1 files changed, 83 insertions, 0 deletions
diff --git a/src/liblzma/delta/delta_decoder.c b/src/liblzma/delta/delta_decoder.c
new file mode 100644
index 0000000..77cf65c
--- /dev/null
+++ b/src/liblzma/delta/delta_decoder.c
@@ -0,0 +1,83 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       delta_decoder.c
+/// \brief      Delta filter decoder
+//
+//  Author:     Lasse Collin
+//
+//  This file has been put into the public domain.
+//  You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include "delta_decoder.h"
+#include "delta_private.h"
+
+
+static void
+decode_buffer(lzma_delta_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-- & 0xFF] = buffer[i];
+	}
+}
+
+
+static lzma_ret
+delta_decode(void *coder_ptr, const 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_delta_coder *coder = coder_ptr;
+
+	assert(coder->next.code != NULL);
+
+	const size_t out_start = *out_pos;
+
+	const lzma_ret ret = coder->next.code(coder->next.coder, allocator,
+			in, in_pos, in_size, out, out_pos, out_size,
+			action);
+
+	// out might be NULL. In that case size == 0. Null pointer + 0 is
+	// undefined behavior so skip the call in that case as it would
+	// do nothing anyway.
+	const size_t size = *out_pos - out_start;
+	if (size > 0)
+		decode_buffer(coder, out + out_start, size);
+
+	return ret;
+}
+
+
+extern lzma_ret
+lzma_delta_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
+		const lzma_filter_info *filters)
+{
+	next->code = &delta_decode;
+	return lzma_delta_coder_init(next, allocator, filters);
+}
+
+
+extern lzma_ret
+lzma_delta_props_decode(void **options, const lzma_allocator *allocator,
+		const uint8_t *props, size_t props_size)
+{
+	if (props_size != 1)
+		return LZMA_OPTIONS_ERROR;
+
+	lzma_options_delta *opt
+			= lzma_alloc(sizeof(lzma_options_delta), allocator);
+	if (opt == NULL)
+		return LZMA_MEM_ERROR;
+
+	opt->type = LZMA_DELTA_TYPE_BYTE;
+	opt->dist = props[0] + 1U;
+
+	*options = opt;
+
+	return LZMA_OK;
+}