refactor(varint): parametrize the canonical LEB128 codec with max_bytes#798
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tcoratger merged 1 commit intoMay 29, 2026
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The networking and snappy modules each carried a self-contained LEB128 implementation. The two algorithms were identical, differing only in byte cap (10 vs 5). One implementation was a slow drift away from the other waiting to happen. Keep the networking varint as the single source of truth and give both encode and decode a max_bytes parameter (default 10 = uint64 cap). Snappy now imports the canonical codec and passes 5 via a new SNAPPY_VARINT_MAX_BYTES constant. Encode now also enforces the cap, so per-cap semantics are symmetric. The snappy length-prefix tests run against the canonical codec, plus an integration test that asserts an oversize prefix surfaces as a SnappyDecompressionError. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
The networking and snappy modules each carried a self-contained LEB128 implementation. The two algorithms were identical, differing only in the byte cap (10 vs 5). One implementation was a slow drift away from the other waiting to happen.
This PR keeps the networking varint as the single source of truth and gives both encode and decode a
max_bytesparameter (default10= uint64 cap). Snappy now imports the canonical codec and passes5via a newSNAPPY_VARINT_MAX_BYTESconstant.Changes
src/lean_spec/node/networking/varint.py— the canonical home:encode_varint(value, max_bytes=10)anddecode_varint(data, offset=0, max_bytes=10)both take an explicit cap.max_bytes * 7bits) — symmetric with decode.src/lean_spec/node/snappy/— caller migration:encoding.py: 159-lineencode_varint32/decode_varint32deleted; module now contains only tag-encoding logic.compress.py: importsencode_varintfrom networking and passesmax_bytes=SNAPPY_VARINT_MAX_BYTES.decompress.py: importsdecode_varintand catchesVarintError(the oldValueErrorpath is gone).constants.py: staleVARINT_CONTINUATION_BIT/VARINT_DATA_MASKremoved; replaced bySNAPPY_VARINT_MAX_BYTES = 5.Tests
tests/lean_spec/node/networking/test_varint.py: newTestMaxBytesParameterclass covers the 5-byte cap boundary — success at the largest value that fits, error at one bit over, truncation, and oversize input.tests/lean_spec/node/snappy/test_snappy.py:TestVarintEncodingrenamed toTestSnappyLengthPrefix. Tests now exercise the canonical codec through the snappy cap, plus an integration test that asserts an oversize prefix surfaces asSnappyDecompressionError.tests/lean_spec/node/networking/test_reqresp.py: the error-message match updated to the new formatted message.Test plan
just check— ruff, format, ty, codespell, mdformat passuv run pytest tests/lean_spec/node/{networking/test_varint,networking/test_reqresp,snappy/test_snappy,snappy/test_framing}.py— 229 tests passNet change: +126/−201 across 8 files. No backward-compatibility shims, no re-exports.
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