FA-79684 / Barcode symbology encoding / Member archive

QR alphanumeric trailing character is written in 5 bits · case 04

Odd-length data ending in a character with value 32 or more corrupts the terminator.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Encode the data part of a QR alphanumeric segment. Character values: 0-9 -> 0-9, A-Z -> 10-35, space 36, $ 37, % 38, * 39, + 40, - 41, . 42, / 43, : 44. Each pair becomes 45*first + second in 11 bits, a final single character becomes its value in 6 bits. Characters outside the set return None.

Why this case matters

Retail, logistics, pharmacy and document workflows depend on encoders that produce exactly the module pattern, code-set switches, separators and quiet zones scanners expect; one misplaced module or separator makes a label unreadable or, worse, scan as different data.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression: trailing character bit width 0	`"1010011101000100"`	`"10100111010000100"`	Failed

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