1/* 2 * Copyright 2007 David Gibson, IBM Corporation. 3 * Based on earlier work, Copyright (C) Paul Mackerras 1997. 4 * 5 * This program is free software; you can redistribute it and/or 6 * modify it under the terms of the GNU General Public License 7 * as published by the Free Software Foundation; either version 8 * 2 of the License, or (at your option) any later version. 9 */ 10 11#include <stddef.h> 12#include "string.h" 13#include "stdio.h" 14#include "ops.h" 15#include "gunzip_util.h" 16 17#define HEAD_CRC 2 18#define EXTRA_FIELD 4 19#define ORIG_NAME 8 20#define COMMENT 0x10 21#define RESERVED 0xe0 22 23/** 24 * gunzip_start - prepare to decompress gzip data 25 * @state: decompressor state structure to be initialized 26 * @src: buffer containing gzip compressed or uncompressed data 27 * @srclen: size in bytes of the buffer at src 28 * 29 * If the buffer at @src contains a gzip header, this function 30 * initializes zlib to decompress the data, storing the decompression 31 * state in @state. The other functions in this file can then be used 32 * to decompress data from the gzipped stream. 33 * 34 * If the buffer at @src does not contain a gzip header, it is assumed 35 * to contain uncompressed data. The buffer information is recorded 36 * in @state and the other functions in this file will simply copy 37 * data from the uncompressed data stream at @src. 38 * 39 * Any errors, such as bad compressed data, cause an error to be 40 * printed an the platform's exit() function to be called. 41 */ 42void gunzip_start(struct gunzip_state *state, void *src, int srclen) 43{ 44 char *hdr = src; 45 int hdrlen = 0; 46 47 memset(state, 0, sizeof(*state)); 48 49 /* Check for gzip magic number */ 50 if ((hdr[0] == 0x1f) && (hdr[1] == 0x8b)) { 51 /* gzip data, initialize zlib parameters */ 52 int r, flags; 53 54 state->s.workspace = state->scratch; 55 if (zlib_inflate_workspacesize() > sizeof(state->scratch)) 56 fatal("insufficient scratch space for gunzip\n\r"); 57 58 /* skip header */ 59 hdrlen = 10; 60 flags = hdr[3]; 61 if (hdr[2] != Z_DEFLATED || (flags & RESERVED) != 0) 62 fatal("bad gzipped data\n\r"); 63 if ((flags & EXTRA_FIELD) != 0) 64 hdrlen = 12 + hdr[10] + (hdr[11] << 8); 65 if ((flags & ORIG_NAME) != 0) 66 while (hdr[hdrlen++] != 0) 67 ; 68 if ((flags & COMMENT) != 0) 69 while (hdr[hdrlen++] != 0) 70 ; 71 if ((flags & HEAD_CRC) != 0) 72 hdrlen += 2; 73 if (hdrlen >= srclen) 74 fatal("gunzip_start: ran out of data in header\n\r"); 75 76 r = zlib_inflateInit2(&state->s, -MAX_WBITS); 77 if (r != Z_OK) 78 fatal("inflateInit2 returned %d\n\r", r); 79 } 80 81 state->s.total_in = hdrlen; 82 state->s.next_in = src + hdrlen; 83 state->s.avail_in = srclen - hdrlen; 84} 85 86/** 87 * gunzip_partial - extract bytes from a gzip data stream 88 * @state: gzip state structure previously initialized by gunzip_start() 89 * @dst: buffer to store extracted data 90 * @dstlen: maximum number of bytes to extract 91 * 92 * This function extracts at most @dstlen bytes from the data stream 93 * previously associated with @state by gunzip_start(), decompressing 94 * if necessary. Exactly @dstlen bytes are extracted unless the data 95 * stream doesn't contain enough bytes, in which case the entire 96 * remainder of the stream is decompressed. 97 * 98 * Returns the actual number of bytes extracted. If any errors occur, 99 * such as a corrupted compressed stream, an error is printed an the 100 * platform's exit() function is called. 