#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define KILOBYTE 1024

static const unsigned long long ITERATIONS = 115;
static const unsigned long long BUFFER_SIZE = 4 * KILOBYTE;


int main() {
    char buffer[ BUFFER_SIZE ];
    char* name = "/tmp/somefile";
    FILE* file = fopen( name, "r+");
    long long size = 0;
    long long read = 0;
    long long random = 0;
    long long i = 0;

    if( file == NULL ) return -1;

    fseek( file, 0, SEEK_END );
    size = ftell( file );
    rewind( file );

    if( size <= BUFFER_SIZE ) return -1;

    srand( time( NULL ) );

    for( ; i < ITERATIONS; ++i ) {
        random = ( long long )rand() + ( long long )rand() * 0xFFFFFFFF;
        random %= (size - BUFFER_SIZE);

        //if( ((random * 100) / size) < 40 ) {
        //    --i;
        //    continue;
        //}

        fseek( file, random, SEEK_SET );
        read = fread( buffer, 1, BUFFER_SIZE, file );
        printf( "Reading 4KB from %lli, read %lli, as far as %lli perc.\n", random, read, (random * 100) / size );
    }

    fclose( file );

    return 0;
}