Python:ctypes 指向局部变量的指针；如何确保他们不被释放？

Question

我有一些与此有些类似的代码:

def castArgToCtype(arg, ctyp):
    if issubclass(ctyp, _ctypes._Pointer): return createPtr(arg, ctyp)
    return ctyp(arg)

def createPtr(arg, ctyp):
    assert isinstance(arg, (list,tuple))
    assert issubclass(ctyp, _ctypes._Pointer)
    o = (ctyp._type_ * (len(arg) + 1))()
    for i in xrange(len(arg)):
        o[i] = castArgToCtype(arg[i], ctyp._type_)
    op = ctypes.cast(ctypes.addressof(o), ctyp)
    # TODO: what when 'o' goes out of scope and freed?
    return op

我将其称为createPtr((1,2,3), ctypes.POINTER(ctypes.c_int))。

如何确保只要 op 未释放，我在那里创建的 ctpes 数组 o 也不会被释放？

我已经看到属性op._objects，它甚至似乎是用于此目的，但它是只读的。

Answer 1

这似乎有效:

import ctypes, _ctypes

def castArgToCtype(arg, ctyp):
    if issubclass(ctyp, _ctypes._Pointer): return createPtr(arg, ctyp)
    return ctyp(arg)

def createPtr(arg, ctyp):
    assert isinstance(arg, (list,tuple))
    assert issubclass(ctyp, _ctypes._Pointer)
    o = (ctyp._type_ * (len(arg) + 1))()
    for i in xrange(len(arg)):
        o[i] = castArgToCtype(arg[i], ctyp._type_)
    op = ctypes.pointer(o)
    op = ctypes.cast(op, ctyp)
    return op

a = createPtr((1,2,3), ctypes.POINTER(ctypes.c_int))
print a, a[0], a[1], a[2], a._objects

输出:

<__main__.LP_c_int object at 0x105dc6680> 1 2 3 {'1': <__main__.c_int_Array_4 object at 0x105dc6560>, '0': {}, 4393297392: <__main__.LP_c_int_Array_4 object at 0x105dc65f0>}