* Add simple hash function for hashing tokens

diff --git a/src/filter.c b/src/filter.c
index d1edbb93005e7ef1fca202e73187290f8e3ce5e2..ae5852efb3c157ecc4a7518001c4abe7a32b7214 100644 (file)
--- a/src/filter.c
+++ b/src/filter.c
@@ -334,3 +334,8 @@ void make_composites (struct worker_task *task)
 {
        g_hash_table_foreach (task->results, composites_metric_callback, task);
 }
+
+
+/* 
+ * vi:ts=4 
+ */

diff --git a/src/fstring.c b/src/fstring.c
index ad0be7d78ddee30827f7732b1555163ccd505780..cad7c87105cb94ba08efead1b9ce4dd575bb0094 100644 (file)
--- a/src/fstring.c
+++ b/src/fstring.c
@@ -232,3 +232,45 @@ fstrgrow (memory_pool_t *pool, f_str_t *orig, size_t newlen)
 
        return res;
 }
+
+/*
+ * Return hash value for a string
+ */
+uint32_t
+fstrhash (f_str_t *str)
+{
+       size_t i;
+       uint32_t hval;
+       uint32_t tmp;
+
+       if (str == NULL) {
+               return 0;
+       }
+       hval = str->len;
+
+       for     (i = 0; i < str->len; i++) {
+               /* 
+                * xor in the current byte against each byte of hval
+                * (which alone gaurantees that every bit of input will have
+                * an effect on the output)
+                */
+               tmp = *(str->begin + i) & 0xFF;
+               tmp = tmp | (tmp << 8) | (tmp << 16) | (tmp << 24);
+               hval ^= tmp;
+
+               /* add some bits out of the middle as low order bits */
+               hval = hval + ((hval >> 12) & 0x0000ffff) ;
+
+               /* swap most and min significative bytes */
+               tmp = (hval << 24) | ((hval >> 24) & 0xff);
+               /* zero most and min significative bytes of hval */
+               hval &= 0x00ffff00;
+               hval |= tmp;
+               /*
+                * rotate hval 3 bits to the left (thereby making the
+                * 3rd msb of the above mess the hsb of the output hash)
+                */
+               hval = (hval << 3) + (hval >> 29);
+       }
+       return hval;
+}

diff --git a/src/fstring.h b/src/fstring.h
index c3087b2c5623a1d35918eda3083b4480b54658f5..6840d9088adb0c8c8e283dd4a0234504d5da930e 100644 (file)
--- a/src/fstring.h
+++ b/src/fstring.h
@@ -6,6 +6,11 @@
 #define FSTRING_H
 
 #include <sys/types.h>
+#include "config.h"
+
+#ifdef HAVE_STDINT_H
+#include <stdint.h>
+#endif
 #include "mem_pool.h"
 
 #define update_buf_size(x) (x)->free = (x)->buf->size - ((x)->pos - (x)->buf->begin); (x)->buf->len = (x)->pos - (x)->buf->begin
@@ -83,4 +88,9 @@ f_str_t* fstrgrow (memory_pool_t *pool, f_str_t *orig, size_t newlen);
  */
 #define fstridx(str, pos) *((str)->begin + (pos))
 
+/*
+ * Return fast hash value for fixed string
+ */
+uint32_t fstrhash (f_str_t *str);
+
 #endif