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88fc0655d4
Add *preserve_metadata* keyword-only argument to `pathlib.Path.copy()`, defaulting to false. When set to true, we copy timestamps, permissions, extended attributes and flags where available, like `shutil.copystat()`. The argument has no effect on Windows, where metadata is always copied. Internally (in the pathlib ABCs), path types gain `_readable_metadata` and `_writable_metadata` attributes. These sets of strings describe what kinds of metadata can be retrieved and stored. We take an intersection of `source._readable_metadata` and `target._writable_metadata` to minimise reads/writes. A new `_read_metadata()` method accepts a set of metadata keys and returns a dict with those keys, and a new `_write_metadata()` method accepts a dict of metadata. We *might* make these public in future, but it's hard to justify while the ABCs are still private.
278 lines
9.1 KiB
Python
278 lines
9.1 KiB
Python
"""
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Low-level OS functionality wrappers used by pathlib.
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"""
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from errno import *
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import os
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import stat
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import sys
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try:
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import fcntl
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except ImportError:
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fcntl = None
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try:
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import posix
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except ImportError:
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posix = None
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try:
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import _winapi
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except ImportError:
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_winapi = None
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__all__ = ["UnsupportedOperation"]
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class UnsupportedOperation(NotImplementedError):
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"""An exception that is raised when an unsupported operation is attempted.
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"""
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pass
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def get_copy_blocksize(infd):
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"""Determine blocksize for fastcopying on Linux.
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Hopefully the whole file will be copied in a single call.
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The copying itself should be performed in a loop 'till EOF is
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reached (0 return) so a blocksize smaller or bigger than the actual
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file size should not make any difference, also in case the file
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content changes while being copied.
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"""
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try:
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blocksize = max(os.fstat(infd).st_size, 2 ** 23) # min 8 MiB
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except OSError:
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blocksize = 2 ** 27 # 128 MiB
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# On 32-bit architectures truncate to 1 GiB to avoid OverflowError,
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# see gh-82500.
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if sys.maxsize < 2 ** 32:
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blocksize = min(blocksize, 2 ** 30)
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return blocksize
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if fcntl and hasattr(fcntl, 'FICLONE'):
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def clonefd(source_fd, target_fd):
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"""
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Perform a lightweight copy of two files, where the data blocks are
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copied only when modified. This is known as Copy on Write (CoW),
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instantaneous copy or reflink.
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"""
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fcntl.ioctl(target_fd, fcntl.FICLONE, source_fd)
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else:
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clonefd = None
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if posix and hasattr(posix, '_fcopyfile'):
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def copyfd(source_fd, target_fd):
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"""
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Copy a regular file content using high-performance fcopyfile(3)
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syscall (macOS).
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"""
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posix._fcopyfile(source_fd, target_fd, posix._COPYFILE_DATA)
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elif hasattr(os, 'copy_file_range'):
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def copyfd(source_fd, target_fd):
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"""
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Copy data from one regular mmap-like fd to another by using a
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high-performance copy_file_range(2) syscall that gives filesystems
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an opportunity to implement the use of reflinks or server-side
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copy.
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This should work on Linux >= 4.5 only.
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"""
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blocksize = get_copy_blocksize(source_fd)
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offset = 0
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while True:
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sent = os.copy_file_range(source_fd, target_fd, blocksize,
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offset_dst=offset)
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if sent == 0:
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break # EOF
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offset += sent
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elif hasattr(os, 'sendfile'):
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def copyfd(source_fd, target_fd):
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"""Copy data from one regular mmap-like fd to another by using
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high-performance sendfile(2) syscall.
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This should work on Linux >= 2.6.33 only.
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"""
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blocksize = get_copy_blocksize(source_fd)
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offset = 0
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while True:
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sent = os.sendfile(target_fd, source_fd, offset, blocksize)
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if sent == 0:
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break # EOF
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offset += sent
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else:
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copyfd = None
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if _winapi and hasattr(_winapi, 'CopyFile2') and hasattr(os.stat_result, 'st_file_attributes'):
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def _is_dirlink(path):
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try:
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st = os.lstat(path)
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except (OSError, ValueError):
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return False
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return (st.st_file_attributes & stat.FILE_ATTRIBUTE_DIRECTORY and
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st.st_reparse_tag == stat.IO_REPARSE_TAG_SYMLINK)
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def copyfile(source, target, follow_symlinks):
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"""
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Copy from one file to another using CopyFile2 (Windows only).
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"""
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if follow_symlinks:
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_winapi.CopyFile2(source, target, 0)
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else:
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# Use COPY_FILE_COPY_SYMLINK to copy a file symlink.
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flags = _winapi.COPY_FILE_COPY_SYMLINK
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try:
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_winapi.CopyFile2(source, target, flags)
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return
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except OSError as err:
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# Check for ERROR_ACCESS_DENIED
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if err.winerror == 5 and _is_dirlink(source):
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pass
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else:
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raise
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# Add COPY_FILE_DIRECTORY to copy a directory symlink.
