tracking_collisions.c: sha1 + crc64 implemented.

utils/tracking_collisions.c

@@ -10,6 +10,11 @@
  * And counts the resulting collisons generated in the 24 bits of output
  * needed for the tracking feature invalidation table (16 millions + entries)
  *
+ * Compile with:
+ *
+ *  cc -O2 ./tracking_collisions.c ../src/crc64.c ../src/sha1.c
+ *  ./a.out
+ *
  * --------------------------------------------------------------------------
  *
  * Copyright (C) 2019 Salvatore Sanfilippo
@@ -20,16 +25,47 @@
 #include <stdint.h>
 #include <string.h>
 #include <stdio.h>
+#include "../src/crc64.h"
+#include "../src/sha1.h"
 
 #define TABLE_SIZE (1<<24)
 int Table[TABLE_SIZE];
 
+uint64_t crc64Hash(char *key, size_t len) {
+    return crc64(0,(unsigned char*)key,len);
+}
+
+uint64_t sha1Hash(char *key, size_t len) {
+    SHA1_CTX ctx;
+    unsigned char hash[20];
+
+    SHA1Init(&ctx);
+    SHA1Update(&ctx,(unsigned char*)key,len);
+    SHA1Final(hash,&ctx);
+    uint64_t hash64;
+    memcpy(&hash64,hash,sizeof(hash64));
+    return hash64;
+}
+
 /* Test the hashing function provided as callback and return the
  * number of collisions found. */
 unsigned long testHashingFunction(uint64_t (*hash)(char *, size_t)) {
     unsigned long collisions = 0;
     memset(Table,0,sizeof(Table));
     char *prefixes[] = {"object", "message", "user", NULL};
+    for (int i = 0; prefixes[i] != NULL; i++) {
+        for (int j = 0; j < TABLE_SIZE/2; j++) {
+            char keyname[128];
+            size_t keylen = snprintf(keyname,sizeof(keyname),"%s:%d",
+                                     prefixes[i],j);
+            uint64_t bucket = hash(keyname,keylen) % TABLE_SIZE;
+            if (Table[bucket]) {
+                collisions++;
+            } else {
+                Table[bucket] = 1;
+            }
+        }
+    }
     return collisions;
 }