memcache files in godep

Godeps/_workspace/src/github.com/bradfitz/gomemcache/memcache/selector.go

+/*
+Copyright 2011 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 memcache
+
+import (
+	"hash/crc32"
+	"net"
+	"strings"
+	"sync"
+)
+
+// ServerSelector is the interface that selects a memcache server
+// as a function of the item's key.
+//
+// All ServerSelector implementations must be safe for concurrent use
+// by multiple goroutines.
+type ServerSelector interface {
+	// PickServer returns the server address that a given item
+	// should be shared onto.
+	PickServer(key string) (net.Addr, error)
+	Each(func(net.Addr) error) error
+}
+
+// ServerList is a simple ServerSelector. Its zero value is usable.
+type ServerList struct {
+	mu    sync.RWMutex
+	addrs []net.Addr
+}
+
+// SetServers changes a ServerList's set of servers at runtime and is
+// safe for concurrent use by multiple goroutines.
+//
+// Each server is given equal weight. A server is given more weight
+// if it's listed multiple times.
+//
+// SetServers returns an error if any of the server names fail to
+// resolve. No attempt is made to connect to the server. If any error
+// is returned, no changes are made to the ServerList.
+func (ss *ServerList) SetServers(servers ...string) error {
+	naddr := make([]net.Addr, len(servers))
+	for i, server := range servers {
+		if strings.Contains(server, "/") {
+			addr, err := net.ResolveUnixAddr("unix", server)
+			if err != nil {
+				return err
+			}
+			naddr[i] = addr
+		} else {
+			tcpaddr, err := net.ResolveTCPAddr("tcp", server)
+			if err != nil {
+				return err
+			}
+			naddr[i] = tcpaddr
+		}
+	}
+
+	ss.mu.Lock()
+	defer ss.mu.Unlock()
+	ss.addrs = naddr
+	return nil
+}
+
+// Each iterates over each server calling the given function
+func (ss *ServerList) Each(f func(net.Addr) error) error {
+	ss.mu.RLock()
+	defer ss.mu.RUnlock()
+	for _, a := range ss.addrs {
+		if err := f(a); nil != err {
+			return err
+		}
+	}
+	return nil
+}
+
+// keyBufPool returns []byte buffers for use by PickServer's call to
+// crc32.ChecksumIEEE to avoid allocations. (but doesn't avoid the
+// copies, which at least are bounded in size and small)
+var keyBufPool = sync.Pool{
+	New: func() interface{} {
+		b := make([]byte, 256)
+		return &b
+	},
+}
+
+func (ss *ServerList) PickServer(key string) (net.Addr, error) {
+	ss.mu.RLock()
+	defer ss.mu.RUnlock()
+	if len(ss.addrs) == 0 {
+		return nil, ErrNoServers
+	}
+	if len(ss.addrs) == 1 {
+		return ss.addrs[0], nil
+	}
+	bufp := keyBufPool.Get().(*[]byte)
+	n := copy(*bufp, key)
+	cs := crc32.ChecksumIEEE((*bufp)[:n])
+	keyBufPool.Put(bufp)
+
+	return ss.addrs[cs%uint32(len(ss.addrs))], nil
+}