src/liblzma/lzma/lzma2_encoder.c - jrn/xz - Git at Google

 ///////////////////////////////////////////////////////////////////////////////
 //
 /// \file       lzma2_encoder.c
 /// \brief      LZMA2 encoder
 ///
 //  Authors:    Igor Pavlov
 //              Lasse Collin
 //
 //  This file has been put into the public domain.
 //  You can do whatever you want with this file.
 //
 ///////////////////////////////////////////////////////////////////////////////

 #include "lz_encoder.h"
 #include "lzma_encoder.h"
 #include "fastpos.h"
 #include "lzma2_encoder.h"


 struct lzma_coder_s {
 	enum {
 		SEQ_INIT,
 		SEQ_LZMA_ENCODE,
 		SEQ_LZMA_COPY,
 		SEQ_UNCOMPRESSED_HEADER,
 		SEQ_UNCOMPRESSED_COPY,
 	} sequence;

 	/// LZMA encoder
 	lzma_coder *lzma;

 	/// LZMA options currently in use.
 	lzma_options_lzma opt_cur;

 	bool need_properties;
 	bool need_state_reset;
 	bool need_dictionary_reset;

 	/// Uncompressed size of a chunk
 	size_t uncompressed_size;

 	/// Compressed size of a chunk (excluding headers); this is also used
 	/// to indicate the end of buf[] in SEQ_LZMA_COPY.
 	size_t compressed_size;

 	/// Read position in buf[]
 	size_t buf_pos;

 	/// Buffer to hold the chunk header and LZMA compressed data
 	uint8_t buf[LZMA2_HEADER_MAX + LZMA2_CHUNK_MAX];
 };


 static void
 lzma2_header_lzma(lzma_coder *coder)
 {
 	assert(coder->uncompressed_size > 0);
 	assert(coder->uncompressed_size <= LZMA2_UNCOMPRESSED_MAX);
 	assert(coder->compressed_size > 0);
 	assert(coder->compressed_size <= LZMA2_CHUNK_MAX);

 	size_t pos;

 	if (coder->need_properties) {
 		pos = 0;

 		if (coder->need_dictionary_reset)
 			coder->buf[pos] = 0x80 + (3 << 5);
 		else
 			coder->buf[pos] = 0x80 + (2 << 5);
 	} else {
 		pos = 1;

 		if (coder->need_state_reset)
 			coder->buf[pos] = 0x80 + (1 << 5);
 		else
 			coder->buf[pos] = 0x80;
 	}

 	// Set the start position for copying.
 	coder->buf_pos = pos;

 	// Uncompressed size
 	size_t size = coder->uncompressed_size - 1;
 	coder->buf[pos++] += size >> 16;
 	coder->buf[pos++] = (size >> 8) & 0xFF;
 	coder->buf[pos++] = size & 0xFF;

 	// Compressed size
 	size = coder->compressed_size - 1;
 	coder->buf[pos++] = size >> 8;
 	coder->buf[pos++] = size & 0xFF;

 	// Properties, if needed
 	if (coder->need_properties)
 		lzma_lzma_lclppb_encode(&coder->opt_cur, coder->buf + pos);

 	coder->need_properties = false;
 	coder->need_state_reset = false;
 	coder->need_dictionary_reset = false;

 	// The copying code uses coder->compressed_size to indicate the end
 	// of coder->buf[], so we need add the maximum size of the header here.
 	coder->compressed_size += LZMA2_HEADER_MAX;

 	return;
 }


 static void
 lzma2_header_uncompressed(lzma_coder *coder)
 {
 	assert(coder->uncompressed_size > 0);
 	assert(coder->uncompressed_size <= LZMA2_CHUNK_MAX);

 	// If this is the first chunk, we need to include dictionary
 	// reset indicator.
 	if (coder->need_dictionary_reset)
 		coder->buf[0] = 1;
 	else
 		coder->buf[0] = 2;

 	coder->need_dictionary_reset = false;

 	// "Compressed" size
 	coder->buf[1] = (coder->uncompressed_size - 1) >> 8;
 	coder->buf[2] = (coder->uncompressed_size - 1) & 0xFF;

