/* Print n strings that are hashed to 0 by universal_hash seeded with seed */
void collide_clever(unsigned int size, unsigned int seed, int n) {
char string[MAXSTRLEN] = { '\0' };
int coeffs[MAXSTRLEN];
int len, c;
if (size > next_prime(UCHAR_MAX)) {
fprintf(stderr, "%d exceeds limit: %d\n", size, next_prime(UCHAR_MAX));
exit(EXIT_FAILURE);
}
print_universal(MAXSTRLEN, seed, size, coeffs);
// Find the position of the first non-zero universal coefficient
for (c = 0; !coeffs[c]; c++);
for (int i = 0; i < n; i++) {
// Generate a random string at least MINLEN long
len = rand() % (MAXSTRLEN - MINLEN) + MINLEN;
string[len] = '\0';
// Constrain the characters to between A to z
for(int j = 0; j < len; j++)
string[j] = rand() % (MAXCHAR - MINCHAR) + MINCHAR;
// Find a value of string[c] so that string hashes to zero
string[c] = hash_zero(coeffs, string, size, c);
printf("%s\n", string);
}
}
int
main(int argc, char **argv) {
hash_t h;
elt *elts, *p;
int nelts = 0;
char *c;
int i;
do {
hash_zero(&h);
if( argc>1 ) {
nelts = strtoul(argv[1], &c, 0);
}
if( nelts == 0 ) {
nelts = 1000;
}
elts = (elt*)calloc(nelts*sizeof(*elts),1);
test_string(nelts);
hash_init(&h, hash_hash_int, hash_cmp_int, 0, 0, 1);
// put everything in
for(i=0, p=elts; i<nelts; i++, p++) {
p->in_hash = 1;
hash_put(&h, p, p);
}
verify(&h, elts, nelts, "put");
verify(&h, elts, nelts, "put");
// delete every even element
for(i=0, p=elts; i<nelts; i+=2, p+=2) {
p->in_hash = 0;
hash_free(&h, hash_get(&h, p));
}
verify(&h, elts, nelts, "delete even");
// delete every odd element
for(i=1, p=elts+1; i<nelts; i+=2, p+=2) {
p->in_hash = 0;
hash_free(&h, hash_get(&h, p));
}
verify(&h, elts, nelts, "delete odd");
// randomly insert and delete stuff
for(i=0; i<3*nelts; i++) {
int j = (int)(1.0*nelts*rand()/RAND_MAX);
p = elts + j;
if( (int)(10.0*rand()/RAND_MAX)+1 > 1 ) {
p->in_hash = 1;
hash_put(&h, p, p);
}
else {
p->in_hash = 0;
hash_free(&h, hash_get(&h, p));
}
}
verify(&h, elts, nelts, "random insert/delete");
hash_clear(&h);
/* loop forever looking for memory leak */
if( 0 ) {
hash_init(&h, hash_hash_int, hash_cmp_int, 0, 0, 1);
for(i=0; ;i++) {
hash_node_t *node;
hash_remove(&h, (void*)(intptr_t)(i-1));
hash_put(&h, (void*)(intptr_t)i, (void*)(intptr_t)i);
node = hash_get(&h, (void*)(intptr_t)(i-1));
assertb(!node);
node = hash_get(&h, (void*)(intptr_t)i);
assertb(node);
assertb((intptr_t)node->node_val == i);
}
}
} while(0);
return 0;
}
