Add support for lz4 read filter.

TODO: detecting liblz4 library by CMake.

1 files changed, 728 insertions, 0 deletions

diff --git a/libarchive/archive_read_support_filter_lz4.c b/libarchive/archive_read_support_filter_lz4.c
new file mode 100644
index 00000000..db62cb35
--- /dev/null
+++ b/libarchive/archive_read_support_filter_lz4.c
@@ -0,0 +1,728 @@
+/*-
+ * Copyright (c) 2014 Michihiro NAKAJIMA
+ * 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("$FreeBSD$");
+
+#ifdef HAVE_ERRNO_H
+#include <errno.h>
+#endif
+#include <stdio.h>
+#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_LZ4_H
+#include <lz4.h>
+#endif
+
+#include "archive.h"
+#include "archive_endian.h"
+#include "archive_private.h"
+#include "archive_read_private.h"
+#include "archive_xxhash.h"
+
+#define LZ4_MAGICNUMBER		0x184d2204
+#define LZ4_SKIPPABLED		0x184d2a50
+#define LZ4_LEGACY		0x184c2102
+
+#if defined(HAVE_LIBLZ4)
+struct private_data {
+	enum {  SELECT_STREAM,
+		READ_DEFAULT_STREAM,
+		READ_DEFAULT_BLOCK,
+		READ_LEGACY_STREAM,
+		READ_LEGACY_BLOCK,
+	}		stage;
+	struct {
+		unsigned block_independence:1;
+		unsigned block_checksum:3;
+		unsigned stream_size:1;
+		unsigned stream_checksum:1;
+		unsigned preset_dictionary:1;
+		int	 block_maximum_size;
+	} flags;
+	int64_t		 stream_size;
+	uint32_t	 dict_id;
+	char		*out_block;
+	size_t		 out_block_size;
+
+	/* Bytes read but not yet consumed via __archive_read_consume() */
+	size_t		 unconsumed;
+	size_t		 decoded_size;
+	void		*xxh32_state;
+
+	char		 valid; /* True = decompressor is initialized */
+	char		 eof; /* True = found end of compressed data. */
+};
+
+#define LEGACY_BLOCK_SIZE	(8 * 1024 * 1024)
+
+/* Lz4 filter */
+static ssize_t	lz4_filter_read(struct archive_read_filter *, const void **);
+static int	lz4_filter_close(struct archive_read_filter *);
+#endif
+
+/*
+ * Note that we can detect lz4 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 liblz4 is unavailable.
+ */
+static int	lz4_reader_bid(struct archive_read_filter_bidder *, struct archive_read_filter *);
+static int	lz4_reader_init(struct archive_read_filter *);
+static int	lz4_reader_free(struct archive_read_filter_bidder *);
+#if defined(HAVE_LIBLZ4)
+static ssize_t  lz4_filter_read_default_stream(struct archive_read_filter *,
+		    const void **);
+static ssize_t  lz4_filter_read_legacy_stream(struct archive_read_filter *,
+		    const void **);
+#endif
+
+int
+archive_read_support_filter_lz4(struct archive *_a)
+{
+	struct archive_read *a = (struct archive_read *)_a;
+	struct archive_read_filter_bidder *reader;
+
+	archive_check_magic(_a, ARCHIVE_READ_MAGIC,
+	    ARCHIVE_STATE_NEW, "archive_read_support_filter_lz4");
+
+	if (__archive_read_get_bidder(a, &reader) != ARCHIVE_OK)
+		return (ARCHIVE_FATAL);
+
+	reader->data = NULL;
+	reader->name = "lz4";
+	reader->bid = lz4_reader_bid;
+	reader->init = lz4_reader_init;
+	reader->options = NULL;
+	reader->free = lz4_reader_free;
+#if defined(HAVE_LIBLZ4)
+	return (ARCHIVE_OK);
+#else
+	archive_set_error(_a, ARCHIVE_ERRNO_MISC,
+	    "Using external lz4 program");
+	return (ARCHIVE_WARN);
+#endif
+}
+
+static int
+lz4_reader_free(struct archive_read_filter_bidder *self){
+	(void)self; /* UNUSED */
+	return (ARCHIVE_OK);
+}
+
+/*
+ * Test whether we can handle this data.