101 */ 102int gunzip_partial(struct gunzip_state *state, void *dst, int dstlen) 103{ 104 int len; 105 106 if (state->s.workspace) { 107 /* gunzipping */ 108 int r; 109 110 state->s.next_out = dst; 111 state->s.avail_out = dstlen; 112 r = zlib_inflate(&state->s, Z_FULL_FLUSH); 113 if (r != Z_OK && r != Z_STREAM_END) 114 fatal("inflate returned %d msg: %s\n\r", r, state->s.msg); 115 len = state->s.next_out - (unsigned char *)dst; 116 } else { 117 /* uncompressed image */ 118 len = min(state->s.avail_in, (unsigned)dstlen); 119 memcpy(dst, state->s.next_in, len); 120 state->s.next_in += len; 121 state->s.avail_in -= len; 122 } 123 return len; 124} 125 126/** 127 * gunzip_exactly - extract a fixed number of bytes from a gzip data stream 128 * @state: gzip state structure previously initialized by gunzip_start() 129 * @dst: buffer to store extracted data 130 * @dstlen: number of bytes to extract 131 * 132 * This function extracts exactly @dstlen bytes from the data stream 133 * previously associated with @state by gunzip_start(), decompressing 134 * if necessary. 135 * 136 * If there are less @dstlen bytes available in the data stream, or if 137 * any other errors occur, such as a corrupted compressed stream, an 138 * error is printed an the platform's exit() function is called. 139 */ 140void gunzip_exactly(struct gunzip_state *state, void *dst, int dstlen) 141{ 142 int len; 143 144 len = gunzip_partial(state, dst, dstlen); 145 if (len < dstlen) 146 fatal("\n\rgunzip_exactly: ran out of data!" 147 " Wanted %d, got %d.\n\r", dstlen, len); 148} 149 150/** 151 * gunzip_discard - discard bytes from a gzip data stream 152 * @state: gzip state structure previously initialized by gunzip_start() 153 * @len: number of bytes to discard 154 * 155 * This function extracts, then discards exactly @len bytes from the 156 * data stream previously associated with @state by gunzip_start(). 157 * Subsequent gunzip_partial(), gunzip_exactly() or gunzip_finish() 158 * calls will extract the data following the discarded bytes in the 159 * data stream. 160 * 161 * If there are less @len bytes available in the data stream, or if 162 * any other errors occur, such as a corrupted compressed stream, an 163 * error is printed an the platform's exit() function is called. 164 */ 165void gunzip_discard(struct gunzip_state *state, int len) 166{ 167 static char discard_buf[128]; 168 169 while (len > sizeof(discard_buf)) { 170 gunzip_exactly(state, discard_buf, sizeof(discard_buf)); 171 len -= sizeof(discard_buf); 172 } 173 174 if (len > 0) 175 gunzip_exactly(state, discard_buf, len); 176} 177 178/** 179 * gunzip_finish - extract all remaining bytes from a gzip data stream 180 * @state: gzip state structure previously initialized by gunzip_start() 181 * @dst: buffer to store extracted data 182 * @dstlen: maximum number of bytes to extract 183 * 184 * This function extracts all remaining data, or at most @dstlen 185 * bytes, from the stream previously associated with @state by 186 * gunzip_start(). zlib is then shut down, so it is an error to use 187 * any of the functions in this file on @state until it is 188 * re-initialized with another call to gunzip_start(). 189 * 190 * If any errors occur, such as a corrupted compressed stream, an 191 * error is printed an the platform's exit() function is called. 192 */ 193int gunzip_finish(struct gunzip_state *state, void *dst, int dstlen) 194{ 195 int len; 196 197 len = gunzip_partial(state, dst, dstlen); 198 199 if (state->s.workspace) { 200 zlib_inflateEnd(&state->s); 201 } 202 203 return len; 204} 205