src/liblzma/simple/simple_coder.c - third_party/xz - Git at Google

 ///////////////////////////////////////////////////////////////////////////////
 //
 /// \file       simple_coder.c
 /// \brief      Wrapper for simple filters
 ///
 /// Simple filters don't change the size of the data i.e. number of bytes
 /// in equals the number of bytes out.
 //
 //  Author:     Lasse Collin
 //
 //  This file has been put into the public domain.
 //  You can do whatever you want with this file.
 //
 ///////////////////////////////////////////////////////////////////////////////

 #include "simple_private.h"


 /// Copied or encodes/decodes more data to out[].
 static lzma_ret
 copy_or_code(lzma_simple_coder *coder, 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)
 {
 	assert(!coder->end_was_reached);

 	if (coder->next.code == NULL) {
 		lzma_bufcpy(in, in_pos, in_size, out, out_pos, out_size);

 		// Check if end of stream was reached.
 		if (coder->is_encoder && action == LZMA_FINISH
 				&& *in_pos == in_size)
 			coder->end_was_reached = true;

 	} else {
 		// Call the next coder in the chain to provide us some data.
 		const lzma_ret ret = coder->next.code(
 				coder->next.coder, allocator,
 				in, in_pos, in_size,
 				out, out_pos, out_size, action);

 		if (ret == LZMA_STREAM_END) {
 			assert(!coder->is_encoder
 					|| action == LZMA_FINISH);
 			coder->end_was_reached = true;

 		} else if (ret != LZMA_OK) {
 			return ret;
 		}
 	}

 	return LZMA_OK;
 }


 static size_t
 call_filter(lzma_simple_coder *coder, uint8_t *buffer, size_t size)
 {
 	const size_t filtered = coder->filter(coder->simple,
 			coder->now_pos, coder->is_encoder,
 			buffer, size);
 	coder->now_pos += filtered;
 	return filtered;
 }


 static lzma_ret
 simple_code(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_simple_coder *coder = coder_ptr;

 	// TODO: Add partial support for LZMA_SYNC_FLUSH. We can support it
 	// in cases when the filter is able to filter everything. With most
 	// simple filters it can be done at offset that is a multiple of 2,
 	// 4, or 16. With x86 filter, it needs good luck, and thus cannot
 	// be made to work predictably.
 	if (action == LZMA_SYNC_FLUSH)
 		return LZMA_OPTIONS_ERROR;

 	// Flush already filtered data from coder->buffer[] to out[].
 	if (coder->pos < coder->filtered) {
 		lzma_bufcpy(coder->buffer, &coder->pos, coder->filtered,
 				out, out_pos, out_size);

 		// If we couldn't flush all the filtered data, return to
 		// application immediately.
 		if (coder->pos < coder->filtered)
 			return LZMA_OK;

 		if (coder->end_was_reached) {
 			assert(coder->filtered == coder->size);
 			return LZMA_STREAM_END;
 		}
 	}

 	// If we get here, there is no filtered data left in the buffer.
 	coder->filtered = 0;

 	assert(!coder->end_was_reached);

 	// If there is more output space left than there is unfiltered data
 	// in coder->buffer[], flush coder->buffer[] to out[], and copy/code
 	// more data to out[] hopefully filling it completely. Then filter
 	// the data in out[]. This step is where most of the data gets
 	// filtered if the buffer sizes used by the application are reasonable.
 	const size_t out_avail = out_size - *out_pos;
 	const size_t buf_avail = coder->size - coder->pos;
 	if (out_avail > buf_avail || buf_avail == 0) {
 		// Store the old position so that we know from which byte
 		// to start filtering.
 		const size_t out_start = *out_pos;

 		// Flush data from coder->buffer[] to out[], but don't reset
 		// coder->pos and coder->size yet. This way the coder can be
 		// restarted if the next filter in the chain returns e.g.
 		// LZMA_MEM_ERROR.
 		memcpy(out + *out_pos, coder->buffer + coder->pos, buf_avail);
 		*out_pos += buf_avail;

 		// Copy/Encode/Decode more data to out[].
 		{
 			const lzma_ret ret = copy_or_code(coder, allocator,
 					in, in_pos, in_size,
 					out, out_pos, out_size, action);
 			assert(ret != LZMA_STREAM_END);
 			if (ret != LZMA_OK)
 				return ret;
 		}

 		// Filter out[].
 		const size_t size = *out_pos - out_start;
 		const size_t filtered = call_filter(
 				coder, out + out_start, size);

 		const size_t unfiltered = size - filtered;
 		assert(unfiltered <= coder->allocated / 2);