+ *
+ * This logic returns zero if any part of the signature fails.  It
+ * also tries to Do The Right Thing if a very short buffer prevents us
+ * from verifying as much as we would like.
+ */
+static int
+lz4_reader_bid(struct archive_read_filter_bidder *self,
+    struct archive_read_filter *filter)
+{
+	const unsigned char *buffer;
+	ssize_t avail;
+	int bits_checked;
+	uint32_t number;
+
+	(void)self; /* UNUSED */
+
+	/* Minimal lz4 archive is 11 bytes. */
+	buffer = __archive_read_filter_ahead(filter, 11, &avail);
+	if (buffer == NULL)
+		return (0);
+
+	/* First four bytes must be LZ4 magic numbers. */
+	bits_checked = 0;
+	if ((number = archive_le32dec(buffer)) == LZ4_MAGICNUMBER) {
+		unsigned char flag, BD;
+
+		bits_checked += 32;
+		/* Next follows a stream descriptor. */
+		/* Descriptor Flags. */
+		flag = buffer[4];
+		/* A version number must be "01". */
+		if (((flag & 0xc0) >> 6) != 1)
+			return (0);
+		/* A reserved bit must be "0". */
+		if (flag & 2)
+			return (0);
+		bits_checked += 8;
+		BD = buffer[5];
+		/* A block maximum size shuld be more than 3. */
+		if (((BD & 0x70) >> 4) < 4)
+			return (0);
+		/* Reserved bits must be "0". */
+		if (BD & ~0x70)
+			return (0);
+		bits_checked += 8;
+	} else if (number == LZ4_LEGACY) {
+		bits_checked += 32;
+	}
+	
+	return (bits_checked);
+}
+
+#if !defined(HAVE_LIBLZ4)
+
+/*
+ * If we don't have the library on this system, we can't actually do the
+ * decompression.  We can, however, still detect compressed archives
+ * and emit a useful message.
+ */
+static int
+lz4_reader_init(struct archive_read_filter *self)
+{
+	int r;
+
+	r = __archive_read_program(self, "lz4 -d -q");
+	/* 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_FILTER_LZ4;
+	self->name = "lz4";
+	return (r);
+}
+
+
+#else
+
+/*
+ * Setup the callbacks.
+ */
+static int
+lz4_reader_init(struct archive_read_filter *self)
+{
+	struct private_data *state;
+
+	self->code = ARCHIVE_FILTER_LZ4;
+	self->name = "lz4";
+
+	state = (struct private_data *)calloc(sizeof(*state), 1);
+	if (state == NULL) {
+		archive_set_error(&self->archive->archive, ENOMEM,
+		    "Can't allocate data for lz4 decompression");
+		return (ARCHIVE_FATAL);
+	}
+
+	self->data = state;
+	state->stage = SELECT_STREAM;
+	self->read = lz4_filter_read;
+	self->skip = NULL; /* not supported */
+	self->close = lz4_filter_close;
+
+	return (ARCHIVE_OK);
+}
+
+static int
+lz4_allocate_out_block(struct archive_read_filter *self)
+{
+	struct private_data *state = (struct private_data *)self->data;
+	size_t out_block_size = state->flags.block_maximum_size;
+	void *out_block;
+
+	if (!state->flags.block_independence)
+		out_block_size += 64 * 1024;
+	if (state->out_block_size < out_block_size) {
+		free(state->out_block);
+		out_block = (unsigned char *)malloc(out_block_size);
+		state->out_block_size = out_block_size;
+		if (out_block == NULL) {
+			archive_set_error(&self->archive->archive, ENOMEM,
+			    "Can't allocate data for lz4 decompression");
+			return (ARCHIVE_FATAL);
+		}
+		state->out_block = out_block;
+	}
+	if (!state->flags.block_independence)
+		memset(state->out_block, 0, 64 * 1024);
+	return (ARCHIVE_OK);
+}
+
+static int
+lz4_allocate_out_block_for_legacy(struct archive_read_filter *self)
+{
+	struct private_data *state = (struct private_data *)self->data;
+	size_t out_block_size = LEGACY_BLOCK_SIZE;
+	void *out_block;
+
+	if (state->out_block_size < out_block_size) {
+		free(state->out_block);
+		out_block = (unsigned char *)malloc(out_block_size);
+		state->out_block_size = out_block_size;
+		if (out_block == NULL) {
+			archive_set_error(&self->archive->archive, ENOMEM,
+			    "Can't allocate data for lz4 decompression");
+			return (ARCHIVE_FATAL);
+		}
+		state->out_block = out_block;
+	}
+	return (ARCHIVE_OK);
+}
+
+/*
+ * Return the next block of decompressed data.
