magnum-bindings/doc/python/corrade.containers.rst

..
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              Vladimír Vondruš <mosra@centrum.cz>

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..

.. doctest setup
    >>> from corrade import containers

.. py:class:: corrade.containers.ArrayView

    Provides one-dimensional tightly packed view on a memory range. Convertible
    both from and to Python objects supporting the Buffer Protocol, with one
    dimension and stride of :py:`1`. See `StridedArrayView1D` and others for
    more generic views. `ArrayView` is immutable, see `MutableArrayView` for
    the mutable alterantive. All slicing operations are supported, specifying a
    non-trivial stride will return `StridedArrayView1D` instead of `ArrayView`.
    Example usage:

    .. code:: pycon

        >>> a = b'hello'
        >>> b = containers.ArrayView(a)
        >>> b[2]
        'l'
        >>> bytes(b[1:4])
        b'ell'

    `Memory ownership and reference counting`_
    ==========================================

    Unlike in C++, the view keeps a reference to the original memory owner
    object, meaning that calling :py:`del` on the original object will *not*
    invalidate the view. Slicing a view creates a new view referencing the same
    original object, without any dependency on the previous view.

    .. code:: pycon

        >>> b.obj is a
        True
        >>> b[1:4].obj is a
        True

    .. block-danger:: Pybind11 Buffer Protocol issues

        Currently, due to how buffer protocol is exposed in pybind11, there are
        several issues with converting array views from and to buffer objects:

        -   readonly property is not preserved when converting an ArrayView
            to Python `memoryview`
        -   subsequent slicing and view conversion keeps reference to the
            previous view instance instead of just to the original object,
            creating unnecesarily long GC chains

    `Comparison to Python's memoryview`_
    ====================================

    The `ArrayView` class is equivalent to one-dimensional `memoryview` with a
    stride of :py:`1`. For multiple dimensions and non-trivial strides,
    `StridedArrayView1D` and friends provide a superset of `memoryview`
    features.

.. py:class:: corrade.containers.MutableArrayView

    Equivalent to `ArrayView`, but implementing `__setitem__()` as well.

.. py:class:: corrade.containers.StridedArrayView1D

    Provides one-dimensional read-only view on a memory range with custom
    stride values. See `StridedArrayView2D`, `StridedArrayView3D`,
    `MutableStridedArrayView1D` and others for multi-dimensional and mutable
    equivalents.

    `Comparison to Python's memoryview`_
    ====================================

    The `StridedArrayView1D` and its multi-dimensional variants are equivalent
    to any `memoryview`, but additionally supporting multi-dimensional slicing
    as well (which raises `NotImplementedError` in Py3.7 `memoryview`).

.. py:class:: corrade.containers.MutableStridedArrayView1D

    Equivalent to `StridedArrayView1D`, but implementing `__setitem__()` as
    well.

.. py:class:: corrade.containers.StridedArrayView2D

    See `StridedArrayView1D` for more information.

.. py:class:: corrade.containers.MutableStridedArrayView2D

    See `StridedArrayView1D` and `MutableStridedArrayView1D` for more
    information.

.. py:class:: corrade.containers.StridedArrayView3D

    See `StridedArrayView1D` for more information.

.. py:class:: corrade.containers.MutableStridedArrayView3D

    See `StridedArrayView1D` and `MutableStridedArrayView1D` for more
    information.