Add some single-call buffer-to-buffer coding functions.

src/liblzma/api/lzma/block.h

@@ -55,6 +55,7 @@ typedef struct {
 	 *  - lzma_block_total_size()
 	 *  - lzma_block_encoder()
 	 *  - lzma_block_decoder()
+	 *  - lzma_block_buffer_encode()
 	 *
 	 * Written by:
 	 *  - lzma_block_header_decode()
@@ -76,6 +77,7 @@ typedef struct {
 	 *
 	 * Written by:
 	 *  - lzma_block_header_size()
+	 *  - lzma_block_buffer_encode()
 	 */
 	uint32_t header_size;
 #	define LZMA_BLOCK_HEADER_SIZE_MIN 8
@@ -95,6 +97,7 @@ typedef struct {
 	 *  - lzma_block_total_size()
 	 *  - lzma_block_encoder()
 	 *  - lzma_block_decoder()
+	 *  - lzma_block_buffer_encode()
 	 */
 	lzma_check check;
 
@@ -147,6 +150,7 @@ typedef struct {
 	 *  - lzma_block_compressed_size()
 	 *  - lzma_block_encoder()
 	 *  - lzma_block_decoder()
+	 *  - lzma_block_buffer_encode()
 	 */
 	lzma_vli compressed_size;
 
@@ -168,6 +172,7 @@ typedef struct {
 	 *  - lzma_block_header_decode()
 	 *  - lzma_block_encoder()
 	 *  - lzma_block_decoder()
+	 *  - lzma_block_buffer_encode()
 	 */
 	lzma_vli uncompressed_size;
 
@@ -182,6 +187,7 @@ typedef struct {
 	 *  - lzma_block_header_encode()
 	 *  - lzma_block_encoder()
 	 *  - lzma_block_decoder()
+	 *  - lzma_block_buffer_encode()
 	 *
 	 * Written by:
 	 *  - lzma_block_header_decode(): Note that this does NOT free()
@@ -415,3 +421,54 @@ extern lzma_ret lzma_block_encoder(lzma_stream *strm, lzma_block *block)
  */
 extern lzma_ret lzma_block_decoder(lzma_stream *strm, lzma_block *block)
 		lzma_attr_warn_unused_result;
+
+
+/**
+ * \brief       Calculate maximum output buffer size for single-call encoding
+ *
+ * This is equivalent to lzma_stream_buffer_bound() but for .xz Blocks.
+ * See the documentation of lzma_stream_buffer_bound().
+ */
+extern size_t lzma_block_buffer_bound(size_t uncompressed_size);
+
+
+/**
+ * \brief       Single-call .xz Block encoder
+ *
+ * In contrast to the multi-call encoder initialized with
+ * lzma_block_encoder(), this function encodes also the Block Header. This
+ * is required to make it possible to write appropriate Block Header also
+ * in case the data isn't compressible, and different filter chain has to be
+ * used to encode the data in uncompressed form using uncompressed chunks
+ * of the LZMA2 filter.
+ *
+ * When the data isn't compressible, header_size, compressed_size, and
+ * uncompressed_size are set just like when the data was compressible, but
+ * it is possible that header_size is too small to hold the filter chain
+ * specified in block->filters, because that isn't necessarily the filter
+ * chain that was actually used to encode the data. lzma_block_unpadded_size()
+ * still works normally, because it doesn't read the filters array.
+ *
+ * \param       block       Block options: block->version, block->check,
+ *                          and block->filters must be initialized.
+ * \param       allocator   lzma_allocator for custom allocator functions.
+ *                          Set to NULL to use malloc() and free().
+ * \param       in          Beginning of the input buffer
+ * \param       in_size     Size of the input buffer
+ * \param       out         Beginning of the output buffer
+ * \param       out_pos     The next byte will be written to out[*out_pos].
+ *                          *out_pos is updated only if encoding succeeds.
+ * \param       out_size    Size of the out buffer; the first byte into
+ *                          which no data is written to is out[out_size].
+ *
+ * \return      - LZMA_OK: Encoding was successful.
+ *              - LZMA_BUF_ERROR: Not enough output buffer space.
+ *              - LZMA_OPTIONS_ERROR
+ *              - LZMA_MEM_ERROR
+ *              - LZMA_DATA_ERROR
+ *              - LZMA_PROG_ERROR
+ */
+extern lzma_ret lzma_block_buffer_encode(
+		lzma_block *block, lzma_allocator *allocator,
+		const uint8_t *in, size_t in_size,
+		uint8_t *out, size_t *out_pos, size_t out_size);

src/liblzma/api/lzma/container.h

@@ -169,6 +169,62 @@ extern lzma_ret lzma_alone_encoder(
 		lzma_attr_warn_unused_result;
 