+ */
+static ssize_t
+lz4_filter_read(struct archive_read_filter *self, const void **p)
+{
+	struct private_data *state = (struct private_data *)self->data;
+	ssize_t ret;
+
+	if (state->eof) {
+		*p = NULL;
+		return (0);
+	}
+
+	__archive_read_filter_consume(self->upstream, state->unconsumed);
+	state->unconsumed = 0;
+
+	switch (state->stage) {
+	case SELECT_STREAM:
+		break;
+	case READ_DEFAULT_STREAM:
+	case READ_LEGACY_STREAM:
+		/* Reading a lz4 stream already failed. */
+		archive_set_error(&self->archive->archive,
+		    ARCHIVE_ERRNO_MISC, "Invalid sequence.");
+		return (ARCHIVE_FATAL);
+	case READ_DEFAULT_BLOCK:
+		ret = lz4_filter_read_default_stream(self, p);
+		if (ret != 0 || state->stage != SELECT_STREAM)
+			return ret;
+		break;
+	case READ_LEGACY_BLOCK:
+		ret = lz4_filter_read_legacy_stream(self, p);
+		if (ret != 0 || state->stage != SELECT_STREAM)
+			return ret;
+		break;
+	default:
+		archive_set_error(&self->archive->archive,
+		    ARCHIVE_ERRNO_MISC, "Program error.");
+		return (ARCHIVE_FATAL);
+		break;
+	}
+
+	while (state->stage == SELECT_STREAM) {
+		const char *read_buf;
+
+		/* Read a magic number. */
+		read_buf = __archive_read_filter_ahead(self->upstream, 4,
+				NULL);
+		if (read_buf == NULL) {
+			state->eof = 1;
+			*p = NULL;
+			return (0);
+		}
+		uint32_t number = archive_le32dec(read_buf);
+		__archive_read_filter_consume(self->upstream, 4);
+		if (number == LZ4_MAGICNUMBER)
+			return lz4_filter_read_default_stream(self, p);
+		else if (number == LZ4_LEGACY)
+			return lz4_filter_read_legacy_stream(self, p);
+		else if ((number & ~0xF) == LZ4_SKIPPABLED) {
+			read_buf = __archive_read_filter_ahead(
+				self->upstream, 4, NULL);
+			if (read_buf == NULL) {
+				archive_set_error(
+				    &self->archive->archive,
+		    		    ARCHIVE_ERRNO_MISC,
+				    "Malformed lz4 data");
+				return (ARCHIVE_FATAL);
+			}
+			uint32_t skip_bytes = archive_le32dec(read_buf);
+			__archive_read_filter_consume(self->upstream,
+				4 + skip_bytes);
+		} else {
+			/* Ignore following unrecognized data. */
+			state->eof = 1;
+			*p = NULL;
+			return (0);
+		}
+	}
+	state->eof = 1;
+	*p = NULL;
+	return (0);
+}
+
+static int
+lz4_filter_read_descriptor(struct archive_read_filter *self)
+{
+	struct private_data *state = (struct private_data *)self->data;
+	const char *read_buf;
+	ssize_t bytes_remaining;
+	ssize_t descriptor_bytes;
+	unsigned char flag, bd;
+	unsigned int chsum, chsum_verifier;
+
+	/* Make sure we have 2 bytes for flags. */
+	read_buf = __archive_read_filter_ahead(self->upstream, 2,
+	    &bytes_remaining);
+	if (read_buf == NULL) {
+		archive_set_error(&self->archive->archive,
+		    ARCHIVE_ERRNO_MISC,
+		    "truncated lz4 input");
+		return (ARCHIVE_FATAL);
+	}
+
+	/*
+	   Parse flags.
