C++中string流的具体使用

std::ostringstream oss;             // 默认空缓冲
oss << "Value=" << 42 << ", Pi=" 
    << std::fixed << std::setprecision(3) << 3.14159;
// 获取结果
std::string s = oss.str();          // s == "Value=42, Pi=3.142"

std::string line = "123  45.6 OK";
// 将 line 内容作为流缓冲
std::istringstream iss(line);

int    a;
double b;
std::string status;

// 按空白自动切分并转换
if (iss >> a >> b >> status) {
    // a==123, b==45.6, status=="OK"
}

// 检查是否完全消费或错误
if (iss.fail() && !iss.eof()) {
    // 转换中发生格式错误
}

std::stringstream ss;
ss << "X=" << 10 << ";Y=" << 20;
// 重设读写位置到开头
ss.seekg(0);

// 逐字符读取、跳过标识
char    ch;
int     x, y;
ss >> ch >> ch >> x;   // 假设格式 "X=10"
ss >> ch >> ch >> y;   // 跳过 ";Y="

iss.exceptions(std::ios::failbit | std::ios::badbit);
try {
  int v; 
  iss >> v;  // 解析失败即抛异常
} catch (const std::ios_base::failure& e) {
  // 处理错误
}

#include <iostream>
#include <sstream>
#include <iomanip>

int main() {
    // 构建字符串
    std::ostringstream oss;
    oss << "Point(" 
        << std::setw(2) << std::setfill('0')
        << 7 << "," 
        << std::fixed << std::setprecision(1)
        << 3.14 << ")";
    std::string desc = oss.str();  // "Point(07,3.1)"
    std::cout << desc << "\n";

    // 解析回数值
    std::istringstream iss(desc);
    char ch;
    int ix;
    double dy;
    if ( (iss >> ch >> ch >> ix >> ch >> dy >> ch).good() ) {
        std::cout << "Parsed: x=" << ix << ", y=" << dy << "\n";
    } else {
        std::cerr << "Parse error\n";
    }

    // 读写混合：累加偏移
    std::stringstream ss("100 200 300");
    int sum = 0, v;
    while (ss >> v) sum += v;  // sum=600
    std::cout << "Sum=" << sum << "\n";

    return 0;
}