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/*
* OSB tokenizer
*/
#include <sys/types.h>
#include "tokenizers.h"
/* Coefficients that are used for OSB tokenizer */
static const int primes[] = {
1, 7,
3, 13,
5, 29,
11, 51,
23, 101,
47, 203,
97, 407,
197, 817,
397, 1637,
797, 3277,
};
token_list_t *
osb_tokenize_text (memory_pool_t *pool, f_str_t *input)
{
token_list_t *new = NULL, *head = NULL, *last = NULL;
f_str_t token = { NULL, 0, 0 };
uint32_t hashpipe[FEATURE_WINDOW_SIZE], h1, h2;
int i;
/* First set all bytes of hashpipe to some common value */
for (i = 0; i < FEATURE_WINDOW_SIZE; i ++) {
hashpipe[i] = 0xABCDEF;
}
while (get_next_word (input, &token)) {
/* Shift hashpipe */
for (i = FEATURE_WINDOW_SIZE - 1; i > 0; i --) {
hashpipe[i] = hashpipe[i - 1];
}
hashpipe[0] = fstrhash (&token);
for (i = 0; i < FEATURE_WINDOW_SIZE - 2; i ++) {
h1 = hashpipe[0]* primes[0] + hashpipe[i] * primes[i<<1];
h2 = hashpipe[0] * primes[1] + hashpipe[i] * primes[(i<<1)-1];
new = memory_pool_alloc (pool, sizeof (token_list_t));
new->h1 = h1;
new->h2 = h2;
if (last) {
last->next = new;
}
else {
head = new;
}
last = new;
msg_debug ("osb_tokenize_text: append new token, h1=%u, h2=%u", h1, h2);
}
}
if (last) {
last->next = NULL;
}
return head;
}
/*
* vi:ts=4
*/
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