 
+/**
+ * \brief       Calculate output buffer size for single-call Stream encoder
+ *
+ * When trying to compress uncompressible data, the encoded size will be
+ * slightly bigger than the input data. This function calculates how much
+ * output buffer space is required to be sure that lzma_stream_buffer_encode()
+ * doesn't return LZMA_BUF_ERROR.
+ *
+ * The calculated value is not exact, but it is guaranteed to be big enough.
+ * The actual maximum output space required may be slightly smaller (up to
+ * about 100 bytes). This should not be a problem in practice.
+ *
+ * If the calculated maximum size doesn't fit into size_t or would make the
+ * Stream grow past LZMA_VLI_MAX (which should never happen in practice),
+ * zero is returned to indicate the error.
+ *
+ * \note        The limit calculated by this function applies only to
+ *              single-call encoding. Multi-call encoding may (and probably
+ *              will) have larger maximum expansion when encoding
+ *              uncompressible data. Currently there is no function to
+ *              calculate the maximum expansion of multi-call encoding.
+ */
+extern size_t lzma_stream_buffer_bound(size_t uncompressed_size);
+
+
+/**
+ * \brief       Single-call Stream encoder
+ *
+ * \param       filters     Array of filters. This must be terminated with
+ *                          filters[n].id = LZMA_VLI_UNKNOWN. See filter.h
+ *                          for more information.
+ * \param       check       Type of the integrity check to calculate from
+ *                          uncompressed data.
+ * \param       allocator   lzma_allocator for custom allocator functions.
+ *                          Set to NULL to use malloc() and free().
+ * \param       in          Beginning of the input buffer
+ * \param       in_size     Size of the input buffer
+ * \param       out         Beginning of the output buffer
+ * \param       out_pos     The next byte will be written to out[*out_pos].
+ *                          *out_pos is updated only if encoding succeeds.
+ * \param       out_size    Size of the out buffer; the first byte into
+ *                          which no data is written to is out[out_size].
+ *
+ * \return      - LZMA_OK: Encoding was successful.
+ *              - LZMA_BUF_ERROR: Not enough output buffer space.
+ *              - LZMA_OPTIONS_ERROR
+ *              - LZMA_MEM_ERROR
+ *              - LZMA_DATA_ERROR
+ *              - LZMA_PROG_ERROR
+ */
+extern lzma_ret lzma_stream_buffer_encode(
+		lzma_filter *filters, lzma_check check,
+		lzma_allocator *allocator, const uint8_t *in, size_t in_size,
+		uint8_t *out, size_t *out_pos, size_t out_size);
+
+
 /************
  * Decoding *
  ************/

src/liblzma/api/lzma/index.h

@@ -255,7 +255,7 @@ extern lzma_ret lzma_index_cat(lzma_index *lzma_restrict dest,
 
 
 /**
- * \brief       Duplicates an Index list
+ * \brief       Duplicate an Index list
  *
  * Makes an identical copy of the Index. Also the read position is copied.
  *
@@ -267,7 +267,7 @@ extern lzma_index *lzma_index_dup(
 
 
 /**
- * \brief       Compares if two Index lists are identical
+ * \brief       Compare if two Index lists are identical
  *
  * \return      True if *a and *b are equal, false otherwise.
  */
@@ -276,7 +276,7 @@ extern lzma_bool lzma_index_equal(const lzma_index *a, const lzma_index *b)
 
 
 /**
- * \brief       Initializes Index encoder
+ * \brief       Initialize Index encoder
  *
  * \param       strm        Pointer to properly prepared lzma_stream
  * \param       i           Pointer to lzma_index which should be encoded.
@@ -294,14 +294,15 @@ extern lzma_ret lzma_index_encoder(lzma_stream *strm, lzma_index *i)
 
