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/* This file is part of the software similarity tester SIM.
Written by Dick Grune, Vrije Universiteit, Amsterdam.
$Id: idf.c,v 2.8 2005/02/20 17:03:00 dick Exp $
*/
#include <string.h>
#include "system.par"
#include "token.h"
#include "idf.h"
TOKEN
idf_in_list(
const char *str,
const struct idf list[],
unsigned int listsize,
TOKEN dflt
) {
register int first = 0;
register int last = (listsize / sizeof (struct idf)) - 1;
while (first < last) {
register int middle = (first + last) / 2;
if (strcmp(str, list[middle].id_tag) > 0) {
first = middle + 1;
}
else {
last = middle;
}
}
return (strcmp(str, list[first].id_tag) == 0
? list[first].id_tr
: dflt
);
}
TOKEN
idf_hashed(const char *str) {
register int32 h = 0;
/* let's be careful about ranges; if done wrong it's hard to debug */
while (*str) {
/* -1 <= h <= 2^31-1 */
h = (h << 1) + (*str++&0377);
/* -2^31 <= h <= 2^31-1 */
if (h < 0) {
/* -2^31 <= h <= -1 */
h += 2147483647; /* 2^31-1 */
/* -1 <= h <= 2^31-2 */
}
else {
/* 0 <= h <= 2^31-1 */
}
/* -1 <= h <= 2^31-1 */
}
/* -1 <= h <= 2^31-1 */
if (h < 0) {
/* h = -1 */
/* a very small chance, but all the same */
h = 0;
}
/* 0 <= h <= 2^31-1 */
h %= 253; /* 0 <= h < 253 */
return NORM(h + 1); /* 1 <= h < 254 */
/* this avoids SKIP (0) and EOL (255) */
}
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