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flags |= _winapi.COPY_FILE_DIRECTORY
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try:
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_winapi.CopyFile2(source, target, flags)
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except OSError as err:
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# Check for ERROR_INVALID_PARAMETER
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if err.winerror == 87:
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raise UnsupportedOperation(err) from None
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else:
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raise
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else:
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copyfile = None
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def copyfileobj(source_f, target_f):
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"""
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Copy data from file-like object source_f to file-like object target_f.
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"""
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try:
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source_fd = source_f.fileno()
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target_fd = target_f.fileno()
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except Exception:
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pass # Fall through to generic code.
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else:
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try:
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# Use OS copy-on-write where available.
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if clonefd:
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try:
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clonefd(source_fd, target_fd)
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return
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except OSError as err:
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if err.errno not in (EBADF, EOPNOTSUPP, ETXTBSY, EXDEV):
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raise err
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# Use OS copy where available.
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if copyfd:
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copyfd(source_fd, target_fd)
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return
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except OSError as err:
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# Produce more useful error messages.
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err.filename = source_f.name
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err.filename2 = target_f.name
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raise err
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# Last resort: copy with fileobj read() and write().
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read_source = source_f.read
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write_target = target_f.write
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while buf := read_source(1024 * 1024):
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write_target(buf)
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# Kinds of metadata supported by the operating system.
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file_metadata_keys = {'mode', 'times_ns'}
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if hasattr(os.stat_result, 'st_flags'):
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file_metadata_keys.add('flags')
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if hasattr(os, 'listxattr'):
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file_metadata_keys.add('xattrs')
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file_metadata_keys = frozenset(file_metadata_keys)
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def read_file_metadata(path, keys=None, *, follow_symlinks=True):
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"""
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Returns local path metadata as a dict with string keys.
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"""
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if keys is None:
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keys = file_metadata_keys
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assert keys.issubset(file_metadata_keys)
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result = {}
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for key in keys:
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if key == 'xattrs':
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try:
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result['xattrs'] = [
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(attr, os.getxattr(path, attr, follow_symlinks=follow_symlinks))
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for attr in os.listxattr(path, follow_symlinks=follow_symlinks)]
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except OSError as err:
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if err.errno not in (EPERM, ENOTSUP, ENODATA, EINVAL, EACCES):
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raise
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continue
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st = os.stat(path, follow_symlinks=follow_symlinks)
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if key == 'mode':
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result['mode'] = stat.S_IMODE(st.st_mode)
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elif key == 'times_ns':
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result['times_ns'] = st.st_atime_ns, st.st_mtime_ns
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elif key == 'flags':
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result['flags'] = st.st_flags
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return result
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def write_file_metadata(path, metadata, *, follow_symlinks=True):
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"""
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Sets local path metadata from the given dict with string keys.
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"""
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assert frozenset(metadata.keys()).issubset(file_metadata_keys)
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def _nop(*args, ns=None, follow_symlinks=None):
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pass
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if follow_symlinks:
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# use the real function if it exists
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def lookup(name):
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return getattr(os, name, _nop)
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else:
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# use the real function only if it exists
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# *and* it supports follow_symlinks
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def lookup(name):
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fn = getattr(os, name, _nop)
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if fn in os.supports_follow_symlinks:
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return fn
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return _nop
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times_ns = metadata.get('times_ns')
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if times_ns is not None:
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lookup("utime")(path, ns=times_ns, follow_symlinks=follow_symlinks)
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# We must copy extended attributes before the file is (potentially)
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# chmod()'ed read-only, otherwise setxattr() will error with -EACCES.
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xattrs = metadata.get('xattrs')
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if xattrs is not None:
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for attr, value in xattrs:
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try:
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os.setxattr(path, attr, value, follow_symlinks=follow_symlinks)
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except OSError as e:
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if e.errno not in (EPERM, ENOTSUP, ENODATA, EINVAL, EACCES):
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raise
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mode = metadata.get('mode')
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if mode is not None:
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try:
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lookup("chmod")(path, mode, follow_symlinks=follow_symlinks)
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except NotImplementedError:
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# if we got a NotImplementedError, it's because
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# * follow_symlinks=False,
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# * lchown() is unavailable, and
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# * either
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# * fchownat() is unavailable or
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# * fchownat() doesn't implement AT_SYMLINK_NOFOLLOW.
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# (it returned ENOSUP.)
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# therefore we're out of options--we simply cannot chown the
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# symlink. give up, suppress the error.
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# (which is what shutil always did in this circumstance.)
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pass
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flags = metadata.get('flags')
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if flags is not None:
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try:
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lookup("chflags")(path, flags, follow_symlinks=follow_symlinks)
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except OSError as why:
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if why.errno not in (EOPNOTSUPP, ENOTSUP):
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raise
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