src/liblzma/lz/lz_decoder.c - jrn/xz - Git at Google

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

 // liblzma supports multiple LZ77-based filters. The LZ part is shared
 // between these filters. The LZ code takes care of dictionary handling
 // and passing the data between filters in the chain. The filter-specific
 // part decodes from the input buffer to the dictionary.


 #include "lz_decoder.h"


 struct lzma_coder_s {
 	/// Dictionary (history buffer)
 	lzma_dict dict;

 	/// The actual LZ-based decoder e.g. LZMA
 	lzma_lz_decoder lz;

 	/// Next filter in the chain, if any. Note that LZMA and LZMA2 are
 	/// only allowed as the last filter, but the long-range filter in
 	/// future can be in the middle of the chain.
 	lzma_next_coder next;

 	/// True if the next filter in the chain has returned LZMA_STREAM_END.
 	bool next_finished;

 	/// True if the LZ decoder (e.g. LZMA) has detected end of payload
 	/// marker. This may become true before next_finished becomes true.
 	bool this_finished;

 	/// Temporary buffer needed when the LZ-based filter is not the last
 	/// filter in the chain. The output of the next filter is first
 	/// decoded into buffer[], which is then used as input for the actual
 	/// LZ-based decoder.
 	struct {
 		size_t pos;
 		size_t size;
 		uint8_t buffer[LZMA_BUFFER_SIZE];
 	} temp;
 };


 static void
 lz_decoder_reset(lzma_coder *coder)
 {
 	coder->dict.pos = 0;
 	coder->dict.full = 0;
 	coder->dict.buf[coder->dict.size - 1] = '\0';
 	coder->dict.need_reset = false;
 	return;
 }


 static lzma_ret
 decode_buffer(lzma_coder *coder,
 		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)
 {
 	while (true) {
 		// Wrap the dictionary if needed.
 		if (coder->dict.pos == coder->dict.size)
 			coder->dict.pos = 0;

 		// Store the current dictionary position. It is needed to know
 		// where to start copying to the out[] buffer.
 		const size_t dict_start = coder->dict.pos;

 		// Calculate how much we allow coder->lz.code() to decode.
 		// It must not decode past the end of the dictionary
 		// buffer, and we don't want it to decode more than is
 		// actually needed to fill the out[] buffer.
 		coder->dict.limit = coder->dict.pos
 				+ my_min(out_size - *out_pos,
 					coder->dict.size - coder->dict.pos);

 		// Call the coder->lz.code() to do the actual decoding.
 		const lzma_ret ret = coder->lz.code(
 				coder->lz.coder, &coder->dict,
 				in, in_pos, in_size);

 		// Copy the decoded data from the dictionary to the out[]
 		// buffer.
 		const size_t copy_size = coder->dict.pos - dict_start;
 		assert(copy_size <= out_size - *out_pos);
 		memcpy(out + *out_pos, coder->dict.buf + dict_start,
 				copy_size);
 		*out_pos += copy_size;

 		// Reset the dictionary if so requested by coder->lz.code().
 		if (coder->dict.need_reset) {
 			lz_decoder_reset(coder);

 			// Since we reset dictionary, we don't check if
 			// dictionary became full.
 			if (ret != LZMA_OK || *out_pos == out_size)
 				return ret;
 		} else {
 			// Return if everything got decoded or an error
 			// occurred, or if there's no more data to decode.
 			//
 			// Note that detecting if there's something to decode
 			// is done by looking if dictionary become full
 			// instead of looking if *in_pos == in_size. This
 			// is because it is possible that all the input was
 			// consumed already but some data is pending to be
 			// written to the dictionary.
 			if (ret != LZMA_OK || *out_pos == out_size
 					|| coder->dict.pos < coder->dict.size)
 				return ret;
 		}
 	}
 }


 static lzma_ret
 lz_decode(lzma_coder *coder,
 		lzma_allocator *allocator lzma_attribute((__unused__)),
 		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)
 {
 	if (coder->next.code == NULL)
 		return decode_buffer(coder, in, in_pos, in_size,
 				out, out_pos, out_size);