 	// Set the start position for copying.
 	coder->buf_pos = 0;
 	return;
 }


 static lzma_ret
 lzma2_encode(lzma_coder *restrict coder, lzma_mf *restrict mf,
 		uint8_t *restrict out, size_t *restrict out_pos,
 		size_t out_size)
 {
 	while (*out_pos < out_size)
 	switch (coder->sequence) {
 	case SEQ_INIT:
 		// If there's no input left and we are flushing or finishing,
 		// don't start a new chunk.
 		if (mf_unencoded(mf) == 0) {
 			// Write end of payload marker if finishing.
 			if (mf->action == LZMA_FINISH)
 				out[(*out_pos)++] = 0;

 			return mf->action == LZMA_RUN
 					? LZMA_OK : LZMA_STREAM_END;
 		}

 		if (coder->need_state_reset)
 			return_if_error(lzma_lzma_encoder_reset(
 					coder->lzma, &coder->opt_cur));

 		coder->uncompressed_size = 0;
 		coder->compressed_size = 0;
 		coder->sequence = SEQ_LZMA_ENCODE;

 	// Fall through

 	case SEQ_LZMA_ENCODE: {
 		// Calculate how much more uncompressed data this chunk
 		// could accept.
 		const uint32_t left = LZMA2_UNCOMPRESSED_MAX
 				- coder->uncompressed_size;
 		uint32_t limit;

 		if (left < mf->match_len_max) {
 			// Must flush immediately since the next LZMA symbol
 			// could make the uncompressed size of the chunk too
 			// big.
 			limit = 0;
 		} else {
 			// Calculate maximum read_limit that is OK from point
 			// of view of LZMA2 chunk size.
 			limit = mf->read_pos - mf->read_ahead
 					+ left - mf->match_len_max;
 		}

 		// Save the start position so that we can update
 		// coder->uncompressed_size.
 		const uint32_t read_start = mf->read_pos - mf->read_ahead;

 		// Call the LZMA encoder until the chunk is finished.
 		const lzma_ret ret = lzma_lzma_encode(coder->lzma, mf,
 				coder->buf + LZMA2_HEADER_MAX,
 				&coder->compressed_size,
 				LZMA2_CHUNK_MAX, limit);

 		coder->uncompressed_size += mf->read_pos - mf->read_ahead
 				- read_start;

 		assert(coder->compressed_size <= LZMA2_CHUNK_MAX);
 		assert(coder->uncompressed_size <= LZMA2_UNCOMPRESSED_MAX);

 		if (ret != LZMA_STREAM_END)
 			return LZMA_OK;

 		// See if the chunk compressed. If it didn't, we encode it
 		// as uncompressed chunk. This saves a few bytes of space
 		// and makes decoding faster.
 		if (coder->compressed_size >= coder->uncompressed_size) {
 			coder->uncompressed_size += mf->read_ahead;
 			assert(coder->uncompressed_size
 					<= LZMA2_UNCOMPRESSED_MAX);
 			mf->read_ahead = 0;
 			lzma2_header_uncompressed(coder);
 			coder->need_state_reset = true;
 			coder->sequence = SEQ_UNCOMPRESSED_HEADER;
 			break;
 		}

 		// The chunk did compress at least by one byte, so we store
 		// the chunk as LZMA.
 		lzma2_header_lzma(coder);

 		coder->sequence = SEQ_LZMA_COPY;
 	}

 	// Fall through

 	case SEQ_LZMA_COPY:
 		// Copy the compressed chunk along its headers to the
 		// output buffer.
 		lzma_bufcpy(coder->buf, &coder->buf_pos,
 				coder->compressed_size,
 				out, out_pos, out_size);
 		if (coder->buf_pos != coder->compressed_size)
 			return LZMA_OK;

 		coder->sequence = SEQ_INIT;
 		break;

 	case SEQ_UNCOMPRESSED_HEADER:
 		// Copy the three-byte header to indicate uncompressed chunk.
 		lzma_bufcpy(coder->buf, &coder->buf_pos,
 				LZMA2_HEADER_UNCOMPRESSED,
 				out, out_pos, out_size);
 		if (coder->buf_pos != LZMA2_HEADER_UNCOMPRESSED)
 			return LZMA_OK;

 		coder->sequence = SEQ_UNCOMPRESSED_COPY;

