对ctypes不太了解,最近刚开始使用它.
我在C-like dll中有一个简单的函数,它返回一个指向动态生成的字符串的指针.
它工作正常,但是,因为我手动为字符串分配内存,我应该在使用后释放它.
我有这样的事情:
extern "C" char* DLL_EXPORT func(const char* str1,const char* str2) { return getSomeString(str1,str2); } // Goal is to call this function correctly from Python. extern "C" void DLL_EXPORT freeMem(void *mem) { if(mem!=NULL) delete mem; }
但我不知道,我如何将收到的指针传回Python中删除?
你走在正确的轨道上.
// TestDLL.cpp #include <string.h> // strcpy extern "C" __declspec(dllexport) char* stringdup(const char* str) { char* p = new char[strlen(str)+1]; strcpy(p,str); return p; } // if you have no good reason to use void*,use the type // you've allocated. while it usually works for built-in // types,it wouldn't work for classes (it wouldn't call // the destructor) extern "C" __declspec(dllexport) void stringfree(char* ptr) { // you don't need to check for 0 before you delete it,// but if you allocate with new[],free with delete[] ! delete [] ptr; }
在python中:
# Test.py import ctypes lib = ctypes.cdll.TestDLL # this creates a c-style char pointer,initialized with a string whose # memory is managed by PYTHON! do not attempt to free it through the DLL! cstr = ctypes.c_char_p("hello ctypes") # call the dll function that returns a char pointer # whose memory is managed by the DLL. p = lib.stringdup(cstr) # p is just an integer containing the memory address of the # char array. therefore,this just prints the address: print p # this prints the actual string print ctypes.c_char_p(p).value # free the memory through the DLL lib.stringfree(p)