Hulk did something

[bytom/vapor.git] / vendor / github.com / golang / groupcache / consistenthash / consistenthash.go

diff --git a/vendor/github.com/golang/groupcache/consistenthash/consistenthash.go b/vendor/github.com/golang/groupcache/consistenthash/consistenthash.go
new file mode 100644 (file)
index 0000000..a9c56f0
--- /dev/null
+++ b/vendor/github.com/golang/groupcache/consistenthash/consistenthash.go
@@ -0,0 +1,81 @@
+/*
+Copyright 2013 Google Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package consistenthash provides an implementation of a ring hash.
+package consistenthash
+
+import (
+       "hash/crc32"
+       "sort"
+       "strconv"
+)
+
+type Hash func(data []byte) uint32
+
+type Map struct {
+       hash     Hash
+       replicas int
+       keys     []int // Sorted
+       hashMap  map[int]string
+}
+
+func New(replicas int, fn Hash) *Map {
+       m := &Map{
+               replicas: replicas,
+               hash:     fn,
+               hashMap:  make(map[int]string),
+       }
+       if m.hash == nil {
+               m.hash = crc32.ChecksumIEEE
+       }
+       return m
+}
+
+// Returns true if there are no items available.
+func (m *Map) IsEmpty() bool {
+       return len(m.keys) == 0
+}
+
+// Adds some keys to the hash.
+func (m *Map) Add(keys ...string) {
+       for _, key := range keys {
+               for i := 0; i < m.replicas; i++ {
+                       hash := int(m.hash([]byte(strconv.Itoa(i) + key)))
+                       m.keys = append(m.keys, hash)
+                       m.hashMap[hash] = key
+               }
+       }
+       sort.Ints(m.keys)
+}
+
+// Gets the closest item in the hash to the provided key.
+func (m *Map) Get(key string) string {
+       if m.IsEmpty() {
+               return ""
+       }
+
+       hash := int(m.hash([]byte(key)))
+
+       // Binary search for appropriate replica.
+       idx := sort.Search(len(m.keys), func(i int) bool { return m.keys[i] >= hash })
+
+       // Means we have cycled back to the first replica.
+       if idx == len(m.keys) {
+               idx = 0
+       }
+
+       return m.hashMap[m.keys[idx]]
+}