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)