liblzma: Add .lz (lzip) decompression support (format versions 0 and 1).

Support for format version 0 was removed from lzip 1.18 for some
reason. .lz format version 0 files are rare (and old) but some
source packages were released in this format, and some people might
have personal files in this format too. It's very little extra code
to support it along side format version 1 so this commits adds
support for both.

The Sync Flush marker extentension to the original .lz format
version 1 isn't supported. It would require changes to the
LZMA decoder itself. Such files are very rare anyway.

See the API doc for lzma_lzip_decoder() for more details about
the .lz format support.

Thanks to Michał Górny for the original patch.

configure.ac

@@ -316,6 +316,27 @@ esac
 AM_CONDITIONAL(COND_MICROLZMA, test "x$enable_microlzma" = xyes)
 
 
+#############################
+# .lz (lzip) format support #
+#############################
+
+AC_MSG_CHECKING([if .lz (lzip) decompression support should be built])
+AC_ARG_ENABLE([lzip-decoder], AS_HELP_STRING([--disable-lzip-decoder],
+		[Disable decompression support for .lz (lzip) files.]),
+	[], [enable_lzip_decoder=yes])
+if test "x$enable_decoder_lzma1" != xyes; then
+	enable_lzip_decoder=no
+	AC_MSG_RESULT([no because LZMA1 decoder is disabled])
+elif test "x$enable_lzip_decoder" = xyes; then
+	AC_DEFINE([HAVE_LZIP_DECODER], [1],
+		[Define to 1 if .lz (lzip) decompression support is enabled.])
+	AC_MSG_RESULT([yes])
+else
+	AC_MSG_RESULT([no])
+fi
+AM_CONDITIONAL(COND_LZIP_DECODER, test "x$enable_lzip_decoder" = xyes)
+
+
 ###########################
 # Assembler optimizations #
 ###########################

src/liblzma/api/lzma/container.h

@@ -602,8 +602,8 @@ extern LZMA_API(lzma_ret) lzma_microlzma_encoder(
 /**
  * This flag enables decoding of concatenated files with file formats that
  * allow concatenating compressed files as is. From the formats currently
- * supported by liblzma, only the .xz format allows concatenated files.
+ * supported by liblzma, only the .xz and .lz formats allow concatenated
- * Concatenated files are not allowed with the legacy .lzma format.
+ * files. Concatenated files are not allowed with the legacy .lzma format.
  *
  * This flag also affects the usage of the `action' argument for lzma_code().
  * When LZMA_CONCATENATED is used, lzma_code() won't return LZMA_STREAM_END
@@ -757,6 +757,64 @@ extern LZMA_API(lzma_ret) lzma_alone_decoder(
 		lzma_nothrow lzma_attr_warn_unused_result;
 
