The trailing "2" follows HDF5's convention for versioned/deprecated
symbols (H5Dopen2, H5Gcreate2, etc.), implying this is a successor to
H5Zget_filter_info registered in H5vers.txt -- it isn't. The two functions
are independent: H5Zget_filter_info returns only encode/decode config
flags, H5Zget_filter_class_info additionally exposes name, description,
and set_config/get_config presence. Renamed across C, Fortran, and both
Java binding variants (JNI + FFM) since it hadn't shipped yet.
Adds a human-readable key=value parameter string API for HDF5 filters,
alongside the existing integer cd_values arrays.
New C API:
- H5Pappend_filter(plist, filter_id, flags, params) — appends a filter
using either a key=value string or raw cd_values (H5Z_params_t)
- H5Pget_filter_params_by_idx(plist, idx, buf, buf_size, content_len) —
retrieves the parameter string for a filter by pipeline index
- H5Zconfig_get_int/double/bool/str — typed accessors for use inside
filter set_config callbacks
- H5Z_filter_id_by_name(name) — look up a filter id by registered name
- H5Zget_filter_info2(id, info) — extended filter info including v3 fields
New H5Z_class3_t fields: name, description, set_config, get_config,
and reserved blob-callback placeholders (write_blob/read_blob/close_blob).
H5Z_pipeline gains dxpl_id, scaled[], and ndims arguments threaded
through from all call sites so v3 filter callbacks have full context.
All six built-in filters (deflate, shuffle, fletcher32, nbit, szip,
scaleoffset) implement set_config/get_config callbacks.
TOML subset parser: tomlc17 (MIT) vendored in src/tomlc17/ and compiled
unconditionally into libhdf5. Hex-float literals are transparently
rewritten to decimal before parsing. tomlc17 symbols are hidden via
-fvisibility=hidden to prevent namespace collisions.
On-disk format: no new pipeline version. Parameter strings are converted
to cd_values by set_config at H5Pappend_filter time and stored using the
existing v2 pipeline message. On read, get_config reconstructs the string.
Full backward read compatibility is preserved.
Fortran, C++, and Java bindings added. Tests in test/tfilter2.c
(~2300 lines) and testpar/t_filters_parallel.c (par-01–par-04).
h5dump displays filter parameter strings; h5repack accepts TOML-form
UD= filter specs.
Code-review fixes included: tomlc17 visibility, H5Pget_filter_params_by_idx
arg validation and true-length two-pass contract, flags re-validation after
set_config, H5Z_register3 runtime plugin validation, Java two-pass protocol
and h5libraryError() consistency, CHANGELOG corrections.
Fixes GitHub issue #6153
FFM build requires Java 25, Jextract 25.
Generates FFM bindings during configure.
JNI is default when the requirements are not met or can be forced.
Presets added for maven and FFM - JNI is default selection.
Enhanced Maven options will work with either JNI or FFM
New Workflows for testing and maven uploads.
Extensive documentation changes for java.
M. Scot Breitenfeld
Allen Byrne