 	// Fall through

 	case SEQ_UNCOMPRESSED_COPY:
 		// Copy the uncompressed data as is from the dictionary
 		// to the output buffer.
 		mf_read(mf, out, out_pos, out_size, &coder->uncompressed_size);
 		if (coder->uncompressed_size != 0)
 			return LZMA_OK;

 		coder->sequence = SEQ_INIT;
 		break;
 	}

 	return LZMA_OK;
 }


 static void
 lzma2_encoder_end(lzma_coder *coder, lzma_allocator *allocator)
 {
 	lzma_free(coder->lzma, allocator);
 	lzma_free(coder, allocator);
 	return;
 }


 static lzma_ret
 lzma2_encoder_options_update(lzma_coder *coder, const lzma_filter *filter)
 {
 	// New options can be set only when there is no incomplete chunk.
 	// This is the case at the beginning of the raw stream and right
 	// after LZMA_SYNC_FLUSH.
 	if (filter->options == NULL || coder->sequence != SEQ_INIT)
 		return LZMA_PROG_ERROR;

 	// Look if there are new options. At least for now,
 	// only lc/lp/pb can be changed.
 	const lzma_options_lzma *opt = filter->options;
 	if (coder->opt_cur.lc != opt->lc || coder->opt_cur.lp != opt->lp
 			|| coder->opt_cur.pb != opt->pb) {
 		// Validate the options.
 		if (opt->lc > LZMA_LCLP_MAX || opt->lp > LZMA_LCLP_MAX
 				|| opt->lc + opt->lp > LZMA_LCLP_MAX
 				|| opt->pb > LZMA_PB_MAX)
 			return LZMA_OPTIONS_ERROR;

 		// The new options will be used when the encoder starts
 		// a new LZMA2 chunk.
 		coder->opt_cur.lc = opt->lc;
 		coder->opt_cur.lp = opt->lp;
 		coder->opt_cur.pb = opt->pb;
 		coder->need_properties = true;
 		coder->need_state_reset = true;
 	}

 	return LZMA_OK;
 }


 static lzma_ret
 lzma2_encoder_init(lzma_lz_encoder *lz, lzma_allocator *allocator,
 		const void *options, lzma_lz_options *lz_options)
 {
 	if (options == NULL)
 		return LZMA_PROG_ERROR;

 	if (lz->coder == NULL) {
 		lz->coder = lzma_alloc(sizeof(lzma_coder), allocator);
 		if (lz->coder == NULL)
 			return LZMA_MEM_ERROR;

 		lz->code = &lzma2_encode;
 		lz->end = &lzma2_encoder_end;
 		lz->options_update = &lzma2_encoder_options_update;

 		lz->coder->lzma = NULL;
 	}

 	lz->coder->opt_cur = *(const lzma_options_lzma *)(options);

 	lz->coder->sequence = SEQ_INIT;
 	lz->coder->need_properties = true;
 	lz->coder->need_state_reset = false;
 	lz->coder->need_dictionary_reset
 			= lz->coder->opt_cur.preset_dict == NULL
 			|| lz->coder->opt_cur.preset_dict_size == 0;

 	// Initialize LZMA encoder
 	return_if_error(lzma_lzma_encoder_create(&lz->coder->lzma, allocator,
 			&lz->coder->opt_cur, lz_options));

 	// Make sure that we will always have enough history available in
 	// case we need to use uncompressed chunks. They are used when the
 	// compressed size of a chunk is not smaller than the uncompressed
 	// size, so we need to have at least LZMA2_COMPRESSED_MAX bytes
 	// history available.
 	if (lz_options->before_size + lz_options->dict_size < LZMA2_CHUNK_MAX)
 		lz_options->before_size
 				= LZMA2_CHUNK_MAX - lz_options->dict_size;

 	return LZMA_OK;
 }


 extern lzma_ret
 lzma_lzma2_encoder_init(lzma_next_coder *next, lzma_allocator *allocator,
 		const lzma_filter_info *filters)
 {
 	return lzma_lz_encoder_init(
 			next, allocator, filters, &lzma2_encoder_init);
 }


 extern uint64_t
 lzma_lzma2_encoder_memusage(const void *options)
 {
 	const uint64_t lzma_mem = lzma_lzma_encoder_memusage(options);
 	if (lzma_mem == UINT64_MAX)
 		return UINT64_MAX;

 	return sizeof(lzma_coder) + lzma_mem;
 }


 extern lzma_ret
 lzma_lzma2_props_encode(const void *options, uint8_t *out)
 {
 	const lzma_options_lzma *const opt = options;
 	uint32_t d = my_max(opt->dict_size, LZMA_DICT_SIZE_MIN);

