Update hashcode to always generate a positive index

helper/hashcode/hashcode.go

@@ -5,6 +5,15 @@ import (
 )
 
 // String hashes a string to a unique hashcode.
+//
+// crc32 returns a uint32, but for our use we need
+// and non negative integer. Here we cast to an integer
+// and invert it if the result is negative.
 func String(s string) int {
- return int(crc32.ChecksumIEEE([]byte(s)))
+ v := int(crc32.ChecksumIEEE([]byte(s)))
+ if v < 0 {
+ return -v
+ }
+
+ return v
 }

helper/hashcode/hashcode_test.go

@@ -10,7 +10,16 @@ func TestString(t *testing.T) {
  for i := 0; i < 100; i++ {
  actual := String(v)
  if actual != expected {
- t.Fatalf("bad: %#v", actual)
+ t.Fatalf("bad: %#v\n\t%#v", actual, expected)
+ }
+ }
+}
+
+func TestString_positiveIndex(t *testing.T) {
+ ips := []string{"192.168.1.3", "192.168.1.5"}
+ for _, ip := range ips {
+ if index := String(ip); index < 0 {
+ t.Fatalf("Bad Index %#v for ip %s", index, ip)
  }
  }
 }