 
 /**
- * \brief       Initializes Index decoder
+ * \brief       Initialize Index decoder
  *
  * \param       strm        Pointer to properly prepared lzma_stream
  * \param       i           Pointer to a pointer that will be made to point
  *                          to the final decoded Index once lzma_code() has
  *                          returned LZMA_STREAM_END. That is,
- *                          lzma_index_decoder() takes care of allocating
+ *                          lzma_index_decoder() always takes care of
- *                          a new lzma_index structure.
+ *                          allocating a new lzma_index structure, and *i
+ *                          doesn't need to be initialized by the caller.
  * \param       memlimit    How much memory the resulting Index is allowed
  *                          to require.
  *
@@ -321,3 +322,60 @@ extern lzma_ret lzma_index_encoder(lzma_stream *strm, lzma_index *i)
 extern lzma_ret lzma_index_decoder(
 		lzma_stream *strm, lzma_index **i, uint64_t memlimit)
 		lzma_attr_warn_unused_result;
+
+
+/**
+ * \brief       Single-call Index encoder
+ *
+ * \param       i         Index to be encoded. The read position will be at
+ *                        the end of the Index if encoding succeeds, or at
+ *                        unspecified position in case an error occurs.
+ * \param       out       Beginning of the output buffer
+ * \param       out_pos   The next byte will be written to out[*out_pos].
+ *                        *out_pos is updated only if encoding succeeds.
+ * \param       out_size  Size of the out buffer; the first byte into
+ *                        which no data is written to is out[out_size].
+ *
+ * \return      - LZMA_OK: Encoding was successful.
+ *              - LZMA_BUF_ERROR: Output buffer is too small. Use
+ *                lzma_index_size() to find out how much output
+ *                space is needed.
+ *              - LZMA_PROG_ERROR
+ *
+ * \note        This function doesn't take allocator argument since all
+ *              the internal data is allocated on stack.
+ */
+extern lzma_ret lzma_index_buffer_encode(lzma_index *i,
+		uint8_t *out, size_t *out_pos, size_t out_size);
+
+
+/**
+ * \brief       Single-call Index decoder
+ *
+ * \param       i           Pointer to a pointer that will be made to point
+ *                          to the final decoded Index if decoding is
+ *                          successful. That is, lzma_index_buffer_decode()
+ *                          always takes care of allocating a new
+ *                          lzma_index structure, and *i doesn't need to be
+ *                          initialized by the caller.
+ * \param       memlimit    Pointer to how much memory the resulting Index
+ *                          is allowed to require. The value pointed by
+ *                          this pointer is modified if and only if
+ *                          LZMA_MEMLIMIT_ERROR is returned.
+ * \param       allocator   Pointer to lzma_allocator, or NULL to use malloc()
+ * \param       in          Beginning of the input buffer
+ * \param       in_pos      The next byte will be read from in[*in_pos].
+ *                          *in_pos is updated only if decoding succeeds.
+ * \param       in_size     Size of the input buffer; the first byte that
+ *                          won't be read is in[in_size].
+ *
+ * \return      - LZMA_OK: Decoding was successful.
+ *              - LZMA_MEM_ERROR
+ *              - LZMA_MEMLIMIT_ERROR: Memory usage limit was reached.
+ *                The minimum required memlimit value was stored to *memlimit.
+ *              - LZMA_DATA_ERROR
+ *              - LZMA_PROG_ERROR
+ */
+extern lzma_ret lzma_index_buffer_decode(
+		lzma_index **i,  uint64_t *memlimit, lzma_allocator *allocator,
+		const uint8_t *in, size_t *in_pos, size_t in_size);

src/liblzma/common/Makefile.am

@@ -39,6 +39,7 @@ libcommon_la_SOURCES = \
 if COND_MAIN_ENCODER
 libcommon_la_SOURCES += \
 	alone_encoder.c \
+	block_buffer_encoder.c \
 	block_encoder.c \
 	block_encoder.h \
 	block_header_encoder.c \
@@ -48,6 +49,7 @@ libcommon_la_SOURCES += \
 	filter_flags_encoder.c \
 	index_encoder.c \
 	index_encoder.h \
+	stream_buffer_encoder.c \
 	stream_encoder.c \
 	stream_encoder.h \
 	stream_flags_encoder.c \

