#include <iostream>
#include <strstream>
 
int main()
{
    char a[] = "123";
    std::strstream ss(a, sizeof a); // in/out
    std::cout << "put pos = " << ss.tellp()
              << " get pos = " << ss.tellg() << '\n';
 
    // 绝对寻位两者的指针
    ss.rdbuf()->pubseekoff(1, std::ios_base::beg); // 前移两者
    std::cout << "put pos = " << ss.tellp()
              << " get pos = " << ss.tellg() << '\n';
 
    // 尝试从当前位置前移二个指针 1 字符
    if(-1 == ss.rdbuf()->pubseekoff(1, std::ios_base::cur))
        std::cout << "moving both pointers from current position failed\n";
    std::cout << "put pos = " << ss.tellp()
              << " get pos = " << ss.tellg() << '\n';
 
    // 前移写指针 1 字符，但不移动读指针
    // can also be called as ss.seekp(1, std::ios_base::cur);
    ss.rdbuf()->pubseekoff(1, std::ios_base::cur, std::ios_base::out);
    std::cout << "put pos = " << ss.tellp()
              << " get pos = " << ss.tellg() << '\n';
 
    ss << 'a'; // 写入放置位置
    std::cout << "Wrote 'a' at put position, the buffer is now: '";
    std::cout.write(a, sizeof a);
    std::cout << "'\n";
    char ch;
    ss >> ch;
    std::cout << "reading at get position gives '" << ch << "'\n";
}