File size: 3,131 Bytes
aaf8747 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 | #!/usr/bin/env python3
"""Extract one manifest-selected clip, verifying member hashes; stdlib only."""
import argparse
import hashlib
import json
from pathlib import Path, PurePosixPath
import tarfile
def safe_relative(name):
path = PurePosixPath(name)
if path.is_absolute() or '..' in path.parts or '\\' in name:
raise ValueError(f'Unsafe relative path: {name!r}')
return path
def find_sample(root, sample_id):
with (root / 'manifests/train.jsonl').open(encoding='utf-8') as stream:
for line in stream:
row = json.loads(line)
if sample_id is None or row['sample_id'] == sample_id:
return row
raise ValueError(f'Sample not found: {sample_id}')
def extract(root, sample_id, destination):
row = find_sample(root, sample_id)
shard = (root / safe_relative(row['shard'])).resolve()
shard.relative_to(root.resolve())
if destination.exists():
raise FileExistsError(f'Choose a new output directory: {destination}')
destination.mkdir(parents=True)
files = {}
try:
with tarfile.open(shard, 'r:') as archive:
for kind, name in row['members'].items():
relative = safe_relative(name)
if len(relative.parts) != 1:
raise ValueError(f'Expected a flat sample member: {name}')
member = archive.getmember(name)
if not member.isfile():
raise ValueError(f'Expected regular file: {name}')
expected = row['sha256'].get(kind)
if not expected:
raise ValueError(f'No expected hash for {kind}')
path = destination / relative.name
digest = hashlib.sha256()
source = archive.extractfile(member)
if source is None:
raise ValueError(f'Unreadable member: {name}')
with source, path.open('xb') as output:
while chunk := source.read(1024 * 1024):
digest.update(chunk)
output.write(chunk)
if digest.hexdigest() != expected:
path.unlink()
raise ValueError(f'SHA256 mismatch: {name}')
files[kind] = str(path)
return {'sample_id': row['sample_id'], 'shard': row['shard'],
'num_frames': row['num_frames'], 'fps': row['fps'],
'duration_seconds': row['duration_seconds'], 'files': files}
except Exception:
# Verified files may remain for inspection; no existing directory is overwritten.
raise
def main():
parser = argparse.ArgumentParser(description=__doc__)
parser.add_argument('--release-root', type=Path, required=True)
parser.add_argument('--sample-id', help='Defaults to the first manifest row')
parser.add_argument('--output', type=Path, required=True)
args = parser.parse_args()
result = extract(args.release_root, args.sample_id, args.output)
print(json.dumps(result, ensure_ascii=False, indent=2))
if __name__ == '__main__':
main()
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