src/liblzma/common/block_buffer_encoder.c

@@ -0,0 +1,305 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       block_buffer_encoder.c
+/// \brief      Single-call .xz Block encoder
+//
+//  Copyright (C) 2009 Lasse Collin
+//
+//  This library is free software; you can redistribute it and/or
+//  modify it under the terms of the GNU Lesser General Public
+//  License as published by the Free Software Foundation; either
+//  version 2.1 of the License, or (at your option) any later version.
+//
+//  This library is distributed in the hope that it will be useful,
+//  but WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+//  Lesser General Public License for more details.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include "block_encoder.h"
+#include "filter_encoder.h"
+#include "lzma2_encoder.h"
+#include "check.h"
+
+
+/// Estimate the maximum size of the Block Header and Check fields for
+/// a Block that uses LZMA2 uncompressed chunks. We could use
+/// lzma_block_header_size() but this is simpler.
+///
+/// Block Header Size + Block Flags + Compressed Size
+/// + Uncompressed Size + Filter Flags for LZMA2 + CRC32 + Check
+/// and round up to the next multiple of four to take Header Padding
+/// into account.
+#define HEADERS_BOUND ((1 + 1 + 2 * LZMA_VLI_BYTES_MAX + 3 + 4 \
+		+ LZMA_CHECK_SIZE_MAX + 3) & ~3)
+
+
+static lzma_vli
+lzma2_bound(lzma_vli uncompressed_size)
+{
+	// Prevent integer overflow in overhead calculation.
+	if (uncompressed_size > COMPRESSED_SIZE_MAX)
+		return 0;
+
+	// Calculate the exact overhead of the LZMA2 headers: Round
+	// uncompressed_size up to the next multiple of LZMA2_CHUNK_MAX,
+	// multiply by the size of per-chunk header, and add one byte for
+	// the end marker.
+	const lzma_vli overhead = ((uncompressed_size + LZMA2_CHUNK_MAX - 1)
+				/ LZMA2_CHUNK_MAX)
+			* LZMA2_HEADER_UNCOMPRESSED + 1;
+
+	// Catch the possible integer overflow.
+	if (COMPRESSED_SIZE_MAX - overhead < uncompressed_size)
+		return 0;
+
+	return uncompressed_size + overhead;
+}
+
+
+extern LZMA_API size_t
+lzma_block_buffer_bound(size_t uncompressed_size)
+{
+	// For now, if the data doesn't compress, we always use uncompressed
+	// chunks of LZMA2. In future we may use Subblock filter too, but
+	// but for simplicity we probably will still use the same bound
+	// calculation even though Subblock filter would have slightly less
+	// overhead.
+	lzma_vli lzma2_size = lzma2_bound(uncompressed_size);
+	if (lzma2_size == 0)
+		return 0;
+
+	// Take Block Padding into account.
+	lzma2_size = (lzma2_size + 3) & ~LZMA_VLI_C(3);
+
+#if SIZE_MAX < LZMA_VLI_MAX
+	// Catch the possible integer overflow on 32-bit systems. There's no
+	// overflow on 64-bit systems, because lzma2_bound() already takes
+	// into account the size of the headers in the Block.
+	if (SIZE_MAX - HEADERS_BOUND < lzma2_size)
+		return 0;
+#endif
+
+	return HEADERS_BOUND + lzma2_size;
+}
+
+
+static lzma_ret
+block_encode_uncompressed(lzma_block *block, const uint8_t *in, size_t in_size,
+		uint8_t *out, size_t *out_pos, size_t out_size)
+{
+	// TODO: Figure out if the last filter is LZMA2 or Subblock and use
+	// that filter to encode the uncompressed chunks.
+
+	// Use LZMA2 uncompressed chunks. We wouldn't need a dictionary at
+	// all, but LZMA2 always requires a dictionary, so use the minimum
+	// value to minimize memory usage of the decoder.
+	lzma_options_lzma lzma2 = {
+		.dict_size = LZMA_DICT_SIZE_MIN,
+	};
+
+	lzma_filter filters[2];
+	filters[0].id = LZMA_FILTER_LZMA2;
+	filters[0].options = &lzma2;
+	filters[1].id = LZMA_VLI_UNKNOWN;
+
+	// Set the above filter options to *block temporarily so that we can
+	// encode the Block Header.
+	lzma_filter *filters_orig = block->filters;
+	block->filters = filters;
+
+	if (lzma_block_header_size(block) != LZMA_OK) {
+		block->filters = filters_orig;
+		return LZMA_PROG_ERROR;
+	}
+
+	// Check that there's enough output space. The caller has already
+	// set block->compressed_size to what lzma2_bound() has returned,
+	// so we can reuse that value. We know that compressed_size is a
+	// known valid VLI and header_size is a small value so their sum
+	// will never overflow.
+	assert(block->compressed_size == lzma2_bound(in_size));
+	if (out_size - *out_pos
+			< block->header_size + block->compressed_size) {
+		block->filters = filters_orig;
+		return LZMA_BUF_ERROR;
+	}
+
+	if (lzma_block_header_encode(block, out + *out_pos) != LZMA_OK) {
+		block->filters = filters_orig;
+		return LZMA_PROG_ERROR;
+	}
+
+	block->filters = filters_orig;
+	*out_pos += block->header_size;
+
+	// Encode the data using LZMA2 uncompressed chunks.
+	size_t in_pos = 0;
+	uint8_t control = 0x01; // Dictionary reset
+
+	while (in_pos < in_size) {
+		// Control byte: Indicate uncompressed chunk, of which
+		// the first resets the dictionary.
+		out[(*out_pos)++] = control;
+		control = 0x02; // No dictionary reset
