C++基础---string类的data/c_str/copy

最新推荐文章于 2025-09-21 17:29:03 发布

原创最新推荐文章于 2025-09-21 17:29:03 发布 · 4.9k 阅读

10 ·

CC 4.0 BY-SA版权

文章标签：

#string #data #c-str #copy #size

C++基础专栏收录该内容

72 篇文章

订阅专栏

本文详细介绍了C++标准库中string类的三种转换方法：data、c_str及copy。通过示例代码展示了如何将string对象转换为C风格字符串，并讨论了它们在实际应用中的差异。

1.string类的data/c_str/copy

1.1 std::string::data

原型： const char *data()const;
功能： string型字符串转化为char型字符串。
说明：将自身转化为一个以空终止符结束（即带”\0“结尾）的char型字符串。
返回值：一个指向字符串数组的指针，字符串数组指针。

代码示例：

(1)示例代码一：

#include <iostream>


#include <string>

using namespace std;
int main ()
{
    string str = "Test string";
    char *cstr = "Test string";

    if (str.length() == strlen(cstr))
    {
        cout<<"str and cstr have the same length."<<endl;

        if (memcmp(cstr, str.data(), str.length()) == 0)
        {
            cout<<"str and cstr have the same content."<<endl;
        }
    }

    system("pause");
    return 0;
}
=>str and cstr have the same length.
  str and cstr have the same content.

(2)示例代码二：

#include <iostream>


#include <string>

using namespace std;
int main ()
{
    string str("Please split this sentence into tokens");
    const char *split = " ";
    char *cstr = new char [str.length()+1];
    strcpy_s(cstr, str.size() + 1, str.data());

    //cstr now contains a c-string copy of str
    char *p = 0;
    char *pNext = 0;
    p = strtok_s(cstr, split, &pNext);
    while(p != 0)
    {
        cout<<p<<endl;
        p = strtok_s(NULL, split, &pNext);
    }

    delete[] cstr;
    system("pause");

    return 0;
}   
=>Please
  split
  this
  sentence
  into
  tokens

1.2 std::string::c_str

原型：const char *c_str()const;
功能： string型字符串转化为char型字符串。
说明：将自身转化为一个以空终止符结束（即带”\0“结尾）的char型字符串。
返回值：一个指向字符串数组的指针，字符串数组指针。

代码示例：

(1)示例代码一：

#include <iostream>


#include <string>

using namespace std;
int main ()
{
    string str = "Test string";
    char *cstr = "Test string";

    if (str.length() == strlen(cstr))
    {
        cout<<"str and cstr have the same length."<<endl;

        if (memcmp(cstr, str.c_str(), str.length()) == 0)
        {
            cout<<"str and cstr have the same content"<<endl;
        }
    }

    system("pause");
    return 0;
}
=>str and cstr have the same length.
  str and cstr have the same content.

(2)示例代码二：

#include <iostream>


#include <string>

using namespace std;
int main ()
{
    string str("Please split this sentence into tokens");
    const char *split = " ";
    char *cstr = new char [str.length()+1];
    strcpy_s(cstr, str.size() + 1, str.c_str());

    //cstr now contains a c-string copy of str
    char *p = 0;
    char *pNext = 0;
    p = strtok_s(cstr, split, &pNext);
    while (p != 0)
    {
        cout<<p<<endl;
        p = strtok_s(NULL, split, &pNext);
    }

    delete[] cstr;
    system("pause");

    return 0;
}
=>Please
  split
  this
  sentence
  into
  tokens

1.3 std::string::copy

原型：size_t copy (char* s, size_t len, size_t pos = 0) const;
功能： string型字符串转化为char型字符串。
说明：从源字符串以下标为pos（默认为0）处开始拷贝n个字符到char型字符串s中。
返回值：实际拷贝的字符个数。

代码示例：


#pragma warning(disable:4996) //全部关掉


#include <iostream>


#include <string>

using namespace std;
int main ()
{
    char buffer[20];
    string str("Test string...");
    size_t length = str.copy(buffer, 6, 5);
    buffer[length]='\0';
    cout<<"buffer contains: "<<buffer<<endl;
    system("pause");
    return 0;
}
=>buffer contains: string