 	// We aren't the last coder in the chain, we need to decode
 	// our input to a temporary buffer.
 	while (*out_pos < out_size) {
 		// Fill the temporary buffer if it is empty.
 		if (!coder->next_finished
 				&& coder->temp.pos == coder->temp.size) {
 			coder->temp.pos = 0;
 			coder->temp.size = 0;

 			const lzma_ret ret = coder->next.code(
 					coder->next.coder,
 					allocator, in, in_pos, in_size,
 					coder->temp.buffer, &coder->temp.size,
 					LZMA_BUFFER_SIZE, action);

 			if (ret == LZMA_STREAM_END)
 				coder->next_finished = true;
 			else if (ret != LZMA_OK || coder->temp.size == 0)
 				return ret;
 		}

 		if (coder->this_finished) {
 			if (coder->temp.size != 0)
 				return LZMA_DATA_ERROR;

 			if (coder->next_finished)
 				return LZMA_STREAM_END;

 			return LZMA_OK;
 		}

 		const lzma_ret ret = decode_buffer(coder, coder->temp.buffer,
 				&coder->temp.pos, coder->temp.size,
 				out, out_pos, out_size);

 		if (ret == LZMA_STREAM_END)
 			coder->this_finished = true;
 		else if (ret != LZMA_OK)
 			return ret;
 		else if (coder->next_finished && *out_pos < out_size)
 			return LZMA_DATA_ERROR;
 	}

 	return LZMA_OK;
 }


 static void
 lz_decoder_end(lzma_coder *coder, lzma_allocator *allocator)
 {
 	lzma_next_end(&coder->next, allocator);
 	lzma_free(coder->dict.buf, allocator);

 	if (coder->lz.end != NULL)
 		coder->lz.end(coder->lz.coder, allocator);
 	else
 		lzma_free(coder->lz.coder, allocator);

 	lzma_free(coder, allocator);
 	return;
 }


 extern lzma_ret
 lzma_lz_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
 		const lzma_filter_info *filters,
 		lzma_ret (*lz_init)(lzma_lz_decoder *lz,
 			lzma_allocator *allocator, const void *options,
 			lzma_lz_options *lz_options))
 {
 	// Allocate the base structure if it isn't already allocated.
 	if (next->coder == NULL) {
 		next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
 		if (next->coder == NULL)
 			return LZMA_MEM_ERROR;

 		next->code = &lz_decode;
 		next->end = &lz_decoder_end;

 		next->coder->dict.buf = NULL;
 		next->coder->dict.size = 0;
 		next->coder->lz = LZMA_LZ_DECODER_INIT;
 		next->coder->next = LZMA_NEXT_CODER_INIT;
 	}

 	// Allocate and initialize the LZ-based decoder. It will also give
 	// us the dictionary size.
 	lzma_lz_options lz_options;
 	return_if_error(lz_init(&next->coder->lz, allocator,
 			filters[0].options, &lz_options));

 	// If the dictionary size is very small, increase it to 4096 bytes.
 	// This is to prevent constant wrapping of the dictionary, which
 	// would slow things down. The downside is that since we don't check
 	// separately for the real dictionary size, we may happily accept
 	// corrupt files.
 	if (lz_options.dict_size < 4096)
 		lz_options.dict_size = 4096;

 	// Make dictionary size a multipe of 16. Some LZ-based decoders like
 	// LZMA use the lowest bits lzma_dict.pos to know the alignment of the
 	// data. Aligned buffer is also good when memcpying from the
 	// dictionary to the output buffer, since applications are
 	// recommended to give aligned buffers to liblzma.
 	//
 	// Avoid integer overflow.
 	if (lz_options.dict_size > SIZE_MAX - 15)
 		return LZMA_MEM_ERROR;

 	lz_options.dict_size = (lz_options.dict_size + 15) & ~((size_t)(15));

