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}