C ++中string和char []类型之间的区别 [英] Difference between string and char[] types in C++

问题描述

我知道一点C，现在我来看看C ++。
我用于处理C字符串的字符数组，但是我看看C ++代码，我看到有使用字符串类型和字符数组的例子：

I know a little C and now I'm taking a look at C++. I'm used to char arrays for dealing with C strings, but while I look at C++ code I see there are examples using both string type and char arrays:

#include <iostream>
#include <string>
using namespace std;

int main () {
  string mystr;
  cout << "What's your name? ";
  getline (cin, mystr);
  cout << "Hello " << mystr << ".\n";
  cout << "What is your favorite team? ";
  getline (cin, mystr);
  cout << "I like " << mystr << " too!\n";
  return 0;
}

和

#include <iostream>
using namespace std;

int main () {
  char name[256], title[256];

  cout << "Enter your name: ";
  cin.getline (name,256);

  cout << "Enter your favourite movie: ";
  cin.getline (title,256);

  cout << name << "'s favourite movie is " << title;

  return 0;
}

（两个示例均来自 http://www.cplusplus.com ）

我想这是一个被广泛提出和回答（明显？）的问题，但它如果有人能告诉我在C ++中处理字符串的两种方式（性能，API集成，每种方式更好，...）之间的区别。

I suppose this is a widely asked and answered (obvious?) question, but it would be nice if someone could tell me what's exactly the difference between that two ways for dealing with strings in C++ (performance, API integration, the way each one is better, ...).

谢谢。

推荐答案

一个字符数组就是一个字符数组：

A char array is just that - an array of characters:

• 如果在堆栈上分配（如在你的例子中），它总是占用eg。


• 如果在堆上分配（使用malloc（）或new char []），您将负责释放内存，然后您将总是有一个堆分配的开销。


• 如果您将超过256个字符的文本复制到数组中，则可能会崩溃，生成丑陋的声明消息或在程序中的其他位置导致无法解释的（误）行为。 >
  
• 要确定文本的长度，必须逐个字符扫描一个\0字符的数组。

字符串是一个包含char数组的类，但会自动为您管理它。大多数字符串实现都有一个16个字符的内置数组（因此，短字符串不会对堆进行分段），并使用堆来获取更长的字符串。

A string is a class that contains a char array, but automatically manages it for you. Most string implementations have a built-in array of 16 characters (so short strings don't fragment the heap) and use the heap for longer strings.

string's char array like this：

You can access a string's char array like this:

std::string myString = "Hello World";
const char *myStringChars = myString.c_str();

C ++字符串可以包含嵌入的\0字符，知道它们的长度不计数，为短文本分配字符数组，并保护您免受缓冲区溢出的影响。

C++ strings can contain embedded \0 characters, know their length without counting, are faster than heap-allocated char arrays for short texts and protect you from buffer overruns. Plus they're more readable and easier to use.

-

但是，C ++字符串不是）适合跨DLL边界使用，因为这将需要这样的DLL函数的任何用户，以确保他使用完全相同的编译器和C ++运行时实现，以免他的字符串类的行为不同。

However, C++ strings are not (very) suitable for usage across DLL boundaries, because this would require any user of such a DLL function to make sure he's using the exact same compiler and C++ runtime implementation, lest he risk his string class behaving differently.

通常，字符串类也会在调用堆上释放其堆内存，因此只有在使用共享（.dll或.so）版本的运行时。

Normally, a string class would also release its heap memory on the calling heap, so it will only be able to free memory again if you're using a shared (.dll or .so) version of the runtime.

简而言之：在所有内部函数和方法中使用C ++字符串。如果你写一个.dll或.so，在你的public（dll / so-exposed）函数中使用C字符串。

In short: use C++ strings in all your internal functions and methods. If you ever write a .dll or .so, use C strings in your public (dll/so-exposed) functions.

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