 	// Allocate and initialize the dictionary.
 	if (next->coder->dict.size != lz_options.dict_size) {
 		lzma_free(next->coder->dict.buf, allocator);
 		next->coder->dict.buf
 				= lzma_alloc(lz_options.dict_size, allocator);
 		if (next->coder->dict.buf == NULL)
 			return LZMA_MEM_ERROR;

 		next->coder->dict.size = lz_options.dict_size;
 	}

 	lz_decoder_reset(next->coder);

 	// Use the preset dictionary if it was given to us.
 	if (lz_options.preset_dict != NULL
 			&& lz_options.preset_dict_size > 0) {
 		// If the preset dictionary is bigger than the actual
 		// dictionary, copy only the tail.
 		const size_t copy_size = my_min(lz_options.preset_dict_size,
 				lz_options.dict_size);
 		const size_t offset = lz_options.preset_dict_size - copy_size;
 		memcpy(next->coder->dict.buf, lz_options.preset_dict + offset,
 				copy_size);
 		next->coder->dict.pos = copy_size;
 		next->coder->dict.full = copy_size;
 	}

 	// Miscellaneous initializations
 	next->coder->next_finished = false;
 	next->coder->this_finished = false;
 	next->coder->temp.pos = 0;
 	next->coder->temp.size = 0;

 	// Initialize the next filter in the chain, if any.
 	return lzma_next_filter_init(&next->coder->next, allocator,
 			filters + 1);
 }


 extern uint64_t
 lzma_lz_decoder_memusage(size_t dictionary_size)
 {
 	return sizeof(lzma_coder) + (uint64_t)(dictionary_size);
 }


 extern void
 lzma_lz_decoder_uncompressed(lzma_coder *coder, lzma_vli uncompressed_size)
 {
 	coder->lz.set_uncompressed(coder->lz.coder, uncompressed_size);
 }
	///////////////////////////////////////////////////////////////////////////////
	//
	/// \file lz_decoder.c
	/// \brief LZ out window
	///
	// Authors: Igor Pavlov
	// Lasse Collin
	//
	// This file has been put into the public domain.
	// You can do whatever you want with this file.
	//
	///////////////////////////////////////////////////////////////////////////////

	// liblzma supports multiple LZ77-based filters. The LZ part is shared
	// between these filters. The LZ code takes care of dictionary handling
	// and passing the data between filters in the chain. The filter-specific
	// part decodes from the input buffer to the dictionary.


	#include "lz_decoder.h"


	struct lzma_coder_s {
	/// Dictionary (history buffer)
	lzma_dict dict;

	/// The actual LZ-based decoder e.g. LZMA
	lzma_lz_decoder lz;

	/// Next filter in the chain, if any. Note that LZMA and LZMA2 are
	/// only allowed as the last filter, but the long-range filter in
	/// future can be in the middle of the chain.
	lzma_next_coder next;

	/// True if the next filter in the chain has returned LZMA_STREAM_END.
	bool next_finished;

	/// True if the LZ decoder (e.g. LZMA) has detected end of payload
	/// marker. This may become true before next_finished becomes true.
	bool this_finished;

	/// Temporary buffer needed when the LZ-based filter is not the last
	/// filter in the chain. The output of the next filter is first
	/// decoded into buffer[], which is then used as input for the actual
	/// LZ-based decoder.
	struct {
	size_t pos;
	size_t size;
	uint8_t buffer[LZMA_BUFFER_SIZE];
	} temp;
	};


	static void
	lz_decoder_reset(lzma_coder *coder)
	{
	coder->dict.pos = 0;
	coder->dict.full = 0;
	coder->dict.buf[coder->dict.size - 1] = '\0';
	coder->dict.need_reset = false;
	return;
	}


	static lzma_ret
	decode_buffer(lzma_coder *coder,
	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)
	{
	while (true) {
	// Wrap the dictionary if needed.
	if (coder->dict.pos == coder->dict.size)
	coder->dict.pos = 0;

