def _from_stream_descriptor_blob(cls, loop: asyncio.AbstractEventLoop, blob_dir: str,
blob: AbstractBlob) -> 'StreamDescriptor':
with blob.reader_context() as blob_reader:
json_bytes = blob_reader.read()
try:
decoded = json.loads(json_bytes.decode())
except json.JSONDecodeError:
blob.delete()
raise InvalidStreamDescriptorError("Does not decode as valid JSON")
if decoded['blobs'][-1]['length'] != 0:
raise InvalidStreamDescriptorError("Does not end with a zero-length blob.")
if any([blob_info['length'] == 0 for blob_info in decoded['blobs'][:-1]]):
raise InvalidStreamDescriptorError("Contains zero-length data blob")
if 'blob_hash' in decoded['blobs'][-1]:
raise InvalidStreamDescriptorError("Stream terminator blob should not have a hash")
if any([i != blob_info['blob_num'] for i, blob_info in enumerate(decoded['blobs'])]):
raise InvalidStreamDescriptorError("Stream contains out of order or skipped blobs")
descriptor = cls(
loop, blob_dir,
binascii.unhexlify(decoded['stream_name']).decode(),
decoded['key'],
binascii.unhexlify(decoded['suggested_file_name']).decode(),
[BlobInfo(info['blob_num'], info['length'], info['iv'], info.get('blob_hash'))
for info in decoded['blobs']],
decoded['stream_hash'],
blob.blob_hash
)
if descriptor.get_stream_hash() != decoded['stream_hash']:
raise InvalidStreamDescriptorError("Stream hash does not match stream metadata")
return descriptor
async def from_stream_descriptor_blob(
cls, loop: asyncio.AbstractEventLoop, blob_dir: str,
blob: AbstractBlob) -> 'StreamDescriptor':
if not blob.is_readable():
raise InvalidStreamDescriptorError(
f"unreadable/missing blob: {blob.blob_hash}")
return await loop.run_in_executor(
None, cls._from_stream_descriptor_blob, loop, blob_dir, blob)