2.2.1 Chunk Size

The LZXD compressor emits chunks of compressed data. A chunk represents exactly 32 KB of uncompressed data until the last chunk in the stream, which can represent less than 32 KB. To ensure that an exact number of input bytes represent an exact number of output bytes for each chunk, after each 32 KB of uncompressed data is represented in the output compressed bitstream, the output bitstream is padded with up to 15 bits of zeros to realign the bitstream on a 16-bit boundary (even byte boundary) for the next 32 KB of data. This results in a compressed chunk of a byte-aligned size. The compressed chunk could be smaller than 32 KB or larger than 32 KB if the data is incompressible when the chunk is not the last one.

The LZXD engine encodes a compressed, chunk-size prefix field preceding each compressed chunk in the compressed byte stream. The compressed, chunk-size prefix field is a byte aligned, little-endian, 16-bit field. The chunk prefix chain could be followed in the compressed stream without decompressing any data. The next chunk prefix is at a location computed by the absolute byte offset location of this chunk prefix plus 2 (for the size of the chunk-size prefix field) plus the current chunk size.