1 files changed, 119 insertions, 0 deletions
diff --git a/src/liblzma/delta/delta_encoder.c b/src/liblzma/delta/delta_encoder.c
new file mode 100644
index 00000000..d8f40287
--- /dev/null
+++ b/src/liblzma/delta/delta_encoder.c
@@ -0,0 +1,119 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       delta_encoder.c
+/// \brief      Delta filter encoder
+//
+//  Copyright (C) 2007, 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 "delta_encoder.h"
+#include "delta_common.h"
+
+
+/// Copies and encodes the data at the same time. This is used when Delta
+/// is the first filter in the chain (and thus the last filter in the
+/// encoder's filter stack).
+static void
+copy_and_encode(lzma_coder *coder,
+		const uint8_t *restrict in, uint8_t *restrict out, 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-- & 0xFF] = in[i];
+		out[i] = in[i] - tmp;
+	}
+}
+
+
+/// Encodes the data in place. This is used when we are the last filter
+/// in the chain (and thus non-last filter in the encoder's filter stack).
+static void
+encode_in_place(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-- & 0xFF] = buffer[i];
+		buffer[i] -= tmp;
+	}
+}
+
+
+static lzma_ret
+delta_encode(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)
+{
+	lzma_ret ret;
+
+	if (coder->next.code == NULL) {
+		const size_t in_avail = in_size - *in_pos;
+		const size_t out_avail = out_size - *out_pos;
+		const size_t size = MIN(in_avail, out_avail);
+
+		copy_and_encode(coder, in + *in_pos, out + *out_pos, size);
+
+		*in_pos += size;
+		*out_pos += size;
+
+		ret = action != LZMA_RUN && *in_pos == in_size
+				? LZMA_STREAM_END : LZMA_OK;
+
+	} else {
+		const size_t out_start = *out_pos;
+
+		ret = coder->next.code(coder->next.coder, allocator,
+				in, in_pos, in_size, out, out_pos, out_size,
+				action);
+
+		encode_in_place(coder, out + out_start, *out_pos - out_start);
+	}
+
+	return ret;
+}
+
+
+extern lzma_ret
+lzma_delta_encoder_init(lzma_next_coder *next, lzma_allocator *allocator,
+		const lzma_filter_info *filters)
+{
+	return lzma_delta_coder_init(next, allocator, filters, &delta_encode);
+}
+
+
+extern lzma_ret
+lzma_delta_props_encode(const void *options, uint8_t *out)
+{
+	if (options == NULL)
+		return LZMA_PROG_ERROR;
+
+	const lzma_options_delta *opt = options;
+
+	// It's possible that newer liblzma versions will support larger
+	// distance values.
+	if (opt->type != LZMA_DELTA_TYPE_BYTE
+			|| opt->distance < LZMA_DELTA_DISTANCE_MIN
+			|| opt->distance > LZMA_DELTA_DISTANCE_MAX)
+		return LZMA_HEADER_ERROR;
+
+	out[0] = opt->distance - LZMA_DELTA_DISTANCE_MIN;
+
+	return LZMA_OK;
+}