+	 */
+	flag = (unsigned char)read_buf[0];
+	/* Verify version number. */
+	if ((flag & 0xc0) != 1<<6)
+		goto malformed_error;
+	/* A reserved bit must be zero. */
+	if (flag & 0x02)
+		goto malformed_error;
+	state->flags.block_independence = (flag & 0x20) != 0;
+	state->flags.block_checksum = (flag & 0x10)?4:0;
+	state->flags.stream_size = (flag & 0x08) != 0;
+	state->flags.stream_checksum = (flag & 0x04) != 0;
+	state->flags.preset_dictionary = (flag & 0x01) != 0;
+
+	/* BD */
+	bd = (unsigned char)read_buf[1];
+	/* Reserved bits must be zero. */
+	if (bd & 0x8f)
+		goto malformed_error;
+	/* Get a maxinum block size. */
+	switch (read_buf[1] >> 4) {
+	case 4: /* 64 KB */
+		state->flags.block_maximum_size = 64 * 1024;
+		break;
+	case 5: /* 256 KB */
+		state->flags.block_maximum_size = 256 * 1024;
+		break;
+	case 6: /* 1 MB */
+		state->flags.block_maximum_size = 1024 * 1024;
+		break;
+	case 7: /* 4 MB */
+		state->flags.block_maximum_size = 4 * 1024 * 1024;
+		break;
+	default:
+		goto malformed_error;
+	}
+
+	/* Read the whole descriptor in a stream block. */
+	descriptor_bytes = 3;
+	if (state->flags.stream_size)
+		descriptor_bytes += 8;
+	if (state->flags.preset_dictionary)
+		descriptor_bytes += 4;
+	if (bytes_remaining < descriptor_bytes) {
+		read_buf = __archive_read_filter_ahead(self->upstream,
+		    descriptor_bytes, &bytes_remaining);
+		if (read_buf == NULL) {
+			archive_set_error(&self->archive->archive,
+			    ARCHIVE_ERRNO_MISC,
+			    "truncated lz4 input");
+			return (ARCHIVE_FATAL);
+		}
+	}
+	/* Check if a descriptor is corrupted */
+	chsum = __archive_xxhash.XXH32(read_buf, (int)descriptor_bytes -1, 0);
+	chsum = (chsum >> 8) & 0xff;
+	chsum_verifier = read_buf[descriptor_bytes-1] & 0xff;
+	if (chsum != chsum_verifier)
+		goto malformed_error;
+
+	__archive_read_filter_consume(self->upstream, descriptor_bytes);
+
+	/* Make sure we have an enough buffer for uncompressed data. */
+	if (lz4_allocate_out_block(self) != ARCHIVE_OK)
+		return (ARCHIVE_FATAL);
+	if (state->flags.stream_checksum)
+		state->xxh32_state = __archive_xxhash.XXH32_init(0);
+
+	state->decoded_size = 0;
+	/* Success */
+	return (ARCHIVE_OK);
+malformed_error:
+	archive_set_error(&self->archive->archive, ARCHIVE_ERRNO_MISC,
+	    "malformed lz4 data");
+	return (ARCHIVE_FATAL);
+}
+
+static ssize_t
+lz4_filter_read_data_block(struct archive_read_filter *self, const void **p)
+{
+	struct private_data *state = (struct private_data *)self->data;
+	ssize_t compressed_size;
+	const char *read_buf;
+	ssize_t bytes_remaining;
+	int checksum_size;
+	ssize_t uncompressed_size;
+	size_t prefix64k;
+
+	*p = NULL;
+
+	/* Make sure we have 4 bytes for a block size. */
+	read_buf = __archive_read_filter_ahead(self->upstream, 4,
+	    &bytes_remaining);
+	if (read_buf == NULL)
+		goto truncated_error;
+	compressed_size = archive_le32dec(read_buf);
+	if ((compressed_size & ~(1 << 31)) > state->flags.block_maximum_size)
+		goto malformed_error;
+	/* A compressed size == 0 means the end of stream blocks. */
+	if (compressed_size == 0) {
+		__archive_read_filter_consume(self->upstream, 4);
+		return 0;
+	}
+
+	checksum_size = state->flags.block_checksum;
+	/* Check if the block is uncompressed. */
+	if (compressed_size & (1 << 31)) {
+		compressed_size &= ~(1 << 31);
+		uncompressed_size = compressed_size;
+	} else
+		uncompressed_size = 0;/* Unknown yet. */
+
+	/*
+	  Unfortunately, lz4 decompression API requires a whole block
+	  for its decompression speed, so we read a whole block and allocate
+	  a huge buffer used for decoded data.