	// Store the current dictionary position. It is needed to know
	// where to start copying to the out[] buffer.
	const size_t dict_start = coder->dict.pos;

	// Calculate how much we allow coder->lz.code() to decode.
	// It must not decode past the end of the dictionary
	// buffer, and we don't want it to decode more than is
	// actually needed to fill the out[] buffer.
	coder->dict.limit = coder->dict.pos
	+ my_min(out_size - *out_pos,
	coder->dict.size - coder->dict.pos);

	// Call the coder->lz.code() to do the actual decoding.
	const lzma_ret ret = coder->lz.code(
	coder->lz.coder, &coder->dict,
	in, in_pos, in_size);

	// Copy the decoded data from the dictionary to the out[]
	// buffer.
	const size_t copy_size = coder->dict.pos - dict_start;
	assert(copy_size <= out_size - *out_pos);
	memcpy(out + *out_pos, coder->dict.buf + dict_start,
	copy_size);
	*out_pos += copy_size;

	// Reset the dictionary if so requested by coder->lz.code().
	if (coder->dict.need_reset) {
	lz_decoder_reset(coder);

	// Since we reset dictionary, we don't check if
	// dictionary became full.
	if (ret != LZMA_OK \|\| *out_pos == out_size)
	return ret;
	} else {
	// Return if everything got decoded or an error
	// occurred, or if there's no more data to decode.
	//
	// Note that detecting if there's something to decode
	// is done by looking if dictionary become full
	// instead of looking if *in_pos == in_size. This
	// is because it is possible that all the input was
	// consumed already but some data is pending to be
	// written to the dictionary.
	if (ret != LZMA_OK \|\| *out_pos == out_size
	\|\| coder->dict.pos < coder->dict.size)
	return ret;
	}
	}
	}


	static lzma_ret
	lz_decode(lzma_coder *coder,
	lzma_allocator *allocator lzma_attribute((__unused__)),
	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)
	{
	if (coder->next.code == NULL)
	return decode_buffer(coder, in, in_pos, in_size,
	out, out_pos, out_size);

	// We aren't the last coder in the chain, we need to decode
	// our input to a temporary buffer.
	while (*out_pos < out_size) {
	// Fill the temporary buffer if it is empty.
	if (!coder->next_finished
	&& coder->temp.pos == coder->temp.size) {
	coder->temp.pos = 0;
	coder->temp.size = 0;

	const lzma_ret ret = coder->next.code(
	coder->next.coder,
	allocator, in, in_pos, in_size,
	coder->temp.buffer, &coder->temp.size,
	LZMA_BUFFER_SIZE, action);

	if (ret == LZMA_STREAM_END)
	coder->next_finished = true;
	else if (ret != LZMA_OK \|\| coder->temp.size == 0)
	return ret;
	}

	if (coder->this_finished) {
	if (coder->temp.size != 0)
	return LZMA_DATA_ERROR;

	if (coder->next_finished)
	return LZMA_STREAM_END;

	return LZMA_OK;
	}

	const lzma_ret ret = decode_buffer(coder, coder->temp.buffer,
	&coder->temp.pos, coder->temp.size,
	out, out_pos, out_size);

	if (ret == LZMA_STREAM_END)
	coder->this_finished = true;
	else if (ret != LZMA_OK)
	return ret;
	else if (coder->next_finished && *out_pos < out_size)
	return LZMA_DATA_ERROR;
	}

	return LZMA_OK;
	}


	static void
	lz_decoder_end(lzma_coder coder, lzma_allocator allocator)
	{
	lzma_next_end(&coder->next, allocator);
	lzma_free(coder->dict.buf, allocator);

