Python Ctypes结构体指针处理(函数参数,函数返回)
Python Ctypes结构体指针处理(函数参数,函数返回)
C函数需要传递结构体指针是常事,但是和Python交互就有点麻烦事了,经过研究也可以了。
<结构体指针作为函数参数>
来看下C测试例子:
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#include <stdio.h>
typedef struct StructPointerTest* StructPointer;
struct StructPointerTest{
int x;
int y;
};
void test(StructPointer p) {
p->x = 101;
p->y = 201;
}
这里test里面需要传入结构体指针,函数中的实现很简单,就是改变x 和 y 的值这个函数将被python调用。
使用Python调用时,需要模拟申明个结构体(class):
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from ctypes import *
class StructPointerTest(Structure):
_fields_ =[('x', c_int),
('y', c_int)]
Usage:
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##Structure Pointer Operation
SPTobj = pointer(StructPointerTest(1, 2))
print SPTobj
print SPTobj.contents.x
print SPTobj.contents.y
<函数返回结构体指针>
C函数测试例子改成如下:
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StructPointer test() {
StructPointer p = (StructPointer)malloc(sizeof(struct StructPointerTest));
p->x = 101;
p->y = 201;
return p;
}
Python程序处理如下:
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from ctypes import *
class StructPointer(Structure):
pass
StructPointer._fields_=[('x', c_int),
('y', c_int),
('next', POINTER(StructPointer))]
lib = cdll.LoadLibrary('./StructPointer.so')
lib.test.restype = POINTER(StructPointer)
p = lib.test()
print p.contents.x
关于resttype可以参见 Tutorial : By default functions are assumed to return the C int type. Other return types can be specified by setting the restype attribute of the function object.
作者“Crazybaby's blog”
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