+
+		// Size of the uncompressed chunk
+		const size_t copy_size
+				= MIN(in_size - in_pos, LZMA2_CHUNK_MAX);
+		out[(*out_pos)++] = (copy_size - 1) >> 8;
+		out[(*out_pos)++] = (copy_size - 1) & 0xFF;
+
+		// The actual data
+		assert(*out_pos + copy_size <= out_size);
+		memcpy(out + *out_pos, in + in_pos, copy_size);
+
+		in_pos += copy_size;
+		*out_pos += copy_size;
+	}
+
+	// End marker
+	out[(*out_pos)++] = 0x00;
+	assert(*out_pos <= out_size);
+
+	return LZMA_OK;
+}
+
+
+static lzma_ret
+block_encode_normal(lzma_block *block, lzma_allocator *allocator,
+		const uint8_t *in, size_t in_size,
+		uint8_t *out, size_t *out_pos, size_t out_size)
+{
+	// Find out the size of the Block Header.
+	block->compressed_size = lzma2_bound(in_size);
+	if (block->compressed_size == 0)
+		return LZMA_DATA_ERROR;
+
+	block->uncompressed_size = in_size;
+	return_if_error(lzma_block_header_size(block));
+
+	// Reserve space for the Block Header and skip it for now.
+	if (out_size - *out_pos <= block->header_size)
+		return LZMA_BUF_ERROR;
+
+	const size_t out_start = *out_pos;
+	*out_pos += block->header_size;
+
+	// Limit out_size so that we stop encoding if the output would grow
+	// bigger than what uncompressed Block would be.
+	if (out_size - *out_pos > block->compressed_size)
+		out_size = *out_pos + block->compressed_size;
+
+	// TODO: In many common cases this could be optimized to use
+	// significantly less memory.
+	lzma_next_coder raw_encoder = LZMA_NEXT_CODER_INIT;
+	lzma_ret ret = lzma_raw_encoder_init(
+			&raw_encoder, allocator, block->filters);
+
+	if (ret == LZMA_OK) {
+		size_t in_pos = 0;
+		ret = raw_encoder.code(raw_encoder.coder, allocator,
+				in, &in_pos, in_size, out, out_pos, out_size,
+				LZMA_FINISH);
+	}
+
+	// NOTE: This needs to be run even if lzma_raw_encoder_init() failed.
+	lzma_next_end(&raw_encoder, allocator);
+
+	if (ret == LZMA_STREAM_END) {
+		// Compression was successful. Write the Block Header.
+		block->compressed_size
+				= *out_pos - (out_start + block->header_size);
+		ret = lzma_block_header_encode(block, out + out_start);
+		if (ret != LZMA_OK)
+			ret = LZMA_PROG_ERROR;
+
+	} else if (ret == LZMA_OK) {
+		// Output buffer became full.
+		ret = LZMA_BUF_ERROR;
+	}
+
+	// Reset *out_pos if something went wrong.
+	if (ret != LZMA_OK)
+		*out_pos = out_start;
+
+	return ret;
+}
+
+
+extern LZMA_API lzma_ret
+lzma_block_buffer_encode(lzma_block *block, lzma_allocator *allocator,
+		const uint8_t *in, size_t in_size,
+		uint8_t *out, size_t *out_pos, size_t out_size)
+{
+	// Sanity checks
+	if (block == NULL || block->filters == NULL
+			|| (in == NULL && in_size != 0) || out == NULL
+			|| out_pos == NULL || *out_pos > out_size)
+		return LZMA_PROG_ERROR;
+
+	// Check the version field.
+	if (block->version != 0)
+		return LZMA_OPTIONS_ERROR;
+
+	// Size of a Block has to be a multiple of four, so limit the size
+	// here already. This way we don't need to check it again when adding
+	// Block Padding.
+	out_size -= (out_size - *out_pos) & 3;
+
+	// Get the size of the Check field.
+	const size_t check_size = lzma_check_size(block->check);
+	if (check_size == UINT32_MAX)
+		return LZMA_PROG_ERROR;
+
+	// Reserve space for the Check field.
+	if (out_size - *out_pos <= check_size)
+		return LZMA_BUF_ERROR;
+
+	out_size -= check_size;
+
+	// Do the actual compression.
+	const lzma_ret ret = block_encode_normal(block, allocator,
+			in, in_size, out, out_pos, out_size);
+	if (ret != LZMA_OK) {
+		// If the error was something else than output buffer
+		// becoming full, return the error now.
+		if (ret != LZMA_BUF_ERROR)
+			return ret;
+
+		// The data was uncompressible (at least with the options
+		// given to us) or the output buffer was too small. Use the
+		// uncompressed chunks of LZMA2 to wrap the data into a valid
+		// Block. If we haven't been given enough output space, even
+		// this may fail.
+		return_if_error(block_encode_uncompressed(block, in, in_size,
+				out, out_pos, out_size));
+	}
+
+	assert(*out_pos <= out_size);
+
+	// Block Padding. No buffer overflow here, because we already adjusted
+	// out_size so that (out_size - out_start) is a multiple of four.
+	// Thus, if the buffer is full, the loop body can never run.
+	for (size_t i = (size_t)(block->compressed_size); i & 3; ++i) {
+		assert(*out_pos < out_size);
+		out[(*out_pos)++] = 0x00;
+	}
+
+	// If there's no Check field, we are done now.
+	if (check_size > 0) {
+		// Calculate the integrity check. We reserved space for
+		// the Check field earlier so we don't need to check for
+		// available output space here.
+		lzma_check_state check;
+		lzma_check_init(&check, block->check);
+		lzma_check_update(&check, block->check, in, in_size);
+		lzma_check_finish(&check, block->check);
+
+		memcpy(out + *out_pos, check.buffer.u8, check_size);
+		*out_pos += check_size;
+	}
+
+	return LZMA_OK;
+}

