Function _determine_linux_fastcopy_blocksize

Lib/shutil.py:118–135

Determine blocksize for fastcopying on Linux. Hopefully the whole file will be copied in a single call. The copying itself should be performed in a loop 'till EOF is reached (0 return) so a blocksize smaller or bigger than the actual file size should not make any difference, also in

(infd)

            raise err from None

def _determine_linux_fastcopy_blocksize(infd):
    """Determine blocksize for fastcopying on Linux.

    Hopefully the whole file will be copied in a single call.
    The copying itself should be performed in a loop 'till EOF is
    reached (0 return) so a blocksize smaller or bigger than the actual
    file size should not make any difference, also in case the file
    content changes while being copied.
    """
    try:
        blocksize = max(os.fstat(infd).st_size, 2 ** 23)  # min 8 MiB
    except OSError:
        blocksize = 2 ** 27  # 128 MiB
    # On 32-bit architectures truncate to 1 GiB to avoid OverflowError,
    # see gh-82500.
    if sys.maxsize < 2 ** 32:
        blocksize = min(blocksize, 2 ** 30)
    return blocksize

def _fastcopy_copy_file_range(fsrc, fdst):
    """Copy data from one regular mmap-like fd to another by using