Source code for swh.core.utils

# Copyright (C) 2016-2022  The Software Heritage developers
# See the AUTHORS file at the top-level directory of this distribution
# License: GNU General Public License version 3, or any later version
# See top-level LICENSE file for more information

import codecs
from contextlib import contextmanager
import itertools
import os
import re
from typing import Iterable, Tuple, TypeVar

[docs] @contextmanager def cwd(path): """Contextually change the working directory to do thy bidding. Then gets back to the original location. """ prev_cwd = os.getcwd() os.chdir(path) try: yield finally: os.chdir(prev_cwd)
[docs] def grouper(iterable, n): """ Collect data into fixed-length size iterables. The last block might contain less elements as it will hold only the remaining number of elements. The invariant here is that the number of elements in the input iterable and the sum of the number of elements of all iterables generated from this function should be equal. If ``iterable`` is an iterable of bytes or strings that you need to join later, then :func:`iter_chunks`` is preferable, as it avoids this join by slicing directly. Args: iterable (Iterable): an iterable n (int): size of block to slice the iterable into Yields: fixed-length blocks as iterables. As mentioned, the last iterable might be less populated. """ args = [iter(iterable)] * n stop_value = object() for _data in itertools.zip_longest(*args, fillvalue=stop_value): yield (d for d in _data if d is not stop_value)
TStr = TypeVar("TStr", bytes, str)
[docs] def iter_chunks( iterable: Iterable[TStr], chunk_size: int, *, remainder: bool = False ) -> Iterable[TStr]: """ Reads ``bytes`` objects (resp. ``str`` objects) from the ``iterable``, and yields them as chunks of exactly ``chunk_size`` bytes (resp. characters). ``iterable`` is typically obtained by repeatedly calling a method like :meth:``; which does only guarantees an upper bound on the size; whereas this function returns chunks of exactly the size. Args: iterable: the input data chunk_size: the exact size of chunks to return remainder: if True, a last chunk with size strictly smaller than ``chunk_size`` may be returned, if the data stream from the ``iterable`` had a length that is not a multiple of ``chunk_size`` """ buf = None iterator = iter(iterable) while True: assert buf is None or len(buf) < chunk_size try: new_data = next(iterator) except StopIteration: if remainder and buf: yield buf # may be shorter than ``chunk_size`` return if buf: buf += new_data else: # spares a copy buf = new_data new_buf = None for i in range(0, len(buf), chunk_size): chunk = buf[i : i + chunk_size] if len(chunk) == chunk_size: yield chunk else: assert not new_buf new_buf = chunk buf = new_buf
[docs] def backslashescape_errors(exception): if isinstance(exception, UnicodeDecodeError): bad_data = exception.object[exception.start : exception.end] escaped = "".join(r"\x%02x" % x for x in bad_data) return escaped, exception.end return codecs.backslashreplace_errors(exception)
codecs.register_error("backslashescape", backslashescape_errors)
[docs] def encode_with_unescape(value): """Encode an unicode string containing \\x<hex> backslash escapes""" slices = [] start = 0 odd_backslashes = False i = 0 while i < len(value): if value[i] == "\\": odd_backslashes = not odd_backslashes else: if odd_backslashes: if value[i] != "x": raise ValueError( "invalid escape for %r at position %d" % (value, i - 1) ) slices.append( value[start : i - 1].replace("\\\\", "\\").encode("utf-8") ) slices.append(bytes.fromhex(value[i + 1 : i + 3])) odd_backslashes = False start = i = i + 3 continue i += 1 slices.append(value[start:i].replace("\\\\", "\\").encode("utf-8")) return b"".join(slices)
[docs] def decode_with_escape(value): """Decode a bytestring as utf-8, escaping the bytes of invalid utf-8 sequences as \\x<hex value>. We also escape NUL bytes as they are invalid in JSON strings. """ # escape backslashes value = value.replace(b"\\", b"\\\\") value = value.replace(b"\x00", b"\\x00") return value.decode("utf-8", "backslashescape")
[docs] def commonname(path0, path1, as_str=False): """Compute the commonname between the path0 and path1.""" return path1.split(path0)[1]
[docs] def numfile_sortkey(fname: str) -> Tuple[int, str]: """Simple function to sort filenames of the form: nnxxx.ext where nn is a number according to the numbers. Returns a tuple (order, remaining), where 'order' is the numeric (int) value extracted from the file name, and 'remaining' is the remaining part of the file name. Typically used to sort sql/nn-swh-xxx.sql files. Unmatched file names will return 999999 as order value. """ m = re.match(r"(\d*)(.*)", fname) assert m is not None num, rem = m.groups() return (int(num) if num else 999999, rem)
[docs] def basename_sortkey(fname: str) -> Tuple[int, str]: "like numfile_sortkey but on basenames" return numfile_sortkey(os.path.basename(fname))