fix(bgcode): DEFLATE is zlib-wrapped, not raw — real-file confirmed (#188) - #236
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…rmed (#188) Phase-1 assumed raw DEFLATE ('deflate-raw'). Validating the decoder against a real Prusa XL ColorMix .bgcode (21 MB, 856 blocks) showed its DEFLATE metadata blocks (Slicer/Print) decode ONLY as zlib-wrapped — raw fails ("invalid stored block lengths"). It went unnoticed because GCode blocks use heatshrink, not DEFLATE, so the DEFLATE path was never exercised until real metadata. Switch the decoder + the test assembler to DecompressionStream('deflate') (zlib), and add a flavor-lock test asserting a raw-DEFLATE block is rejected (E_BGCODE_INFLATE) so the flavor can't silently regress. Real-file validation (local): all 856 CRC32 verified; 848 heatshrink-12 + MeatPack-comments GCode blocks → 51.4 MB of valid Prusa G-code (1,892,006 G1 moves, comments + ;WIPE_START preserved, MeatPack no-spaces mode exercised) in ~3 s — so the phase-2/3 decoders are correct on real data. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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July 27, 2026 21:17
This was referenced Jul 28, 2026
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The first fruit of validating the decoder against a real Prusa XL ColorMix
.bgcode(thanks for the file!). Part of #188 phase 4.The bug the real file caught
Phase 1 assumed raw DEFLATE (
'deflate-raw'). Prusa actually uses zlib-wrapped DEFLATE — the real file's Slicer/Print metadata blocks decode only with the zlib header (zlib.decompress(data)); raw fails withinvalid stored block lengths. It was invisible until now because GCode blocks use heatshrink, not DEFLATE — so the DEFLATE path was never exercised on real data until a real file's metadata.Fix:
DecompressionStream('deflate')(+ the test assembler), and a flavor-lock test asserting a raw-DEFLATE block is now rejected, so this can't silently regress.Real-file validation (local, conclusive)
Decoding the 21 MB / 856-block file end-to-end:
G1moves, comments +;WIPE_STARTpreserved, and the file uses MeatPack no-spaces mode (G1X177.233Y194.747E.02659) — so the phase-2 no-spaces handling and the phase-3 heatshrink are correct on real data.So the phase-2/3 codec ports are validated against real Prusa output; this PR fixes the one thing that was wrong (the DEFLATE flavor).
Verification
typeCheck✓,lint✓ (0 errors), CI-liketest:packages✓ (31 bgcode tests),pack:check✓ (no snapshot change).🤖 Generated with Claude Code