libarchive/archive_read_support_compression_gzip.c - third_party/libarchive - Git at Google

 /*-
  * Copyright (c) 2003-2007 Tim Kientzle
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "archive_platform.h"

 __FBSDID("$FreeBSD: head/lib/libarchive/archive_read_support_compression_gzip.c 201082 2009-12-28 02:05:28Z kientzle $");


 #ifdef HAVE_ERRNO_H
 #include <errno.h>
 #endif
 #ifdef HAVE_STDLIB_H
 #include <stdlib.h>
 #endif
 #ifdef HAVE_STRING_H
 #include <string.h>
 #endif
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>
 #endif
 #ifdef HAVE_ZLIB_H
 #include <zlib.h>
 #endif

 #include "archive.h"
 #include "archive_private.h"
 #include "archive_read_private.h"

 #ifdef HAVE_ZLIB_H
 struct private_data {
 	z_stream	 stream;
 	char		 in_stream;
 	unsigned char	*out_block;
 	size_t		 out_block_size;
 	int64_t		 total_out;
 	unsigned long	 crc;
 	char		 eof; /* True = found end of compressed data. */
 };

 /* Gzip Filter. */
 static ssize_t	gzip_filter_read(struct archive_read_filter *, const void **);
 static int	gzip_filter_close(struct archive_read_filter *);
 #endif

 /*
  * Note that we can detect gzip archives even if we can't decompress
  * them.  (In fact, we like detecting them because we can give better
  * error messages.)  So the bid framework here gets compiled even
  * if zlib is unavailable.
  *
  * TODO: If zlib is unavailable, gzip_bidder_init() should
  * use the compress_program framework to try to fire up an external
  * gunzip program.
  */
 static int	gzip_bidder_bid(struct archive_read_filter_bidder *,
 		    struct archive_read_filter *);
 static int	gzip_bidder_init(struct archive_read_filter *);

 int
 archive_read_support_compression_gzip(struct archive *_a)
 {
 	struct archive_read *a = (struct archive_read *)_a;
 	struct archive_read_filter_bidder *bidder = __archive_read_get_bidder(a);

 	if (bidder == NULL)
 		return (ARCHIVE_FATAL);

 	bidder->data = NULL;
 	bidder->bid = gzip_bidder_bid;
 	bidder->init = gzip_bidder_init;
 	bidder->options = NULL;
 	bidder->free = NULL; /* No data, so no cleanup necessary. */
 	/* Signal the extent of gzip support with the return value here. */
 #if HAVE_ZLIB_H
 	return (ARCHIVE_OK);
 #else
 	archive_set_error(_a, ARCHIVE_ERRNO_MISC,
 	    "Using external gunzip program");
 	return (ARCHIVE_WARN);
 #endif
 }

 /*
  * Read and verify the header.
  *
  * Returns zero if the header couldn't be validated, else returns
  * number of bytes in header.  If pbits is non-NULL, it receives a
  * count of bits verified, suitable for use by bidder.
  */
 static int
 peek_at_header(struct archive_read_filter *filter, int *pbits)
 {
 	const unsigned char *p;
 	ssize_t avail, len;
 	int bits = 0;
 	int header_flags;

 	/* Start by looking at the first ten bytes of the header, which
 	 * is all fixed layout. */
 	len = 10;
 	p = __archive_read_filter_ahead(filter, len, &avail);
 	if (p == NULL || avail == 0)
 		return (0);
 	if (p[0] != 037)
 		return (0);
 	bits += 8;
 	if (p[1] != 0213)
 		return (0);
 	bits += 8;
 	if (p[2] != 8) /* We only support deflation. */
 		return (0);
 	bits += 8;
 	if ((p[3] & 0xE0)!= 0)	/* No reserved flags set. */
 		return (0);
 	bits += 3;
 	header_flags = p[3];
 	/* Bytes 4-7 are mod time. */
 	/* Byte 8 is deflate flags. */
 	/* XXXX TODO: return deflate flags back to consume_header for use
 	   in initializing the decompressor. */
 	/* Byte 9 is OS. */

 	/* Optional extra data:  2 byte length plus variable body. */
 	if (header_flags & 4) {
 		p = __archive_read_filter_ahead(filter, len + 2, &avail);
 		if (p == NULL)
 			return (0);
 		len += ((int)p[len + 1] << 8) | (int)p[len];
 		len += 2;
 	}