+	*/
+	read_buf = __archive_read_filter_ahead(self->upstream,
+	    4 + compressed_size + checksum_size, &bytes_remaining);
+	if (read_buf == NULL)
+		goto truncated_error;
+
+	/* Optional process, checking a block sum. */
+	if (checksum_size) {
+		unsigned int chsum = __archive_xxhash.XXH32(
+			read_buf + 4, (int)compressed_size, 0);
+		unsigned int chsum_block =
+		    archive_le32dec(read_buf + 4 + compressed_size);
+		if (chsum != chsum_block)
+			goto malformed_error;
+	}
+
+
+	/* If the block is uncompressed, there is nothing to do. */
+	if (uncompressed_size) {
+		/* Prepare a prefix 64k block for next block. */
+		if (!state->flags.block_independence) {
+			prefix64k = 64 * 1024;
+			if (uncompressed_size < (ssize_t)prefix64k) {
+				memcpy(state->out_block
+					+ prefix64k - uncompressed_size,
+				    read_buf + 4,
+				    uncompressed_size);
+				memset(state->out_block, 0,
+				    prefix64k - uncompressed_size);
+			} else {
+				memcpy(state->out_block,
+				    read_buf + 4
+					+ uncompressed_size - prefix64k,
+				    prefix64k);
+			}
+			state->decoded_size = 0;
+		}
+		state->unconsumed = 4 + uncompressed_size + checksum_size;
+		*p = read_buf + 4;
+		return uncompressed_size;
+	}
+
+	/*
+	   Decompress a block data.
+	 */
+	if (state->flags.block_independence) {
+		prefix64k = 0;
+		uncompressed_size = LZ4_decompress_safe(read_buf + 4,
+		    state->out_block, (int)compressed_size,
+		    state->flags.block_maximum_size);
+	} else {
+		prefix64k = 64 * 1024;
+		if (state->decoded_size) {
+			if (state->decoded_size < prefix64k) {
+				memmove(state->out_block
+					+ prefix64k - state->decoded_size,
+				    state->out_block + prefix64k,
+				    state->decoded_size);
+				memset(state->out_block, 0,
+				    prefix64k - state->decoded_size);
+			} else {
+				memmove(state->out_block,
+				    state->out_block + state->decoded_size,
+				    prefix64k);
+			}
+		}
+		uncompressed_size = LZ4_decompress_safe_withPrefix64k(
+		    read_buf + 4,
+		    state->out_block + prefix64k, (int)compressed_size,
+		    state->flags.block_maximum_size);
+	}
+
+	/* Check if an error happend in decompression process. */
+	if (uncompressed_size < 0) {
+		archive_set_error(&(self->archive->archive),
+		    ARCHIVE_ERRNO_MISC, "lz4 decompression failed");
+		return (ARCHIVE_FATAL);
+	}
+
+	state->unconsumed = 4 + compressed_size + checksum_size;
+	*p = state->out_block + prefix64k;
+	state->decoded_size = uncompressed_size;
+	return uncompressed_size;
+
+malformed_error:
+	archive_set_error(&self->archive->archive, ARCHIVE_ERRNO_MISC,
+	    "malformed lz4 data");
+	return (ARCHIVE_FATAL);
+truncated_error:
+	archive_set_error(&self->archive->archive, ARCHIVE_ERRNO_MISC,
+	    "truncated lz4 input");
+	return (ARCHIVE_FATAL);
+}
+
+static ssize_t
+lz4_filter_read_default_stream(struct archive_read_filter *self, const void **p)
+{
+	struct private_data *state = (struct private_data *)self->data;
+	const char *read_buf;
+	ssize_t bytes_remaining;
+	ssize_t ret;
+
+	if (state->stage == SELECT_STREAM) {
+		state->stage = READ_DEFAULT_STREAM;
