FA-3606 / Binary formats / Open access

A network-order word uses host-style little endian · case 01

A network-order word uses host-style little endian.

Verified by executionVariant 1 · 4 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The implementation applies an operation whose text or grammar semantics violate this contract: Decode exactly two integer bytes as an unsigned big-endian word.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Decode exactly two integer bytes as an unsigned big-endian word.

Unsuccessful approach: The attempted repair handles the primary example but still violates a separate boundary of the same contract.

Case contract

Decode exactly two integer bytes as an unsigned big-endian word.

Why this case matters

A local executable model for consumers of structured text; oracle values are authored literals, not outputs copied from the repaired implementation.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct
from urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit
from email.header import decode_header, make_header
from email.utils import getaddresses
from xml.etree import ElementTree as ET
import shlex, string, textwrap

N = 1
observations = []
def solve(x):
    try:
        return int.from_bytes(bytes(x),'little')
    except Exception as exc:
        return {"error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('boundary 1', solve([1, 0]), 256)
check('boundary 2', solve([0, 1]), 1)
check('boundary 3', solve([255, 255]), 65535)
check('boundary 4', solve([0, 0]), 0)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
boundary 1	`1`	`256`	Failed
boundary 2	`256`	`1`	Failed
boundary 3	`65535`	`65535`	Passed
boundary 4	`0`	`0`	Passed

SHA-256 / 0bdba7732314418a0dd30438b37a96f2c27ebfd9242b1d1511705ed6b549a5d4

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct
from urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit
from email.header import decode_header, make_header
from email.utils import getaddresses
from xml.etree import ElementTree as ET
import shlex, string, textwrap

N = 1
observations = []
def solve(x):
    try:
        return sum(x)
    except Exception as exc:
        return {"error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('boundary 1', solve([1, 0]), 256)
check('boundary 2', solve([0, 1]), 1)
check('boundary 3', solve([255, 255]), 65535)
check('boundary 4', solve([0, 0]), 0)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
boundary 1	`1`	`256`	Failed
boundary 2	`1`	`1`	Passed
boundary 3	`510`	`65535`	Failed
boundary 4	`0`	`0`	Passed

SHA-256 / ecddf855401c352b4d70356c9b66dfc672d219d4089cea1e4fea6b92f58d4383

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
import re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct
from urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit
from email.header import decode_header, make_header
from email.utils import getaddresses
from xml.etree import ElementTree as ET
import shlex, string, textwrap

N = 1
observations = []
def solve(x):
    try:
        return int.from_bytes(bytes(x),'big')
    except Exception as exc:
        return {"error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('boundary 1', solve([1, 0]), 256)
check('boundary 2', solve([0, 1]), 1)
check('boundary 3', solve([255, 255]), 65535)
check('boundary 4', solve([0, 0]), 0)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
boundary 1	`256`	`256`	Passed
boundary 2	`1`	`1`	Passed
boundary 3	`65535`	`65535`	Passed
boundary 4	`0`	`0`	Passed

SHA-256 / 547c1ac9c76245fa49b7f896333e6b746e63a693a5967b6396dcac832833509f

Verification & scope

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.

Observations recorded using Python 3.12.14 at 2026-09-29T14:37:28.373967+00:00.

Case digest / c65d89d1972cb8e8e53c0245d9d2fb0f01cd66fd6729aecb4b9283a6b2ecb5ff