 	/* Null-terminated optional filename. */
 	if (header_flags & 8) {
 		do {
 			++len;
 			if (avail < len)
 				p = __archive_read_filter_ahead(filter,
 				    len, &avail);
 			if (p == NULL)
 				return (0);
 		} while (p[len - 1] != 0);
 	}

 	/* Null-terminated optional comment. */
 	if (header_flags & 16) {
 		do {
 			++len;
 			if (avail < len)
 				p = __archive_read_filter_ahead(filter,
 				    len, &avail);
 			if (p == NULL)
 				return (0);
 		} while (p[len - 1] != 0);
 	}

 	/* Optional header CRC */
 	if ((header_flags & 2)) {
 		p = __archive_read_filter_ahead(filter, len + 2, &avail);
 		if (p == NULL)
 			return (0);
 #if 0
 	int hcrc = ((int)p[len + 1] << 8) | (int)p[len];
 	int crc = /* XXX TODO: Compute header CRC. */;
 	if (crc != hcrc)
 		return (0);
 	bits += 16;
 #endif
 		len += 2;
 	}

 	if (pbits != NULL)
 		*pbits = bits;
 	return (len);
 }

 /*
  * Bidder just verifies the header and returns the number of verified bits.
  */
 static int
 gzip_bidder_bid(struct archive_read_filter_bidder *self,
     struct archive_read_filter *filter)
 {
 	int bits_checked;

 	(void)self; /* UNUSED */

 	if (peek_at_header(filter, &bits_checked))
 		return (bits_checked);
 	return (0);
 }


 #ifndef HAVE_ZLIB_H

 /*
  * If we don't have the library on this system, we can't do the
  * decompression directly.  We can, however, try to run gunzip
  * in case that's available.
  */
 static int
 gzip_bidder_init(struct archive_read_filter *self)
 {
 	int r;

 	r = __archive_read_program(self, "gunzip");
 	/* Note: We set the format here even if __archive_read_program()
 	 * above fails.  We do, after all, know what the format is
 	 * even if we weren't able to read it. */
 	self->code = ARCHIVE_COMPRESSION_GZIP;
 	self->name = "gzip";
 	return (r);
 }

 #else

 /*
  * Initialize the filter object.
  */
 static int
 gzip_bidder_init(struct archive_read_filter *self)
 {
 	struct private_data *state;
 	static const size_t out_block_size = 64 * 1024;
 	void *out_block;

 	self->code = ARCHIVE_COMPRESSION_GZIP;
 	self->name = "gzip";

 	state = (struct private_data *)calloc(sizeof(*state), 1);
 	out_block = (unsigned char *)malloc(out_block_size);
 	if (state == NULL || out_block == NULL) {
 		free(out_block);
 		free(state);
 		archive_set_error(&self->archive->archive, ENOMEM,
 		    "Can't allocate data for gzip decompression");
 		return (ARCHIVE_FATAL);
 	}

 	self->data = state;
 	state->out_block_size = out_block_size;
 	state->out_block = out_block;
 	self->read = gzip_filter_read;
 	self->skip = NULL; /* not supported */
 	self->close = gzip_filter_close;

 	state->in_stream = 0; /* We're not actually within a stream yet. */

 	return (ARCHIVE_OK);
 }

 static int
 consume_header(struct archive_read_filter *self)
 {
 	struct private_data *state;
 	ssize_t avail;
 	size_t len;
 	int ret;

 	state = (struct private_data *)self->data;

 	/* If this is a real header, consume it. */
 	len = peek_at_header(self->upstream, NULL);
 	if (len == 0)
 		return (ARCHIVE_EOF);
 	__archive_read_filter_consume(self->upstream, len);

 	/* Initialize CRC accumulator. */
 	state->crc = crc32(0L, NULL, 0);

 	/* Initialize compression library. */
 	state->stream.next_in = (unsigned char *)(uintptr_t)
 	    __archive_read_filter_ahead(self->upstream, 1, &avail);
 	state->stream.avail_in = avail;
 	ret = inflateInit2(&(state->stream),
 	    -15 /* Don't check for zlib header */);

