/* * tinfgzip - tiny gzip decompressor * * Copyright (c) 2003 by Joergen Ibsen / Jibz * All Rights Reserved * * http://www.ibsensoftware.com/ * * This software is provided 'as-is', without any express * or implied warranty. In no event will the authors be * held liable for any damages arising from the use of * this software. * * Permission is granted to anyone to use this software * for any purpose, including commercial applications, * and to alter it and redistribute it freely, subject to * the following restrictions: * * 1. The origin of this software must not be * misrepresented; you must not claim that you * wrote the original software. If you use this * software in a product, an acknowledgment in * the product documentation would be appreciated * but is not required. * * 2. Altered source versions must be plainly marked * as such, and must not be misrepresented as * being the original software. * * 3. This notice may not be removed or altered from * any source distribution. */ #include "tinf.h" #define FTEXT 1 #define FHCRC 2 #define FEXTRA 4 #define FNAME 8 #define FCOMMENT 16 int tinf_gzip_uncompress(void *dest, unsigned int *destLen, const void *source, unsigned int sourceLen) { unsigned char *src = (unsigned char *)source; unsigned char *dst = (unsigned char *)dest; unsigned char *start; unsigned int dlen, crc32; int res; unsigned char flg; /* -- check format -- */ /* check id bytes */ if (src[0] != 0x1f || src[1] != 0x8b) return TINF_DATA_ERROR; /* check method is deflate */ if (src[2] != 8) return TINF_DATA_ERROR; /* get flag byte */ flg = src[3]; /* check that reserved bits are zero */ if (flg & 0xe0) return TINF_DATA_ERROR; /* -- find start of compressed data -- */ /* skip base header of 10 bytes */ start = src + 10; /* skip extra data if present */ if (flg & FEXTRA) { unsigned int xlen = start[1]; xlen = 256*xlen + start[0]; start += xlen + 2; } /* skip file name if present */ if (flg & FNAME) { while (*start) ++start; ++start; } /* skip file comment if present */ if (flg & FCOMMENT) { while (*start) ++start; ++start; } /* check header crc if present */ if (flg & FHCRC) { unsigned int hcrc = start[1]; hcrc = 256*hcrc + start[0]; if (hcrc != (tinf_crc32(src, start - src) & 0x0000ffff)) return TINF_DATA_ERROR; start += 2; } /* -- get decompressed length -- */ dlen = src[sourceLen - 1]; dlen = 256*dlen + src[sourceLen - 2]; dlen = 256*dlen + src[sourceLen - 3]; dlen = 256*dlen + src[sourceLen - 4]; /* -- get crc32 of decompressed data -- */ crc32 = src[sourceLen - 5]; crc32 = 256*crc32 + src[sourceLen - 6]; crc32 = 256*crc32 + src[sourceLen - 7]; crc32 = 256*crc32 + src[sourceLen - 8]; /* -- decompress data -- */ res = tinf_uncompress(dst, destLen, start, src + sourceLen - start - 8); if (res != TINF_OK) return TINF_DATA_ERROR; if (*destLen != dlen) return TINF_DATA_ERROR; /* -- check CRC32 checksum -- */ if (crc32 != tinf_crc32(dst, dlen)) return TINF_DATA_ERROR; return TINF_OK; }