2 * Copyright 2007 David Gibson, IBM Corporation.
3 * Based on earlier work, Copyright (C) Paul Mackerras 1997.
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.
15 #include "gunzip_util.h"
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
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.
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.
39 * Any errors, such as bad compressed data, cause an error to be
40 * printed an the platform's exit() function to be called.
42 void gunzip_start(struct gunzip_state *state, void *src, int srclen)
47 memset(state, 0, sizeof(*state));
49 /* Check for gzip magic number */
50 if ((hdr[0] == 0x1f) && (hdr[1] == 0x8b)) {
51 /* gzip data, initialize zlib parameters */
54 state->s.workspace = state->scratch;
55 if (zlib_inflate_workspacesize() > sizeof(state->scratch))
56 fatal("insufficient scratch space for gunzip\n\r");
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)
68 if ((flags & COMMENT) != 0)
69 while (hdr[hdrlen++] != 0)
71 if ((flags & HEAD_CRC) != 0)
74 fatal("gunzip_start: ran out of data in header\n\r");
76 r = zlib_inflateInit2(&state->s, -MAX_WBITS);
78 fatal("inflateInit2 returned %d\n\r", r);
81 state->s.next_in = src + hdrlen;
82 state->s.avail_in = srclen - hdrlen;
86 * gunzip_partial - extract bytes from a gzip data stream
87 * @state: gzip state structure previously initialized by gunzip_start()
88 * @dst: buffer to store extracted data
89 * @dstlen: maximum number of bytes to extract
91 * This function extracts at most @dstlen bytes from the data stream
92 * previously associated with @state by gunzip_start(), decompressing
93 * if necessary. Exactly @dstlen bytes are extracted unless the data
94 * stream doesn't contain enough bytes, in which case the entire
95 * remainder of the stream is decompressed.
97 * Returns the actual number of bytes extracted. If any errors occur,
98 * such as a corrupted compressed stream, an error is printed an the
99 * platform's exit() function is called.
101 int gunzip_partial(struct gunzip_state *state, void *dst, int dstlen)
105 if (state->s.workspace) {
109 state->s.next_out = dst;
110 state->s.avail_out = dstlen;
111 r = zlib_inflate(&state->s, Z_FULL_FLUSH);
112 if (r != Z_OK && r != Z_STREAM_END)
113 fatal("inflate returned %d msg: %s\n\r", r, state->s.msg);
114 len = state->s.next_out - (unsigned char *)dst;
116 /* uncompressed image */
117 len = min(state->s.avail_in, (unsigned)dstlen);
118 memcpy(dst, state->s.next_in, len);
119 state->s.next_in += len;
120 state->s.avail_in -= len;
126 * gunzip_exactly - extract a fixed number of bytes from a gzip data stream
127 * @state: gzip state structure previously initialized by gunzip_start()
128 * @dst: buffer to store extracted data
129 * @dstlen: number of bytes to extract
131 * This function extracts exactly @dstlen bytes from the data stream
132 * previously associated with @state by gunzip_start(), decompressing
135 * If there are less @dstlen bytes available in the data stream, or if
136 * any other errors occur, such as a corrupted compressed stream, an
137 * error is printed an the platform's exit() function is called.
139 void gunzip_exactly(struct gunzip_state *state, void *dst, int dstlen)
143 len = gunzip_partial(state, dst, dstlen);
145 fatal("gunzip_block: ran out of data\n\r");
149 * gunzip_discard - discard bytes from a gzip data stream
150 * @state: gzip state structure previously initialized by gunzip_start()
151 * @len: number of bytes to discard
153 * This function extracts, then discards exactly @len bytes from the
154 * data stream previously associated with @state by gunzip_start().
155 * Subsequent gunzip_partial(), gunzip_exactly() or gunzip_finish()
156 * calls will extract the data following the discarded bytes in the
159 * If there are less @len bytes available in the data stream, or if
160 * any other errors occur, such as a corrupted compressed stream, an
161 * error is printed an the platform's exit() function is called.
163 void gunzip_discard(struct gunzip_state *state, int len)
165 static char discard_buf[128];
167 while (len > sizeof(discard_buf)) {
168 gunzip_exactly(state, discard_buf, sizeof(discard_buf));
169 len -= sizeof(discard_buf);
173 gunzip_exactly(state, discard_buf, len);
177 * gunzip_finish - extract all remaining bytes from a gzip data stream
178 * @state: gzip state structure previously initialized by gunzip_start()
179 * @dst: buffer to store extracted data
180 * @dstlen: maximum number of bytes to extract
182 * This function extracts all remaining data, or at most @dstlen
183 * bytes, from the stream previously associated with @state by
184 * gunzip_start(). zlib is then shut down, so it is an error to use
185 * any of the functions in this file on @state until it is
186 * re-initialized with another call to gunzip_start().
188 * If any errors occur, such as a corrupted compressed stream, an
189 * error is printed an the platform's exit() function is called.
191 int gunzip_finish(struct gunzip_state *state, void *dst, int dstlen)
195 if (state->s.workspace) {
196 len = gunzip_partial(state, dst, dstlen);
197 zlib_inflateEnd(&state->s);
199 /* uncompressed image */
200 len = min(state->s.avail_in, (unsigned)dstlen);
201 memcpy(dst, state->s.next_in, len);