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""" |
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Compression-aware reading and writing of files. |
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""" |
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from __future__ import annotations |
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import abc |
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import bz2 |
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import gzip |
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import lzma |
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import os |
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from collections.abc import Callable |
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from dataclasses import dataclass |
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from datetime import datetime |
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from pathlib import Path, PurePath |
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from typing import Any, Self |
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import brotli |
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import lz4.frame |
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import snappy |
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import zstandard |
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from pocketutils import WritePermissionsError |
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PathLike = str | PurePath |
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@dataclass(frozen=True) |
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class Compression(metaclass=abc.ABCMeta): |
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name: str |
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suffixes: set[str] |
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compress: Callable[[bytes], bytes] |
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decompress: Callable[[bytes], bytes] |
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def identity(x): |
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return x |
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@dataclass(frozen=True) |
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class CompressionSet: |
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mapping: dict[str, Compression] |
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@classmethod |
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def empty(cls) -> Self: |
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return CompressionSet({"": Compression("", set(), identity, identity)}) |
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def __add__(self, fmt: Compression): |
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new = {fmt.name: fmt} | {s: fmt for s in fmt.suffixes} |
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already = {v for k, v in self.mapping.items() if k in new} |
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if len(already) > 1 or len(already) == 1 and already != {fmt}: |
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raise ValueError(f"Keys from {fmt} already mapped to {already}") |
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return CompressionSet(self.mapping | new) |
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def __sub__(self, fmt: Compression): |
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return CompressionSet( |
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{k: v for k, v in self.mapping.items() if k != fmt.name and k not in fmt.suffixes} |
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) |
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def __or__(self, fmt: CompressionSet): |
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return CompressionSet(self.mapping | fmt.mapping) |
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def __getitem__(self, t: Compression | str) -> Compression: |
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""" |
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Returns a FileFormat from a name (e.g. "gz" or "gzip"). |
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Case-insensitive. |
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Example: |
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``Compression.of("gzip").suffix # ".gz"`` |
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""" |
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if isinstance(t, Compression): |
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return t |
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return self.mapping[t] |
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def guess(self, path: PathLike) -> Compression: |
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if "." not in path.name: |
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return self[""] |
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try: |
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return self[path.suffix] |
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except KeyError: |
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return self[""] |
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82
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83
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COMPRESSIONS = ( |
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CompressionSet.empty() |
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+ Compression("gzip", {".gz", ".gzip"}, gzip.compress, gzip.decompress) |
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+ Compression("brotli", {".bro", ".brotli"}, brotli.compress, brotli.decompress) |
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+ Compression("zstandard", {".zst", ".zstd"}, zstandard.compress, zstandard.decompress) |
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+ Compression("lz4", {".lz4"}, lz4.frame.compress, lz4.frame.decompress) |
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+ Compression("snappy", {".snappy"}, snappy.compress, snappy.decompress) |
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+ Compression("bzip2", {".bz2", ".bzip2"}, bz2.compress, bz2.decompress) |
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+ Compression("xz", {".xz"}, lzma.compress, lzma.decompress) |
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) |
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95
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@dataclass(slots=True, frozen=True) |
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96
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class SmartIo: |
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@classmethod |
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def write( |
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cls, data: Any, path: PathLike, *, atomic: bool = False, mkdirs: bool = False |
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) -> None: |
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path = Path(path) |
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compressed = COMPRESSIONS.guess(path).compress(data) |
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if path.exists() and not path.is_file(): |
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raise WritePermissionsError(f"Path {path} is not a file", path=path) |
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if path.exists() and not os.access(path, os.W_OK): |
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raise WritePermissionsError(f"Cannot write to {path}", path=path) |
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if mkdirs: |
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path.parent.mkdir(parents=True, exist_ok=True) |
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if atomic: |
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tmp = cls.tmp_path(path) |
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path.write_bytes(compressed) |
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tmp.rename(path) |
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else: |
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path.write_bytes(compressed) |
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115
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116
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@classmethod |
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def read_text(cls, path: PathLike) -> str: |
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118
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""" |
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119
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Similar to :meth:`read_bytes`, but then converts to UTF-8. |
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""" |
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return cls.read_bytes(path).decode(encoding="utf-8") |
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123
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@classmethod |
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def read_bytes(cls, path: PathLike) -> bytes: |
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""" |
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Reads, decompressing according to the filename suffix. |
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""" |
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data = Path(path).read_bytes() |
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return COMPRESSIONS.guess(path).decompress(data) |
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@classmethod |
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def tmp_path(cls, path: PathLike, extra: str = "tmp") -> Path: |
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now = datetime.now().isoformat(timespec="microsecond").replace(":", "").replace("-", "") |
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path = Path(path) |
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suffix = "".join(path.suffixes) |
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return path.parent / f".part_{extra}.{now}{suffix}" |
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138
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139
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__all__ = ["Compression", "CompressionSet", "COMPRESSIONS", "SmartIo"] |
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dmyersturnbull /
pocketutils
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