src: Add DMA localagent

[barometer.git] / src / dma / vendor / github.com / go-redis / redis / internal / singleflight / singleflight.go

diff --git a/src/dma/vendor/github.com/go-redis/redis/internal/singleflight/singleflight.go b/src/dma/vendor/github.com/go-redis/redis/internal/singleflight/singleflight.go
new file mode 100644 (file)
index 0000000..3b17417
--- /dev/null
+++ b/src/dma/vendor/github.com/go-redis/redis/internal/singleflight/singleflight.go
@@ -0,0 +1,64 @@
+/*
+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 singleflight provides a duplicate function call suppression
+// mechanism.
+package singleflight
+
+import "sync"
+
+// call is an in-flight or completed Do call
+type call struct {
+       wg  sync.WaitGroup
+       val interface{}
+       err error
+}
+
+// Group represents a class of work and forms a namespace in which
+// units of work can be executed with duplicate suppression.
+type Group struct {
+       mu sync.Mutex       // protects m
+       m  map[string]*call // lazily initialized
+}
+
+// Do executes and returns the results of the given function, making
+// sure that only one execution is in-flight for a given key at a
+// time. If a duplicate comes in, the duplicate caller waits for the
+// original to complete and receives the same results.
+func (g *Group) Do(key string, fn func() (interface{}, error)) (interface{}, error) {
+       g.mu.Lock()
+       if g.m == nil {
+               g.m = make(map[string]*call)
+       }
+       if c, ok := g.m[key]; ok {
+               g.mu.Unlock()
+               c.wg.Wait()
+               return c.val, c.err
+       }
+       c := new(call)
+       c.wg.Add(1)
+       g.m[key] = c
+       g.mu.Unlock()
+
+       c.val, c.err = fn()
+       c.wg.Done()
+
+       g.mu.Lock()
+       delete(g.m, key)
+       g.mu.Unlock()
+
+       return c.val, c.err
+}