 	// Round up to to the next 2^n - 1 or 2^n + 2^(n - 1) - 1 depending
 	// on which one is the next:
 	--d;
 	d |= d >> 2;
 	d |= d >> 3;
 	d |= d >> 4;
 	d |= d >> 8;
 	d |= d >> 16;

 	// Get the highest two bits using the proper encoding:
 	if (d == UINT32_MAX)
 		out[0] = 40;
 	else
 		out[0] = get_pos_slot(d + 1) - 24;

 	return LZMA_OK;
 }
	///////////////////////////////////////////////////////////////////////////////
	//
	/// \file lzma2_encoder.c
	/// \brief LZMA2 encoder
	///
	// Authors: Igor Pavlov
	// Lasse Collin
	//
	// This file has been put into the public domain.
	// You can do whatever you want with this file.
	//
	///////////////////////////////////////////////////////////////////////////////

	#include "lz_encoder.h"
	#include "lzma_encoder.h"
	#include "fastpos.h"
	#include "lzma2_encoder.h"


	struct lzma_coder_s {
	enum {
	SEQ_INIT,
	SEQ_LZMA_ENCODE,
	SEQ_LZMA_COPY,
	SEQ_UNCOMPRESSED_HEADER,
	SEQ_UNCOMPRESSED_COPY,
	} sequence;

	/// LZMA encoder
	lzma_coder *lzma;

	/// LZMA options currently in use.
	lzma_options_lzma opt_cur;

	bool need_properties;
	bool need_state_reset;
	bool need_dictionary_reset;

	/// Uncompressed size of a chunk
	size_t uncompressed_size;

	/// Compressed size of a chunk (excluding headers); this is also used
	/// to indicate the end of buf[] in SEQ_LZMA_COPY.
	size_t compressed_size;

	/// Read position in buf[]
	size_t buf_pos;

	/// Buffer to hold the chunk header and LZMA compressed data
	uint8_t buf[LZMA2_HEADER_MAX + LZMA2_CHUNK_MAX];
	};


	static void
	lzma2_header_lzma(lzma_coder *coder)
	{
	assert(coder->uncompressed_size > 0);
	assert(coder->uncompressed_size <= LZMA2_UNCOMPRESSED_MAX);
	assert(coder->compressed_size > 0);
	assert(coder->compressed_size <= LZMA2_CHUNK_MAX);

	size_t pos;

	if (coder->need_properties) {
	pos = 0;

	if (coder->need_dictionary_reset)
	coder->buf[pos] = 0x80 + (3 << 5);
	else
	coder->buf[pos] = 0x80 + (2 << 5);
	} else {
	pos = 1;

	if (coder->need_state_reset)
	coder->buf[pos] = 0x80 + (1 << 5);
	else
	coder->buf[pos] = 0x80;
	}

	// Set the start position for copying.
	coder->buf_pos = pos;

	// Uncompressed size
	size_t size = coder->uncompressed_size - 1;
	coder->buf[pos++] += size >> 16;
	coder->buf[pos++] = (size >> 8) & 0xFF;
	coder->buf[pos++] = size & 0xFF;

	// Compressed size
	size = coder->compressed_size - 1;
	coder->buf[pos++] = size >> 8;
	coder->buf[pos++] = size & 0xFF;

	// Properties, if needed
	if (coder->need_properties)
	lzma_lzma_lclppb_encode(&coder->opt_cur, coder->buf + pos);

	coder->need_properties = false;
	coder->need_state_reset = false;
	coder->need_dictionary_reset = false;

	// The copying code uses coder->compressed_size to indicate the end
	// of coder->buf[], so we need add the maximum size of the header here.
	coder->compressed_size += LZMA2_HEADER_MAX;

	return;
	}


	static void
	lzma2_header_uncompressed(lzma_coder *coder)
	{
	assert(coder->uncompressed_size > 0);
	assert(coder->uncompressed_size <= LZMA2_CHUNK_MAX);

	// If this is the first chunk, we need to include dictionary
	// reset indicator.
	if (coder->need_dictionary_reset)
	coder->buf[0] = 1;
	else
	coder->buf[0] = 2;

	coder->need_dictionary_reset = false;

	// "Compressed" size
	coder->buf[1] = (coder->uncompressed_size - 1) >> 8;
	coder->buf[2] = (coder->uncompressed_size - 1) & 0xFF;

