lzma_block_unpadded_size(const lzma_block *block)
{
// Validate the values that we are interested in i.e. all but
// Uncompressed Size and the filters.
//
// NOTE: This function is used for validation too, so it is
// essential that these checks are always done even if
// Compressed Size is unknown.
if (block == NULL || block->version != 0
|| block->header_size < LZMA_BLOCK_HEADER_SIZE_MIN
|| block->header_size > LZMA_BLOCK_HEADER_SIZE_MAX
|| (block->header_size & 3)
|| !lzma_vli_is_valid(block->compressed_size)
|| block->compressed_size == 0
|| (unsigned int)(block->check) > LZMA_CHECK_ID_MAX)
return 0;
// If Compressed Size is unknown, return that we cannot know
// size of the Block either.
if (block->compressed_size == LZMA_VLI_UNKNOWN)
return LZMA_VLI_UNKNOWN;
// Calculate Unpadded Size and validate it.
const lzma_vli unpadded_size = block->compressed_size
+ block->header_size
+ lzma_check_size(block->check);
assert(unpadded_size >= UNPADDED_SIZE_MIN);
if (unpadded_size > UNPADDED_SIZE_MAX)
return 0;
return unpadded_size;
}
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
unaligned_write32le(out + out_size, lzma_crc32(out, out_size, 0));
return LZMA_OK;
}
