dailz
94da39bb79
Per design §3.2 line 359, all WAL CRC computations must use crc32c
(Castagnoli polynomial 0x82F63B78). The previous code used crc32.IEEE
(Ethernet/PNG polynomial 0xEDB88320) in 5 places. While the system was
self-consistent (encode + decode both used IEEE), it diverged from the
design spec and lost SSE4.2 hardware acceleration (the native CRC32
instruction only supports Castagnoli).
Changes:
- wal/crc32c.go (new): package-level crc32cTable = crc32.MakeTable(
crc32.Castagnoli). Central definition prevents future drift.
- wal/header.go: 2 ChecksumIEEE calls replaced with crc32.Checksum(
data, crc32cTable). Comment updated to reference design §3.2 line 341, 359.
- wal/record.go: 2 ChecksumIEEE calls replaced.
- wal/block_writer_test.go: 1 ChecksumIEEE call in test helper replaced.
- wal/crc32c_test.go (new): 4 regression guards:
- TestCRC32CStandardVector: RFC 3720 fixed vector (crc32c("123456789")
= 0xE3069283).
- TestCRC32CEdistinctFromIEEE: confirms IEEE produces different value.
- TestHeaderCRCUsesCastagnoli: direct assertion on stored header CRC
(catches paired encode/decode reversion that round-trip tests miss).
- TestPhysicalRecordCRCUsesCastagnoli: same for physical record CRC.
BREAKING CHANGE: WAL files written before this fix (with IEEE CRC)
cannot be read after this fix (expects crc32c). Phase 1 has not been
released, so no real data migration is needed. Production users
post-release would need to drain + re-create the database.
Developers pulling this change should delete any local Phase-1 WAL
directories (`rm -rf <db-dir>/segment-*.wal`) before running the code;
old IEEE-encoded WALs will fail recovery on local dev machines.
Verified: all existing round-trip tests pass (encode + decode both use
crc32c, still self-consistent). Full suite green including
go test -race ./... .
Audit context: docs/audit-3.2.md C1.
13 lines
525 B
Go
13 lines
525 B
Go
package wal
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import "hash/crc32"
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// crc32cTable is the CRC-32 table using the Castagnoli polynomial (0x82F63B78
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// reflected). Required by design §3.2 line 359 for all WAL CRC computations.
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//
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// Distinct from crc32.IEEE (Ethernet/PNG polynomial 0xEDB88320) — the two
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// produce unrelated checksums for the same input. SSE4.2 native CRC32
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// instruction only supports Castagnoli, so this table also enables hardware
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// acceleration via Go's standard library internals.
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var crc32cTable = crc32.MakeTable(crc32.Castagnoli)
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