#include <iostream>
#include <sstream>
#include <fstream>
 
std::stringstream fs("AAAAAAA");
int buffSize = 100;
int bytesRead = 0;
char* buffer = new char[buffSize]{};
 
int main()
{
    fs.write("hello", 5);
    fs.seekp(0, std::ios::beg);
 
    fs.read(buffer, buffSize);
    /* ==== */ fs.clear(); /* ==== */
    bytesRead = fs.gcount();
 
    std::cout << buffer << "\n";
 
    fs.seekp(1, std::ios::beg);
    fs.write("E", 1);
 
    std::cout << fs.str();
}

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