pool.py 文件源码

def _reduce_memmap_backed(a, m):
    """Pickling reduction for memmap backed arrays

    a is expected to be an instance of np.ndarray (or np.memmap)
    m is expected to be an instance of np.memmap on the top of the ``base``
    attribute ancestry of a. ``m.base`` should be the real python mmap object.
    """
    # offset that comes from the striding differences between a and m
    a_start, a_end = np.byte_bounds(a)
    m_start = np.byte_bounds(m)[0]
    offset = a_start - m_start

    # offset from the backing memmap
    offset += m.offset

    if m.flags['F_CONTIGUOUS']:
        order = 'F'
    else:
        # The backing memmap buffer is necessarily contiguous hence C if not
        # Fortran
        order = 'C'

    if a.flags['F_CONTIGUOUS'] or a.flags['C_CONTIGUOUS']:
        # If the array is a contiguous view, no need to pass the strides
        strides = None
        total_buffer_len = None
    else:
        # Compute the total number of items to map from which the strided
        # view will be extracted.
        strides = a.strides
        total_buffer_len = (a_end - a_start) // a.itemsize
    return (_strided_from_memmap,
            (m.filename, a.dtype, m.mode, offset, order, a.shape, strides,
             total_buffer_len))