	// Set the start position for copying.
	coder->buf_pos = 0;
	return;
	}


	static lzma_ret
	lzma2_encode(lzma_coder restrict coder, lzma_mf restrict mf,
	uint8_t restrict out, size_t restrict out_pos,
	size_t out_size)
	{
	while (*out_pos < out_size)
	switch (coder->sequence) {
	case SEQ_INIT:
	// If there's no input left and we are flushing or finishing,
	// don't start a new chunk.
	if (mf_unencoded(mf) == 0) {
	// Write end of payload marker if finishing.
	if (mf->action == LZMA_FINISH)
	out[(*out_pos)++] = 0;

	return mf->action == LZMA_RUN
	? LZMA_OK : LZMA_STREAM_END;
	}

	if (coder->need_state_reset)
	return_if_error(lzma_lzma_encoder_reset(
	coder->lzma, &coder->opt_cur));

	coder->uncompressed_size = 0;
	coder->compressed_size = 0;
	coder->sequence = SEQ_LZMA_ENCODE;

	// Fall through

	case SEQ_LZMA_ENCODE: {
	// Calculate how much more uncompressed data this chunk
	// could accept.
	const uint32_t left = LZMA2_UNCOMPRESSED_MAX
	- coder->uncompressed_size;
	uint32_t limit;

	if (left < mf->match_len_max) {
	// Must flush immediately since the next LZMA symbol
	// could make the uncompressed size of the chunk too
	// big.
	limit = 0;
	} else {
	// Calculate maximum read_limit that is OK from point
	// of view of LZMA2 chunk size.
	limit = mf->read_pos - mf->read_ahead
	+ left - mf->match_len_max;
	}

	// Save the start position so that we can update
	// coder->uncompressed_size.
	const uint32_t read_start = mf->read_pos - mf->read_ahead;

	// Call the LZMA encoder until the chunk is finished.
	const lzma_ret ret = lzma_lzma_encode(coder->lzma, mf,
	coder->buf + LZMA2_HEADER_MAX,
	&coder->compressed_size,
	LZMA2_CHUNK_MAX, limit);

	coder->uncompressed_size += mf->read_pos - mf->read_ahead
	- read_start;

	assert(coder->compressed_size <= LZMA2_CHUNK_MAX);
	assert(coder->uncompressed_size <= LZMA2_UNCOMPRESSED_MAX);

	if (ret != LZMA_STREAM_END)
	return LZMA_OK;

	// See if the chunk compressed. If it didn't, we encode it
	// as uncompressed chunk. This saves a few bytes of space
	// and makes decoding faster.
	if (coder->compressed_size >= coder->uncompressed_size) {
	coder->uncompressed_size += mf->read_ahead;
	assert(coder->uncompressed_size
	<= LZMA2_UNCOMPRESSED_MAX);
	mf->read_ahead = 0;
	lzma2_header_uncompressed(coder);
	coder->need_state_reset = true;
	coder->sequence = SEQ_UNCOMPRESSED_HEADER;
	break;
	}

	// The chunk did compress at least by one byte, so we store
	// the chunk as LZMA.
	lzma2_header_lzma(coder);

	coder->sequence = SEQ_LZMA_COPY;
	}

	// Fall through

	case SEQ_LZMA_COPY:
	// Copy the compressed chunk along its headers to the
	// output buffer.
	lzma_bufcpy(coder->buf, &coder->buf_pos,
	coder->compressed_size,
	out, out_pos, out_size);
	if (coder->buf_pos != coder->compressed_size)
	return LZMA_OK;

	coder->sequence = SEQ_INIT;
	break;

	case SEQ_UNCOMPRESSED_HEADER:
	// Copy the three-byte header to indicate uncompressed chunk.
	lzma_bufcpy(coder->buf, &coder->buf_pos,
	LZMA2_HEADER_UNCOMPRESSED,
	out, out_pos, out_size);
	if (coder->buf_pos != LZMA2_HEADER_UNCOMPRESSED)
	return LZMA_OK;

	coder->sequence = SEQ_UNCOMPRESSED_COPY;

	// Fall through

	case SEQ_UNCOMPRESSED_COPY:
	// Copy the uncompressed data as is from the dictionary
	// to the output buffer.
	mf_read(mf, out, out_pos, out_size, &coder->uncompressed_size);
	if (coder->uncompressed_size != 0)
	return LZMA_OK;

	coder->sequence = SEQ_INIT;
	break;
	}

	return LZMA_OK;
	}


	static void
	lzma2_encoder_end(lzma_coder coder, lzma_allocator allocator)
	{
	lzma_free(coder->lzma, allocator);
	lzma_free(coder, allocator);
	return;
	}


	static lzma_ret
	lzma2_encoder_options_update(lzma_coder coder, const lzma_filter filter)
	{
	// New options can be set only when there is no incomplete chunk.
	// This is the case at the beginning of the raw stream and right
	// after LZMA_SYNC_FLUSH.
	if (filter->options == NULL \|\| coder->sequence != SEQ_INIT)
	return LZMA_PROG_ERROR;

