FA-72222 / Error-correcting codes / Member archive

CRC correction never considers the CRC byte · case 02

Frames whose CRC byte took the hit are declared uncorrectable.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

Frames of 2..15 bytes end with a CRC-8 (polynomial 0x07, initial value 0, MSB first, no final XOR) over the preceding bytes. A matching CRC is "clean"; otherwise try every single-bit flip across the whole frame, including the CRC byte, and accept the first that makes the CRC match ("corrected"). Otherwise "uncorrectable". Return [status, payload bytes or None].

Why this case matters

Sensor buses use short CRC-protected frames and correct single-bit upsets instead of retransmitting.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression [[72, 197, 62, 201]]	`["uncorrectable", null]`	`["corrected", [72, 197, 62]]`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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