src/liblzma/common/index_decoder.c

@@ -225,6 +225,27 @@ index_decoder_memconfig(lzma_coder *coder, uint64_t *memusage,
 }
 
 
+static lzma_ret
+index_decoder_reset(lzma_coder *coder, lzma_allocator *allocator,
+		lzma_index **i, uint64_t memlimit)
+{
+	// We always allocate a new lzma_index.
+	*i = lzma_index_init(NULL, allocator);
+	if (*i == NULL)
+		return LZMA_MEM_ERROR;
+
+	// Initialize the rest.
+	coder->sequence = SEQ_INDICATOR;
+	coder->memlimit = memlimit;
+	coder->index = *i;
+	coder->count = 0; // Needs to be initialized due to _memconfig().
+	coder->pos = 0;
+	coder->crc32 = 0;
+
+	return LZMA_OK;
+}
+
+
 static lzma_ret
 index_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
 		lzma_index **i, uint64_t memlimit)
@@ -247,20 +268,7 @@ index_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
 		lzma_index_end(next->coder->index, allocator);
 	}
 
-	// We always allocate a new lzma_index.
+	return index_decoder_reset(next->coder, allocator, i, memlimit);
-	*i = lzma_index_init(NULL, allocator);
-	if (*i == NULL)
-		return LZMA_MEM_ERROR;
-
-	// Initialize the rest.
-	next->coder->sequence = SEQ_INDICATOR;
-	next->coder->memlimit = memlimit;
-	next->coder->index = *i;
-	next->coder->count = 0; // Needs to be initialized due to _memconfig().
-	next->coder->pos = 0;
-	next->coder->crc32 = 0;
-
-	return LZMA_OK;
 }
 
 
@@ -273,3 +281,50 @@ lzma_index_decoder(lzma_stream *strm, lzma_index **i, uint64_t memlimit)
 
 	return LZMA_OK;
 }
+
+
+extern LZMA_API lzma_ret
+lzma_index_buffer_decode(
+		lzma_index **i, uint64_t *memlimit, lzma_allocator *allocator,
+		const uint8_t *in, size_t *in_pos, size_t in_size)
+{
+	// Sanity checks
+	if (i == NULL || in == NULL || in_pos == NULL || *in_pos > in_size)
+		return LZMA_PROG_ERROR;
+
+	// Initialize the decoder.
+	lzma_coder coder;
+	return_if_error(index_decoder_reset(&coder, allocator, i, *memlimit));
+
+	// Store the input start position so that we can restore it in case
+	// of an error.
+	const size_t in_start = *in_pos;
+
+	// Do the actual decoding.
+	lzma_ret ret = index_decode(&coder, allocator, in, in_pos, in_size,
+			NULL, NULL, 0, LZMA_RUN);
+
+	if (ret == LZMA_STREAM_END) {
+		ret = LZMA_OK;
+	} else {
+		// Something went wrong, free the Index structure and restore
+		// the input position.
+		lzma_index_end(*i, allocator);
+		*i = NULL;
+		*in_pos = in_start;
+
+		if (ret == LZMA_OK) {
+			// The input is truncated or otherwise corrupt.
+			// Use LZMA_DATA_ERROR instead of LZMA_BUF_ERROR
+			// like lzma_vli_decode() does in single-call mode.
+			ret = LZMA_DATA_ERROR;
+
+		} else if (ret == LZMA_MEMLIMIT_ERROR) {
+			// Tell the caller how much memory would have
+			// been needed.
+			*memlimit = lzma_index_memusage(coder.count);
+		}
+	}
+
+	return ret;
+}

src/liblzma/common/index_encoder.c

@@ -178,6 +178,20 @@ index_encoder_end(lzma_coder *coder, lzma_allocator *allocator)
 }
 
