1.介绍
当我们需要在程序中使用字符串和数字数据互相转换的时候，可以使用stringstream类，
- 通过运算符 ”<<“ 将数据传递给 stringstream 对象；
- 通过调用stringstream 类的函数str() 将对象所包含的内容赋给一个string对象；
- 可以方便的以流运算符<<将数值以各种数据(字串、数值)写入stringstream对象，且不用担心写越界等问题；
2.使用
代码语言：javascript复制#include <iostream>
#include <sstream>
int main()
{
// default constructor (input/output stream)
std::stringstream buf1;
buf1 << 7;//将int转换为stringstream对象
int n = 0;
buf1 >> n;
std::cout << "buf1 = " << buf1.str() << " n = " << n << 'n';
// input stream
std::istringstream inbuf("-10");
inbuf >> n;//可以将stringstream对象转换为int
std::cout << "n = " << n << 'n';
// output stream in append mode (C 11)
std::ostringstream buf2("test", std::ios_base::ate);//如果不设置第二个参数的话，就会变为1est
buf2 << '1';
std::cout << buf2.str() << 'n';
}输出：
代码语言：javascript复制buf1 = 7 n = 7
n = -10
test1 转换过程：
- 数字 -> stringstream对象 -> string
- string -> stringstream对象 -> 数字
#include <sstream>
#include <iostream>
int main()
{
int n;
std::istringstream in; // could also use in("1 2")
in.str("1 2");
in >> n;
std::cout << "after reading the first int from "1 2", the int is "
<< n << ", str() = "" << in.str() << ""n";
std::ostringstream out("1 2");
out << 3;
std::cout << "after writing the int '3' to output stream "1 2""
<< ", str() = "" << out.str() << ""n";
out << 4;
std::cout << "after writing the int '4' to output stream "1 2""
<< ", str() = "" << out.str() << ""n";
out << 5;
std::cout << "after writing the int '5' to output stream "1 2""
<< ", str() = "" << out.str() << ""n";
std::ostringstream ate("1 2", std::ios_base::ate);
ate << 3;
std::cout << "after writing the int '3' to append stream "1 2""
<< ", str() = "" << ate.str() << ""n";
return 0;
}输出为：
代码语言：javascript复制after reading the first int from "1 2", the int is 1, str() = "1 2"
after writing the int '3' to output stream "1 2", str() = "3 2"//插入时如果不设置，默认从头开始插入
after writing the int '4' to output stream "1 2", str() = "342"
after writing the int '5' to output stream "1 2", str() = "345"
after writing the int '3' to append stream "1 2", str() = "1 23">>操作也默认从头开始输出，<<默认从头开始输入。（感觉好反直觉。。）
3.效率
此链接的实验中， =和append操作，效率都高，但是stringstream由于是类，频繁地创建和销毁代价较高，涉及到内存分配、对象构造和销毁。如果循环中需要频繁使用stringstream对象的话，可以共用一个，在使用中clear和清空：
代码语言：javascript复制void* test_stringstream(void * arg)
{
stringstream oss;
for(int i=0;i<10000;i )
{
oss.clear();这仅仅置流标记
oss.str("");/这是才是真正清空操作
oss << i;
}
}stringstream不会主动释放内存，stream.str("")清除缓冲。
