Add initial sandbox management implementation

Signed-off-by: Random-Liu <lantaol@google.com>

pkg/registrar/registrar.go

@@ -0,0 +1,101 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+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 registrar
+
+import (
+	"fmt"
+	"sync"
+)
+
+// Registrar stores one-to-one name<->key mappings.
+// Names and keys must be unique.
+// Registrar is safe for concurrent access.
+type Registrar struct {
+	lock      sync.Mutex
+	nameToKey map[string]string
+	keyToName map[string]string
+}
+
+// NewRegistrar creates a new Registrar with the empty indexes.
+func NewRegistrar() *Registrar {
+	return &Registrar{
+		nameToKey: make(map[string]string),
+		keyToName: make(map[string]string),
+	}
+}
+
+// Reserve registers a name<->key mapping, name or key must not
+// be empty.
+// Reserve is idempotent.
+// Attempting to reserve a conflict key<->name mapping results
+// in an error.
+// A name<->key reservation is globally unique.
+func (r *Registrar) Reserve(name, key string) error {
+	r.lock.Lock()
+	defer r.lock.Unlock()
+
+	if name == "" || key == "" {
+		return fmt.Errorf("invalid name %q or key %q", name, key)
+	}
+
+	if k, exists := r.nameToKey[name]; exists {
+		if k != key {
+			return fmt.Errorf("name %q is reserved for %q", name, k)
+		}
+		return nil
+	}
+
+	if n, exists := r.keyToName[key]; exists {
+		if n != name {
+			return fmt.Errorf("key %q is reserved for %q", key, n)
+		}
+		return nil
+	}
+
+	r.nameToKey[name] = key
+	r.keyToName[key] = name
+	return nil
+}
+
+// ReleaseByName releases the reserved name<->key mapping by name.
+// Once released, the name and the key can be reserved again.
+func (r *Registrar) ReleaseByName(name string) {
+	r.lock.Lock()
+	defer r.lock.Unlock()
+
+	key, exists := r.nameToKey[name]
+	if !exists {
+		return
+	}
+
+	delete(r.nameToKey, name)
+	delete(r.keyToName, key)
+}
+
+// ReleaseByKey release the reserved name<->key mapping by key.
+func (r *Registrar) ReleaseByKey(key string) {
+	r.lock.Lock()
+	defer r.lock.Unlock()
+
+	name, exists := r.keyToName[key]
+	if !exists {
+		return
+	}
+
+	delete(r.nameToKey, name)
+	delete(r.keyToName, key)
+}