	// Look if there are new options. At least for now,
	// only lc/lp/pb can be changed.
	const lzma_options_lzma *opt = filter->options;
	if (coder->opt_cur.lc != opt->lc \|\| coder->opt_cur.lp != opt->lp
	\|\| coder->opt_cur.pb != opt->pb) {
	// Validate the options.
	if (opt->lc > LZMA_LCLP_MAX \|\| opt->lp > LZMA_LCLP_MAX
	\|\| opt->lc + opt->lp > LZMA_LCLP_MAX
	\|\| opt->pb > LZMA_PB_MAX)
	return LZMA_OPTIONS_ERROR;

	// The new options will be used when the encoder starts
	// a new LZMA2 chunk.
	coder->opt_cur.lc = opt->lc;
	coder->opt_cur.lp = opt->lp;
	coder->opt_cur.pb = opt->pb;
	coder->need_properties = true;
	coder->need_state_reset = true;
	}

	return LZMA_OK;
	}


	static lzma_ret
	lzma2_encoder_init(lzma_lz_encoder lz, lzma_allocator allocator,
	const void options, lzma_lz_options lz_options)
	{
	if (options == NULL)
	return LZMA_PROG_ERROR;

	if (lz->coder == NULL) {
	lz->coder = lzma_alloc(sizeof(lzma_coder), allocator);
	if (lz->coder == NULL)
	return LZMA_MEM_ERROR;

	lz->code = &lzma2_encode;
	lz->end = &lzma2_encoder_end;
	lz->options_update = &lzma2_encoder_options_update;

	lz->coder->lzma = NULL;
	}

	lz->coder->opt_cur = (const lzma_options_lzma )(options);

	lz->coder->sequence = SEQ_INIT;
	lz->coder->need_properties = true;
	lz->coder->need_state_reset = false;
	lz->coder->need_dictionary_reset
	= lz->coder->opt_cur.preset_dict == NULL
	\|\| lz->coder->opt_cur.preset_dict_size == 0;

	// Initialize LZMA encoder
	return_if_error(lzma_lzma_encoder_create(&lz->coder->lzma, allocator,
	&lz->coder->opt_cur, lz_options));

	// Make sure that we will always have enough history available in
	// case we need to use uncompressed chunks. They are used when the
	// compressed size of a chunk is not smaller than the uncompressed
	// size, so we need to have at least LZMA2_COMPRESSED_MAX bytes
	// history available.
	if (lz_options->before_size + lz_options->dict_size < LZMA2_CHUNK_MAX)
	lz_options->before_size
	= LZMA2_CHUNK_MAX - lz_options->dict_size;

	return LZMA_OK;
	}


	extern lzma_ret
	lzma_lzma2_encoder_init(lzma_next_coder next, lzma_allocator allocator,
	const lzma_filter_info *filters)
	{
	return lzma_lz_encoder_init(
	next, allocator, filters, &lzma2_encoder_init);
	}


	extern uint64_t
	lzma_lzma2_encoder_memusage(const void *options)
	{
	const uint64_t lzma_mem = lzma_lzma_encoder_memusage(options);
	if (lzma_mem == UINT64_MAX)
	return UINT64_MAX;

	return sizeof(lzma_coder) + lzma_mem;
	}


	extern lzma_ret
	lzma_lzma2_props_encode(const void options, uint8_t out)
	{
	const lzma_options_lzma *const opt = options;
	uint32_t d = my_max(opt->dict_size, LZMA_DICT_SIZE_MIN);

	// Round up to to the next 2^n - 1 or 2^n + 2^(n - 1) - 1 depending
	// on which one is the next:
	--d;
	d \|= d >> 2;
	d \|= d >> 3;
	d \|= d >> 4;
	d \|= d >> 8;
	d \|= d >> 16;

	// Get the highest two bits using the proper encoding:
	if (d == UINT32_MAX)
	out[0] = 40;
	else
	out[0] = get_pos_slot(d + 1) - 24;

	return LZMA_OK;
	}