 	/* Decipher the error code. */
 	switch (ret) {
 	case Z_OK:
 		state->in_stream = 1;
 		return (ARCHIVE_OK);
 	case Z_STREAM_ERROR:
 		archive_set_error(&self->archive->archive,
 		    ARCHIVE_ERRNO_MISC,
 		    "Internal error initializing compression library: "
 		    "invalid setup parameter");
 		break;
 	case Z_MEM_ERROR:
 		archive_set_error(&self->archive->archive, ENOMEM,
 		    "Internal error initializing compression library: "
 		    "out of memory");
 		break;
 	case Z_VERSION_ERROR:
 		archive_set_error(&self->archive->archive,
 		    ARCHIVE_ERRNO_MISC,
 		    "Internal error initializing compression library: "
 		    "invalid library version");
 		break;
 	default:
 		archive_set_error(&self->archive->archive,
 		    ARCHIVE_ERRNO_MISC,
 		    "Internal error initializing compression library: "
 		    " Zlib error %d", ret);
 		break;
 	}
 	return (ARCHIVE_FATAL);
 }

 static int
 consume_trailer(struct archive_read_filter *self)
 {
 	struct private_data *state;
 	const unsigned char *p;
 	ssize_t avail;

 	state = (struct private_data *)self->data;

 	state->in_stream = 0;
 	switch (inflateEnd(&(state->stream))) {
 	case Z_OK:
 		break;
 	default:
 		archive_set_error(&self->archive->archive,
 		    ARCHIVE_ERRNO_MISC,
 		    "Failed to clean up gzip decompressor");
 		return (ARCHIVE_FATAL);
 	}

 	/* GZip trailer is a fixed 8 byte structure. */
 	p = __archive_read_filter_ahead(self->upstream, 8, &avail);
 	if (p == NULL || avail == 0)
 		return (ARCHIVE_FATAL);

 	/* XXX TODO: Verify the length and CRC. */

 	/* We've verified the trailer, so consume it now. */
 	__archive_read_filter_consume(self->upstream, 8);

 	return (ARCHIVE_OK);
 }

 static ssize_t
 gzip_filter_read(struct archive_read_filter *self, const void **p)
 {
 	struct private_data *state;
 	size_t decompressed;
 	ssize_t avail_in;
 	int ret;

 	state = (struct private_data *)self->data;

 	/* Empty our output buffer. */
 	state->stream.next_out = state->out_block;
 	state->stream.avail_out = state->out_block_size;

 	/* Try to fill the output buffer. */
 	while (state->stream.avail_out > 0 && !state->eof) {
 		/* If we're not in a stream, read a header
 		 * and initialize the decompression library. */
 		if (!state->in_stream) {
 			ret = consume_header(self);
 			if (ret == ARCHIVE_EOF) {
 				state->eof = 1;
 				break;
 			}
 			if (ret < ARCHIVE_OK)
 				return (ret);
 		}

 		/* Peek at the next available data. */
 		/* ZLib treats stream.next_in as const but doesn't declare
 		 * it so, hence this ugly cast. */
 		state->stream.next_in = (unsigned char *)(uintptr_t)
 		    __archive_read_filter_ahead(self->upstream, 1, &avail_in);
 		if (state->stream.next_in == NULL)
 			return (ARCHIVE_FATAL);
 		state->stream.avail_in = avail_in;

 		/* Decompress and consume some of that data. */
 		ret = inflate(&(state->stream), 0);
 		switch (ret) {
 		case Z_OK: /* Decompressor made some progress. */
 			__archive_read_filter_consume(self->upstream,
 			    avail_in - state->stream.avail_in);
 			break;
 		case Z_STREAM_END: /* Found end of stream. */
 			__archive_read_filter_consume(self->upstream,
 			    avail_in - state->stream.avail_in);
 			/* Consume the stream trailer; release the
 			 * decompression library. */
 			ret = consume_trailer(self);
 			if (ret < ARCHIVE_OK)
 				return (ret);
 			break;
 		default:
 			/* Return an error. */
 			archive_set_error(&self->archive->archive,
 			    ARCHIVE_ERRNO_MISC,
 			    "gzip decompression failed");
 			return (ARCHIVE_FATAL);
 		}
 	}

 	/* We've read as much as we can. */
 	decompressed = state->stream.next_out - state->out_block;
 	state->total_out += decompressed;
 	if (decompressed == 0)
 		*p = NULL;
 	else
 		*p = state->out_block;
 	return (decompressed);
 }

