{"abstract":"Aligned payloads gain a spurious 0x00 codeword before the pad bytes.","category":"Barcode symbology encoding","checks":8,"contract":"Finish a QR data bit stream for a symbol with `capacity` data codewords: data longer than capacity*8 bits returns None; append a terminator of up to four 0 bits (truncated if capacity is reached), pad with 0 bits to a byte boundary, split into codewords, then append pad codewords alternating 0xEC, 0x11 starting with 0xEC until the capacity is filled.","contract_signature":"bits, capacity","evaluation_group":"w2-barcode-symbology-encoding-qr-terminator-padding","failed_approach":"Adding len % 8 bits aligns only by coincidence.","family":"w2-barcode-symbology-encoding-qr-terminator-padding-byte-align","id":"FA-79716","implementations":{"attempt":{"sha256":"8bea9b0b80ff39b6721af6850d738cee4ea9f5cfb0895cbd738779c6259376b1","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(bits, capacity):\n    cap = capacity * 8\n    if len(bits) > cap:\n        return None\n    bits += '0' * min(4, cap - len(bits))\n    bits += '0' * (len(bits) % 8)\n    words = [int(bits[i:i + 8], 2) for i in range(0, len(bits), 8)]\n    pads = [0xEC, 0x11]\n    k = 0\n    while len(words) < capacity:\n        words.append(pads[k % 2])\n        k += 1\n    return words\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[[('11110', 1), [240]], [('11000111110010110000011101', 7), [199, 203, 7, 64, 236, 17, 236]], [('011111010101101111101000', 5), [125, 91, 232, 0, 236]], [('001110011011101011101000', 4), [57, 186, 232, 0]], [('101011111101111010101001010011000', 4), None], [('001101110111100101001100111101010', 4), None], [('00001110010101111011010001101111', 6), [14, 87, 180, 111, 0, 236]], [('10111110000100110101101101110110', 4), [190, 19, 91, 118]]], [[('010111100111111111101011010111010101', 6), [94, 127, 235, 93, 80, 236]], [('1100010000000100010111100', 6), [196, 4, 94, 0, 236, 17]], [('1110011111000110', 7), [231, 198, 0, 236, 17, 236, 17]], [('00101010101111110010011110110010011100110', 5), None], [('1110111100000001110000101', 3), None], [('10110001001101011', 2), None], [('000010111001001111110001111000101', 4), None], [('000100', 1), [16]]], [[('10110101', 1), [181]], [('111111110110110111', 3), [255, 109, 192]], [('0110000101010010', 7), [97, 82, 0, 236, 17, 236, 17]], [('11010010000000100000001', 4), [210, 2, 2, 0]], [('', 3), [0, 236, 17]], [('10100010001101111', 2), None], [('111010111110010110000100101101100011001010010011111010111', 7), None], [('1110100000110001011011010010010', 4), [232, 49, 109, 36]]], [[('01110011101100110010100111000111100111011111110101101110', 7), [115, 179, 41, 199, 157, 253, 110]], [('1101011000', 2), [214, 0]], [('0001101010100101110100100000001001110111000110110', 6), None], [('01000011', 2), [67, 0]], [('10110010', 2), [178, 0]], [('10001101000010011', 2), None], [('1010100000100110011011001000111101000001101100001', 6), None], [('00011', 1), [24]]], [[('100100000001111010001', 3), [144, 30, 136]], [('0010010011000011011010100', 7), [36, 195, 106, 0, 236, 17, 236]], [('010001110011110110111010011110011100001110101010100001101', 7), None], [('000101100', 1), None], [('11001010', 5), [202, 0, 236, 17, 236]], [('100010101011001101000110110111110', 4), None], [('0100011110111010010001', 5), [71, 186, 68, 0, 236]], [('1001000010101110001111000110111010001110', 5), [144, 174, 60, 110, 142]]]]\nlabels = [\"regression: byte boundary padding\", \"repair trap\", \"combined fault\", \"control\", \"control\", \"boundary\", \"boundary\", \"control\"]\nfor i, (args, expected) in enumerate(fixtures[N-1]):\n    check(\"%s %d\" % (labels[i % len(labels)], i), solve(*args), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"4fd117b0f6de5c3d864e6fade66b3b288b2a572dbe6e324293797bb0048fb5ae","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(bits, capacity):\n    cap = capacity * 8\n    if len(bits) > cap:\n        return None\n    bits += '0' * min(4, cap - len(bits))\n    bits += '0' * (8 - len(bits) % 8)\n    words = [int(bits[i:i + 8], 2) for i in range(0, len(bits), 8)]\n    pads = [0xEC, 0x11]\n    k = 0\n    while len(words) < capacity:\n        words.append(pads[k % 2])\n        k += 1\n    return words\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[[('11110', 1), [240]], [('11000111110010110000011101', 7), [199, 203, 7, 64, 236, 17, 236]], [('011111010101101111101000', 5), [125, 91, 232, 0, 236]], [('001110011011101011101000', 4), [57, 186, 232, 0]], [('101011111101111010101001010011000', 4), None], [('001101110111100101001100111101010', 4), None], [('00001110010101111011010001101111', 6), [14, 87, 180, 111, 0, 236]], [('10111110000100110101101101110110', 4), [190, 19, 91, 118]]], [[('010111100111111111101011010111010101', 6), [94, 127, 235, 93, 80, 236]], [('1100010000000100010111100', 6), [196, 4, 94, 0, 236, 17]], [('1110011111000110', 7), [231, 198, 0, 236, 17, 236, 17]], [('00101010101111110010011110110010011100110', 5), None], [('1110111100000001110000101', 3), None], [('10110001001101011', 2), None], [('000010111001001111110001111000101', 4), None], [('000100', 1), [16]]], [[('10110101', 1), [181]], [('111111110110110111', 3), [255, 109, 192]], [('0110000101010010', 7), [97, 82, 0, 236, 17, 236, 17]], [('11010010000000100000001', 4), [210, 2, 2, 0]], [('', 3), [0, 236, 17]], [('10100010001101111', 2), None], [('111010111110010110000100101101100011001010010011111010111', 7), None], [('1110100000110001011011010010010', 4), [232, 49, 109, 36]]], [[('01110011101100110010100111000111100111011111110101101110', 7), [115, 179, 41, 199, 157, 253, 110]], [('1101011000', 2), [214, 0]], [('0001101010100101110100100000001001110111000110110', 6), None], [('01000011', 2), [67, 0]], [('10110010', 2), [178, 0]], [('10001101000010011', 2), None], [('1010100000100110011011001000111101000001101100001', 6), None], [('00011', 1), [24]]], [[('100100000001111010001', 3), [144, 30, 136]], [('0010010011000011011010100', 7), [36, 195, 106, 0, 236, 17, 236]], [('010001110011110110111010011110011100001110101010100001101', 7), None], [('000101100', 1), None], [('11001010', 5), [202, 0, 236, 17, 236]], [('100010101011001101000110110111110', 4), None], [('0100011110111010010001', 5), [71, 186, 68, 0, 236]], [('1001000010101110001111000110111010001110', 5), [144, 174, 60, 110, 142]]]]\nlabels = [\"regression: byte boundary padding\", \"repair trap\", \"combined fault\", \"control\", \"control\", \"boundary\", \"boundary\", \"control\"]\nfor i, (args, expected) in enumerate(fixtures[N-1]):\n    check(\"%s %d\" % (labels[i % len(labels)], i), solve(*args), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":"A deterministic bounded teaching model with a stipulated contract; it makes no claim of conformance to any published specification. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"w2-barcode-symbology-encoding-qr-terminator-padding-byte-align","generated_at":"2026-09-29T14:49:47.026061+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"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.","root_cause":"The alignment adds 8 - len % 8 bits, which is 8 when already aligned.","sha256":"3a4db8a478564b8a8b114325f1352c20978abec50963a5cfc8a4be6b6152fe5e","title":"Byte alignment adds a whole zero byte to aligned data · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":40.738,"exit_code":1,"observations":[{"actual":[240],"check":"regression: byte boundary padding 0","expected":[240],"passed":true},{"actual":[199,203,7,64,0,236,17],"check":"repair trap 1","expected":[199,203,7,64,236,17,236],"passed":false},{"actual":[125,91,232,0,236],"check":"combined fault 2","expected":[125,91,232,0,236],"passed":true},{"actual":[57,186,232,0],"check":"control 3","expected":[57,186,232,0],"passed":true},{"actual":null,"check":"control 4","expected":null,"passed":true},{"actual":null,"check":"boundary 5","expected":null,"passed":true},{"actual":[14,87,180,111,0,236],"check":"boundary 6","expected":[14,87,180,111,0,236],"passed":true},{"actual":[190,19,91,118],"check":"control 7","expected":[190,19,91,118],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"regression: byte boundary padding 0\", \"actual\": [240], \"expected\": [240], \"passed\": true}, {\"check\": \"repair trap 1\", \"actual\": [199, 203, 7, 64, 0, 236, 17], \"expected\": [199, 203, 7, 64, 236, 17, 236], \"passed\": false}, {\"check\": \"combined fault 2\", \"actual\": [125, 91, 232, 0, 236], \"expected\": [125, 91, 232, 0, 236], \"passed\": true}, {\"check\": \"control 3\", \"actual\": [57, 186, 232, 0], \"expected\": [57, 186, 232, 0], \"passed\": true}, {\"check\": \"control 4\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"boundary 5\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"boundary 6\", \"actual\": [14, 87, 180, 111, 0, 236], \"expected\": [14, 87, 180, 111, 0, 236], \"passed\": true}, {\"check\": \"control 7\", \"actual\": [190, 19, 91, 118], \"expected\": [190, 19, 91, 118], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":40.832,"exit_code":1,"observations":[{"actual":[240,0],"check":"regression: byte boundary padding 0","expected":[240],"passed":false},{"actual":[199,203,7,64,236,17,236],"check":"repair trap 1","expected":[199,203,7,64,236,17,236],"passed":true},{"actual":[125,91,232,0,236],"check":"combined fault 2","expected":[125,91,232,0,236],"passed":true},{"actual":[57,186,232,0],"check":"control 3","expected":[57,186,232,0],"passed":true},{"actual":null,"check":"control 4","expected":null,"passed":true},{"actual":null,"check":"boundary 5","expected":null,"passed":true},{"actual":[14,87,180,111,0,236],"check":"boundary 6","expected":[14,87,180,111,0,236],"passed":true},{"actual":[190,19,91,118,0],"check":"control 7","expected":[190,19,91,118],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"regression: byte boundary padding 0\", \"actual\": [240, 0], \"expected\": [240], \"passed\": false}, {\"check\": \"repair trap 1\", \"actual\": [199, 203, 7, 64, 236, 17, 236], \"expected\": [199, 203, 7, 64, 236, 17, 236], \"passed\": true}, {\"check\": \"combined fault 2\", \"actual\": [125, 91, 232, 0, 236], \"expected\": [125, 91, 232, 0, 236], \"passed\": true}, {\"check\": \"control 3\", \"actual\": [57, 186, 232, 0], \"expected\": [57, 186, 232, 0], \"passed\": true}, {\"check\": \"control 4\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"boundary 5\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"boundary 6\", \"actual\": [14, 87, 180, 111, 0, 236], \"expected\": [14, 87, 180, 111, 0, 236], \"passed\": true}, {\"check\": \"control 7\", \"actual\": [190, 19, 91, 118, 0], \"expected\": [190, 19, 91, 118], \"passed\": false}], \"passed\": false}\n"}},"member_only":{"stages":["fixed"],"fields":["implementations.fixed","verification.fixed","harness","repair"],"note":"The verified repair, its recorded checks, the repair description, and the scoring harness are available to members."}}