 
+static void
+index_encoder_reset(lzma_coder *coder, lzma_index *i)
+{
+	lzma_index_rewind(i);
+
+	coder->sequence = SEQ_INDICATOR;
+	coder->index = i;
+	coder->pos = 0;
+	coder->crc32 = 0;
+
+	return;
+}
+
+
 extern lzma_ret
 lzma_index_encoder_init(lzma_next_coder *next, lzma_allocator *allocator,
 		lzma_index *i)
@@ -196,12 +210,7 @@ lzma_index_encoder_init(lzma_next_coder *next, lzma_allocator *allocator,
 		next->end = &index_encoder_end;
 	}
 
-	lzma_index_rewind(i);
+	index_encoder_reset(next->coder, i);
-
-	next->coder->sequence = SEQ_INDICATOR;
-	next->coder->index = i;
-	next->coder->pos = 0;
-	next->coder->crc32 = 0;
 
 	return LZMA_OK;
 }
@@ -216,3 +225,41 @@ lzma_index_encoder(lzma_stream *strm, lzma_index *i)
 
 	return LZMA_OK;
 }
+
+
+extern LZMA_API lzma_ret
+lzma_index_buffer_encode(lzma_index *i,
+		uint8_t *out, size_t *out_pos, size_t out_size)
+{
+	// Validate the arugments.
+	if (i == NULL || out == NULL || out_pos == NULL || *out_pos > out_size)
+		return LZMA_PROG_ERROR;
+
+	// Don't try to encode if there's not enough output space.
+	if (out_size - *out_pos < lzma_index_size(i))
+		return LZMA_BUF_ERROR;
+
+	// The Index encoder needs just one small data structure so we can
+	// allocate it on stack.
+	lzma_coder coder;
+	index_encoder_reset(&coder, i);
+
+	// Do the actual encoding. This should never fail, but store
+	// the original *out_pos just in case.
+	const size_t out_start = *out_pos;
+	lzma_ret ret = index_encode(&coder, NULL, NULL, NULL, 0,
+			out, out_pos, out_size, LZMA_RUN);
+
+	if (ret == LZMA_STREAM_END) {
+		ret = LZMA_OK;
+	} else {
+		// We should never get here, but just in case, restore the
+		// output position and set the error accordingly if something
+		// goes wrong and debugging isn't enabled.
+		assert(0);
+		*out_pos = out_start;
+		ret = LZMA_PROG_ERROR;
+	}
+
+	return ret;
+}