+		/* First, read a desciprtor. */
+		if((ret = lz4_filter_read_descriptor(self)) != ARCHIVE_OK)
+			return (ret);
+		state->stage = READ_DEFAULT_BLOCK;
+	}
+	/* Decompress a block. */
+	ret = lz4_filter_read_data_block(self, p);
+
+	/* If the end of block is detected, change the filter status
+	   to read next stream. */
+	if (ret == 0 && *p == NULL)
+		state->stage = SELECT_STREAM;
+
+	/* Optional process, checking a stream sum. */
+	if (state->flags.stream_checksum) {
+		if (state->stage == SELECT_STREAM) {
+			unsigned int checksum;
+			unsigned int checksum_stream;
+			read_buf = __archive_read_filter_ahead(self->upstream,
+			    4, &bytes_remaining);
+			if (read_buf == NULL) {
+				archive_set_error(&self->archive->archive,
+				    ARCHIVE_ERRNO_MISC, "truncated lz4 input");
+				return (ARCHIVE_FATAL);
+			}
+			checksum = archive_le32dec(read_buf);
+			__archive_read_filter_consume(self->upstream, 4);
+			checksum_stream = __archive_xxhash.XXH32_digest(
+			    state->xxh32_state);
+			state->xxh32_state = NULL;
+			if (checksum != checksum_stream) {
+				archive_set_error(&self->archive->archive,
+				    ARCHIVE_ERRNO_MISC,
+				    "lz4 stream cheksum error");
+				return (ARCHIVE_FATAL);
+			}
+		} else if (ret > 0)
+			__archive_xxhash.XXH32_update(state->xxh32_state,
+			    *p, (int)ret);
+	}
+	return (ret);
+}
+
+static ssize_t
+lz4_filter_read_legacy_stream(struct archive_read_filter *self, const void **p)
+{
+	struct private_data *state = (struct private_data *)self->data;
+	int compressed;
+	const char *read_buf;
+	ssize_t ret;
+
+	*p = NULL;
+	ret = lz4_allocate_out_block_for_legacy(self);
+	if (ret != ARCHIVE_OK)
+		return ret;
+
+	/* Make sure we have 4 bytes for a block size. */
+	read_buf = __archive_read_filter_ahead(self->upstream, 4, NULL);
+	if (read_buf == NULL) {
+		if (state->stage == SELECT_STREAM) {
+			state->stage = READ_LEGACY_STREAM;
+			archive_set_error(&self->archive->archive,
+			    ARCHIVE_ERRNO_MISC,
+			    "truncated lz4 input");
+			return (ARCHIVE_FATAL);
+		}
+		state->stage = SELECT_STREAM;
+		return 0;
+	}
+	state->stage = READ_LEGACY_BLOCK;
+	compressed = archive_le32dec(read_buf);
+	if (compressed > LZ4_COMPRESSBOUND(LEGACY_BLOCK_SIZE)) {
+		state->stage = SELECT_STREAM;
+		return 0;
+	}
+
+	/* Make sure we have a whole block. */
+	read_buf = __archive_read_filter_ahead(self->upstream,
+	    4 + compressed, NULL);
+	ret = LZ4_decompress_safe(read_buf + 4, state->out_block,
+	    compressed, (int)state->out_block_size);
+	if (ret < 0) {
+		archive_set_error(&(self->archive->archive),
+		    ARCHIVE_ERRNO_MISC, "lz4 decompression failed");
+		return (ARCHIVE_FATAL);
+	}
+	*p = state->out_block;
+	state->unconsumed = 4 + compressed;
+	return ret;
+}
+
+/*
+ * Clean up the decompressor.
+ */
+static int
+lz4_filter_close(struct archive_read_filter *self)
+{
+	struct private_data *state;
+	int ret = ARCHIVE_OK;
+
+	state = (struct private_data *)self->data;
+	free(state->xxh32_state);
+	free(state->out_block);
+	free(state);
+	return (ret);
+}
+
+#endif /* HAVE_LIBLZ4 */