使用Python ctypes的dll的工作 - 結構OUT參數

Question

在DLL中我有以下結構

typedef struct USMC_Devices_st{ 
DWORD NOD;   // Number of the devices ready to work 

char **Serial;  // Array of 16 byte ASCII strings 
char **Version;  // Array of 4 byte ASCII strings 
} USMC_Devices;   // Structure representing connected devices 

的頭文件，我想調用DLL函數： DWORD USMC_Init（USMC_Devices & STR） ;

我試着用這樣的：

class USMCDevices(Structure): 
    _fields_ = [("NOD", c_long), 
      ("Serial", c_char_p), 
      ("Version", c_char_p)] 

usmc = cdll.USMCDLL #this is the dll file 
init = usmc.USMC_Init 
init.restype = c_int32; # return type 
init.argtypes = [USMCDevices]; # argument 
dev = USMCDevices() 
init(dev) 

我這裏得到一個錯誤。我想問題是「串行」和「版本」，這兩個數組都對應於NOD（設備數量）。

任何想法如何解決這個問題？

我真的很感謝你的幫助！

Answer 1

對於char **指針使用POINTER(c_char_p)。索引Serial或Version爲給定的以null結尾的字符串創建一個Python字符串。請注意，超出NOD - 1範圍的數組中的索引要麼產生垃圾值，要麼會導致解釋器崩潰。

C：

#include <windows.h> 

typedef struct USMC_Devices_st { 
    DWORD NOD;  // Number of the devices ready to work 
    char **Serial; // Array of 16 byte ASCII strings 
    char **Version; // Array of 4 byte ASCII strings 
} USMC_Devices; 

char *Serial[] = {"000000000000001", "000000000000002"}; 
char *Version[] = {"001", "002"}; 

__declspec(dllexport) DWORD USMC_Init(USMC_Devices *devices) { 

    devices->NOD = 2; 
    devices->Serial = Serial; 
    devices->Version = Version; 

    return 0; 
} 

// build: cl usmcdll.c /LD 

的Python：

import ctypes 
from ctypes import wintypes 

class USMCDevices(ctypes.Structure): 
    _fields_ = [("NOD", wintypes.DWORD), 
       ("Serial", ctypes.POINTER(ctypes.c_char_p)), 
       ("Version", ctypes.POINTER(ctypes.c_char_p))] 

usmc = ctypes.cdll.USMCDLL 
init = usmc.USMC_Init 
init.restype = wintypes.DWORD 
init.argtypes = [ctypes.POINTER(USMCDevices)] 
dev = USMCDevices() 
init(ctypes.byref(dev)) 

devices = [dev.Serial[i] + b':' + dev.Version[i] 
      for i in range(dev.NOD)] 
print('\n'.join(d.decode('ascii') for d in devices)) 

輸出：

000000000000001:001 
000000000000002:002