C++基础---string类的data/c_str/copy

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

参考文献：

[1] 网络资源： http://www.cplusplus.com/reference/string/string/data/

       http://www.cplusplus.com/reference/string/string/c_str/

       http://www.cplusplus.com/reference/string/string/copy/