雷电芽衣
ed34831c20
_managed_files owns the file snapshot reader and public metadata helpers used by pinned directories, durable copies, and opaque snapshots; transaction staging owns read_target and same_identity_and_contents; dead helpers removed; hook_template no longer re-exports the guard generator; mypy targets win32 so _windows_security type-checks. Claude-Session: https://claude.ai/code/session_01Agoc9bRVE9KL7mmWtey9Vq
124 lines
4.3 KiB
Python
124 lines
4.3 KiB
Python
"""Durable, identity-bound file copy and replacement primitives."""
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from __future__ import annotations
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import os
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import stat
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from typing import Any, Optional, Tuple
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from ._managed_files import same_file_metadata
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from ._pinned_directory import PinnedDirectory
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_COPY_CHUNK_BYTES = 1024 * 1024
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FileIdentity = Tuple[int, int]
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def _regular_identity(
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metadata: os.stat_result,
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expected: FileIdentity,
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path: str,
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label: str,
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) -> None:
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if (
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not stat.S_ISREG(metadata.st_mode)
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or stat.S_ISLNK(metadata.st_mode)
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or (metadata.st_dev, metadata.st_ino) != expected
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):
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raise OSError(f"{label} changed while copying: {path}")
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def copy_into_reserved(
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directory: PinnedDirectory,
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source_path: str,
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destination_path: str,
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source_identity: FileIdentity,
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destination_identity: FileIdentity,
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mode: int,
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label: str,
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maximum_bytes: Optional[int] = None,
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) -> None:
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"""Copy one physical file into an existing private reservation and fsync it."""
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source_name = directory.name_for(source_path)
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destination_name = directory.name_for(destination_path)
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read_flags = os.O_RDONLY | getattr(os, "O_BINARY", 0)
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read_flags |= getattr(os, "O_CLOEXEC", 0) | getattr(os, "O_NOFOLLOW", 0)
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write_flags = os.O_WRONLY | getattr(os, "O_BINARY", 0)
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write_flags |= getattr(os, "O_CLOEXEC", 0) | getattr(os, "O_NOFOLLOW", 0)
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source_descriptor = -1
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destination_descriptor = -1
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try:
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source_descriptor = directory.open_file(source_name, read_flags)
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before = os.fstat(source_descriptor)
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_regular_identity(before, source_identity, source_path, label)
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destination_descriptor = directory.open_file(destination_name, write_flags)
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destination = os.fstat(destination_descriptor)
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_regular_identity(
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destination,
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destination_identity,
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destination_path,
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f"{label} destination",
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)
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os.ftruncate(destination_descriptor, 0)
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total = 0
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while True:
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chunk = os.read(source_descriptor, _COPY_CHUNK_BYTES)
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if not chunk:
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break
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total += len(chunk)
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if maximum_bytes is not None and total > maximum_bytes:
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raise ValueError(
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f"{label} exceeds {maximum_bytes} bytes: {source_path}"
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)
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offset = 0
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while offset < len(chunk):
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written = os.write(destination_descriptor, chunk[offset:])
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if written <= 0:
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raise OSError(f"Copy {label} made no progress: {destination_path}")
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offset += written
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directory.chmod_descriptor(destination_descriptor, mode)
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os.fsync(destination_descriptor)
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after = os.fstat(source_descriptor)
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if not same_file_metadata(after, before):
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raise OSError(f"{label} changed while copying: {source_path}")
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finally:
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for descriptor in (destination_descriptor, source_descriptor):
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if descriptor >= 0:
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os.close(descriptor)
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visible = directory.stat_file(source_name)
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_regular_identity(visible, source_identity, source_path, label)
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directory.sync()
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def atomic_replace(
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directory: PinnedDirectory,
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source_path: str,
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destination_path: str,
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) -> None:
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"""Atomically replace one same-directory name and persist its entry."""
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if os.name == "nt":
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import ctypes as ctypes_module
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from ctypes import wintypes
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ctypes: Any = ctypes_module
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source = directory.path_for(directory.name_for(source_path))
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destination = directory.path_for(directory.name_for(destination_path))
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kernel32 = ctypes.WinDLL("kernel32", use_last_error=True)
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move = kernel32.MoveFileExW
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move.argtypes = [wintypes.LPCWSTR, wintypes.LPCWSTR, wintypes.DWORD]
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move.restype = wintypes.BOOL
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replace_existing = 0x00000001
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write_through = 0x00000008
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if not move(source, destination, replace_existing | write_through):
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error = ctypes.get_last_error()
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raise OSError(f"Atomically replace {destination}: {ctypes.WinError(error)}")
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return
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directory.replace_file(
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directory.name_for(source_path),
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directory.name_for(destination_path),
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)
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directory.sync()
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__all__ = ["atomic_replace", "copy_into_reserved"]
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