cython

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from cython.cimports.libc.stdlib import malloc
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from cython.cimports.libc.string import strcpy, strlen
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hello_world = cython.declare(cython.p_char, 'hello world')
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n = cython.declare(cython.Py_ssize_t, strlen(hello_world))
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@cython.cfunc
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def c_call_returning_a_c_string() -> cython.p_char:
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    c_string: cython.p_char = cython.cast(cython.p_char, malloc(
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        (n + 1) * cython.sizeof(cython.char)))
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    if not c_string:
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        return cython.NULL  # malloc failed
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    strcpy(c_string, hello_world)
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    return c_string
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@cython.cfunc
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def get_a_c_string(c_string_ptr: cython.pp_char,
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                   length: cython.pointer(cython.Py_ssize_t)) -> cython.int:
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    c_string_ptr[0] = cython.cast(cython.p_char, malloc(
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        (n + 1) * cython.sizeof(cython.char)))
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    if not c_string_ptr[0]:
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        return -1  # malloc failed
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    strcpy(c_string_ptr[0], hello_world)
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    length[0] = n
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    return 0
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