The R Project SVN R

///////////////////////////////////////////////////////////////////////////////

//

/// \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_coder *coder, 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_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(lzma_coder *coder, 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)

{

	// 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(lzma_coder *coder, lzma_allocator *allocator)

{

	lzma_next_end(&coder->next, allocator);

	lzma_free(coder->simple, allocator);

	lzma_free(coder, allocator);

	return;

}

static lzma_ret

simple_coder_update(lzma_coder *coder, lzma_allocator *allocator,

		const lzma_filter *filters_null lzma_attribute((__unused__)),

		const lzma_filter *reversed_filters)

{

	// 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, lzma_allocator *allocator,

		const lzma_filter_info *filters,

		size_t (*filter)(lzma_simple *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_coder structure if needed.

	if (next->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.

		next->coder = lzma_alloc(sizeof(lzma_coder)

				+ 2 * unfiltered_max, allocator);

		if (next->coder == NULL)

			return LZMA_MEM_ERROR;

		next->code = &simple_code;

		next->end = &simple_coder_end;

		next->update = &simple_coder_update;

		next->coder->next = LZMA_NEXT_CODER_INIT;

		next->coder->filter = filter;

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

		// Allocate memory for filter-specific data structure.

		if (simple_size > 0) {

			next->coder->simple = lzma_alloc(

					simple_size, allocator);

			if (next->coder->simple == NULL)

				return LZMA_MEM_ERROR;

		} else {

			next->coder->simple = NULL;

		}

	}

	if (filters[0].options != NULL) {

		const lzma_options_bcj *simple = filters[0].options;

		next->coder->now_pos = simple->start_offset;

		if (next->coder->now_pos & (alignment - 1))

			return LZMA_OPTIONS_ERROR;

	} else {

		next->coder->now_pos = 0;

	}

	// Reset variables.

	next->coder->is_encoder = is_encoder;

	next->coder->end_was_reached = false;

	next->coder->pos = 0;

	next->coder->filtered = 0;

	next->coder->size = 0;

	return lzma_next_filter_init(

			&next->coder->next, allocator, filters + 1);

}