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

1 files changed, 305 insertions, 0 deletions

diff --git a/src/liblzma/common/block_buffer_encoder.c b/src/liblzma/common/block_buffer_encoder.c
new file mode 100644
index 00000000..67412a7d
--- /dev/null
+++ b/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;
+}