FA-11571 / Filesystem semantics / Open access

Sparse holes disappear when file bytes are reconstructed · case 01

Sparse holes disappear when file bytes are reconstructed.

Verified by executionVariant 1 · 6 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Only allocated cells are concatenated, collapsing logical offsets.

VERIFIED REPAIR

Read each logical position and substitute a zero byte for unallocated cells.

Unsuccessful approach: Padding at the end preserves size but moves bytes that follow internal holes.

Case contract

Deterministic in-memory filesystem model. Logical file has nonnegative size and a map from allocated integer offsets to byte values 0..255. Return all logical bytes as a list; offsets outside size are ignored.

Why this case matters

An offline semantic experiment for file API clients; it models only the stated operations, not a complete operating system.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(size, cells):
    return [cells[p] for p in sorted(cells) if 0<=p<size]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('leading hole',solve(N+1,{N:65}),[0]*N+[65])
check('internal hole',solve(3,{0:65,2:66}),[65,0,66])
check('trailing hole',solve(3,{0:65}),[65,0,0])
check('all hole',solve(N,{}),[0]*N)
check('empty file',solve(0,{0:65}),[])
check('allocated zero retained',solve(2,{0:0,1:66}),[0,66])
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
leading hole	`[65]`	`[0, 65]`	Failed
internal hole	`[65, 66]`	`[65, 0, 66]`	Failed
trailing hole	`[65]`	`[65, 0, 0]`	Failed
all hole	`[]`	`[0]`	Failed
empty file	`[]`	`[]`	Passed
allocated zero retained	`[0, 66]`	`[0, 66]`	Passed

SHA-256 / ec0ee2fc6de107c6b7c4b345b12ce985b4f2ee1e065312fe523756c8c18c8b8a

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(size, cells):
    values=[cells[p] for p in sorted(cells) if 0<=p<size]
    return values+[0]*(size-len(values))
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('leading hole',solve(N+1,{N:65}),[0]*N+[65])
check('internal hole',solve(3,{0:65,2:66}),[65,0,66])
check('trailing hole',solve(3,{0:65}),[65,0,0])
check('all hole',solve(N,{}),[0]*N)
check('empty file',solve(0,{0:65}),[])
check('allocated zero retained',solve(2,{0:0,1:66}),[0,66])
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
leading hole	`[65, 0]`	`[0, 65]`	Failed
internal hole	`[65, 66, 0]`	`[65, 0, 66]`	Failed
trailing hole	`[65, 0, 0]`	`[65, 0, 0]`	Passed
all hole	`[0]`	`[0]`	Passed
empty file	`[]`	`[]`	Passed
allocated zero retained	`[0, 66]`	`[0, 66]`	Passed

SHA-256 / e7f0534a9a3084e192c127c53c70974301f1f98335cab1da2849827c877d0021

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(size, cells):
    return [cells.get(p,0) for p in range(size)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('leading hole',solve(N+1,{N:65}),[0]*N+[65])
check('internal hole',solve(3,{0:65,2:66}),[65,0,66])
check('trailing hole',solve(3,{0:65}),[65,0,0])
check('all hole',solve(N,{}),[0]*N)
check('empty file',solve(0,{0:65}),[])
check('allocated zero retained',solve(2,{0:0,1:66}),[0,66])
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
leading hole	`[0, 65]`	`[0, 65]`	Passed
internal hole	`[65, 0, 66]`	`[65, 0, 66]`	Passed
trailing hole	`[65, 0, 0]`	`[65, 0, 0]`	Passed
all hole	`[0]`	`[0]`	Passed
empty file	`[]`	`[]`	Passed
allocated zero retained	`[0, 66]`	`[0, 66]`	Passed

SHA-256 / d872122492a43c8a1899b47c7189de38c10b263915bff3f082db255e98332e8f

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 2026-09-29T14:38:49.125405+00:00.

Case digest / 1c5440ca3ba32aeaa061184d93181b2573b8f84a5ae882d49383a52b998db0a2