Merge pull request orcaman#33 from redbaron/nolock-fnv

Replace hash/fnv + sync.pool magic with simple fnv32 func

concurrent_map.go

@@ -2,13 +2,9 @@ package cmap
 
 import (
 	"encoding/json"
-	"hash"
-	"hash/fnv"
 	"sync"
 )
 
-var hashPool = new(sync.Pool)
-
 var SHARD_COUNT = 32
 
 // A "thread" safe map of type string:Anything.
@@ -32,17 +28,7 @@ func New() ConcurrentMap {
 
 // Returns shard under given key
 func (m ConcurrentMap) GetShard(key string) *ConcurrentMapShared {
-	hasherAsInterface := hashPool.Get()
-	var hasher hash.Hash32
-	if hasherAsInterface == nil {
-		hasher = fnv.New32()
-	} else {
-		hasher = hasherAsInterface.(hash.Hash32)
-		hasher.Reset()
-	}
-	hasher.Write([]byte(key))
-	sum := hasher.Sum32()
-	hashPool.Put(hasher)
+	sum := fnv32([]byte(key))
 	return m[uint(sum)%uint(SHARD_COUNT)]
 }
 
@@ -236,6 +222,16 @@ func (m ConcurrentMap) MarshalJSON() ([]byte, error) {
 	return json.Marshal(tmp)
 }
 
+func fnv32(key []byte) uint32 {
+	hash := uint32(2166136261)
+	prime32 := uint32(16777619)
+	for _, c := range key {
+		hash *= prime32
+		hash ^= uint32(c)
+	}
+	return hash
+}
+
 // Concurrent map uses Interface{} as its value, therefor JSON Unmarshal
 // will probably won't know which to type to unmarshal into, in such case
 // we'll end up with a value of type map[string]interface{}, In most cases this isn't

concurrent_map_test.go

@@ -2,6 +2,7 @@ package cmap
 
 import (
 	"encoding/json"
+	"hash/fnv"
 	"sort"
 	"strconv"
 	"testing"
@@ -316,3 +317,13 @@ func TestMInsert(t *testing.T) {
 		t.Error("map should contain exactly two elements.")
 	}
 }
+
+func TestFnv32(t *testing.T) {
+	key := []byte("ABC")
+
+	hasher := fnv.New32()
+	hasher.Write(key)
+	if fnv32(key) != hasher.Sum32() {
+		t.Errorf("Bundled fnv32 produced %d, expected result from hash/fnv32 is %d", fnv32(key), hasher.Sum32())
+	}
+}