TinyEXR v3 JPH Status

Current state:

• src/exr_jph.c is a clean-room C11 HTJ2K/JPH front end under BSD-3-Clause.
• OpenEXR HT wrapper parsing is implemented.
• JPEG 2000 marker/profile validation is implemented for the intended OpenEXR subset: SOC/SIZ/CAP/COD/QCD/QCC/NLT/SOT/SOD/EOC handling, RPCL, one layer, 5 reversible 5/3 decompositions, 128×32 HT codeblocks, default precincts, and single tile part.
• Packet parsing validates precinct order, inclusion tag trees, missing-MSB tag trees, pass counts, pass lengths, codeblock byte bounds, cleanup Scup, and HT stream stuffing.
• Internal HT forward/reverse/MEL readers exist and are covered by tests.
• Codeblock callback boundary exists. Validated codeblock descriptors include component, resolution, band, subband coordinates, dimensions, pass lengths, missing MSBs, and byte ranges.
• Component coefficient planes are allocated with the codec allocator.
• Cleanup pass decode (MagSgn + MEL + VLC, quad-based) is fully implemented for both the int32 (all-HALF) and int64 (FLOAT/UINT) code paths.
• SPP and MRP refinement passes are fully implemented for the int32 path and the int64 path.
• Non-empty codeblocks decode correctly through the full pipeline: cleanup → SPP → MRP → coefficient reconstruction → subband-to-plane mapping → inverse 5/3 → inverse RCT (if enabled) → NLT type 3 → TinyEXR block layout store.
• All-empty JPH codestreams decode to zero blocks (short-circuit at the first all-empty band).
• Both scanline and tiled OpenEXR HTJ2K files are supported (decode and encode).
• make c11-gate passes (strict -std=c11 -Wall -Wextra -Werror).
• make test-c passes: 170 passed, 0 failed (including 12 real-file decode-match tests against openexr-images fixtures, 2 in-tree regression-fixture decode tests, 9 HTJ2K round-trip encode-decode tests, subsampling round-trip, UINT round-trip, mixed HALF/FLOAT round-trip, and synthetic malformed-payload rejection).
• make fuzz-corpus passes: 27 regression files, no crash, no sanitizer error (ASan+UBSan+LSan).
• src/exr_jph.c has no assert(), abort(), or exit() calls.

Feature support matrix

Intentionally unsupported (non-goals)

• DWA (DWAA / DWAB): lossy DCT codec; returns EXR_ERROR_UNSUPPORTED.
• Irreversible 9/7 wavelet: out of scope for clean-room HTJ2K subset.
• Multi-tile-part codestreams: one tile part per tile.
• Precinct sizes ≠ default: only default precincts (full-tile, single precinct) are accepted.
• Progression order ≠ LRCP/RPCL: progression-order changes (POC) outside the default are rejected.

Key files

• src/exr_jph.c (6066 lines): JPH parser, packet parser, HT entropy decoder (cleanup + SPP + MRP), inverse 5/3 wavelet, inverse RCT, NLT, writer pipeline.
• src/exr_jph_simd.c (277 lines): runtime-dispatched SSE2/AVX2 NLT, pack, and inverse 5/3 kernels.
• src/exr_ht_decode.c (40 lines): stub for future T2 refactoring.
• src/exr_internal.h: internal JPH helper declarations.
• test/unit/test_exr_v3.c (1421 lines): synthetic JPH profile, transform, packet, HT reader, SIMD parity, and round-trip tests.
• jph.md: earlier OpenEXR JPH investigation and implementation plan.

Continue implementing TinyEXR v3 JPH/HTJ2K decode in /mnt/nvme02/work/tinyexr.

Read tasks.md, jph.md, src/exr_jph.c, src/exr_internal.h, and test/unit/test_exr_v3.c first. The current JPH front end parses OpenEXR HT wrapper/JPEG2000 profile, validates RPCL packet metadata and HT codeblock segment structure, has HT forward/reverse/MEL readers, allocates coefficient planes, decodes complete all-empty JPH codestreams through inverse 5/3/RCT/NLT and block store, and returns EXR_ERROR_UNSUPPORTED for non-empty codeblocks.

Continue from the non-empty codeblock boundary. Implement the next smallest verifiable piece toward HT cleanup entropy decode in pure C11, keeping it portable, low-memory, and hardened. Do not use assert(), abort(), or exit(); return exr_result errors for all malformed input. Preserve permissive licensing: if referencing/copying OpenJPH tables or code from /mnt/nvme02/work/openexr/external/OpenJPH, keep BSD-2 copyright/license attribution and do not introduce GPL code.

Use apply_patch for edits. Keep unrelated dirty files untouched. After each slice run:
- make c11-gate
- make test-c
- rg -n "assert\\(|abort\\(|exit\\(" src/exr_jph.c

Current known passing state before this continuation: make c11-gate passes, make test-c reports 129 passed, 0 failed.