 /*
  * Clean up the decompressor.
  */
 static int
 gzip_filter_close(struct archive_read_filter *self)
 {
 	struct private_data *state;
 	int ret;

 	state = (struct private_data *)self->data;
 	ret = ARCHIVE_OK;

 	if (state->in_stream) {
 		switch (inflateEnd(&(state->stream))) {
 		case Z_OK:
 			break;
 		default:
 			archive_set_error(&(self->archive->archive),
 			    ARCHIVE_ERRNO_MISC,
 			    "Failed to clean up gzip compressor");
 			ret = ARCHIVE_FATAL;
 		}
 	}

 	free(state->out_block);
 	free(state);
 	return (ret);
 }

 #endif /* HAVE_ZLIB_H */
	/*-
	* Copyright (c) 2003-2007 Tim Kientzle
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	* IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "archive_platform.h"

	__FBSDID("$FreeBSD: head/lib/libarchive/archive_read_support_compression_gzip.c 201082 2009-12-28 02:05:28Z kientzle $");


	#ifdef HAVE_ERRNO_H
	#include <errno.h>
	#endif
	#ifdef HAVE_STDLIB_H
	#include <stdlib.h>
	#endif
	#ifdef HAVE_STRING_H
	#include <string.h>
	#endif
	#ifdef HAVE_UNISTD_H
	#include <unistd.h>
	#endif
	#ifdef HAVE_ZLIB_H
	#include <zlib.h>
	#endif

	#include "archive.h"
	#include "archive_private.h"
	#include "archive_read_private.h"

	#ifdef HAVE_ZLIB_H
	struct private_data {
	z_stream stream;
	char in_stream;
	unsigned char *out_block;
	size_t out_block_size;
	int64_t total_out;
	unsigned long crc;
	char eof; /* True = found end of compressed data. */
	};

	/* Gzip Filter. */
	static ssize_t gzip_filter_read(struct archive_read_filter , const void *);
	static int gzip_filter_close(struct archive_read_filter *);
	#endif

	/*
	* Note that we can detect gzip archives even if we can't decompress
	* them. (In fact, we like detecting them because we can give better
	* error messages.) So the bid framework here gets compiled even
	* if zlib is unavailable.
	*
	* TODO: If zlib is unavailable, gzip_bidder_init() should
	* use the compress_program framework to try to fire up an external
	* gunzip program.
	*/
	static int gzip_bidder_bid(struct archive_read_filter_bidder *,
	struct archive_read_filter *);
	static int gzip_bidder_init(struct archive_read_filter *);

	int
	archive_read_support_compression_gzip(struct archive *_a)
	{
	struct archive_read a = (struct archive_read )_a;
	struct archive_read_filter_bidder *bidder = __archive_read_get_bidder(a);

	if (bidder == NULL)
	return (ARCHIVE_FATAL);

	bidder->data = NULL;
	bidder->bid = gzip_bidder_bid;
	bidder->init = gzip_bidder_init;
	bidder->options = NULL;
	bidder->free = NULL; /* No data, so no cleanup necessary. */
	/* Signal the extent of gzip support with the return value here. */
	#if HAVE_ZLIB_H
	return (ARCHIVE_OK);
	#else
	archive_set_error(_a, ARCHIVE_ERRNO_MISC,
	"Using external gunzip program");
	return (ARCHIVE_WARN);
	#endif
	}

	/*
	* Read and verify the header.
	*
	* Returns zero if the header couldn't be validated, else returns
	* number of bytes in header. If pbits is non-NULL, it receives a
	* count of bits verified, suitable for use by bidder.
	*/
	static int
	peek_at_header(struct archive_read_filter filter, int pbits)
	{
	const unsigned char *p;
	ssize_t avail, len;
	int bits = 0;
	int header_flags;

	/* Start by looking at the first ten bytes of the header, which
	* is all fixed layout. */
	len = 10;
	p = __archive_read_filter_ahead(filter, len, &avail);
	if (p == NULL \|\| avail == 0)
	return (0);
	if (p[0] != 037)
	return (0);
	bits += 8;
	if (p[1] != 0213)
	return (0);
	bits += 8;
	if (p[2] != 8) /* We only support deflation. */
	return (0);
	bits += 8;
	if ((p[3] & 0xE0)!= 0) /* No reserved flags set. */
	return (0);
	bits += 3;
	header_flags = p[3];
	/* Bytes 4-7 are mod time. */
	/* Byte 8 is deflate flags. */
	/* XXXX TODO: return deflate flags back to consume_header for use
	in initializing the decompressor. */
	/* Byte 9 is OS. */

