New CompressionAlgorithm that emits a standard Zstandard frame: zero/0xFF runs
become RLE_Blocks (like BSHUF_ZSTD_RLE) and literal regions become
Compressed_Blocks with per-block adaptive Huffman literals and no sequences
(Number_of_Sequences=0). Short runs are absorbed into the literal stream;
incompressible literals fall back to Raw_Blocks so the worst case stays within
ZSTD_compressBound.
The Huffman tree + bitstream are produced by zstd's own HUF_compress{1,4}X_repeat
(the same calls ZSTD_compressLiterals uses); only the frame/block/literals-section
framing is hand-written, with comments citing zstd_compression_format.md so it can
be checked clause by clause. Output decodes with stock ZSTD_decompress, so no
reader changes are needed (decode routes like BSHUF_ZSTD).
On sparse diffraction this gives ~12% smaller files than bitshuffle/LZ4 at about
the same end-to-end speed, sitting between LZ4 and full ZSTD; for maximum ratio
use BSHUF_ZSTD. Robust on any input: tests round-trip pure zeros, Poisson(10),
Mersenne-Twister noise (checked against the size bound), an extreme-sparsity mask,
and a real lyso image through stock ZSTD_decompress.
API: exposed as "bszstd_rlehuf"; regenerate the Python/TS clients (update_version.sh)
to surface the new value there.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Replace the fixed-element DefaultBlockSize with a byte target divided by
elem_size to get the block element count, so the per-block working set (and
thus cache behaviour) stays constant across pixel bit depths instead of halving
from 8- to 16- to 32-bit. The target is per-algorithm, following the measured
sweet spots on sparse data: LZ4 wants a small, cache-resident block for
throughput (16 kB), ZSTD/RLE want a large block for ratio (128 kB). The gap is
widest on extreme-sparsity inputs such as the uint32 pixel_mask, where
large-block ZSTD reaches 100-1800x vs ~160x for LZ4.
The block size is read back per-dataset from the bitshuffle stream header
(block_size = header_bytes / elem_size) and the HDF5 filter params, so the
decompressor and external readers (XDS/Neggia/Durin/CrystFEL) need no change.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
leonarski_fandClaude Opus 4.8