/* -*-c-*-
*
- * $Id: unihash.c,v 1.1 2003/10/12 14:43:24 mdw Exp $
+ * $Id: unihash.c,v 1.3 2004/04/08 01:36:13 mdw Exp $
*
* Simple and efficient universal hashing for hashtables
*
* MA 02111-1307, USA.
*/
-/*----- Revision history --------------------------------------------------*
- *
- * $Log: unihash.c,v $
- * Revision 1.1 2003/10/12 14:43:24 mdw
- * Universal hashing.
- *
- */
-
/*----- Header files ------------------------------------------------------*/
#include <assert.h>
* @const void *p@ = pointer to data to hash
* @size_t sz@ = size of the data
*
- * Returns: ---
+ * Returns: Hash of data so far.
*
* Use: Hashes data. Call this as many times as needed.
*/
a ^= BYTEMULT(2, *pp++);
a ^= BYTEMULT(1, *pp++);
a ^= BYTEMULT(0, *pp++);
+ sz -= UNIHASH_NBATCH;
}
/* --- The tail end is a smaller batch --- */
return (UNIHASH(i, p, sz));
}
+/*----- Test rig ----------------------------------------------------------*/
+
+#ifdef TEST_RIG
+
+#include "testrig.h"
+
+static int verify(dstr *v)
+{
+ unihash_info ui;
+ uint32 k;
+ uint32 h, hh;
+ size_t n;
+ int i, c;
+ const char *p;
+ int ok = 1;
+
+ static const int step[] = { 0, 1, 5, 6, 7, 8, 23, -1 };
+
+ /* --- Set up for using this key --- */
+
+ k = *(uint32 *)v[0].buf;
+ h = *(uint32 *)v[2].buf;
+ unihash_setkey(&ui, k);
+
+ /* --- Hash the data a lot --- */
+
+ for (i = 0; step[i] >= 0; i++) {
+ c = step[i];
+ if (!c)
+ hh = unihash(&ui, v[1].buf, v[1].len);
+ else {
+ hh = UNIHASH_INIT(&ui);
+ p = v[1].buf;
+ n = v[1].len;
+ while (n) {
+ if (c > n) c = n;
+ hh = unihash_hash(&ui, hh, p, c);
+ p += c;
+ n -= c;
+ }
+ }
+ if (h != hh) {
+ ok = 0;
+ fprintf(stderr, "\nunihash failed\n");
+ fprintf(stderr, " key = %08lx\n", (unsigned long)k);
+ fprintf(stderr, " data = %s\n", v[1].buf);
+ fprintf(stderr, " step = %d\n", step[i]);
+ fprintf(stderr, " expected = %08lx\n", (unsigned long)h);
+ fprintf(stderr, " computed = %08lx\n", (unsigned long)hh);
+ }
+ }
+ return (ok);
+}
+
+static const test_chunk tests[] = {
+ { "hash", verify, { &type_uint32, &type_string, &type_uint32 } },
+ { 0, 0, { 0 } }
+};
+
+int main(int argc, char *argv[])
+{
+ test_run(argc, argv, tests, "unihash.in");
+ return (0);
+}
+
+#endif
+
/*----- That's all, folks -------------------------------------------------*/