cython

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__doc__ = u"""
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>>> b1 = UserBuffer1()
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>>> m1 = memoryview(b1)
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>>> m1.tolist()
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[0, 1, 2, 3, 4]
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>>> del m1, b1
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>>> b2 = UserBuffer2()
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>>> m2 = memoryview(b2)
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UserBuffer2: getbuffer
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>>> m2.tolist()
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[5, 6, 7, 8, 9]
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>>> del m2, b2
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UserBuffer2: release
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"""
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cdef extern from *:
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    ctypedef struct Py_buffer # redeclared
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    enum: PyBUF_SIMPLE
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    int PyBuffer_FillInfo(Py_buffer *, object, void *, Py_ssize_t, bint, int) except -1
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    int  PyObject_GetBuffer(object, Py_buffer *, int) except -1
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    void PyBuffer_Release(Py_buffer *)
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cdef char global_buf[5]
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global_buf[0:5] = [0, 1, 2, 3, 4]
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cdef class UserBuffer1:
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    def __getbuffer__(self, Py_buffer* view, int flags):
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        PyBuffer_FillInfo(view, None, global_buf, 5, 1, flags)
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cdef class UserBuffer2:
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    cdef char buf[5]
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    def __cinit__(self):
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        self.buf[0:5] = [5, 6, 7, 8, 9]
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    def __getbuffer__(self, Py_buffer* view, int flags):
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        print('UserBuffer2: getbuffer')
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        PyBuffer_FillInfo(view, self, self.buf, 5, 0, flags)
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    def __releasebuffer__(self, Py_buffer* view):
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        print('UserBuffer2: release')
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cdef extern from *:
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    ctypedef struct PyBuffer"Py_buffer":
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        void *buf
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        Py_ssize_t len
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        bint readonly
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cdef class _memoryview:
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    """
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    Memory
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    """
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    cdef PyBuffer view
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    def __cinit__(self, obj):
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        cdef Py_buffer *view = <Py_buffer*>&self.view
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        PyObject_GetBuffer(obj, view, PyBUF_SIMPLE)
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    def __dealloc__(self):
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        cdef Py_buffer *view = <Py_buffer*>&self.view
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        PyBuffer_Release(view )
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    def __getbuffer__(self, Py_buffer *view, int flags):
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        PyBuffer_FillInfo(view, self,
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                          self.view.buf, self.view.len,
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                          self.view.readonly, flags)
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    def tolist(self):
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        cdef char *b = <char *> self.view.buf
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        return [b[i] for i in range(self.view.len)]
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