liblzma: Rename EROFS LZMA to MicroLZMA.

It still exists primarily for EROFS but MicroLZMA is
a more generic name (that hopefully doesn't clash with
something that already exists).

1 files changed, 219 insertions, 0 deletions

diff --git a/src/liblzma/common/microlzma_decoder.c b/src/liblzma/common/microlzma_decoder.c
new file mode 100644
index 00000000..37907109
--- /dev/null
+++ b/src/liblzma/common/microlzma_decoder.c
@@ -0,0 +1,219 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       microlzma_decoder.c
+/// \brief      Decode MicroLZMA 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;
+
+	/// Compressed size of the stream as given by the application.
+	/// This must be exactly correct.
+	///
+	/// This will be decremented when input is read.
+	uint64_t comp_size;
+
+	/// Uncompressed size of the stream as given by the application.
+	/// This may be less than the actual uncompressed size if
+	/// uncomp_size_is_exact is false.
+	///
+	/// This will be decremented when output is produced.
+	lzma_vli uncomp_size;
+
+	/// LZMA dictionary size as given by the application
+	uint32_t dict_size;
+
+	/// If true, the exact uncompressed size is known. If false,
+	/// uncomp_size may be smaller than the real uncompressed size;
+	/// uncomp_size may never be bigger than the real uncompressed size.
+	bool uncomp_size_is_exact;
+
+	/// True once the first byte of the MicroLZMA stream
+	/// has been processed.
+	bool props_decoded;
+} lzma_microlzma_coder;
+
+
+static lzma_ret
+microlzma_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_microlzma_coder *coder = coder_ptr;
+
+	// Remember the in start position so that we can update comp_size.
+	const size_t in_start = *in_pos;
+
+	// Remember the out start position so that we can update uncomp_size.
+	const size_t out_start = *out_pos;
+
+	// Limit the amount of input so that the decoder won't read more than
+	// comp_size. This is required when uncomp_size isn't exact because
+	// in that case the LZMA decoder will try to decode more input even
+	// when it has no output space (it can be looking for EOPM).
+	if (in_size - *in_pos > coder->comp_size)
+		in_size = *in_pos + (size_t)(coder->comp_size);
+
+	// When the exact uncompressed size isn't known, we must limit
+	// the available output space to prevent the LZMA decoder from
+	// trying to decode too much.
+	if (!coder->uncomp_size_is_exact
+			&& out_size - *out_pos > coder->uncomp_size)
+		out_size = *out_pos + (size_t)(coder->uncomp_size);
+
+	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.
+		if (coder->uncomp_size_is_exact)
+			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.
+	lzma_ret ret = coder->lzma.code(coder->lzma.coder, allocator,
+				in, in_pos, in_size,
+				out, out_pos, out_size, action);
+
+	// Update the remaining compressed size.
+	assert(coder->comp_size >= *in_pos - in_start);
+	coder->comp_size -= *in_pos - in_start;
+
+	if (coder->uncomp_size_is_exact) {
+		// After successful decompression of the complete stream
+		// the compressed size must match.
+		if (ret == LZMA_STREAM_END && coder->comp_size != 0)
+			ret = LZMA_DATA_ERROR;
+	} else {
+		// Update the amount of output remaining.
+		assert(coder->uncomp_size >= *out_pos - out_start);
+		coder->uncomp_size -= *out_pos - out_start;
+
+		// - We must not get LZMA_STREAM_END because the stream
+		//   shouldn't have EOPM.
+		// - We must use uncomp_size to determine when to
+		//   return LZMA_STREAM_END.
+		if (ret == LZMA_STREAM_END)
+			ret = LZMA_DATA_ERROR;
+		else if (coder->uncomp_size == 0)
+			ret = LZMA_STREAM_END;
+	}
+
+	return ret;
+}
+
+
+static void
+microlzma_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
+{
+	lzma_microlzma_coder *coder = coder_ptr;
+	lzma_next_end(&coder->lzma, allocator);
+	lzma_free(coder, allocator);
+	return;
+}
+
+
+static lzma_ret
+microlzma_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
+		uint64_t comp_size,
+		uint64_t uncomp_size, bool uncomp_size_is_exact,
+		uint32_t dict_size)
+{
+	lzma_next_coder_init(&microlzma_decoder_init, next, allocator);
+
+	lzma_microlzma_coder *coder = next->coder;
+
+	if (coder == NULL) {
+		coder = lzma_alloc(sizeof(lzma_microlzma_coder), allocator);
+		if (coder == NULL)
+			return LZMA_MEM_ERROR;
+
+		next->coder = coder;
+		next->code = &microlzma_decode;
+		next->end = &microlzma_decoder_end;
+
+		coder->lzma = LZMA_NEXT_CODER_INIT;
+	}
+
+	// The public API is uint64_t but the internal LZ decoder API uses
+	// lzma_vli.
+	if (uncomp_size > LZMA_VLI_MAX)
+		return LZMA_OPTIONS_ERROR;
+
+	coder->comp_size = comp_size;
+	coder->uncomp_size = uncomp_size;
+	coder->uncomp_size_is_exact = uncomp_size_is_exact;
+	coder->dict_size = dict_size;
+
+	coder->props_decoded = false;
+
+	return LZMA_OK;
+}
+
+
+extern LZMA_API(lzma_ret)
+lzma_microlzma_decoder(lzma_stream *strm, uint64_t comp_size,
+		uint64_t uncomp_size, lzma_bool uncomp_size_is_exact,
+		uint32_t dict_size)
+{
+	lzma_next_strm_init(microlzma_decoder_init, strm, comp_size,
+			uncomp_size, uncomp_size_is_exact, dict_size);
+
+	strm->internal->supported_actions[LZMA_RUN] = true;
+	strm->internal->supported_actions[LZMA_FINISH] = true;
+
+	return LZMA_OK;
+}