 
+/**
+ * \brief       Initialize .lz (lzip) decoder (a foreign file format)
+ *
+ * \param       strm        Pointer to properly prepared lzma_stream
+ * \param       memlimit    Memory usage limit as bytes. Use UINT64_MAX
+ *                          to effectively disable the limiter.
+ * \param       flags       Bitwise-or of flags, or zero for no flags.
+ *                          All decoder flags listed above are supported
+ *                          although only LZMA_CONCATENATED and (in very rare
+ *                          cases) LZMA_IGNORE_CHECK are actually useful.
+ *                          LZMA_TELL_NO_CHECK, LZMA_TELL_UNSUPPORTED_CHECK,
+ *                          and LZMA_FAIL_FAST do nothing. LZMA_TELL_ANY_CHECK
+ *                          is supported for consistency only as CRC32 is
+ *                          always used in the .lz format.
+ *
+ * This decoder supports the .lz format version 0 and the unextended .lz
+ * format version 1:
+ *
+ *   - Files in the format version 0 were produced by lzip 1.3 and older.
+ *     Such files aren't common but may be found from file archives
+ *     as a few source packages were released in this format. People
+ *     might have old personal files in this format too. Decompression
+ *     support for the format version 0 was removed in lzip 1.18.
+ *
+ *   - lzip 1.3 added decompression support for .lz format version 1 files.
+ *     Compression support was added in lzip 1.4. In lzip 1.6 the .lz format
+ *     version 1 was extended to support the Sync Flush marker. This extension
+ *     is not supported by liblzma. lzma_code() will return LZMA_DATA_ERROR
+ *     at the location of the Sync Flush marker. In practice files with
+ *     the Sync Flush marker are very rare and thus liblzma can decompress
+ *     almost all .lz files.
+ *
+ * Just like with lzma_stream_decoder() for .xz files, LZMA_CONCATENATED
+ * should be used when decompressing normal standalone .lz files.
+ *
+ * The .lz format allows putting non-.lz data at the end of a file after at
+ * least one valid .lz member. That is, one can append custom data at the end
+ * of a .lz file and the decoder is required to ignore it. In liblzma this
+ * is relevant only when LZMA_CONCATENATED is used. In that case lzma_code()
+ * will return LZMA_STREAM_END and leave lzma_stream.next_in pointing to
+ * the first byte of the non-.lz data. An exception to this is if the first
+ * 1-3 bytes of the non-.lz data are identical to the .lz magic bytes
+ * (0x4C, 0x5A, 0x49, 0x50; "LZIP" in US-ASCII). In such a case the 1-3 bytes
+ * will have been ignored by lzma_code(). If one wishes to locate the non-.lz
+ * data reliably, one must ensure that the first byte isn't 0x4C. Actually
+ * one should ensure that none of the first four bytes of trailing data are
+ * equal to the magic bytes because lzip >= 1.20 requires it by default.
+ *
+ * \return      - LZMA_OK: Initialization was successful.
+ *              - LZMA_MEM_ERROR: Cannot allocate memory.
+ *              - LZMA_OPTIONS_ERROR: Unsupported flags
+ *              - LZMA_PROG_ERROR
+ */
+extern LZMA_API(lzma_ret) lzma_lzip_decoder(
+		lzma_stream *strm, uint64_t memlimit, uint32_t flags)
+		lzma_nothrow lzma_attr_warn_unused_result;
+
+
 /**
  * \brief       Single-call .xz Stream decoder
  *

src/liblzma/common/Makefile.inc

@@ -94,4 +94,9 @@ if COND_MICROLZMA
 liblzma_la_SOURCES += \
 	common/microlzma_decoder.c
 endif
+
+if COND_LZIP_DECODER
+liblzma_la_SOURCES += \
+	common/lzip_decoder.c
+endif
 endif

