1 files changed, 148 insertions, 0 deletions
diff --git a/src/liblzma/common/erofs_decoder.c b/src/liblzma/common/erofs_decoder.c
new file mode 100644
index 00000000..ef584373
--- /dev/null
+++ b/src/liblzma/common/erofs_decoder.c
@@ -0,0 +1,148 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       erofs_decoder.c
+/// \brief      Decode EROFS LZMA format
+//
+//  Author:     Lasse Collin
+//
+//  This file has been put into the public domain.
+//  You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include "lzma_decoder.h"
+#include "lz_decoder.h"
+
+
+typedef struct {
+	/// LZMA1 decoder
+	lzma_next_coder lzma;
+
+	/// Uncompressed size of the stream as given by the application
+	lzma_vli uncomp_size;
+
+	/// LZMA dictionary size as given by the application
+	uint32_t dict_size;
+
+	/// True once the first byte of the EROFS LZMA stream
+	/// has been processed.
+	bool props_decoded;
+} lzma_erofs_coder;
+
+
+static lzma_ret
+erofs_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_erofs_coder *coder = coder_ptr;
+
+	if (!coder->props_decoded) {
+		// There must be at least one byte of input to decode
+		// the properties byte.
+		if (*in_pos >= in_size)
+			return LZMA_OK;
+
+		lzma_options_lzma options = {
+			.preset_dict = NULL,
+			.preset_dict_size = 0,
+		};
+
+		// The properties are stored as bitwise-negation
+		// of the typical encoding.
+		if (lzma_lzma_lclppb_decode(&options, ~in[*in_pos]))
+			return LZMA_OPTIONS_ERROR;
+
+		++*in_pos;
+
+		// Initialize the decoder.
+		options.dict_size = coder->dict_size;
+		lzma_filter_info filters[2] = {
+			{
+				.init = &lzma_lzma_decoder_init,
+				.options = &options,
+			}, {
+				.init = NULL,
+			}
+		};
+
+		return_if_error(lzma_next_filter_init(&coder->lzma,
+				allocator, filters));
+
+		// Use a hack to set the uncompressed size.
+		lzma_lz_decoder_uncompressed(coder->lzma.coder,
+				coder->uncomp_size);
+
+		// Pass one dummy 0x00 byte to the LZMA decoder since that
+		// is what it expects the first byte to be.
+		const uint8_t dummy_in = 0;
+		size_t dummy_in_pos = 0;
+		if (coder->lzma.code(coder->lzma.coder, allocator,
+				&dummy_in, &dummy_in_pos, 1,
+				out, out_pos, out_size, LZMA_RUN) != LZMA_OK)
+			return LZMA_PROG_ERROR;
+
+		assert(dummy_in_pos == 1);
+		coder->props_decoded = true;
+	}
+
+	// The rest is normal LZMA decoding.
+	return coder->lzma.code(coder->lzma.coder, allocator,
+				in, in_pos, in_size,
+				out, out_pos, out_size, action);
+}
+
+
+static void
+erofs_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
+{
+	lzma_erofs_coder *coder = coder_ptr;
+	lzma_next_end(&coder->lzma, allocator);
+	lzma_free(coder, allocator);
+	return;
+}
+
+
+static lzma_ret
+erofs_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
+		uint64_t uncomp_size, uint32_t dict_size)
+{
+	lzma_next_coder_init(&erofs_decoder_init, next, allocator);
+
+	lzma_erofs_coder *coder = next->coder;
+
+	if (coder == NULL) {
+		coder = lzma_alloc(sizeof(lzma_erofs_coder), allocator);
+		if (coder == NULL)
+			return LZMA_MEM_ERROR;
+
+		next->coder = coder;
+		next->code = &erofs_decode;
+		next->end = &erofs_decoder_end;
+
+		coder->lzma = LZMA_NEXT_CODER_INIT;
+	}
+
+	if (uncomp_size > LZMA_VLI_MAX)
+		return LZMA_OPTIONS_ERROR;
+
+	coder->uncomp_size = uncomp_size;
+	coder->dict_size = dict_size;
+
+	coder->props_decoded = false;
+
+	return LZMA_OK;
+}
+
+
+extern LZMA_API(lzma_ret)
+lzma_erofs_decoder(lzma_stream *strm, uint64_t uncomp_size, uint32_t dict_size)
+{
+	lzma_next_strm_init(erofs_decoder_init, strm, uncomp_size, dict_size);
+
+	strm->internal->supported_actions[LZMA_RUN] = true;
+	strm->internal->supported_actions[LZMA_FINISH] = true;
+
+	return LZMA_OK;
+}