	/* Optional extra data: 2 byte length plus variable body. */
	if (header_flags & 4) {
	p = __archive_read_filter_ahead(filter, len + 2, &avail);
	if (p == NULL)
	return (0);
	len += ((int)p[len + 1] << 8) \| (int)p[len];
	len += 2;
	}

	/* Null-terminated optional filename. */
	if (header_flags & 8) {
	do {
	++len;
	if (avail < len)
	p = __archive_read_filter_ahead(filter,
	len, &avail);
	if (p == NULL)
	return (0);
	} while (p[len - 1] != 0);
	}

	/* Null-terminated optional comment. */
	if (header_flags & 16) {
	do {
	++len;
	if (avail < len)
	p = __archive_read_filter_ahead(filter,
	len, &avail);
	if (p == NULL)
	return (0);
	} while (p[len - 1] != 0);
	}

	/* Optional header CRC */
	if ((header_flags & 2)) {
	p = __archive_read_filter_ahead(filter, len + 2, &avail);
	if (p == NULL)
	return (0);
	#if 0
	int hcrc = ((int)p[len + 1] << 8) \| (int)p[len];
	int crc = /* XXX TODO: Compute header CRC. */;
	if (crc != hcrc)
	return (0);
	bits += 16;
	#endif
	len += 2;
	}

	if (pbits != NULL)
	*pbits = bits;
	return (len);
	}

	/*
	* Bidder just verifies the header and returns the number of verified bits.
	*/
	static int
	gzip_bidder_bid(struct archive_read_filter_bidder *self,
	struct archive_read_filter *filter)
	{
	int bits_checked;

	(void)self; /* UNUSED */

	if (peek_at_header(filter, &bits_checked))
	return (bits_checked);
	return (0);
	}


	#ifndef HAVE_ZLIB_H

	/*
	* If we don't have the library on this system, we can't do the
	* decompression directly. We can, however, try to run gunzip
	* in case that's available.
	*/
	static int
	gzip_bidder_init(struct archive_read_filter *self)
	{
	int r;

	r = __archive_read_program(self, "gunzip");
	/* Note: We set the format here even if __archive_read_program()
	* above fails. We do, after all, know what the format is
	* even if we weren't able to read it. */
	self->code = ARCHIVE_COMPRESSION_GZIP;
	self->name = "gzip";
	return (r);
	}

	#else

	/*
	* Initialize the filter object.
	*/
	static int
	gzip_bidder_init(struct archive_read_filter *self)
	{
	struct private_data *state;
	static const size_t out_block_size = 64 * 1024;
	void *out_block;

	self->code = ARCHIVE_COMPRESSION_GZIP;
	self->name = "gzip";

	state = (struct private_data )calloc(sizeof(state), 1);
	out_block = (unsigned char *)malloc(out_block_size);
	if (state == NULL \|\| out_block == NULL) {
	free(out_block);
	free(state);
	archive_set_error(&self->archive->archive, ENOMEM,
	"Can't allocate data for gzip decompression");
	return (ARCHIVE_FATAL);
	}

	self->data = state;
	state->out_block_size = out_block_size;
	state->out_block = out_block;
	self->read = gzip_filter_read;
	self->skip = NULL; /* not supported */
	self->close = gzip_filter_close;

	state->in_stream = 0; /* We're not actually within a stream yet. */

	return (ARCHIVE_OK);
	}

	static int
	consume_header(struct archive_read_filter *self)
	{
	struct private_data *state;
	ssize_t avail;
	size_t len;
	int ret;

	state = (struct private_data *)self->data;

	/* If this is a real header, consume it. */
	len = peek_at_header(self->upstream, NULL);
	if (len == 0)
	return (ARCHIVE_EOF);
	__archive_read_filter_consume(self->upstream, len);

	/* Initialize CRC accumulator. */
	state->crc = crc32(0L, NULL, 0);

	/* Initialize compression library. */
	state->stream.next_in = (unsigned char *)(uintptr_t)
	__archive_read_filter_ahead(self->upstream, 1, &avail);
	state->stream.avail_in = avail;
	ret = inflateInit2(&(state->stream),
	-15 /* Don't check for zlib header */);

