#include <stdint.h>
#include <stdio.h>
#include <string.h>

#undef get16bits
#if (defined(__GNUC__) && defined(__i386__)) || defined(__WATCOMC__) \
  || defined(_MSC_VER) || defined (__BORLANDC__) || defined (__TURBOC__)
#define get16bits(d) (*((const uint16_t *) (d)))
#endif

#if !defined (get16bits)
#define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
                       +(uint32_t)(((const uint8_t *)(d))[0]) )
#endif

uint32_t SuperFastHash (const char * data, int len) {
uint32_t hash = len, tmp;
int rem;

    if (len <= 0 || data == NULL) return 0;

    rem = len & 3;
    len >>= 2;

    /* Main loop */
    for (;len > 0; len--) {
        hash  += get16bits (data);
        tmp    = (get16bits (data+2) << 11) ^ hash;
        hash   = (hash << 16) ^ tmp;
        data  += 2*sizeof (uint16_t);
        hash  += hash >> 11;
    }

    /* Handle end cases */
    switch (rem) {
        case 3: hash += get16bits (data);
                hash ^= hash << 16;
                hash ^= ((signed char)data[sizeof (uint16_t)]) << 18;
                hash += hash >> 11;
                break;
        case 2: hash += get16bits (data);
                hash ^= hash << 11;
                hash += hash >> 17;
                break;
        case 1: hash += (signed char)*data;
                hash ^= hash << 10;
                hash += hash >> 1;
    }

    /* Force "avalanching" of final 127 bits */
    hash ^= hash << 3;
    hash += hash >> 5;
    hash ^= hash << 4;
    hash += hash >> 17;
    hash ^= hash << 25;
    hash += hash >> 6;

    return hash;
}

int CheckCollision(const char* s1, const char* s2) {
  //printf("\nChecking %s vs. %s\n  ", s1, s2);
  return (SuperFastHash(s1, strlen(s1)) ==  SuperFastHash(s2, strlen(s2))) ? 1 : 0;
}

int main() {
  int i;
  int j;

  for (j = 1; j < 64; ++j) {
    int count = 0;
    char orig[128];
    memset(orig, 'a', j);
    sprintf(orig + j, "0000");
    for (i = 1; i < 10000; ++i) {
      char x[128];
      memset(x, 'a', j);
      sprintf(x + j, "%04d", i);
      count += CheckCollision(orig, x);
    }
    if (count)
      printf("Collisions for length: %d =  %d\n", j, count);
  }
  return 0;
}


OUTPUT:
$ gcc -o test test.c && ./test ù
Collisions for length: 2 =  1
Collisions for length: 3 =  3
Collisions for length: 6 =  1
Collisions for length: 7 =  1
Collisions for length: 14 =  1
Collisions for length: 15 =  4
Collisions for length: 19 =  4
Collisions for length: 22 =  1
Collisions for length: 23 =  4
Collisions for length: 26 =  1
Collisions for length: 30 =  1
Collisions for length: 31 =  3
Collisions for length: 35 =  2
Collisions for length: 42 =  1
Collisions for length: 43 =  1
Collisions for length: 46 =  1
Collisions for length: 47 =  2
Collisions for length: 50 =  1
Collisions for length: 51 =  4
Collisions for length: 54 =  1
Collisions for length: 58 =  1
Collisions for length: 59 =  2
Collisions for length: 63 =  1