Python ctypes返回函数指针数组 [英] Python ctypes to return an array of function pointers
问题描述
我正在使用一个包含单个调用的.dll，该调用返回一个函数指针数组。 GetMyApi（）返回指向结构的指针，该结构是函数指针的数组。函数本身具有不同的单独输入和输出。到目前为止，我已经尝试过：
I am working with a .dll that contains a single call which returns an array of function pointers. GetMyApi() returns a pointer to a struct, which is an array of function pointers. The functions themselves have different individual inputs and outputs. What I have tried so far:
我无法轻易更改的C代码：
-
C中的代码：
Code in C :
typedef struct My_Api_V2
{
int (__cdecl *IsValidInt)(int i);
int (__cdecl *InvalidInt)();
int (__cdecl *IsValidSize)(size_t i);
} my_Api_V2;
const my_Api_V2* GetMyApi(int version); // This function is accessed from DLL
Python工作量访问此函数：
Python effort:
from ctypes import *
my_dll = cdll.LoadLibrary(path_to_my_dll)
my_api = my_dll.GetMyApi
my_api.argtypes[c_int] #version number
my_api.restypes = c_void_p
firstfuncptr = my_api(2)
firstfunc = prototype(firstfuncptr)
firstfunc.argtypes[c_int]
firstfunc.restypes = c_int
test = firstfunc(23)
至此，我只是想让功能列表的第一个功能恢复工作。
At this point, I am just trying to get the first function of the function list returned to work. Any help pointing me in better direction is appreciated.
推荐答案
事情并不像人们想到的1 st那样容易一目了然。我将发布一个虚拟示例，该示例恰好包含使用 .dll s（ .so s）中的函数的2种方式（如 [Python 3.Docs]：ctypes-Python的外部函数库 ）。
Things are not as easy as one might think at 1st glance. I'm going to post a dummy example that happens to contain the 2 ways of working with functions from .dlls (.sos) (as explained in [Python 3.Docs]: ctypes - A foreign function library for Python).
dll00.c ：
#include <stdio.h>
#if defined(_WIN32)
# define DLL00_EXPORT __declspec(dllexport)
# pragma warning(disable: 4477) // !!! Just to avoid having additional code (macro for size_t), do NOT do this !!!
#else
# define DLL00_EXPORT
#endif
#define PRINT_MSG_0() printf(" [%s] (%d) - [%s]\n", __FILE__, __LINE__, __FUNCTION__)
#define PRINT_MSG_1I(ARG0) printf(" [%s] (%d) - [%s]: ARG0: %d\n", __FILE__, __LINE__, __FUNCTION__, ARG0)
static int IsValidInt(int i) {
PRINT_MSG_1I(i);
return -i;
}
static int InvalidInt() {
PRINT_MSG_0();
return 0;
}
static int IsValidSize (size_t i) {
PRINT_MSG_1I(i);
return -i;
}
typedef struct DllInterfaceV2Struct {
int (__cdecl *IsValidIntFuncPtr)(int i);
int (__cdecl *InvalidIntFuncPtr)();
int (__cdecl *IsValidSizeFuncPtr)(size_t i);
} DllInterfaceV2;
static DllInterfaceV2 intfV2 = { IsValidInt, InvalidInt, IsValidSize };
#if defined(__cplusplus)
extern "C" {
#endif
DLL00_EXPORT const DllInterfaceV2 *GetInterfaceV2(int version);
#if defined(__cplusplus)
}
#endif
DLL_EXPORT const DllInterfaceV2 *GetInterfaceV2(int version) {
if (version == 2) {
return &intfV2;
} else {
return NULL;
}
}
code00.py ：
#!/usr/bin/env python3
import sys
import ctypes
DLL_NAME = "test00.dll"
DLL_FUNC_NAME = "GetInterfaceV2"
# "Define" the Python counterparts for C stuff in order to be able to use it
IsValidIntFuncPtr = ctypes.CFUNCTYPE(ctypes.c_int, ctypes.c_int)
InvalidIntFuncPtr = ctypes.CFUNCTYPE(ctypes.c_int)
IsValidSizeFuncPtr = ctypes.CFUNCTYPE(ctypes.c_int, ctypes.c_size_t)
class DllInterfaceV2(ctypes.Structure):
_fields_ = [
("is_valid_int", IsValidIntFuncPtr),
("invalid_int", InvalidIntFuncPtr),
("is_valid_size", IsValidSizeFuncPtr)
]
# Now, play with C stuff
def test_interface_ptr(intf_ptr):
