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7c38097add
Add a `Path.copy()` method that copies the content of one file to another. This method is similar to `shutil.copyfile()` but differs in the following ways: - Uses `fcntl.FICLONE` where available (see GH-81338) - Uses `os.copy_file_range` where available (see GH-81340) - Uses `_winapi.CopyFile2` where available, even though this copies more metadata than the other implementations. This makes `WindowsPath.copy()` more similar to `shutil.copy2()`. The method is presently _less_ specified than the `shutil` functions to allow OS-specific optimizations that might copy more or less metadata. Incorporates code from GH-81338 and GH-93152. Co-authored-by: Eryk Sun <eryksun@gmail.com>
138 lines
4.2 KiB
Python
138 lines
4.2 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 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'):
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def copyfile(source, target):
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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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_winapi.CopyFile2(source, target, 0)
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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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