fill the rest bytes of header */ 161 bytesread = read(in, hdr + prelen, PACK_HEADER_LENGTH - prelen); 162 if (bytesread < 0) 163 maybe_err("Error reading pack header"); 164 165 accepted_bytes(bytes_in, PACK_HEADER_LENGTH); 166 167 /* Obtain uncompressed length (bytes 2,3,4,5)*/ 168 unpackd->uncompressed_size = 0; 169 for (i = 2; i <= 5; i++) { 170 unpackd->uncompressed_size <<= 8; 171 unpackd->uncompressed_size |= hdr[i]; 172 } 173 174 /* Get the levels of the tree */ 175 unpackd->treelevels = hdr[6]; 176 if (unpackd->treelevels > HTREE_MAXLEVEL || unpackd->treelevels < 1) 177 maybe_errx("Huffman tree has insane levels"); 178 179 /* Let libc take care for buffering from now on */ 180 if ((unpackd->fpIn = fdopen(in, "r")) == NULL) 181 maybe_err("Can not fdopen() input stream"); 182 if ((unpackd->fpOut = fdopen(out, "w")) == NULL) 183 maybe_err("Can not fdopen() output stream"); 184 185 /* Allocate for the tables of bounds and the tree itself */ 186 unpackd->inodesin = 187 calloc(unpackd->treelevels, sizeof(*(unpackd->inodesin))); 188 unpackd->symbolsin = 189 calloc(unpackd->treelevels, sizeof(*(unpackd->symbolsin))); 190 unpackd->tree = 191 calloc(unpackd->treelevels, (sizeof (*(unpackd->tree)))); 192 if (unpackd->inodesin == NULL || unpackd->symbolsin == NULL || 193 unpackd->tree == NULL) 194 maybe_err("calloc"); 195 196 /* We count from 0 so adjust to match array upper bound */ 197 unpackd->treelevels--; 198 199 /* Read the levels symbol count table and calculate total */ 200 unpackd->symbol_size = 1; /* EOB */ 201 for (i = 0; i <= unpackd->treelevels; i++) { 202 if ((thisbyte = fgetc(unpackd->fpIn)) == EOF) 203 maybe_err("File appears to be truncated"); 204 unpackd->symbolsin[i] = (unsigned char)thisbyte; 205 unpackd->symbol_size += unpackd->symbolsin[i]; 206 } 207 accepted_bytes(bytes_in, unpackd->treelevels); 208 if (unpackd->symbol_size > 256) 209 maybe_errx("Bad symbol table"); 210 211 /* Allocate for the symbol table, point symbol_eob at the beginning */ 212 unpackd->symbol_eob = unpackd->symbol = calloc(1, unpackd->symbol_size); 213 if (unpackd->symbol == NULL) 214 maybe_err("calloc"); 215 216 /* 217 * Read in the symbol table, which contain [2, 256] symbols. 218 * In order to fit the count in one byte, pack(1) would offset 219 * it by reducing 2 from the actual number from the last level. 220 * 221 * We adjust the last level's symbol count by 1 here, because 222 * the EOB symbol is not being transmitted explicitly. Another 223 * adjustment would be done later afterward. 224 */ 225 unpackd->symbolsin[unpackd->treelevels]++; 226 for (i = 0; i <= unpackd->treelevels; i++) { 227 unpackd->tree[i] = unpackd->symbol_eob; 228 for (j = 0; j < unpackd->symbolsin[i]; j++) { 229 if ((thisbyte = fgetc(unpackd->fpIn)) == EOF) 230 maybe_errx("Symbol table truncated"); 231 *unpackd->symbol_eob++ = (char)thisbyte; 232 } 233 accepted_bytes(bytes_in, unpackd->symbolsin[i]); 234 } 235 236 /* Now, take account for the EOB symbol as well */ 237 unpackd->symbolsin[unpackd->treelevels]++; 238 239 /* 240 * The symbolsin table has been constructed now. 241 * Calculate the internal nodes count table based on it. 242 */ 243 unpackd_fill_inodesin(unpackd, 0); 244} 245 246/* 247 * Decode huffman stream, based on the huffman tree. 248 */ 249static void 250unpack_decode(const unpack_descriptor_t *unpackd, off_t *bytes_in) 251{ 252 int thislevel, thiscode, thisbyte, inlevelindex; 253 int i; 254 off_t bytes_out = 0; 255 const char *thissymbol; /* The symbol pointer decoded from stream */ 256 257 /* 258 * Decode huffman. Fetch every bytes from the file, get it 259 * into 'thiscode' bit-by-bit, then output the symbol we got 260 * when one has been found. 261 * 262 * Assumption: sizeof(int) > ((max tree levels + 1) / 8). 263 * bad things could happen if not. 264 */ 265 thislevel = 0; 266 thiscode = thisbyte = 0; 267 268 while ((thisbyte = fgetc(unpackd->fpIn)) != EOF) { 269 accepted_bytes(bytes_in, 1); 270 271 /* 272 * Split one bit from thisbyte, from highest to lowest, 273 * feed the bit into thiscode, until we got a symbol from 274 * the tree. 275 */ 276 for (i = 7; i >= 0; i--) { 277 thiscode = (thiscode << 1) | ((thisbyte >> i) & 1); 278 279 /* Did we got a symbol? (referencing leaf node) */ 280 if (thiscode >= unpackd->inodesin[thislevel]) { 281 inlevelindex = 282 thiscode - unpackd->inodesin[thislevel]; 283 if (inlevelindex > unpackd->symbolsin[thislevel]) 284 maybe_errx("File corrupt"); 285 286 thissymbol = 287 &(unpackd->tree[thislevel][inlevelindex]); 288 if ((thissymbol == unpackd->symbol_eob) && 289 (bytes_out == unpackd->uncompressed_size)) 290 goto finished; 291 292 fputc((*thissymbol), unpackd->fpOut); 293 bytes_out++; 294 295 /* Prepare for next input */ 296 thislevel = 0; thiscode = 0; 297 } else { 298 thislevel++; 299 if (thislevel > unpackd->treelevels) 300 maybe_errx("File corrupt"); 301 } 302 } 303 } 304 305finished: 306 if (bytes_out != unpackd->uncompressed_size) 307 maybe_errx("Premature EOF"); 308} 309 310/* Handler for pack(1)'ed file */ 311static off_t 312unpack(int in, int out, char *pre, size_t prelen, off_t *bytes_in) 313{ 314 unpack_descriptor_t unpackd; 315 316 unpack_parse_header(dup(in), dup(out), pre, prelen, bytes_in, &unpackd); 317 unpack_decode(&unpackd, bytes_in); 318 unpack_descriptor_fini(&unpackd); 319 320 /* If we reached here, the unpack was successful */ 321 return (unpackd.uncompressed_size); 322} 323 324