1 files changed, 210 insertions, 0 deletions
diff --git a/src/liblzma/common/delta_coder.c b/src/liblzma/common/delta_coder.c
new file mode 100644
index 00000000..ec8c6d59
--- /dev/null
+++ b/src/liblzma/common/delta_coder.c
@@ -0,0 +1,210 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       delta_coder.c
+/// \brief      Encoder and decoder for the Delta filter
+//
+//  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 "delta_coder.h"
+
+
+struct lzma_coder_s {
+	/// Next coder in the chain
+	lzma_next_coder next;
+
+	/// Uncompressed size - This is needed when we are the last
+	/// filter in the chain.
+	lzma_vli uncompressed_size;
+
+	/// Delta distance
+	size_t distance;
+
+	/// True if we are encoding; false if decoding
+	bool is_encoder;
+
+	/// Position in history[]
+	uint8_t pos;
+
+	/// Buffer to hold history of the original data
+	uint8_t history[LZMA_DELTA_DISTANCE_MAX];
+};
+
+
+static void
+encode_buffer(lzma_coder *coder, uint8_t *buffer, size_t size)
+{
+	const size_t distance = coder->distance;
+
+	for (size_t i = 0; i < size; ++i) {
+		const uint8_t tmp = coder->history[
+				(distance + coder->pos) & 0xFF];
+		coder->history[coder->pos--] = buffer[i];
+		buffer[i] -= tmp;
+	}
+
+	return;
+}
+
+
+static void
+decode_buffer(lzma_coder *coder, uint8_t *buffer, size_t size)
+{
+	const size_t distance = coder->distance;
+
+	for (size_t i = 0; i < size; ++i) {
+		buffer[i] += coder->history[(distance + coder->pos) & 0xFF];
+		coder->history[coder->pos--] = buffer[i];
+	}
+
+	return;
+}
+
+
+static lzma_ret
+delta_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)
+{
+	const size_t out_start = *out_pos;
+	size_t size;
+	lzma_ret ret;
+
+	if (coder->next.code == NULL) {
+		const size_t in_avail = in_size - *in_pos;
+
+		if (coder->is_encoder) {
+			// Check that we don't have too much input.
+			if ((lzma_vli)(in_avail) > coder->uncompressed_size)
+				return LZMA_DATA_ERROR;
+
+			// Check that once LZMA_FINISH has been given, the
+			// amount of input matches uncompressed_size if it
+			// is known.
+			if (action == LZMA_FINISH && coder->uncompressed_size
+						!= LZMA_VLI_VALUE_UNKNOWN
+					&& coder->uncompressed_size
+						!= (lzma_vli)(in_avail))
+				return LZMA_DATA_ERROR;
+
+		} else {
+			// Limit in_size so that we don't copy too much.
+			if ((lzma_vli)(in_avail) > coder->uncompressed_size)
+				in_size = *in_pos + (size_t)(
+						coder->uncompressed_size);
+		}
+
+		size = bufcpy(in, in_pos, in_size, out, out_pos, out_size);
+
+		if (coder->uncompressed_size != LZMA_VLI_VALUE_UNKNOWN)
+			coder->uncompressed_size -= size;
+
+		// action can be LZMA_FINISH only in the encoder.
+		ret = (action == LZMA_FINISH && *in_pos == in_size)
+					|| coder->uncompressed_size == 0
+				? LZMA_STREAM_END : LZMA_OK;
+
+	} else {
+		ret = coder->next.code(coder->next.coder, allocator,
+				in, in_pos, in_size, out, out_pos, out_size,
+				action);
+		if (ret != LZMA_OK && ret != LZMA_STREAM_END)
+			return ret;
+
+		size = *out_pos - out_start;
+	}
+
+	if (coder->is_encoder)
+		encode_buffer(coder, out + out_start, size);
+	else
+		decode_buffer(coder, out + out_start, size);
+
+	return ret;
+}
+
+
+static void
+delta_coder_end(lzma_coder *coder, lzma_allocator *allocator)
+{
+	lzma_next_coder_end(&coder->next, allocator);
+	lzma_free(coder, allocator);
+	return;
+}
+
+
+static lzma_ret
+delta_coder_init(lzma_next_coder *next, lzma_allocator *allocator,
+		const lzma_filter_info *filters, bool is_encoder)
+{
+	// Allocate memory for the decoder if needed.
+	if (next->coder == NULL) {
+		next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
+		if (next->coder == NULL)
+			return LZMA_MEM_ERROR;
+
+		next->code = &delta_code;
+		next->end = &delta_coder_end;
+		next->coder->next = LZMA_NEXT_CODER_INIT;
+	}
+
+	// Copy Uncompressed Size which is used to limit the output size.
+	next->coder->uncompressed_size = filters[0].uncompressed_size;
+
+	// The coder acts slightly differently as encoder and decoder.
+	next->coder->is_encoder = is_encoder;
+
+	// Set the delta distance.
+	if (filters[0].options == NULL)
+		return LZMA_PROG_ERROR;
+	next->coder->distance = ((lzma_options_delta *)(filters[0].options))
+			->distance;
+	if (next->coder->distance < LZMA_DELTA_DISTANCE_MIN
+			|| next->coder->distance > LZMA_DELTA_DISTANCE_MAX)
+		return LZMA_HEADER_ERROR;
+
+	// Initialize the rest of the variables.
+	next->coder->pos = 0;
+	memzero(next->coder->history, LZMA_DELTA_DISTANCE_MAX);
+
+	// Initialize the next decoder in the chain, if any.
+	{
+		const lzma_ret ret = lzma_next_filter_init(&next->coder->next,
+				allocator, filters + 1);
+		if (ret != LZMA_OK)
+			return ret;
+	}
+
+	return LZMA_OK;
+}
+
+
+#ifdef HAVE_ENCODER
+extern lzma_ret
+lzma_delta_encoder_init(lzma_next_coder *next, lzma_allocator *allocator,
+		const lzma_filter_info *filters)
+{
+	return delta_coder_init(next, allocator, filters, true);
+}
+#endif
+
+
+#ifdef HAVE_DECODER
+extern lzma_ret
+lzma_delta_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
+		const lzma_filter_info *filters)
+{
+	return delta_coder_init(next, allocator, filters, false);
+}
+#endif