1 files changed, 373 insertions, 0 deletions
diff --git a/src/liblzma/common/block_header_decoder.c b/src/liblzma/common/block_header_decoder.c
new file mode 100644
index 00000000..7676c795
--- /dev/null
+++ b/src/liblzma/common/block_header_decoder.c
@@ -0,0 +1,373 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       block_header_decoder.c
+/// \brief      Decodes Block Header from .lzma files
+//
+//  Copyright (C) 2007 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 "common.h"
+#include "check.h"
+
+
+struct lzma_coder_s {
+	lzma_options_block *options;
+
+	enum {
+		SEQ_FLAGS_1,
+		SEQ_FLAGS_2,
+		SEQ_COMPRESSED_SIZE,
+		SEQ_UNCOMPRESSED_SIZE,
+		SEQ_FILTER_FLAGS_INIT,
+		SEQ_FILTER_FLAGS_DECODE,
+		SEQ_CRC32,
+		SEQ_PADDING
+	} sequence;
+
+	/// Position in variable-length integers
+	size_t pos;
+
+	/// CRC32 of the Block Header
+	uint32_t crc32;
+
+	lzma_next_coder filter_flags_decoder;
+};
+
+
+static bool
+update_sequence(lzma_coder *coder)
+{
+	switch (coder->sequence) {
+	case SEQ_FLAGS_2:
+		if (coder->options->compressed_size
+				!= LZMA_VLI_VALUE_UNKNOWN) {
+			coder->pos = 0;
+			coder->sequence = SEQ_COMPRESSED_SIZE;
+			break;
+		}
+
+	// Fall through
+
+	case SEQ_COMPRESSED_SIZE:
+		if (coder->options->uncompressed_size
+				!= LZMA_VLI_VALUE_UNKNOWN) {
+			coder->pos = 0;
+			coder->sequence = SEQ_UNCOMPRESSED_SIZE;
+			break;
+		}
+
+	// Fall through
+
+	case SEQ_UNCOMPRESSED_SIZE:
+		coder->pos = 0;
+
+	// Fall through
+
+	case SEQ_FILTER_FLAGS_DECODE:
+		if (coder->options->filters[coder->pos].id
+				!= LZMA_VLI_VALUE_UNKNOWN) {
+			coder->sequence = SEQ_FILTER_FLAGS_INIT;
+			break;
+		}
+
+		if (coder->options->has_crc32) {
+			coder->pos = 0;
+			coder->sequence = SEQ_CRC32;
+			break;
+		}
+
+	case SEQ_CRC32:
+		if (coder->options->padding != 0) {
+			coder->pos = 0;
+			coder->sequence = SEQ_PADDING;
+			break;
+		}
+
+		return true;
+
+	default:
+		assert(0);
+		return true;
+	}
+
+	return false;
+}
+
+
+static lzma_ret
+block_header_decode(lzma_coder *coder, lzma_allocator *allocator,
+		const uint8_t *restrict in, size_t *restrict in_pos,
+		size_t in_size, uint8_t *restrict out lzma_attribute((unused)),
+		size_t *restrict out_pos lzma_attribute((unused)),
+		size_t out_size lzma_attribute((unused)),
+		lzma_action action lzma_attribute((unused)))
+{
+	while (*in_pos < in_size)
+	switch (coder->sequence) {
+	case SEQ_FLAGS_1:
+		// Check that the reserved bit is unset. Use HEADER_ERROR
+		// because newer version of liblzma may support the reserved
+		// bit, although it is likely that this is just a broken file.
+		if (in[*in_pos] & 0x40)
+			return LZMA_HEADER_ERROR;
+
+		// Number of filters: we prepare appropriate amount of
+		// variables for variable-length integer parsing. The
+		// initialization function has already reset the rest
+		// of the values to LZMA_VLI_VALUE_UNKNOWN, which allows
+		// us to later know how many filters there are.
