[C/C++标准库]_[初级]_[使用string stream]
sstream
stringstream
ostringstream
istringstream
场景:
1.需要对字符进行逐个处理,比如加密.
2.int,float和string互相转换.
3.简单提取以isspace分割的字符串或数字.如 "ab asdf 3 4 5 6 7 8 9 10"
4.以单个字符为分割符来分割字符串.
#include <stdlib.h>
#include <sstream>
#include <iostream>
using namespace std;
void TestConvertStringToFloat()
{
istringstream stream1;
float num;
// use it once
//1.支持isspace分割
string string1 = "23 1 3.235\n1111111\n222222";
stream1.str(string1);
while( stream1 >> num ) cout << "num1: " << num << endl; // displays numbers, one per line
// use the same string stream again with clear() and str()
string string2 = "1 2 3 4 5 6 7 8 9 10";
stream1.clear();
stream1.str(string2);
while( stream1 >> num ) cout << "num2: " << num << endl; // displays numbers, one per line
string string3 = "ab asdf 3 4 5 6 7 8 9 10";
string mystr;
stream1.clear();
stream1.str(string3);
while( stream1 >> mystr ) cout << "mystr: " << mystr << endl; // displays numbers, one per line
}
void TestConvertFloatToString()
{
stringstream stream1;
stream1 << 123;
string str = stream1.str();
cout << str << endl;
stream1.seekp(0,std::ios::beg); //1.重复使用时注意移动到stringstream前面.
stream1 << 3.2;
str = stream1.str();
cout << str << endl;
}
void TestGetLineWithStringStream()
{
//1.线程安全的,但是只能以字符作为分隔符
stringstream ss("google|twitter|facebook|microsoft|apple|ibm|");
string str;
while(getline(ss,str,'|'))
{
cout << str << endl;
}
}
//1.Characters can be inserted and/or extracted from
//the stream using any operation allowed on both input and output streams.
//2.即它可以像流那样对字符进行逐个处理,可用于转码.
int main(int argc, char const *argv[])
{
cout << "TestConvertIntToString" << endl;
TestConvertFloatToString();
cout << "TestConvertStringToFloat" << endl;
TestConvertStringToFloat();
cout << "TestGetLineWithStringStream" << endl;
TestGetLineWithStringStream();
return 0;
}
//参考
//1. http://www.cplusplus.com/reference/sstream/stringstream/
//2. http://www.usidcbbs.com/read-htm-tid-1898.html
//3. http://faculty.virginia.edu/comp-phys/phys2660/html/references/www.cppreference.com/cppsstream/all.html
//4. http://stackoverflow.com/questions/236129/how-to-split-a-string-in-c
输出:
TestConvertIntToString 123 3.2 TestConvertStringToFloat num1: 23 num1: 1 num1: 3.235 num1: 1.11111e+006 num1: 222222 num2: 1 num2: 2 num2: 3 num2: 4 num2: 5 num2: 6 num2: 7 num2: 8 num2: 9 num2: 10 mystr: ab mystr: asdf mystr: 3 mystr: 4 mystr: 5 mystr: 6 mystr: 7 mystr: 8 mystr: 9 mystr: 10 TestGetLineWithStringStream google twitter facebook microsoft apple ibm [Finished in 0.1s]
2015.5.19 补充.
1. stringstream作为sprintf的替换和重用stringstream.
#include "stdafx.h"
#include <sstream>
#include <string.h>
#include <string>
#include <iostream>
int _tmain(int argc, _TCHAR* argv[])
{
//1. 使用stringstream来存储不定长字符串.
std::stringstream ss;
int i = 10;
int j = 20;
ss << i << " is smaller than " << j;
std::cout << ss.str() << std::endl;
//1. C使用sprintf来实现.
char buf[32];
sprintf(buf,"%d is smaller than %d",i,j);
std::cout << buf << std::endl;
//1. 重用ss.必须调用clear()和str("")
//////////
ss.clear();
ss.str("");
ss << "hello world";
std::cout << ss.str() << std::endl;
return 0;
}
输出:
10 is smaller than 20 10 is smaller than 20 hello world