 		// Now we can update coder->pos and coder->size, because
 		// the next coder in the chain (if any) was successful.
 		coder->pos = 0;
 		coder->size = unfiltered;

 		if (coder->end_was_reached) {
 			// The last byte has been copied to out[] already.
 			// They are left as is.
 			coder->size = 0;

 		} else if (unfiltered > 0) {
 			// There is unfiltered data left in out[]. Copy it to
 			// coder->buffer[] and rewind *out_pos appropriately.
 			*out_pos -= unfiltered;
 			memcpy(coder->buffer, out + *out_pos, unfiltered);
 		}
 	} else if (coder->pos > 0) {
 		memmove(coder->buffer, coder->buffer + coder->pos, buf_avail);
 		coder->size -= coder->pos;
 		coder->pos = 0;
 	}

 	assert(coder->pos == 0);

 	// If coder->buffer[] isn't empty, try to fill it by copying/decoding
 	// more data. Then filter coder->buffer[] and copy the successfully
 	// filtered data to out[]. It is probable, that some filtered and
 	// unfiltered data will be left to coder->buffer[].
 	if (coder->size > 0) {
 		{
 			const lzma_ret ret = copy_or_code(coder, allocator,
 					in, in_pos, in_size,
 					coder->buffer, &coder->size,
 					coder->allocated, action);
 			assert(ret != LZMA_STREAM_END);
 			if (ret != LZMA_OK)
 				return ret;
 		}

 		coder->filtered = call_filter(
 				coder, coder->buffer, coder->size);

 		// Everything is considered to be filtered if coder->buffer[]
 		// contains the last bytes of the data.
 		if (coder->end_was_reached)
 			coder->filtered = coder->size;

 		// Flush as much as possible.
 		lzma_bufcpy(coder->buffer, &coder->pos, coder->filtered,
 				out, out_pos, out_size);
 	}

 	// Check if we got everything done.
 	if (coder->end_was_reached && coder->pos == coder->size)
 		return LZMA_STREAM_END;

 	return LZMA_OK;
 }


 static void
 simple_coder_end(void *coder_ptr, const lzma_allocator *allocator)
 {
 	lzma_simple_coder *coder = coder_ptr;
 	lzma_next_end(&coder->next, allocator);
 	lzma_free(coder->simple, allocator);
 	lzma_free(coder, allocator);
 	return;
 }


 static lzma_ret
 simple_coder_update(void *coder_ptr, const lzma_allocator *allocator,
 		const lzma_filter *filters_null lzma_attribute((__unused__)),
 		const lzma_filter *reversed_filters)
 {
 	lzma_simple_coder *coder = coder_ptr;

 	// No update support, just call the next filter in the chain.
 	return lzma_next_filter_update(
 			&coder->next, allocator, reversed_filters + 1);
 }


 extern lzma_ret
 lzma_simple_coder_init(lzma_next_coder *next, const lzma_allocator *allocator,
 		const lzma_filter_info *filters,
 		size_t (*filter)(void *simple, uint32_t now_pos,
 			bool is_encoder, uint8_t *buffer, size_t size),
 		size_t simple_size, size_t unfiltered_max,
 		uint32_t alignment, bool is_encoder)
 {
 	// Allocate memory for the lzma_simple_coder structure if needed.
 	lzma_simple_coder *coder = next->coder;
 	if (coder == NULL) {
 		// Here we allocate space also for the temporary buffer. We
 		// need twice the size of unfiltered_max, because then it
 		// is always possible to filter at least unfiltered_max bytes
 		// more data in coder->buffer[] if it can be filled completely.
 		coder = lzma_alloc(sizeof(lzma_simple_coder)
 				+ 2 * unfiltered_max, allocator);
 		if (coder == NULL)
 			return LZMA_MEM_ERROR;

 		next->coder = coder;
 		next->code = &simple_code;
 		next->end = &simple_coder_end;
 		next->update = &simple_coder_update;

 		coder->next = LZMA_NEXT_CODER_INIT;
 		coder->filter = filter;
 		coder->allocated = 2 * unfiltered_max;

 		// Allocate memory for filter-specific data structure.
 		if (simple_size > 0) {
 			coder->simple = lzma_alloc(simple_size, allocator);
 			if (coder->simple == NULL)
 				return LZMA_MEM_ERROR;
 		} else {
 			coder->simple = NULL;
 		}
 	}

 	if (filters[0].options != NULL) {
 		const lzma_options_bcj *simple = filters[0].options;
 		coder->now_pos = simple->start_offset;
 		if (coder->now_pos & (alignment - 1))
 			return LZMA_OPTIONS_ERROR;
 	} else {
 		coder->now_pos = 0;
 	}