src/liblzma/common/lzip_decoder.c

@@ -0,0 +1,413 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       lzip_decoder.c
+/// \brief      Decodes .lz (lzip) files
+//
+//  Author:     Michał Górny
+//              Lasse Collin
+//
+//  This file has been put into the public domain.
+//  You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include "lzip_decoder.h"
+#include "lzma_decoder.h"
+#include "check.h"
+
+
+// .lz format version 0 lacks the 64-bit Member size field in the footer.
+#define LZIP_V0_FOOTER_SIZE 12
+#define LZIP_V1_FOOTER_SIZE 20
+#define LZIP_FOOTER_SIZE_MAX LZIP_V1_FOOTER_SIZE
+
+// lc/lp/pb are hardcoded in the .lz format.
+#define LZIP_LC 3
+#define LZIP_LP 0
+#define LZIP_PB 2
+
+
+typedef struct {
+	enum {
+		SEQ_ID_STRING,
+		SEQ_VERSION,
+		SEQ_DICT_SIZE,
+		SEQ_CODER_INIT,
+		SEQ_LZMA_STREAM,
+		SEQ_MEMBER_FOOTER,
+	} sequence;
+
+	/// .lz member format version
+	uint32_t version;
+
+	/// CRC32 of the uncompressed data in the .lz member
+	uint32_t crc32;
+
+	/// Uncompressed size of the .lz member
+	uint64_t uncompressed_size;
+
+	/// Compressed size of the .lz member
+	uint64_t member_size;
+
+	/// Memory usage limit
+	uint64_t memlimit;
+
+	/// Amount of memory actually needed
+	uint64_t memusage;
+
+	/// If true, LZMA_GET_CHECK is returned after decoding the header
+	/// fields. As all files use CRC32 this is redundant but it's
+	/// implemented anyway since the initialization functions supports
+	/// all other flags in addition to LZMA_TELL_ANY_CHECK.
+	bool tell_any_check;
+
+	/// If true, we won't calculate or verify the CRC32 of
+	/// the uncompressed data.
+	bool ignore_check;
+
+	/// If true, we will decode concatenated .lz members and stop if
+	/// non-.lz data is seen after at least one member has been
+	/// successfully decoded.
+	bool concatenated;
+
+	/// When decoding concatenated .lz members, this is true as long as
+	/// we are decoding the first .lz member. This is needed to avoid
+	/// incorrect LZMA_FORMAT_ERROR in case there is non-.lz data at
+	/// the end of the file.
+	bool first_member;
+
+	/// Reading position in the header and footer fields
+	size_t pos;
+
+	/// Buffer to hold the .lz footer fields
+	uint8_t buffer[LZIP_FOOTER_SIZE_MAX];
+
+	/// Options decoded from the .lz header that needed to initialize
+	/// the LZMA1 decoder.
+	lzma_options_lzma options;
+
+	/// LZMA1 decoder
+	lzma_next_coder lzma_decoder;
+
+} lzma_lzip_coder;
+
+
+static lzma_ret
+lzip_decode(void *coder_ptr, const lzma_allocator *allocator,
+		const uint8_t *restrict in, size_t *restrict in_pos,
+		size_t in_size, uint8_t *restrict out,
+		size_t *restrict out_pos, size_t out_size, lzma_action action)
+{
+	lzma_lzip_coder *coder = coder_ptr;
+
+	while (true)
+	switch (coder->sequence) {
+	case SEQ_ID_STRING: {
+		// The "ID string" or magic bytes are "LZIP" in US-ASCII.
+		const uint8_t lzip_id_string[4] = { 0x4C, 0x5A, 0x49, 0x50 };
+
+		while (coder->pos < sizeof(lzip_id_string)) {
+			if (*in_pos >= in_size) {
+				// If we are on the 2nd+ concatenated member
+				// and the input ends before we can read
+				// the magic bytes, we discard the bytes that
+				// were already read (up to 3) and finish.
+				// See the reasoning below.
+				return !coder->first_member
+						&& action == LZMA_FINISH
+					? LZMA_STREAM_END : LZMA_OK;
+			}
+
+			if (in[*in_pos] != lzip_id_string[coder->pos]) {
+				// The .lz format allows putting non-.lz data
+				// at the end of the file. If we have seen
+				// at least one valid .lz member already,
+				// then we won't consume the byte at *in_pos
+				// and will return LZMA_STREAM_END. This way
+				// apps can easily locate and read the non-.lz
+				// data after the .lz member(s).
+				//
+				// NOTE: If the first 1-3 bytes of the non-.lz
+				// data match the .lz ID string then the first
