2024-heraklion-testing-debu.../hands_on/bug_hunt/file_datastore.py

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2024-08-26 13:54:13 +02:00
import os
class FileDatastore:
"""Datastore based on a regular file system.
Parameters
----------
base_path: str
Filesystem path at which the data store is based.
"""
def __init__(self, base_path):
if not os.path.exists(base_path):
raise FileNotFoundError(f'Base path {base_path} does not exist')
if not os.path.isdir(base_path):
raise NotADirectoryError(f'Base path {base_path} exists but is not a directory')
self.base_path = base_path
def open(self, path, mode):
""" Open a file-like object
Parameters
----------
path: str
Path relative to the root of the data store.
mode: str
Specifies the mode in which the file is opened.
Returns
-------
IO[Any]
An open file-like object.
"""
path = os.path.join(self.base_path, path)
return open(path, mode)
def read(self, path):
""" Read a sequence of bytes from the data store.
Parameters
----------
path: str
Path relative to the root of the data store.
Returns
-------
bytes
The sequence of bytes read from `path`.
"""
with self.open(path, 'rb') as f:
data = f.read()
return data
def write(self, path, data) -> None:
""" Write a sequence of bytes to the data store.
`path` contains the path relative to the root of the data store, including the name
of the file to be created. If a file already exists at `path`, it is overwritten.
Intermediate directories that do not exist will be created.
Parameters
----------
path: str
Path relative to the root of the data store.
data: bytes
Sequence of bytes to write at `path`.
"""
path = os.path.join(self.base_path, path)
self.makedirs(os.path.dirname(path))
with self.open(path, 'wb') as f:
f.write(data)
def exists(self, path):
""" Returns True if the file exists.
Parameters
----------
path: str
Path relative to the root of the data store.
Returns
-------
bool
True if the file exists, false otherwise
"""
complete_path = os.path.join(self.base_path, path)
return os.path.exists(complete_path)
def makedirs(self, path):
""" Creates the specified directory if needed.
If the directories already exist, the method does not do anything.
Parameters
----------
path: str
Path relative to the root of the data store.
"""
complete_path = os.path.join(self.base_path, path)
os.makedirs(complete_path, exist_ok=True)
if __name__ == '__main__':
data = b'A test! 012'
datastore = FileDatastore(base_path='./datastore')
datastore.write('a/mydata.bin', data)
# This should pass!
# The code works correctly if `base_path` is an absolute path :-(
assert os.path.exists('./datastore/a/mydata.bin')