c++ - TCHAR 数组的深拷贝被截断

Question

我创建了一个类来测试我需要使用的一些功能。本质上，该类将获取传入字符串的深层拷贝，并通过 getter 使其可用。我正在使用 Visual Studio 2012。在项目设置中启用了 Unicode。

问题是 memcpy 操作产生了截断的字符串。输出是这样的；

THISISATEST: InstanceDataConstructor: Testing testing 123
Testing te_READY

其中第一行是对传入的 TCHAR* 字符串的检查，第二行是使用 memcpy 操作填充分配的内存的输出。预期输出是； “测试测试123”。

谁能解释一下这里出了什么问题？

注意从这里得到#ifndef UNICODE typedefs:how-to-convert-tchar-array-to-stdstring

#ifndef INSTANCE_DATA_H//if not defined already
#define INSTANCE_DATA_H//then define it

#include <string>

//TCHAR is just a typedef, that depending on your compilation configuration, either defaults to char or wchar.
//Standard Template Library supports both ASCII (with std::string) and wide character sets (with std::wstring).
//All you need to do is to typedef String as either std::string or std::wstring depending on your compilation configuration.
//To maintain flexibility you can use the following code:
#ifndef UNICODE  
  typedef std::string String; 
#else
  typedef std::wstring String; 
#endif
//Now you may use String in your code and let the compiler handle the nasty parts. String will now have constructors that lets you convert TCHAR to std::string or std::wstring.


class InstanceData
{
public: 
    InstanceData(TCHAR* strIn) : strMessage(strIn)//constructor     
        {
        //Check to passed in string
        String outMsg(L"THISISATEST: InstanceDataConstructor: ");//L for wide character string literal
        outMsg += strMessage;//concatenate message
        const wchar_t* finalMsg = outMsg.c_str();//prepare for outputting
        OutputDebugStringW(finalMsg);//print the message    

        //Prepare TCHAR dynamic array.  Deep copy.
        charArrayPtr = new TCHAR[strMessage.size() +1];
        charArrayPtr[strMessage.size()] = 0;//null terminate
        std::memcpy(charArrayPtr, strMessage.data(), strMessage.size());//copy characters from array pointed to by the passed in TCHAR*.

        OutputDebugStringW(charArrayPtr);//print the copied message to check    
        }

    ~InstanceData()//destructor
        {
            delete[] charArrayPtr;
        }

//Getter
TCHAR* getMessage() const
{
    return charArrayPtr;
}

private:
    TCHAR* charArrayPtr;
    String strMessage;//is used to conveniently ascertain the length of the passed in underlying TCHAR array.
};
#endif//header guard

Answer 1

没有所有动态分配内存的解决方案。

#include <tchar.h>
#include <vector>
//...
class InstanceData
{
    public: 
        InstanceData(TCHAR* strIn) : strMessage(strIn),
        {   
            charArrayPtr.insert(charArrayPtr.begin(), strMessage.begin(), strMessage.end())
            charArrayPtr.push_back(0);   
        }

        TCHAR* getMessage()
        { return &charArrayPtr[0]; }

    private:
        String strMessage;
        std::vector<TCHAR> charArrayPtr;
};

这与您的类所做的一样，但主要区别在于它不执行任何手动动态分配代码。该类还可以安全地复制，这与具有动态分配的代码不同(缺少用户定义的复制构造函数和赋值运算符)。

std::vector 类已经取代了几乎在所有情况下都必须执行的new[]/delete[]。原因是 vector 将其数据存储在连续的内存中，与调用 new[] 没有什么不同。