+				// 1-3 bytes of the junk will get ignored by
+				// us. If apps want to properly locate the
+				// trailing data they must ensure that the
+				// first byte of their custom data isn't the
+				// same as the first byte of .lz ID string.
+				// With the liblzma API we cannot rewind the
+				// input position across calls to lzma_code().
+				return !coder->first_member
+					? LZMA_STREAM_END : LZMA_FORMAT_ERROR;
+			}
+
+			++*in_pos;
+			++coder->pos;
+		}
+
+		coder->pos = 0;
+
+		coder->crc32 = 0;
+		coder->uncompressed_size = 0;
+		coder->member_size = sizeof(lzip_id_string);
+
+		coder->sequence = SEQ_VERSION;
+	}
+
+	// Fall through
+
+	case SEQ_VERSION:
+		if (*in_pos >= in_size)
+			return LZMA_OK;
+
+		coder->version = in[(*in_pos)++];
+
+		// We support version 0 and unextended version 1.
+		if (coder->version > 1)
+			return LZMA_OPTIONS_ERROR;
+
+		++coder->member_size;
+		coder->sequence = SEQ_DICT_SIZE;
+
+		// .lz versions 0 and 1 use CRC32 as the integrity check
+		// so if the application wanted to know that
+		// (LZMA_TELL_ANY_CHECK) we can tell it now.
+		if (coder->tell_any_check)
+			return LZMA_GET_CHECK;
+
+	// Fall through
+
+	case SEQ_DICT_SIZE: {
+		if (*in_pos >= in_size)
+			return LZMA_OK;
+
+		const uint32_t ds = in[(*in_pos)++];
+		++coder->member_size;
+
+		// The five lowest bits are for the base-2 logarithm of
+		// the dictionary size and the highest three bits are
+		// the fractional part (0/16 to 7/16) that will be
+		// substracted to get the final value.
+		//
+		// For example, with 0xB5:
+		//     b2log = 21
+		//     fracnum = 5
+		//     dict_size = 2^21 - 2^21 * 5 / 16 = 1408 KiB
+		const uint32_t b2log = ds & 0x1F;
+		const uint32_t fracnum = ds >> 5;
+
+		// The format versions 0 and 1 allow dictionary size in the
+		// range [4 KiB, 512 MiB].
+		if (b2log < 12 || b2log > 29 || (b2log == 12 && fracnum > 0))
+			return LZMA_DATA_ERROR;
+
+		//   2^[b2log] - 2^[b2log] * [fracnum] / 16
+		// = 2^[b2log] - [fracnum] * 2^([b2log] - 4)
+		coder->options.dict_size = (UINT32_C(1) << b2log)
+				- (fracnum << (b2log - 4));
+
+		assert(coder->options.dict_size >= 4096);
+		assert(coder->options.dict_size <= (UINT32_C(512) << 20));
+
+		coder->options.preset_dict = NULL;
+		coder->options.lc = LZIP_LC;
+		coder->options.lp = LZIP_LP;
+		coder->options.pb = LZIP_PB;
+
+		// Calculate the memory usage.
+		coder->memusage = lzma_lzma_decoder_memusage(&coder->options)
+				+ LZMA_MEMUSAGE_BASE;
+
+		// Initialization is a separate step because if we return
+		// LZMA_MEMLIMIT_ERROR we need to be able to restart after
+		// the memlimit has been increased.
+		coder->sequence = SEQ_CODER_INIT;
+	}
+
+	// Fall through
+
+	case SEQ_CODER_INIT: {
+		if (coder->memusage > coder->memlimit)
+			return LZMA_MEMLIMIT_ERROR;
+
+		const lzma_filter_info filters[2] = {
+			{
+				.init = &lzma_lzma_decoder_init,
+				.options = &coder->options,
+			}, {
+				.init = NULL,
+			}
+		};
+
+		return_if_error(lzma_next_filter_init(&coder->lzma_decoder,
+				allocator, filters));
+
+		coder->crc32 = 0;
+		coder->sequence = SEQ_LZMA_STREAM;
+	}
+
+	// Fall through
+
+	case SEQ_LZMA_STREAM: {
+		const size_t in_start = *in_pos;
+		const size_t out_start = *out_pos;
+
+		const lzma_ret ret = coder->lzma_decoder.code(
+				coder->lzma_decoder.coder, allocator,
+				in, in_pos, in_size, out, out_pos, out_size,
+				action);
+
+		const size_t out_used = *out_pos - out_start;
+
+		coder->member_size += *in_pos - in_start;
+		coder->uncompressed_size += out_used;
+
+		if (!coder->ignore_check)
+			coder->crc32 = lzma_crc32(out + out_start, out_used,
+					coder->crc32);
+
+		if (ret != LZMA_STREAM_END)
+			return ret;
+
+		coder->sequence = SEQ_MEMBER_FOOTER;
+	}
+
+	// Fall through
+
+	case SEQ_MEMBER_FOOTER: {
