1 files changed, 132 insertions, 0 deletions
diff --git a/src/liblzma/common/block_header_encoder.c b/src/liblzma/common/block_header_encoder.c
new file mode 100644
index 0000000..160425d
--- /dev/null
+++ b/src/liblzma/common/block_header_encoder.c
@@ -0,0 +1,132 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       block_header_encoder.c
+/// \brief      Encodes Block Header for .xz files
+//
+//  Author:     Lasse Collin
+//
+//  This file has been put into the public domain.
+//  You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include "common.h"
+#include "check.h"
+
+
+extern LZMA_API(lzma_ret)
+lzma_block_header_size(lzma_block *block)
+{
+	if (block->version > 1)
+		return LZMA_OPTIONS_ERROR;
+
+	// Block Header Size + Block Flags + CRC32.
+	uint32_t size = 1 + 1 + 4;
+
+	// Compressed Size
+	if (block->compressed_size != LZMA_VLI_UNKNOWN) {
+		const uint32_t add = lzma_vli_size(block->compressed_size);
+		if (add == 0 || block->compressed_size == 0)
+			return LZMA_PROG_ERROR;
+
+		size += add;
+	}
+
+	// Uncompressed Size
+	if (block->uncompressed_size != LZMA_VLI_UNKNOWN) {
+		const uint32_t add = lzma_vli_size(block->uncompressed_size);
+		if (add == 0)
+			return LZMA_PROG_ERROR;
+
+		size += add;
+	}
+
+	// List of Filter Flags
+	if (block->filters == NULL || block->filters[0].id == LZMA_VLI_UNKNOWN)
+		return LZMA_PROG_ERROR;
+
+	for (size_t i = 0; block->filters[i].id != LZMA_VLI_UNKNOWN; ++i) {
+		// Don't allow too many filters.
+		if (i == LZMA_FILTERS_MAX)
+			return LZMA_PROG_ERROR;
+
+		uint32_t add;
+		return_if_error(lzma_filter_flags_size(&add,
+				block->filters + i));
+
+		size += add;
+	}
+
+	// Pad to a multiple of four bytes.
+	block->header_size = (size + 3) & ~UINT32_C(3);
+
+	// NOTE: We don't verify that the encoded size of the Block stays
+	// within limits. This is because it is possible that we are called
+	// with exaggerated Compressed Size (e.g. LZMA_VLI_MAX) to reserve
+	// space for Block Header, and later called again with lower,
+	// real values.
+
+	return LZMA_OK;
+}
+
+
+extern LZMA_API(lzma_ret)
+lzma_block_header_encode(const lzma_block *block, uint8_t *out)
+{
+	// Validate everything but filters.
+	if (lzma_block_unpadded_size(block) == 0
+			|| !lzma_vli_is_valid(block->uncompressed_size))
+		return LZMA_PROG_ERROR;
+
+	// Indicate the size of the buffer _excluding_ the CRC32 field.
+	const size_t out_size = block->header_size - 4;
+
+	// Store the Block Header Size.
+	out[0] = out_size / 4;
+
+	// We write Block Flags in pieces.
+	out[1] = 0x00;
+	size_t out_pos = 2;
+
+	// Compressed Size
+	if (block->compressed_size != LZMA_VLI_UNKNOWN) {
+		return_if_error(lzma_vli_encode(block->compressed_size, NULL,
+				out, &out_pos, out_size));
+
+		out[1] |= 0x40;
+	}
+
+	// Uncompressed Size
+	if (block->uncompressed_size != LZMA_VLI_UNKNOWN) {
+		return_if_error(lzma_vli_encode(block->uncompressed_size, NULL,
+				out, &out_pos, out_size));
+
+		out[1] |= 0x80;
+	}
+
+	// Filter Flags
+	if (block->filters == NULL || block->filters[0].id == LZMA_VLI_UNKNOWN)
+		return LZMA_PROG_ERROR;
+
+	size_t filter_count = 0;
+	do {
+		// There can be a maximum of four filters.
+		if (filter_count == LZMA_FILTERS_MAX)
+			return LZMA_PROG_ERROR;
+
+		return_if_error(lzma_filter_flags_encode(
+				block->filters + filter_count,
+				out, &out_pos, out_size));
+
+	} while (block->filters[++filter_count].id != LZMA_VLI_UNKNOWN);
+
+	out[1] |= filter_count - 1;
+
+	// Padding
+	memzero(out + out_pos, out_size - out_pos);
+
+	// CRC32
+	write32le(out + out_size, lzma_crc32(out, out_size, 0));
+
+	return LZMA_OK;
+}