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utils.py
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utils.py
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# Copyright (C) 2019-2020 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
from datetime import datetime, timezone
import re
from typing import Callable, Dict, Optional, Tuple, TypeVar
from swh.model.hashutil import DEFAULT_ALGORITHMS, hash_to_bytes, hash_to_hex
def now() -> datetime:
return datetime.now(tz=timezone.utc)
T1 = TypeVar("T1")
T2 = TypeVar("T2")
def map_optional(f: Callable[[T1], T2], x: Optional[T1]) -> Optional[T2]:
if x is None:
return None
else:
return f(x)
def _is_power_of_two(n: int) -> bool:
return n > 0 and n & (n - 1) == 0
def get_partition_bounds_bytes(
i: int, n: int, nb_bytes: int
) -> Tuple[bytes, Optional[bytes]]:
r"""Splits the range [0; 2^(nb_bytes*8)) into n same-length intervals,
and returns the boundaries of this interval (both inclusive); or None
as upper bound, if this is the last partition
n must be a power of 2.
>>> get_partition_bounds_bytes(0, 16, 2) == (b'\x00\x00', b'\x10\x00')
True
>>> get_partition_bounds_bytes(1, 16, 2) == (b'\x10\x00', b'\x20\x00')
True
>>> get_partition_bounds_bytes(14, 16, 2) == (b'\xe0\x00', b'\xf0\x00')
True
>>> get_partition_bounds_bytes(15, 16, 2) == (b'\xf0\x00', None)
True
"""
if not _is_power_of_two(n):
raise ValueError("number of partitions must be a power of two")
if not 0 <= i < n:
raise ValueError(
"partition index must be between 0 and the number of partitions."
)
space_size = 1 << (nb_bytes * 8)
partition_size = space_size // n
start = (partition_size * i).to_bytes(nb_bytes, "big")
end = None if i == n - 1 else (partition_size * (i + 1)).to_bytes(nb_bytes, "big")
return (start, end)
def extract_collision_hash(error_message: str) -> Optional[Tuple[str, bytes]]:
"""Utilities to extract the hash information from a hash collision error.
Hash collision error message are of the form:
'Key (<hash-type>)=(<double-escaped-hash) already exists.'
for example:
'Key (sha1)=(\\x34973274ccef6ab4dfaaf86599792fa9c3fe4689) already exists.'
Return:
A formatted string
"""
pattern = r"\w* \((?P<type>[^)]+)\)=\(\\x(?P<id>[a-f0-9]+)\) \w*"
result = re.match(pattern, error_message)
if result:
hash_type = result.group("type")
hash_id = result.group("id")
return hash_type, hash_to_bytes(hash_id)
return None
def content_hex_hashes(content: Dict[str, bytes]) -> Dict[str, str]:
"""Convert bytes hashes into hex hashes.
"""
return {algo: hash_to_hex(content[algo]) for algo in DEFAULT_ALGORITHMS}
def content_bytes_hashes(content: Dict[str, str]) -> Dict[str, bytes]:
"""Convert bytes hashes into hex hashes.
"""
return {algo: hash_to_bytes(content[algo]) for algo in DEFAULT_ALGORITHMS}
def remove_keys(d: Dict[T1, T2], keys: Tuple[T1, ...]) -> Dict[T1, T2]:
"""Returns a copy of ``d`` minus the given keys."""
return {k: v for (k, v) in d.items() if k not in keys}
def round_to_milliseconds(date):
"""Round datetime to milliseconds before insertion, so equality doesn't fail after a
round-trip through a DB (eg. Cassandra)
"""
return date.replace(microsecond=(date.microsecond // 1000) * 1000)

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