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https://github.com/python/cpython
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![Barney Gale](/assets/img/avatar_default.png)
Add support for not following symlinks in `pathlib.Path.copy()`. On Windows we add the `COPY_FILE_COPY_SYMLINK` flag is following symlinks is disabled. If the source is symlink to a directory, this call will fail with `ERROR_ACCESS_DENIED`. In this case we add `COPY_FILE_DIRECTORY` to the flags and retry. This can fail on old Windowses, which we note in the docs. No news as `copy()` was only just added.
160 lines
4.9 KiB
Python
160 lines
4.9 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 EBADF, EOPNOTSUPP, ETXTBSY, EXDEV
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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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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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flags = 0
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else:
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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 or not _is_dirlink(source):
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raise
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flags |= _winapi.COPY_FILE_DIRECTORY
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_winapi.CopyFile2(source, target, flags)
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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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