+		// The footer of .lz version 0 lacks the Member size field.
+		// This is the only difference between version 0 and
+		// unextended version 1 formats.
+		const size_t footer_size = coder->version == 0
+				? LZIP_V0_FOOTER_SIZE
+				: LZIP_V1_FOOTER_SIZE;
+
+		// Copy the CRC32, Data size, and Member size fields to
+		// the internal buffer.
+		lzma_bufcpy(in, in_pos, in_size, coder->buffer, &coder->pos,
+				footer_size);
+
+		// Return if we didn't get the whole footer yet.
+		if (coder->pos < footer_size)
+			return LZMA_OK;
+
+		coder->pos = 0;
+		coder->member_size += footer_size;
+
+		// Check that the footer fields match the observed data.
+		if (!coder->ignore_check
+				&& coder->crc32 != read32le(&coder->buffer[0]))
+			return LZMA_DATA_ERROR;
+
+		if (coder->uncompressed_size != read64le(&coder->buffer[4]))
+			return LZMA_DATA_ERROR;
+
+		if (coder->version > 0) {
+			// .lz version 0 has no Member size field.
+			if (coder->member_size != read64le(&coder->buffer[12]))
+				return LZMA_DATA_ERROR;
+		}
+
+		// Decoding is finished if we weren't requested to decode
+		// more than one .lz member.
+		if (!coder->concatenated)
+			return LZMA_STREAM_END;
+
+		coder->first_member = false;
+		coder->sequence = SEQ_ID_STRING;
+		break;
+	}
+
+	default:
+		assert(0);
+		return LZMA_PROG_ERROR;
+	}
+
+	// Never reached
+}
+
+
+static void
+lzip_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
+{
+	lzma_lzip_coder *coder = coder_ptr;
+	lzma_next_end(&coder->lzma_decoder, allocator);
+	lzma_free(coder, allocator);
+	return;
+}
+
+
+static lzma_check
+lzip_decoder_get_check(const void *coder_ptr lzma_attribute((__unused__)))
+{
+	return LZMA_CHECK_CRC32;
+}
+
+
+static lzma_ret
+lzip_decoder_memconfig(void *coder_ptr, uint64_t *memusage,
+		uint64_t *old_memlimit, uint64_t new_memlimit)
+{
+	lzma_lzip_coder *coder = coder_ptr;
+
+	*memusage = coder->memusage;
+	*old_memlimit = coder->memlimit;
+
+	if (new_memlimit != 0) {
+		if (new_memlimit < coder->memusage)
+			return LZMA_MEMLIMIT_ERROR;
+
+		coder->memlimit = new_memlimit;
+	}
+
+	return LZMA_OK;
+}
+
+
+extern lzma_ret
+lzma_lzip_decoder_init(
+		lzma_next_coder *next, const lzma_allocator *allocator,
+		uint64_t memlimit, uint32_t flags)
+{
+	lzma_next_coder_init(&lzma_lzip_decoder_init, next, allocator);
+
+	if (flags & ~LZMA_SUPPORTED_FLAGS)
+		return LZMA_OPTIONS_ERROR;
+
+	lzma_lzip_coder *coder = next->coder;
+	if (coder == NULL) {
+		coder = lzma_alloc(sizeof(lzma_lzip_coder), allocator);
+		if (coder == NULL)
+			return LZMA_MEM_ERROR;
+
+		next->coder = coder;
+		next->code = &lzip_decode;
+		next->end = &lzip_decoder_end;
+		next->get_check = &lzip_decoder_get_check;
+		next->memconfig = &lzip_decoder_memconfig;
+
+		coder->lzma_decoder = LZMA_NEXT_CODER_INIT;
+	}
+
+	coder->sequence = SEQ_ID_STRING;
+	coder->memlimit = my_max(1, memlimit);
+	coder->memusage = LZMA_MEMUSAGE_BASE;
+	coder->tell_any_check = (flags & LZMA_TELL_ANY_CHECK) != 0;
+	coder->ignore_check = (flags & LZMA_IGNORE_CHECK) != 0;
+	coder->concatenated = (flags & LZMA_CONCATENATED) != 0;
+	coder->first_member = true;
+	coder->pos = 0;
+
+	return LZMA_OK;
+}
+
+
+extern LZMA_API(lzma_ret)
+lzma_lzip_decoder(lzma_stream *strm, uint64_t memlimit, uint32_t flags)
+{
+	lzma_next_strm_init(lzma_lzip_decoder_init, strm, memlimit, flags);
+
+	strm->internal->supported_actions[LZMA_RUN] = true;
+	strm->internal->supported_actions[LZMA_FINISH] = true;
+
+	return LZMA_OK;
+}

src/liblzma/liblzma_generic.map

@@ -113,4 +113,5 @@ global:
 	lzma_microlzma_encoder;
 	lzma_file_info_decoder;
 	lzma_stream_decoder_mt;
+	lzma_lzip_decoder;
 } XZ_5.2;

src/liblzma/liblzma_linux.map

@@ -128,4 +128,5 @@ global:
 	lzma_microlzma_encoder;
 	lzma_file_info_decoder;
 	lzma_stream_decoder_mt;
+	lzma_lzip_decoder;
 } XZ_5.2;