Function _copyfileobj_readinto

Lib/shutil.py:229–247

readinto()/memoryview() based variant of copyfileobj(). *fsrc* must support readinto() method and both files must be open in binary mode.

(fsrc, fdst, length=COPY_BUFSIZE)

            offset += sent

def _copyfileobj_readinto(fsrc, fdst, length=COPY_BUFSIZE):
    """readinto()/memoryview() based variant of copyfileobj().
    *fsrc* must support readinto() method and both files must be
    open in binary mode.
    """
    # Localize variable access to minimize overhead.
    fsrc_readinto = fsrc.readinto
    fdst_write = fdst.write
    with memoryview(bytearray(length)) as mv:
        while True:
            n = fsrc_readinto(mv)
            if not n:
                break
            elif n < length:
                with mv[:n] as smv:
                    fdst_write(smv)
                break
            else:
                fdst_write(mv)

def copyfileobj(fsrc, fdst, length=0):
    """copy data from file-like object fsrc to file-like object fdst"""