 	// Reset variables.
 	coder->is_encoder = is_encoder;
 	coder->end_was_reached = false;
 	coder->pos = 0;
 	coder->filtered = 0;
 	coder->size = 0;

 	return lzma_next_filter_init(&coder->next, allocator, filters + 1);
 }
	///////////////////////////////////////////////////////////////////////////////
	//
	/// \file simple_coder.c
	/// \brief Wrapper for simple filters
	///
	/// Simple filters don't change the size of the data i.e. number of bytes
	/// in equals the number of bytes out.
	//
	// Author: Lasse Collin
	//
	// This file has been put into the public domain.
	// You can do whatever you want with this file.
	//
	///////////////////////////////////////////////////////////////////////////////

	#include "simple_private.h"


	/// Copied or encodes/decodes more data to out[].
	static lzma_ret
	copy_or_code(lzma_simple_coder coder, 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)
	{
	assert(!coder->end_was_reached);

	if (coder->next.code == NULL) {
	lzma_bufcpy(in, in_pos, in_size, out, out_pos, out_size);

	// Check if end of stream was reached.
	if (coder->is_encoder && action == LZMA_FINISH
	&& *in_pos == in_size)
	coder->end_was_reached = true;

	} else {
	// Call the next coder in the chain to provide us some data.
	const lzma_ret ret = coder->next.code(
	coder->next.coder, allocator,
	in, in_pos, in_size,
	out, out_pos, out_size, action);

	if (ret == LZMA_STREAM_END) {
	assert(!coder->is_encoder
	\|\| action == LZMA_FINISH);
	coder->end_was_reached = true;

	} else if (ret != LZMA_OK) {
	return ret;
	}
	}

	return LZMA_OK;
	}


	static size_t
	call_filter(lzma_simple_coder coder, uint8_t buffer, size_t size)
	{
	const size_t filtered = coder->filter(coder->simple,
	coder->now_pos, coder->is_encoder,
	buffer, size);
	coder->now_pos += filtered;
	return filtered;
	}


	static lzma_ret
	simple_code(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_simple_coder *coder = coder_ptr;

	// TODO: Add partial support for LZMA_SYNC_FLUSH. We can support it
	// in cases when the filter is able to filter everything. With most
	// simple filters it can be done at offset that is a multiple of 2,
	// 4, or 16. With x86 filter, it needs good luck, and thus cannot
	// be made to work predictably.
	if (action == LZMA_SYNC_FLUSH)
	return LZMA_OPTIONS_ERROR;

	// Flush already filtered data from coder->buffer[] to out[].
	if (coder->pos < coder->filtered) {
	lzma_bufcpy(coder->buffer, &coder->pos, coder->filtered,
	out, out_pos, out_size);

	// If we couldn't flush all the filtered data, return to
	// application immediately.
	if (coder->pos < coder->filtered)
	return LZMA_OK;

	if (coder->end_was_reached) {
	assert(coder->filtered == coder->size);
	return LZMA_STREAM_END;
	}
	}

	// If we get here, there is no filtered data left in the buffer.
	coder->filtered = 0;

	assert(!coder->end_was_reached);

	// If there is more output space left than there is unfiltered data
	// in coder->buffer[], flush coder->buffer[] to out[], and copy/code
	// more data to out[] hopefully filling it completely. Then filter
	// the data in out[]. This step is where most of the data gets
	// filtered if the buffer sizes used by the application are reasonable.
	const size_t out_avail = out_size - *out_pos;
	const size_t buf_avail = coder->size - coder->pos;
	if (out_avail > buf_avail \|\| buf_avail == 0) {
	// Store the old position so that we know from which byte
	// to start filtering.
	const size_t out_start = *out_pos;

	// Flush data from coder->buffer[] to out[], but don't reset
	// coder->pos and coder->size yet. This way the coder can be
	// restarted if the next filter in the chain returns e.g.
	// LZMA_MEM_ERROR.
	memcpy(out + *out_pos, coder->buffer + coder->pos, buf_avail);
	*out_pos += buf_avail;

	// Copy/Encode/Decode more data to out[].
	{
	const lzma_ret ret = copy_or_code(coder, allocator,
	in, in_pos, in_size,
	out, out_pos, out_size, action);
	assert(ret != LZMA_STREAM_END);
	if (ret != LZMA_OK)
	return ret;
	}

	// Filter out[].
	const size_t size = *out_pos - out_start;
	const size_t filtered = call_filter(
	coder, out + out_start, size);

	const size_t unfiltered = size - filtered;
	assert(unfiltered <= coder->allocated / 2);