+		for (int i = (int)(in[*in_pos] & 0x07) - 1; i >= 0; --i)
+			coder->options->filters[i].id = 0;
+
+		// End of Payload Marker flag
+		coder->options->has_eopm = (in[*in_pos] & 0x08) != 0;
+
+		// Compressed Size: Prepare for variable-length integer
+		// parsing if it is known.
+		if (in[*in_pos] & 0x10)
+			coder->options->compressed_size = 0;
+
+		// Uncompressed Size: the same.
+		if (in[*in_pos] & 0x20)
+			coder->options->uncompressed_size = 0;
+
+		// Is Metadata Block flag
+		coder->options->is_metadata = (in[*in_pos] & 0x80) != 0;
+
+		// We need at least one: Uncompressed Size or EOPM.
+		if (coder->options->uncompressed_size == LZMA_VLI_VALUE_UNKNOWN
+				&& !coder->options->has_eopm)
+			return LZMA_DATA_ERROR;
+
+		// Update header CRC32.
+		coder->crc32 = lzma_crc32(in + *in_pos, 1, coder->crc32);
+
+		++*in_pos;
+		coder->sequence = SEQ_FLAGS_2;
+		break;
+
+	case SEQ_FLAGS_2:
+		// Check that the reserved bits are unset.
+		if (in[*in_pos] & 0xE0)
+			return LZMA_DATA_ERROR;
+
+		// Get the size of Header Padding.
+		coder->options->padding = in[*in_pos] & 0x1F;
+
+		coder->crc32 = lzma_crc32(in + *in_pos, 1, coder->crc32);
+
+		++*in_pos;
+
+		if (update_sequence(coder))
+			return LZMA_STREAM_END;
+
+		break;
+
+	case SEQ_COMPRESSED_SIZE: {
+		// Store the old input position to be used when
+		// updating coder->header_crc32.
+		const size_t in_start = *in_pos;
+
+		const lzma_ret ret = lzma_vli_decode(
+				&coder->options->compressed_size,
+				&coder->pos, in, in_pos, in_size);
+
+		const size_t in_used = *in_pos - in_start;
+
+		coder->options->compressed_reserve += in_used;
+		assert(coder->options->compressed_reserve
+				<= LZMA_VLI_BYTES_MAX);
+
+		coder->options->header_size += in_used;
+
+		coder->crc32 = lzma_crc32(in + in_start, in_used,
+				coder->crc32);
+
+		if (ret != LZMA_STREAM_END)
+			return ret;
+
+		if (update_sequence(coder))
+			return LZMA_STREAM_END;
+
+		break;
+	}
+
+	case SEQ_UNCOMPRESSED_SIZE: {
+		const size_t in_start = *in_pos;
+
+		const lzma_ret ret = lzma_vli_decode(
+				&coder->options->uncompressed_size,
+				&coder->pos, in, in_pos, in_size);
+
+		const size_t in_used = *in_pos - in_start;
+
+		coder->options->uncompressed_reserve += in_used;
+		assert(coder->options->uncompressed_reserve
+				<= LZMA_VLI_BYTES_MAX);
+
+		coder->options->header_size += in_used;
+
+		coder->crc32 = lzma_crc32(in + in_start, in_used,
+				coder->crc32);
+
+		if (ret != LZMA_STREAM_END)
+			return ret;
+
+		if (update_sequence(coder))
+			return LZMA_STREAM_END;
+
+		break;
+	}
+
+	case SEQ_FILTER_FLAGS_INIT: {
+		assert(coder->options->filters[coder->pos].id
+				!= LZMA_VLI_VALUE_UNKNOWN);
+
+		const lzma_ret ret = lzma_filter_flags_decoder_init(
+				&coder->filter_flags_decoder, allocator,
+				&coder->options->filters[coder->pos]);
+		if (ret != LZMA_OK)
+			return ret;
+
+		coder->sequence = SEQ_FILTER_FLAGS_DECODE;
+	}
+
+	// Fall through
+
+	case SEQ_FILTER_FLAGS_DECODE: {
+		const size_t in_start = *in_pos;
+
+		const lzma_ret ret = coder->filter_flags_decoder.code(
+				coder->filter_flags_decoder.coder,
+				allocator, in, in_pos, in_size,
+				NULL, NULL, 0, LZMA_RUN);
+
+		const size_t in_used = *in_pos - in_start;
+		coder->options->header_size += in_used;
+		coder->crc32 = lzma_crc32(in + in_start,
+				in_used, coder->crc32);
+
+		if (ret != LZMA_STREAM_END)
+			return ret;
+
+		++coder->pos;
+
+		if (update_sequence(coder))
+			return LZMA_STREAM_END;
+
+		break;
+	}
+
+	case SEQ_CRC32:
+		assert(coder->options->has_crc32);
+
+		if (in[*in_pos] != ((coder->crc32 >> (coder->pos * 8)) & 0xFF))
+			return LZMA_DATA_ERROR;
+
+		++*in_pos;
+		++coder->pos;
+
+		// Check if we reached end of the CRC32 field.