src/liblzma/common/stream_buffer_encoder.c

@@ -0,0 +1,138 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       stream_buffer_encoder.c
+/// \brief      Single-call .xz Stream encoder
+//
+//  Copyright (C) 2009 Lasse Collin
+//
+//  This library is free software; you can redistribute it and/or
+//  modify it under the terms of the GNU Lesser General Public
+//  License as published by the Free Software Foundation; either
+//  version 2.1 of the License, or (at your option) any later version.
+//
+//  This library is distributed in the hope that it will be useful,
+//  but WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+//  Lesser General Public License for more details.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include "index.h"
+
+
+/// Maximum size of Index that has exactly one Record.
+/// Index Indicator + Number of Records + Record + CRC32 rounded up to
+/// the next multiple of four.
+#define INDEX_BOUND ((1 + 1 + 2 * LZMA_VLI_BYTES_MAX + 4 + 3) & ~3)
+
+/// Stream Header, Stream Footer, and Index
+#define HEADERS_BOUND (2 * LZMA_STREAM_HEADER_SIZE + INDEX_BOUND)
+
+
+extern LZMA_API size_t
+lzma_stream_buffer_bound(size_t uncompressed_size)
+{
+	// Get the maximum possible size of a Block.
+	const size_t block_bound = lzma_block_buffer_bound(uncompressed_size);
+	if (block_bound == 0)
+		return 0;
+
+	// Catch the possible integer overflow and also prevent the size of
+	// the Stream exceeding LZMA_VLI_MAX (theoretically possible on
+	// 64-bit systems).
+	if (MIN(SIZE_MAX, LZMA_VLI_MAX) - block_bound < HEADERS_BOUND)
+		return 0;
+
+	return block_bound + HEADERS_BOUND;
+}
+
+
+extern LZMA_API lzma_ret
+lzma_stream_buffer_encode(lzma_filter *filters, lzma_check check,
+		lzma_allocator *allocator, const uint8_t *in, size_t in_size,
+		uint8_t *out, size_t *out_pos_ptr, size_t out_size)
+{
+	// Sanity checks
+	if (filters == NULL || (unsigned int)(check) > LZMA_CHECK_ID_MAX
+			|| (in == NULL && in_size != 0) || out == NULL
+			|| out_pos_ptr == NULL || *out_pos_ptr > out_size)
+		return LZMA_PROG_ERROR;
+
+	// Note for the paranoids: Index encoder prevents the Stream from
+	// getting too big and still being accepted with LZMA_OK, and Block
+	// encoder catches if the input is too big. So we don't need to
+	// separately check if the buffers are too big.
+
+	// Use a local copy. We update *out_pos_ptr only if everything
+	// succeeds.
+	size_t out_pos = *out_pos_ptr;
+
+	// Check that there's enough space for both Stream Header and
+	// Stream Footer.
+	if (out_size - out_pos <= 2 * LZMA_STREAM_HEADER_SIZE)
+		return LZMA_BUF_ERROR;
+
+	// Reserve space for Stream Footer so we don't need to check for
+	// available space again before encoding Stream Footer.
+	out_size -= LZMA_STREAM_HEADER_SIZE;
+
+	// Encode the Stream Header.
+	lzma_stream_flags stream_flags = {
+		.version = 0,
+		.check = check,
+	};
+
+	if (lzma_stream_header_encode(&stream_flags, out + out_pos)
+			!= LZMA_OK)
+		return LZMA_PROG_ERROR;
+
+	out_pos += LZMA_STREAM_HEADER_SIZE;
+
+	// Block
+	lzma_block block = {
+		.version = 0,
+		.check = check,
+		.filters = filters,
+	};
+
+	return_if_error(lzma_block_buffer_encode(&block, allocator,
+			in, in_size, out, &out_pos, out_size));
+
+	// Index
+	{
+		// Create an Index with one Record.
+		lzma_index *i = lzma_index_init(NULL, NULL);
+		if (i == NULL)
+			return LZMA_MEM_ERROR;
+
+		lzma_ret ret = lzma_index_append(i, NULL,
+				lzma_block_unpadded_size(&block),
+				block.uncompressed_size);
+
+		// If adding the Record was successful, encode the Index
+		// and get its size which will be stored into Stream Footer.
+		if (ret == LZMA_OK) {
+			ret = lzma_index_buffer_encode(
+					i, out, &out_pos, out_size);
+
+			stream_flags.backward_size = lzma_index_size(i);
+		}
+
+		lzma_index_end(i, NULL);
+
+		if (ret != LZMA_OK)
+			return ret;
+	}
+
+	// Stream Footer. We have already reserved space for this.
+	if (lzma_stream_footer_encode(&stream_flags, out + out_pos)
+			!= LZMA_OK)
+		return LZMA_PROG_ERROR;
+
+	out_pos += LZMA_STREAM_HEADER_SIZE;
+
+	// Everything went fine, make the new output position available
+	// to the application.
+	*out_pos_ptr = out_pos;
+	return LZMA_OK;
+}

tests/test_index.c

@@ -197,6 +197,30 @@ test_code(lzma_index *i)
 
 	lzma_index_hash_end(h, NULL);
 
+	// Encode buffer
+	size_t buf_pos = 1;
+	expect(lzma_index_buffer_encode(i, buf, &buf_pos, index_size)
+			== LZMA_BUF_ERROR);
+	expect(buf_pos == 1);
+
+	succeed(lzma_index_buffer_encode(i, buf, &buf_pos, index_size + 1));
+	expect(buf_pos == index_size + 1);
+
+	// Decode buffer
+	buf_pos = 1;
+	uint64_t memlimit = MEMLIMIT;
+	expect(lzma_index_buffer_decode(&d, &memlimit, NULL, buf, &buf_pos,
+			index_size) == LZMA_DATA_ERROR);
+	expect(buf_pos == 1);
+	expect(d == NULL);
+
+	succeed(lzma_index_buffer_decode(&d, &memlimit, NULL, buf, &buf_pos,
+			index_size + 1));
+	expect(buf_pos == index_size + 1);
+	expect(lzma_index_equal(i, d));
+
+	lzma_index_end(d, NULL);
+
 	free(buf);
 }