	if (coder->lz.end != NULL)
	coder->lz.end(coder->lz.coder, allocator);
	else
	lzma_free(coder->lz.coder, allocator);

	lzma_free(coder, allocator);
	return;
	}


	extern lzma_ret
	lzma_lz_decoder_init(lzma_next_coder next, lzma_allocator allocator,
	const lzma_filter_info *filters,
	lzma_ret (lz_init)(lzma_lz_decoder lz,
	lzma_allocator allocator, const void options,
	lzma_lz_options *lz_options))
	{
	// Allocate the base structure if it isn't already allocated.
	if (next->coder == NULL) {
	next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
	if (next->coder == NULL)
	return LZMA_MEM_ERROR;

	next->code = &lz_decode;
	next->end = &lz_decoder_end;

	next->coder->dict.buf = NULL;
	next->coder->dict.size = 0;
	next->coder->lz = LZMA_LZ_DECODER_INIT;
	next->coder->next = LZMA_NEXT_CODER_INIT;
	}

	// Allocate and initialize the LZ-based decoder. It will also give
	// us the dictionary size.
	lzma_lz_options lz_options;
	return_if_error(lz_init(&next->coder->lz, allocator,
	filters[0].options, &lz_options));

	// If the dictionary size is very small, increase it to 4096 bytes.
	// This is to prevent constant wrapping of the dictionary, which
	// would slow things down. The downside is that since we don't check
	// separately for the real dictionary size, we may happily accept
	// corrupt files.
	if (lz_options.dict_size < 4096)
	lz_options.dict_size = 4096;

	// Make dictionary size a multipe of 16. Some LZ-based decoders like
	// LZMA use the lowest bits lzma_dict.pos to know the alignment of the
	// data. Aligned buffer is also good when memcpying from the
	// dictionary to the output buffer, since applications are
	// recommended to give aligned buffers to liblzma.
	//
	// Avoid integer overflow.
	if (lz_options.dict_size > SIZE_MAX - 15)
	return LZMA_MEM_ERROR;

	lz_options.dict_size = (lz_options.dict_size + 15) & ~((size_t)(15));

	// Allocate and initialize the dictionary.
	if (next->coder->dict.size != lz_options.dict_size) {
	lzma_free(next->coder->dict.buf, allocator);
	next->coder->dict.buf
	= lzma_alloc(lz_options.dict_size, allocator);
	if (next->coder->dict.buf == NULL)
	return LZMA_MEM_ERROR;

	next->coder->dict.size = lz_options.dict_size;
	}

	lz_decoder_reset(next->coder);

	// Use the preset dictionary if it was given to us.
	if (lz_options.preset_dict != NULL
	&& lz_options.preset_dict_size > 0) {
	// If the preset dictionary is bigger than the actual
	// dictionary, copy only the tail.
	const size_t copy_size = my_min(lz_options.preset_dict_size,
	lz_options.dict_size);
	const size_t offset = lz_options.preset_dict_size - copy_size;
	memcpy(next->coder->dict.buf, lz_options.preset_dict + offset,
	copy_size);
	next->coder->dict.pos = copy_size;
	next->coder->dict.full = copy_size;
	}

	// Miscellaneous initializations
	next->coder->next_finished = false;
	next->coder->this_finished = false;
	next->coder->temp.pos = 0;
	next->coder->temp.size = 0;

	// Initialize the next filter in the chain, if any.
	return lzma_next_filter_init(&next->coder->next, allocator,
	filters + 1);
	}


	extern uint64_t
	lzma_lz_decoder_memusage(size_t dictionary_size)
	{
	return sizeof(lzma_coder) + (uint64_t)(dictionary_size);
	}


	extern void
	lzma_lz_decoder_uncompressed(lzma_coder *coder, lzma_vli uncompressed_size)
	{
	coder->lz.set_uncompressed(coder->lz.coder, uncompressed_size);
	}