Cython如何使用memcpy从numpy缓冲区复制到C结构？

# setup.py
from setuptools import setup
from Cython.Build import cythonize
import numpy as np

setup(
    ext_modules=cythonize("example.pyx"),
    include_dirs=[np.get_include()]
)

# example.pyx
import numpy as np
cimport numpy as np

cdef extern from "string.h":
    void* memcpy(void *dest, const void *src, size_t n)

cdef class MyStruct:
    cdef int a
    cdef float b

def copy_from_numpy(np.ndarray[np.float32_t, ndim=1] arr):
    cdef MyStruct my_struct
    cdef np.float32_t* src_ptr = <np.float32_t*> arr.data
    cdef float* dest_ptr = &my_struct.b
    memcpy(dest_ptr, src_ptr, arr.size * sizeof(np.float32_t))
    return my_struct