How to get pointer of memoryview (and how to break python object)

memoryview_pointer.py

# How to get pointer of memoryview (and how to break python object)

from ctypes import *

PyBUF_FULL_RO = 0x0100 | 0x0010 | 0x0008 | 0x0004

class Py_buffer(Structure):
    _fields_ = [
        ("buf", c_void_p),
        ("obj", c_void_p),
        ("len", c_ssize_t),
        ("itemsize", c_ssize_t),
        ("readonly", c_int),
        ("ndim", c_int),
        ("format", c_char_p),
        ("shape", POINTER(c_ssize_t)),
        ("strides", POINTER(c_ssize_t)),
        ("suboffsets", POINTER(c_ssize_t)),
        ("internal", c_void_p),
    ]


PyObject_GetBuffer = pythonapi.PyObject_GetBuffer
PyObject_GetBuffer.argtypes = [py_object, POINTER(Py_buffer), c_int]
PyObject_GetBuffer.restype = c_int

PyBuffer_GetPointer = pythonapi.PyBuffer_GetPointer
PyBuffer_GetPointer.argtypes = [POINTER(Py_buffer), POINTER(c_ssize_t)]
PyBuffer_GetPointer.restype = c_void_p

PyBuffer_Release = pythonapi.PyBuffer_Release
PyBuffer_Release.argtypes = [POINTER(Py_buffer)]
PyBuffer_Release.restype = None


def memoryview_pointer(obj):
    buf = Py_buffer()
    PyObject_GetBuffer(obj, buf, PyBUF_FULL_RO)
    try:
        return PyBuffer_GetPointer(buf, c_ssize_t(0))
    finally:
        PyBuffer_Release(buf)

obj = b"hello"
p = memoryview_pointer(obj)
o = c_byte.from_address(p)
o.value = 32
print(obj)  # => b" ello"