/*
* Copyright 2007 David Gibson, IBM Corporation.
* Based on earlier work, Copyright (C) Paul Mackerras 1997.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <stddef.h>
#include "string.h"
#include "stdio.h"
#include "ops.h"
#include "gunzip_util.h"
#define HEAD_CRC 2
#define EXTRA_FIELD 4
#define ORIG_NAME 8
#define COMMENT 0x10
#define RESERVED 0xe0
/**
* gunzip_start - prepare to decompress gzip data
* @state: decompressor state structure to be initialized
* @src: buffer containing gzip compressed or uncompressed data
* @srclen: size in bytes of the buffer at src
*
* If the buffer at @src contains a gzip header, this function
* initializes zlib to decompress the data, storing the decompression
* state in @state. The other functions in this file can then be used
* to decompress data from the gzipped stream.
*
* If the buffer at @src does not contain a gzip header, it is assumed
* to contain uncompressed data. The buffer information is recorded
* in @state and the other functions in this file will simply copy
* data from the uncompressed data stream at @src.
*
* Any errors, such as bad compressed data, cause an error to be
* printed an the platform's exit() function to be called.
*/
void gunzip_start(struct gunzip_state *state, void *src, int srclen)
{
char *hdr = src;
int hdrlen = 0;
memset(state, 0, sizeof(*state));
/* Check for gzip magic number */
if ((hdr[0] == 0x1f) && (hdr[1] == 0x8b)) {
/* gzip data, initialize zlib parameters */
int r, flags;
state->s.workspace = state->scratch;
if (zlib_inflate_workspacesize() > sizeof(state->scratch))
fatal("insufficient scratch space for gunzip\n\r");
/* skip header */
hdrlen = 10;
flags = hdr[3];
if (hdr[2] != Z_DEFLATED || (flags & RESERVED) != 0)
fatal("bad gzipped data\n\r");
if ((flags & EXTRA_FIELD) != 0)
hdrlen = 12 + hdr[10] + (hdr[11] << 8);
if ((flags & ORIG_NAME) != 0)
while (hdr[hdrlen++] != 0)
;
if ((flags & COMMENT) != 0)
while (hdr[hdrlen++] != 0)
;
if ((flags & HEAD_CRC) != 0)
hdrlen += 2;
if (hdrlen >= srclen)
fatal("gunzip_start: ran out of data in header\n\r");
r = zlib_inflateInit2(&state->s, -MAX_WBITS);
if (r != Z_OK)
fatal("inflateInit2 returned %d\n\r", r);
}
state->s.next_in = src + hdrlen;
state->s.avail_in = srclen - hdrlen;
}
/**
* gunzip_partial - extract bytes from a gzip data stream
* @state: gzip state structure previously initialized by gunzip_start()
* @dst: buffer to store extracted data
* @dstlen: maximum number of bytes to extract
*
* This function extracts at most @dstlen bytes from the data stream
* previously associated with @state by gunzip_start(), decompressing
* if necessary. Exactly @dstlen bytes are extracted unless the data
* stream doesn't contain enough bytes, in which case the entire
* remainder of the stream is decompressed.
*
* Returns the actual number of bytes extracted. If any errors occur,
* such as a corrupted compressed stream, an error is printed an the
* platform's exit() function is called.
*/
int gunzip_partial(struct gunzip_state *state, void *dst, int dstlen)
{
int len;
if (state->s.workspace) {
/* gunzipping */
int r;
state->s.next_out = dst;
state->s.avail_out = dstlen;
r = zlib_inflate(&state->s, Z_FULL_FLUSH);
if (r != Z_OK && r != Z_STREAM_END)
fatal("inflate returned %d msg: %s\n\r", r, state->s.msg);
len = state->s.next_out - (unsigned char *)dst;
} else {
/* uncompressed image */
len = min(state->s.avail_in, (unsigned)dstlen);
memcpy(dst, state->s.next_in, len);
state->s.next_in += len;
state->s.avail_in -= len;
}
return len;
}
/**
* gunzip_exactly - extract a fixed number of bytes from a gzip data stream
* @state: gzip state structure previously initialized by gunzip_start()
* @dst: buffer to store extracted data
* @dstlen: number of bytes to extract
*
* This function extracts exactly @dstlen bytes from the data stream
* previously associated with @state by gunzip_start(), decompressing
* if necessary.
*
* If there are less @dstlen bytes available in the data stream, or if
* any other errors occur, such as a corrupted compressed stream, an
* error is printed an the platform's exit() function is called.
*/
void gunzip_exactly(struct gunzip_state *state, void *dst, int dstlen)
{
int len;
len = gunzip_partial(state, dst, dstlen);
if (len < dstlen)
fatal("gunzip_block: ran out of data\n\r");
}
/**
* gunzip_discard - discard bytes from a gzip data stream
* @state: gzip state structure previously initialized by gunzip_start()
* @len: number of bytes to discard
*
* This function extracts, then discards exactly @len bytes from the
* data stream previously associated with @state by gunzip_start().
* Subsequent gunzip_partial(), gunzip_exactly() or gunzip_finish()
* calls will extract the data following the discarded bytes in the
* data stream.
*
* If there are less @len bytes available in the data stream, or if
* any other errors occur, such as a corrupted compressed stream, an
* error is printed an the platform's exit() function is called.
*/
void gunzip_discard(struct gunzip_state *state, int len)
{
static char discard_buf[128];
while (len > sizeof(discard_buf)) {
gunzip_exactly(state, discard_buf, sizeof(discard_buf));
len -= sizeof(discard_buf);
}
if (len > 0)
gunzip_exactly(state, discard_buf, len);
}
/**
* gunzip_finish - extract all remaining bytes from a gzip data stream
* @state: gzip state structure previously initialized by gunzip_start()
* @dst: buffer to store extracted data
* @dstlen: maximum number of bytes to extract
*
* This function extracts all remaining data, or at most @dstlen
* bytes, from the stream previously associated with @state by
* gunzip_start(). zlib is then shut down, so it is an error to use
* any of the functions in this file on @state until it is
* re-initialized with another call to gunzip_start().
*
* If any errors occur, such as a corrupted compressed stream, an
* error is printed an the platform's exit() function is called.
*/
int gunzip_finish(struct gunzip_state *state, void *dst, int dstlen)
{
int len;
if (state->s.workspace) {
len = gunzip_partial(state, dst, dstlen);
zlib_inflateEnd(&state->s);
} else {
/* uncompressed image */
len = min(state->s.avail_in, (unsigned)dstlen);
memcpy(dst, state->s.next_in, len);
}
return len;
}
