utils.c

#include <stdlib.h>

unsigned int rand_lim(unsigned int limit) {
    /* return a random number between 0 and limit inclusive.
     */
    int divisor = RAND_MAX/(limit+1);
    int retval;
    
    do {
        retval = rand() / divisor;
    } while (retval > limit);
    
    
    return retval;
}

unsigned long upper_power_of_two(unsigned long v){
    v--; v |= v >> 1; v |= v >> 2; v |= v >> 4; v |= v >> 8; v |= v >> 16; v++;
    return v;
}


/*log2 malato*/
const unsigned int tab64[64] = {
    63,  0, 58,  1, 59, 47, 53,  2,
    60, 39, 48, 27, 54, 33, 42,  3,
    61, 51, 37, 40, 49, 18, 28, 20,
    55, 30, 34, 11, 43, 14, 22,  4,
    62, 57, 46, 52, 38, 26, 32, 41,
    50, 36, 17, 19, 29, 10, 13, 21,
    56, 45, 25, 31, 35, 16,  9, 12,
    44, 24, 15,  8, 23,  7,  6,  5};

unsigned int log2_ (unsigned long value){
    if(value == 0) return -1;
    return 63 - __builtin_clzl(value);
    value |= value >> 1;
    value |= value >> 2;
    value |= value >> 4;
    value |= value >> 8;
    value |= value >> 16;
    value |= value >> 32;
    return tab64[((unsigned long)((value - (value >> 1))*0x07EDD5E59A4E28C2)) >> 58];
}