Test the speed of iostream

// g++ -O3 std=c++0x filename.cpp -o filename.out
#include <chrono>
#include <iostream>
#include <cstdio>
#include <cstdlib>

char buf[4096];

void clrscr()
{
#ifdef _WIN32
    system("CLS");
#else
    system("clear");
#endif
}

int main()
{
    using namespace std;
    enum { TIMES = 40960 };
#ifdef USE_BUFFER
    cout.rdbuf()->pubsetbuf(buf, sizeof(buf));
#endif
    getchar();

    clrscr();
    auto timer = std::chrono::system_clock::now();
    for (int i=0; i!=TIMES; ++i)
        cout << "asdfghjklasdfghjklasdfghjkl;asdfghjklasdfghjklasdfghjkl;\n";
    cout.flush();
    auto t1 = std::chrono::system_clock::now() - timer;

    clrscr();
    timer = std::chrono::system_clock::now();
    for (int i=0; i!=TIMES; ++i)
        printf("%s", "asdfghjklasdfghjklasdfghjkl;asdfghjklasdfghjklasdfghjkl;\n");
    fflush(stdout);
    auto t2 = std::chrono::system_clock::now() - timer;

    clrscr();
    timer = std::chrono::system_clock::now();
    for (int i=0; i!=TIMES; ++i)
        printf("asdfghjklasdfghjklasdfghjkl;asdfghjklasdfghjklasdfghjkl;\n");
    fflush(stdout);
    auto t3 = std::chrono::system_clock::now() - timer;

    clrscr();
    cout << t1.count() << endl << t2.count() << endl << t3.count() << endl;
}