1 files changed, 252 insertions, 0 deletions
diff --git a/src/liblzma/common/index_decoder.c b/src/liblzma/common/index_decoder.c
new file mode 100644
index 00000000..1635948c
--- /dev/null
+++ b/src/liblzma/common/index_decoder.c
@@ -0,0 +1,252 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       index_decoder.c
+/// \brief      Decodes the Index field
+//
+//  Copyright (C) 2008 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 "index.h"
+#include "check.h"
+
+
+struct lzma_coder_s {
+	enum {
+		SEQ_INDICATOR,
+		SEQ_COUNT,
+		SEQ_TOTAL,
+		SEQ_UNCOMPRESSED,
+		SEQ_PADDING_INIT,
+		SEQ_PADDING,
+		SEQ_CRC32,
+	} sequence;
+
+	/// Target Index
+	lzma_index *index;
+
+	/// Number of Records left to decode.
+	lzma_vli count;
+
+	/// The most recent Total Size field
+	lzma_vli total_size;
+
+	/// The most recent Uncompressed Size field
+	lzma_vli uncompressed_size;
+
+	/// Position in integers
+	size_t pos;
+
+	/// CRC32 of the List of Records field
+	uint32_t crc32;
+};
+
+
+static lzma_ret
+index_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)))
+{
+	// Similar optimization as in index_encoder.c
+	const size_t in_start = *in_pos;
+	lzma_ret ret = LZMA_OK;
+
+	while (*in_pos < in_size)
+	switch (coder->sequence) {
+	case SEQ_INDICATOR:
+		// Return LZMA_DATA_ERROR instead of e.g. LZMA_PROG_ERROR or
+		// LZMA_FORMAT_ERROR, because a typical usage case for Index
+		// decoder is when parsing the Stream backwards. If seeking
+		// backward from the Stream Footer gives us something that
+		// doesn't begin with Index Indicator, the file is considered
+		// corrupt, not "programming error" or "unrecognized file
+		// format". One could argue that the application should
+		// verify the Index Indicator before trying to decode the
+		// Index, but well, I suppose it is simpler this way.
+		if (in[(*in_pos)++] != 0x00)
+			return LZMA_DATA_ERROR;
+
+		coder->sequence = SEQ_COUNT;
+		break;
+
+	case SEQ_COUNT: {
+		ret = lzma_vli_decode(&coder->count, &coder->pos,
+				in, in_pos, in_size);
+		if (ret != LZMA_STREAM_END)
+			goto out;
+
+		ret = LZMA_OK;
+		coder->pos = 0;
+		coder->sequence = coder->count == 0
+				? SEQ_PADDING_INIT : SEQ_TOTAL;
+		break;
+	}
+
+	case SEQ_TOTAL:
+	case SEQ_UNCOMPRESSED: {
+		lzma_vli *size = coder->sequence == SEQ_TOTAL
+				? &coder->total_size
+				: &coder->uncompressed_size;
+
+		ret = lzma_vli_decode(size, &coder->pos,
+				in, in_pos, in_size);
+		if (ret != LZMA_STREAM_END)
+			goto out;
+
+		ret = LZMA_OK;
+		coder->pos = 0;
+
+		if (coder->sequence == SEQ_TOTAL) {
+			// Validate that encoded Total Size isn't too big.
+			if (coder->total_size > TOTAL_SIZE_ENCODED_MAX)
+				return LZMA_DATA_ERROR;
+
+			// Convert the encoded Total Size to the real
+			// Total Size.
+			coder->total_size = total_size_decode(
+					coder->total_size);
+			coder->sequence = SEQ_UNCOMPRESSED;
+		} else {
+			// Add the decoded Record to the Index.
+			return_if_error(lzma_index_append(
+					coder->index, allocator,
+					coder->total_size,
+					coder->uncompressed_size));
+
+			// Check if this was the last Record.
+			coder->sequence = --coder->count == 0
+					? SEQ_PADDING_INIT
+					: SEQ_TOTAL;
+		}
+
+		break;
+	}
+
+	case SEQ_PADDING_INIT:
+		coder->pos = lzma_index_padding_size(coder->index);
+		coder->sequence = SEQ_PADDING;
+
+	// Fall through
+
+	case SEQ_PADDING:
+		if (coder->pos > 0) {
+			--coder->pos;
+			if (in[(*in_pos)++] != 0x00)
+				return LZMA_DATA_ERROR;
+
+			break;
+		}
+
+		// Finish the CRC32 calculation.
+		coder->crc32 = lzma_crc32(in + in_start,
+				*in_pos - in_start, coder->crc32);
+
+		coder->sequence = SEQ_CRC32;
+
+	// Fall through
+
+	case SEQ_CRC32:
+		do {
+			if (*in_pos == in_size)
+				return LZMA_OK;
+
+			if (((coder->crc32 >> (coder->pos * 8)) & 0xFF)
+					!= in[(*in_pos)++])
+				return LZMA_DATA_ERROR;
+
+		} while (++coder->pos < 4);
+
+		// Make index NULL so we don't free it unintentionally.
+		coder->index = NULL;
+
+		return LZMA_STREAM_END;
+
+	default:
+		assert(0);
+		return LZMA_PROG_ERROR;
+	}
+
+out:
+	// Update the CRC32,
+	coder->crc32 = lzma_crc32(in + in_start,
+			*in_pos - in_start, coder->crc32);
+
+	return ret;
+}
+
+
+static void
+index_decoder_end(lzma_coder *coder, lzma_allocator *allocator)
+{
+	lzma_index_end(coder->index, allocator);
+	lzma_free(coder, allocator);
+	return;
+}
+
+
+static lzma_ret
+index_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
+		lzma_index **i)
+{
+	if (i == NULL)
+		return LZMA_PROG_ERROR;
+
+	if (next->coder == NULL) {
+		next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
+		if (next->coder == NULL)
+			return LZMA_MEM_ERROR;
+
+		next->code = &index_decode;
+		next->end = &index_decoder_end;
+		next->coder->index = NULL;
+	} else {
+		lzma_index_end(next->coder->index, allocator);
+	}
+
+	// We always allocate a new lzma_index.
+	*i = lzma_index_init(NULL, allocator);
+	if (*i == NULL)
+		return LZMA_MEM_ERROR;
+
+	// Initialize the rest.
+	next->coder->sequence = SEQ_INDICATOR;
+	next->coder->index = *i;
+	next->coder->pos = 0;
+	next->coder->crc32 = 0;
+
+	return LZMA_OK;
+}
+
+
+/*
+extern lzma_ret
+lzma_index_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
+		lzma_index **i)
+{
+	lzma_next_coder_init(index_decoder_init, next, allocator, i);
+}
+*/
+
+
+extern LZMA_API lzma_ret
+lzma_index_decoder(lzma_stream *strm, lzma_index **i)
+{
+	lzma_next_strm_init(strm, index_decoder_init, i);
+
+	strm->internal->supported_actions[LZMA_RUN] = true;
+
+	return LZMA_OK;
+}