memcpy.cpp

#include <iostream>
#include <cstdio>
#include <fstream>
#include <cstdlib>
#include <string>
#include <cstring>
#include <ctime>
#include <chrono>

using namespace std;

static uint64_t now_us() {
  std::chrono::time_point<std::chrono::system_clock> now = std::chrono::system_clock::now();
  return static_cast<uint64_t>(std::chrono::duration_cast<std::chrono::microseconds>(now.time_since_epoch()).count());
}

int main() {
    string data(1024 * 128, 'a');
    char buffer[1024 * 128 * 40];
    int  tail_ = 0;
    fstream local;
    local.rdbuf()->pubsetbuf(0, 0);
    local.open("test_output", std::ios::out | std::ios::trunc | std::ios::binary);
    for(int i = 0; i < 40; i++) {
        auto start_time_1 = now_us();
        
        local.seekp(tail_, std::ios::beg);
        local.write(data.c_str(), 128 * 1024);
        local.flush();
        
        auto end_time_1 = now_us();
        std::memcpy(&buffer[tail_], data.c_str(), 128 * 1024);
        auto end_time_2 = now_us();
        
        tail_ += 128 * 1024;
        cout << "Persistent: " << " " << end_time_1 - start_time_1 << " Memory: " << end_time_2 - end_time_1 << endl;
    }
    return 0;
}