print("Testing returned interface: {:}\n".format(intf_ptr))
if not intf_ptr:
print(" NULL pointer returned from C\n")
return
intf = intf_ptr.contents # Dereference the pointer
res = intf.is_valid_int(-2718281)
print(" `is_valid_int` member returned: {:d}\n".format(res))
res = intf.invalid_int()
print(" `invalid_int` member returned: {:d}\n".format(res))
res = intf.is_valid_size(3141592)
print(" `is_valid_size` member returned: {:d}\n\n".format(res))
def main():
test_dll = ctypes.CDLL(DLL_NAME)
get_interface_v2_func = getattr(test_dll, DLL_FUNC_NAME) # Or simpler: test_dll.GetInterfaceV2
get_interface_v2_func.argtypes = [ctypes.c_int]
get_interface_v2_func.restype = ctypes.POINTER(DllInterfaceV2)
pintf0 = get_interface_v2_func(0)
test_interface_ptr(pintf0)
pintf2 = get_interface_v2_func(2)
test_interface_ptr(pintf2)
if __name__ == "__main__":
print("Python {:s} on {:s}\n".format(sys.version, sys.platform))
main()
注释：
-
C 部分：
- 我必须添加一些伪代码才能测试和说明行为
- 尽管您提到它不可修改，但我更改了内容（主要是命名/编码样式，...）：
- 两个字母都用+ 下划线看起来不太好（至少对我来说）
- my （或其任何变体）在（函数，类或其他任何名称）的名字简直就是我的脑子
- I had to add some dummy code in order to test and illustrate the behavior
- Although you mentioned that it's not modifiable, I changed stuff (mostly naming / coding style, ...):
- Both letter cases + underscores don't look nice (at least to me)
- "my" (or any of its variants) in (functions, classes, or any other) names simply scratches my brain
Python 部分：
- 正如我在评论中所述， C 东西必须在 Python
- As I stated in my comment, the C stuff would have to be "duplicated" in Python
中复制，尽管我认为这是主要设计缺陷，为了使问题尽可能接近问题，我只是遵循了它（ GetInterfaceV2 （ V2 部分）考虑到其arg（ version ）毫无意义）
Although I consider this a major design flaw, in order to keep things as close as possible to the question, I simply followed it (GetInterfaceV2 (the V2 part) doesn't make any sense considering its arg (version))
- 我个人的观点（尽管没有所有上下文）是（为了确保可伸缩性），该函数应返回通用结构，并带有一个附加字段（例如版本），可以由客户端应用检查。
- My personal opinion (without having all the context, though) is that (in order to ensure scalability) the function should return a generic structure, with an additional field (e.g. version) that could be checked by client apps.
输出：
(py35x64_test) e:\Work\Dev\StackOverflow\q051507196>"c:\Install\x86\Microsoft\Visual Studio Community\2015\vc\vcvarsall.bat" x64 (py35x64_test) e:\Work\Dev\StackOverflow\q051507196>dir /b code00.py dll00.c (py35x64_test) e:\Work\Dev\StackOverflow\q051507196>cl /nologo dll00.c /link /DLL /OUT:test00.dll dll00.c Creating library test00.lib and object test00.exp (py35x64_test) e:\Work\Dev\StackOverflow\q051507196>dir /b code00.py dll00.c dll00.obj test00.dll test00.exp test00.lib (py35x64_test) e:\Work\Dev\StackOverflow\q051507196>"e:\Work\Dev\VEnvs\py35x64_test\Scripts\python.exe" code00.py Python 3.5.4 (v3.5.4:3f56838, Aug 8 2017, 02:17:05) [MSC v.1900 64 bit (AMD64)] on win32 Testing returned interface: <__main__.LP_DllInterfaceV2 object at 0x00000219984EBAC8> NULL pointer returned from C Testing returned interface: <__main__.LP_DllInterfaceV2 object at 0x00000219984EBB48> [dll00.c] (16) - [IsValidInt]: ARG0: -2718281 `is_valid_int` member returned: 2718281 [dll00.c] (22) - [InvalidInt] `invalid_int` member returned: 0 [dll00.c] (28) - [IsValidSize]: ARG0: 3141592 `is_valid_size` member returned: -3141592
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