docs: ZFP reads (changelog, README feature table, known issues)

ZFP (32013) was the one plugin filter still listed as UnsupportedFilter.
Conformance on tank, `conformance/run.sh --no-fetch` (2026-09-26): 600 of
697 files ok (baseline 599); h5ex_d_zfp.h5 is newly ok.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

CHANGELOG.md

@@ -2,6 +2,30 @@
 
 ## Unreleased
 
+### ZFP (2026-09-26)
+- **ZFP (filter 32013, H5Z-ZFP) reads, in pure Rust.** It was the last
+  filter in the conformance corpus that failed with `UnsupportedFilter`.
+  New feature `zfp` (`clawhdf5-format` and `clawhdf5`, included in
+  `plugin-filters`, no dependencies) ports the zfp 1.0.1 decoder and the
+  decompression half of H5Z-ZFP 1.1.1: every mode (fixed rate, fixed
+  precision, fixed accuracy, reversible, expert), int32, int64, float and
+  double, 1-4-D fields with partial blocks, and headers written by
+  big-endian machines (values byte-swapped as H5Z-ZFP does). Read only:
+  there is no ZFP encoder. The decoder is deterministic, so lossy modes have
+  one right answer, and clawhdf5 returns exactly libzfp's values.
+- Tests: `crates/clawhdf5/tests/zfp_interop.rs` has h5py + hdf5plugin 7.1
+  (H5Z-ZFP 1.1.1, zfp 1.0.1) write 2205 datasets over 16 mode settings
+  (including expert parameters at their edges) x the four types x 1-4-D
+  shapes with partial edge chunks, partial blocks and unit chunk
+  dimensions x smooth, noisy, wide-range, zero and inf/NaN data; each must
+  read byte for byte as h5py reads it. `tests/zfp_alloc_bounds.rs` fuzzes
+  headers and streams under a counting allocator: no panics, and the output
+  is allocated only when it matches the chunk's size and the stream holds at
+  least a bit per block. A stream that ends before the decoder is done is an
+  error (libzfp reads past its buffer).
+- Conformance on tank (2026-09-26, `conformance/run.sh --no-fetch`): 600 of
+  697 files ok (599 before); `h5ex_d_zfp.h5` now reads.
+
 ### Chunked full reads (2026-09-26)
 - **Chunks are decoded straight into the output, into reused buffers.** A
   full read of a chunked dataset faulted in about three times its size in

CLAUDE.md

@@ -11,7 +11,7 @@ Cargo workspace with 18 crates under `crates/` (plus `libaec-sys`, an internal F
 |-------|------|
 | `clawhdf5-format` | HDF5 binary spec parser (superblock, B-tree, heap) — also holds shared type definitions and physical constants |
 | `clawhdf5-io` | Read/write implementation |
-| `clawhdf5-filters` | Deflate backends (zlib-rs, zlib-ng, Apple Compression); the HDF5 filter pipeline, the filter registry (`clawhdf5_format::filter_registry`) and the other codecs (LZ4, Zstd, SZIP, N-Bit, scale-offset, pcodec, and the pure-Rust plugin filters LZF, bitshuffle, bzip2, Blosc 1, and Blosc2 read-only) live in `clawhdf5-format`. No ZFP. |
+| `clawhdf5-filters` | Deflate backends (zlib-rs, zlib-ng, Apple Compression); the HDF5 filter pipeline, the filter registry (`clawhdf5_format::filter_registry`) and the other codecs (LZ4, Zstd, SZIP, N-Bit, scale-offset, pcodec, and the pure-Rust plugin filters LZF, bitshuffle, bzip2, Blosc 1, and Blosc2 and ZFP read-only) live in `clawhdf5-format`. |
 | `clawhdf5-derive` | Proc-macro derive for HDF5-serializable structs |
 | `clawhdf5` | Main facade crate |
 | `clawhdf5-netcdf4` | NetCDF-4 compatibility layer |

README.md

@@ -780,14 +780,14 @@ stores keep their setting. Opt out with `float16 = false` or
 | `bzip2` | no | bzip2 filter (id 307): read and write. Pure Rust (the `bzip2` crate's libbz2-rs-sys backend compiles no C) |
 | `blosc` | no | Blosc 1 filter (id 32001): reads BloscLZ, LZ4/LZ4HC, Snappy, Zlib and Zstandard frames with byte or bit shuffle; writes LZ4, Snappy, Zlib or Zstandard (not BloscLZ). Pure Rust |
 | `blosc2` | no | Blosc2 filter (id 32026), read only: hdf5plugin's frames and B2ND (n-D) chunks, BloscLZ, LZ4/LZ4HC, Zlib and Zstandard, with shuffle, bit shuffle, delta or truncated precision. Pure Rust |
-| `plugin-filters` | no | All five above |
+| `zfp` | no | ZFP filter (id 32013, H5Z-ZFP), read only: every mode (rate, precision, accuracy, reversible, expert) for int32, int64, float and double, 1-4-D, returning exactly libzfp's values. Pure Rust, no dependencies |
+| `plugin-filters` | no | All six above |
 
-ZFP (32013) is not implemented: reading it fails with `UnsupportedFilter`,
+clawhdf5 cannot write Blosc2 or ZFP. Any other
-whose message names the filter. clawhdf5 cannot write Blosc2. Any other
 filter can be supplied at run time with `filter_registry::register_filter` (a
 decoder closure, or a `FilterCodec` that also encodes). The facade
-(`clawhdf5`) forwards `lzf`, `bitshuffle`, `bzip2`, `blosc`, `blosc2` and
+(`clawhdf5`) forwards `lzf`, `bitshuffle`, `bzip2`, `blosc`, `blosc2`, `zfp`
-`plugin-filters`. Write
+and `plugin-filters`. Write
 with `DatasetBuilder::with_lzf()`, `with_bitshuffle(..)`, `with_bzip2(..)`
 and `with_blosc(..)`; h5py + hdf5plugin read the result (tested both ways in
 `crates/clawhdf5/tests/plugin_filters_interop.rs`). The pure-Rust Zstandard

docs/known-issues.md

@@ -293,10 +293,14 @@ fill-value item that did is fixed).
   697 ok, tank, `conformance/run.sh --no-fetch`). Blosc2 frames using
   dictionaries, lazy chunks, variable-length blocks, user-defined codecs or
   registered filters (e.g. bytedelta) are refused with an error.
-  **Still open:** ZFP (32013) fails with an `UnsupportedFilter` error that
+  **Fixed 2026-09-26** for ZFP (32013, `zfp` feature, also in
-  names the filter, and can be plugged in with
+  `plugin-filters`), read only: every H5Z-ZFP mode and type, bit-exact
-  `filter_registry::register_filter` (32023, Granular BitRound, too, since
+  against h5py + hdf5plugin 7.1 (`crates/clawhdf5/tests/zfp_interop.rs`);
-  2026-09-26 even with the `pcodec` feature). clawhdf5 cannot write Blosc2.
+  h5ex_d_zfp now reads (conformance 600 of 697 ok, tank,
+  `conformance/run.sh --no-fetch`). **Still open:** clawhdf5 cannot write
+  Blosc2 or ZFP. Other filters (32023, Granular BitRound, too, since
+  2026-09-26 even with the `pcodec` feature) can be plugged in with
+  `filter_registry::register_filter`.
 - **Wrong data: a chunk whose filters decode to fewer bytes than the chunk
   read with zeros for the missing bytes** (any filter; found reviewing the plugin
   filters). **Fixed 2026-09-26:** it is an error naming the chunk. A corrupt