	// Now we can update coder->pos and coder->size, because
	// the next coder in the chain (if any) was successful.
	coder->pos = 0;
	coder->size = unfiltered;

	if (coder->end_was_reached) {
	// The last byte has been copied to out[] already.
	// They are left as is.
	coder->size = 0;

	} else if (unfiltered > 0) {
	// There is unfiltered data left in out[]. Copy it to
	// coder->buffer[] and rewind *out_pos appropriately.
	*out_pos -= unfiltered;
	memcpy(coder->buffer, out + *out_pos, unfiltered);
	}
	} else if (coder->pos > 0) {
	memmove(coder->buffer, coder->buffer + coder->pos, buf_avail);
	coder->size -= coder->pos;
	coder->pos = 0;
	}

	assert(coder->pos == 0);

	// If coder->buffer[] isn't empty, try to fill it by copying/decoding
	// more data. Then filter coder->buffer[] and copy the successfully
	// filtered data to out[]. It is probable, that some filtered and
	// unfiltered data will be left to coder->buffer[].
	if (coder->size > 0) {
	{
	const lzma_ret ret = copy_or_code(coder, allocator,
	in, in_pos, in_size,
	coder->buffer, &coder->size,
	coder->allocated, action);
	assert(ret != LZMA_STREAM_END);
	if (ret != LZMA_OK)
	return ret;
	}

	coder->filtered = call_filter(
	coder, coder->buffer, coder->size);

	// Everything is considered to be filtered if coder->buffer[]
	// contains the last bytes of the data.
	if (coder->end_was_reached)
	coder->filtered = coder->size;

	// Flush as much as possible.
	lzma_bufcpy(coder->buffer, &coder->pos, coder->filtered,
	out, out_pos, out_size);
	}

	// Check if we got everything done.
	if (coder->end_was_reached && coder->pos == coder->size)
	return LZMA_STREAM_END;

	return LZMA_OK;
	}


	static void
	simple_coder_end(void coder_ptr, const lzma_allocator allocator)
	{
	lzma_simple_coder *coder = coder_ptr;
	lzma_next_end(&coder->next, allocator);
	lzma_free(coder->simple, allocator);
	lzma_free(coder, allocator);
	return;
	}


	static lzma_ret
	simple_coder_update(void coder_ptr, const lzma_allocator allocator,
	const lzma_filter *filters_null lzma_attribute((__unused__)),
	const lzma_filter *reversed_filters)
	{
	lzma_simple_coder *coder = coder_ptr;

	// No update support, just call the next filter in the chain.
	return lzma_next_filter_update(
	&coder->next, allocator, reversed_filters + 1);
	}


	extern lzma_ret
	lzma_simple_coder_init(lzma_next_coder next, const lzma_allocator allocator,
	const lzma_filter_info *filters,
	size_t (filter)(void simple, uint32_t now_pos,
	bool is_encoder, uint8_t *buffer, size_t size),
	size_t simple_size, size_t unfiltered_max,
	uint32_t alignment, bool is_encoder)
	{
	// Allocate memory for the lzma_simple_coder structure if needed.
	lzma_simple_coder *coder = next->coder;
	if (coder == NULL) {
	// Here we allocate space also for the temporary buffer. We
	// need twice the size of unfiltered_max, because then it
	// is always possible to filter at least unfiltered_max bytes
	// more data in coder->buffer[] if it can be filled completely.
	coder = lzma_alloc(sizeof(lzma_simple_coder)
	+ 2 * unfiltered_max, allocator);
	if (coder == NULL)
	return LZMA_MEM_ERROR;

	next->coder = coder;
	next->code = &simple_code;
	next->end = &simple_coder_end;
	next->update = &simple_coder_update;

	coder->next = LZMA_NEXT_CODER_INIT;
	coder->filter = filter;
	coder->allocated = 2 * unfiltered_max;

	// Allocate memory for filter-specific data structure.
	if (simple_size > 0) {
	coder->simple = lzma_alloc(simple_size, allocator);
	if (coder->simple == NULL)
	return LZMA_MEM_ERROR;
	} else {
	coder->simple = NULL;
	}
	}

	if (filters[0].options != NULL) {
	const lzma_options_bcj *simple = filters[0].options;
	coder->now_pos = simple->start_offset;
	if (coder->now_pos & (alignment - 1))
	return LZMA_OPTIONS_ERROR;
	} else {
	coder->now_pos = 0;
	}

	// Reset variables.
	coder->is_encoder = is_encoder;
	coder->end_was_reached = false;
	coder->pos = 0;
	coder->filtered = 0;
	coder->size = 0;

	return lzma_next_filter_init(&coder->next, allocator, filters + 1);
	}