def reconstruct_as_pointer(path, index):
"""
Reconstruct a block by reassembling a codeword it was part of and plucking it
from the result.
Args:
path(str): Path to the file the block belongs to
index(int): Index of the block
Returns:
bytes: The constructed block
Raises:
ValueError: If path is not a string or is empty or if the index is
negative
RuntimeError: If the block has never been pointed at
"""
if not isinstance(path, str) or not path:
raise ValueError("path argument must be a non empty string")
if not isinstance(index, int) or index < 0:
raise ValueError("index argument must be an integer greater or equal to 0")
metablock = get_block_metadata(path, index)
documents = find_pointing_documents(path, index)
if not documents:
raise RuntimeError("Could not find any pointing document")
with open(os.path.join(os.path.dirname(__file__), "..", "dispatcher.json"), "r") as handle:
entanglement_configuration = json.load(handle)["entanglement"]["configuration"]
source_blocks = entanglement_configuration["s"]
pointer_blocks = entanglement_configuration["t"]
offset = source_blocks + pointer_blocks
files = Files()
for document in documents:
index_to_reconstruct = get_position_in_codeword(document, metablock)
coder_client = CoderClient()
reconstructed_block = coder_client.reconstruct(document.path, [index_to_reconstruct])[index_to_reconstruct].data
elements = split_strip_header(reconstructed_block)
fragment_header = elements[2]
metadata = files.get(path)
fragment_header.metadata.index = offset + index
fragment_size = int(math.ceil(metadata.original_size / float(source_blocks)))
if (fragment_size % 2) == 1:
fragment_size += 1
fragment_header.metadata.size = fragment_size
fragment_header.metadata.orig_data_size = fragment_size * (offset)
brand_new = json.dumps(metadata.entangling_blocks) + HEADER_DELIMITER + \
str(metadata.original_size) + HEADER_DELIMITER + \
fragment_header.pack() + \
get_fragment(reconstructed_block)
brand_new = brand_new[:metablock.size]
computed_checksum = hashlib.sha256(brand_new).digest()
if computed_checksum == metablock.checksum:
return brand_new
raise RuntimeError("Could not reconstruct {:s} from pointing documents".format(metablock.key))
def test_files_get(monkeypatch):
with mock.patch("socket.gethostbyname", return_value="127.0.0.1"):
files = Files()
def mock_pipeline_get(path):
return [{
"path": "path",
"original_size": "0",
"creation_date": "2017-01-01 00:00:00.42",
"blocks": "",
"providers": "",
"block_type": BlockType.DATA.name,
"entangling_blocks": "[]"
}]
monkeypatch.setattr(FakeRedisPipeline, "execute", mock_pipeline_get)
monkeypatch.setattr(files.redis, "pipeline", get_me_a_fake_redis_pipeline)
metadata = files.get("path")
assert metadata.path == "path"
def test_files_get_raises_keyerror_when_path_not_in_files(monkeypatch):
with mock.patch("socket.gethostbyname", return_value="127.0.0.1"):
files = Files()
monkeypatch.setattr(files.redis, "pipeline", get_me_a_fake_redis_pipeline)
with pytest.raises(KeyError, match="path NonExistingKey not found"):
files.get("NonExistingKey")
def test_files_get_raises_valueerror_when_path_is_empty():
with mock.patch("socket.gethostbyname", return_value="127.0.0.1"):
files = Files()
with pytest.raises(ValueError, match="path argument must be a valid non-empty string"):
files.get("")