+		if (coder->pos == 4) {
+			coder->options->header_size += 4;
+
+			if (update_sequence(coder))
+				return LZMA_STREAM_END;
+		}
+
+		break;
+
+	case SEQ_PADDING:
+		if (in[*in_pos] != 0x00)
+			return LZMA_DATA_ERROR;
+
+		++*in_pos;
+		++coder->options->header_size;
+		++coder->pos;
+
+		if (coder->pos < (size_t)(coder->options->padding))
+			break;
+
+		return LZMA_STREAM_END;
+
+	default:
+		return LZMA_PROG_ERROR;
+	}
+
+	return LZMA_OK;
+}
+
+
+static void
+block_header_decoder_end(lzma_coder *coder, lzma_allocator *allocator)
+{
+	lzma_next_coder_end(&coder->filter_flags_decoder, allocator);
+	lzma_free(coder, allocator);
+	return;
+}
+
+
+extern lzma_ret
+lzma_block_header_decoder_init(lzma_next_coder *next,
+		lzma_allocator *allocator, lzma_options_block *options)
+{
+	if (next->coder == NULL) {
+		next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
+		if (next->coder == NULL)
+			return LZMA_MEM_ERROR;
+
+		next->code = &block_header_decode;
+		next->end = &block_header_decoder_end;
+		next->coder->filter_flags_decoder = LZMA_NEXT_CODER_INIT;
+	}
+
+	// Assume that Compressed Size and Uncompressed Size are unknown.
+	options->compressed_size = LZMA_VLI_VALUE_UNKNOWN;
+	options->uncompressed_size = LZMA_VLI_VALUE_UNKNOWN;
+
+	// We will calculate the sizes of these fields too so that the
+	// application may rewrite the header if it wishes so.
+	options->compressed_reserve = 0;
+	options->uncompressed_reserve = 0;
+
+	// The Block Flags field is always present, so include its size here
+	// and we don't need to worry about it in block_header_decode().
+	options->header_size = 2;
+
+	// Reset filters[] to indicate empty list of filters.
+	// See SEQ_FLAGS_1 in block_header_decode() for reasoning of this.
+	for (size_t i = 0; i < 8; ++i) {
+		options->filters[i].id = LZMA_VLI_VALUE_UNKNOWN;
+		options->filters[i].options = NULL;
+	}
+
+	next->coder->options = options;
+	next->coder->sequence = SEQ_FLAGS_1;
+	next->coder->pos = 0;
+	next->coder->crc32 = 0;
+
+	return LZMA_OK;
+}
+
+
+extern LZMA_API lzma_ret
+lzma_block_header_decoder(lzma_stream *strm,
+		lzma_options_block *options)
+{
+	lzma_next_strm_init(strm, lzma_block_header_decoder_init, options);
+
+	strm->internal->supported_actions[LZMA_RUN] = true;
+
+	return LZMA_OK;
+}