	/* Decipher the error code. */
	switch (ret) {
	case Z_OK:
	state->in_stream = 1;
	return (ARCHIVE_OK);
	case Z_STREAM_ERROR:
	archive_set_error(&self->archive->archive,
	ARCHIVE_ERRNO_MISC,
	"Internal error initializing compression library: "
	"invalid setup parameter");
	break;
	case Z_MEM_ERROR:
	archive_set_error(&self->archive->archive, ENOMEM,
	"Internal error initializing compression library: "
	"out of memory");
	break;
	case Z_VERSION_ERROR:
	archive_set_error(&self->archive->archive,
	ARCHIVE_ERRNO_MISC,
	"Internal error initializing compression library: "
	"invalid library version");
	break;
	default:
	archive_set_error(&self->archive->archive,
	ARCHIVE_ERRNO_MISC,
	"Internal error initializing compression library: "
	" Zlib error %d", ret);
	break;
	}
	return (ARCHIVE_FATAL);
	}

	static int
	consume_trailer(struct archive_read_filter *self)
	{
	struct private_data *state;
	const unsigned char *p;
	ssize_t avail;

	state = (struct private_data *)self->data;

	state->in_stream = 0;
	switch (inflateEnd(&(state->stream))) {
	case Z_OK:
	break;
	default:
	archive_set_error(&self->archive->archive,
	ARCHIVE_ERRNO_MISC,
	"Failed to clean up gzip decompressor");
	return (ARCHIVE_FATAL);
	}

	/* GZip trailer is a fixed 8 byte structure. */
	p = __archive_read_filter_ahead(self->upstream, 8, &avail);
	if (p == NULL \|\| avail == 0)
	return (ARCHIVE_FATAL);

	/* XXX TODO: Verify the length and CRC. */

	/* We've verified the trailer, so consume it now. */
	__archive_read_filter_consume(self->upstream, 8);

	return (ARCHIVE_OK);
	}

	static ssize_t
	gzip_filter_read(struct archive_read_filter self, const void *p)
	{
	struct private_data *state;
	size_t decompressed;
	ssize_t avail_in;
	int ret;

	state = (struct private_data *)self->data;

	/* Empty our output buffer. */
	state->stream.next_out = state->out_block;
	state->stream.avail_out = state->out_block_size;

	/* Try to fill the output buffer. */
	while (state->stream.avail_out > 0 && !state->eof) {
	/* If we're not in a stream, read a header
	* and initialize the decompression library. */
	if (!state->in_stream) {
	ret = consume_header(self);
	if (ret == ARCHIVE_EOF) {
	state->eof = 1;
	break;
	}
	if (ret < ARCHIVE_OK)
	return (ret);
	}

	/* Peek at the next available data. */
	/* ZLib treats stream.next_in as const but doesn't declare
	* it so, hence this ugly cast. */
	state->stream.next_in = (unsigned char *)(uintptr_t)
	__archive_read_filter_ahead(self->upstream, 1, &avail_in);
	if (state->stream.next_in == NULL)
	return (ARCHIVE_FATAL);
	state->stream.avail_in = avail_in;

	/* Decompress and consume some of that data. */
	ret = inflate(&(state->stream), 0);
	switch (ret) {
	case Z_OK: /* Decompressor made some progress. */
	__archive_read_filter_consume(self->upstream,
	avail_in - state->stream.avail_in);
	break;
	case Z_STREAM_END: /* Found end of stream. */
	__archive_read_filter_consume(self->upstream,
	avail_in - state->stream.avail_in);
	/* Consume the stream trailer; release the
	* decompression library. */
	ret = consume_trailer(self);
	if (ret < ARCHIVE_OK)
	return (ret);
	break;
	default:
	/* Return an error. */
	archive_set_error(&self->archive->archive,
	ARCHIVE_ERRNO_MISC,
	"gzip decompression failed");
	return (ARCHIVE_FATAL);
	}
	}

	/* We've read as much as we can. */
	decompressed = state->stream.next_out - state->out_block;
	state->total_out += decompressed;
	if (decompressed == 0)
	*p = NULL;
	else
	*p = state->out_block;
	return (decompressed);
	}

	/*
	* Clean up the decompressor.
	*/
	static int
	gzip_filter_close(struct archive_read_filter *self)
	{
	struct private_data *state;
	int ret;

	state = (struct private_data *)self->data;
	ret = ARCHIVE_OK;

	if (state->in_stream) {
	switch (inflateEnd(&(state->stream))) {
	case Z_OK:
	break;
	default:
	archive_set_error(&(self->archive->archive),
	ARCHIVE_ERRNO_MISC,
	"Failed to clean up gzip compressor");
	ret = ARCHIVE_FATAL;
	}
	}

	free(state->out_block);
	free(state);
	return (ret);
	}

	#endif /* HAVE_ZLIB_H */