nx_webp_huff.nx

nx_webp_huff.nx -- VP8L Huffman code-group reader (WebP lossless). VP8L transmits every Huffman tree in one of two forms: SIMPLE -- 1 or 2 symbols written literally, no code-length layer NORMAL -- a 19-symbol code-length alphabet (3 bits each, sent in a fixed permuted order) which then codes the real symbol lengths, with run-length symbols 16/17/18 Both forms resolve to a canonical Huffman table, so both compose onto the existing nx_huffman primitive: VP8L reads bits LSB-first out of the byte stream and sends each code MSB-of-code first, which is exactly what nx_huffman_decode_lsb implements (contract re-verified against nx_bitstream.nx and nx_huffman.nx on 2026-07-31, not assumed from docs). THE ZERO-BIT CASE. A tree carrying exactly one symbol must decode that symbol while consuming NO bits. nx_huffman_decode_lsb always consumes at least one bit, so a bare canonical table is wrong here and would desync the whole stream. NxWlTree carries the single-symbol case explicitly rather than leaving it to the table -- this is the defect that silently corrupts every VP8L image whose alpha or red channel is constant, which is most synthetic images. genealogy_id: webp_lossless_bitstream_spec_2012 lineage_id: nx_webp_huff_v1 license_tier: ORIGINAL