About File.rawWrite

[bearophile]

This D2 program runs in about 5.13 seconds on my PC:


import std.stdio;
void main() {
    auto f = File("bytes_test.dat", "wb");
    ubyte[3] RGB;
    foreach (_; 0 .. 1_000_000)
        f.rawWrite(RGB);
}



While this C program runs in about 0.14 seconds:


#include <stdio.h>
int main() {
    FILE *f = fopen("bytes_test.dat", "wb");
    unsigned char RGB[3] = {0};
    int i;
    for (i = 0; i < 1000000; i++)
        fwrite(RGB, 1, 3, f);
    return 0;
}


Is my D2 program wrong, or is File.rawWrite in need of some improvements?

(Writing 3 bytes at a time is not efficient, but the C code shows that the 
runtime is acceptable for me for small files).

Bye,
bearophile