First implementation

vendor/github.com/eclipse/paho.mqtt.golang/messageids.go

@@ -0,0 +1,176 @@
+/*
+ * Copyright (c) 2013 IBM Corp.
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *    Seth Hoenig
+ *    Allan Stockdill-Mander
+ *    Mike Robertson
+ */
+
+package mqtt
+
+import (
+	"fmt"
+	"sync"
+	"time"
+)
+
+// MId is 16 bit message id as specified by the MQTT spec.
+// In general, these values should not be depended upon by
+// the client application.
+type MId uint16
+
+type messageIds struct {
+	sync.RWMutex
+	index map[uint16]tokenCompletor
+
+	lastIssuedID uint16 // The most recently issued ID. Used so we cycle through ids rather than immediately reusing them (can make debugging easier)
+}
+
+const (
+	midMin uint16 = 1
+	midMax uint16 = 65535
+)
+
+func (mids *messageIds) cleanUp() {
+	mids.Lock()
+	for _, token := range mids.index {
+		switch token.(type) {
+		case *PublishToken:
+			token.setError(fmt.Errorf("connection lost before Publish completed"))
+		case *SubscribeToken:
+			token.setError(fmt.Errorf("connection lost before Subscribe completed"))
+		case *UnsubscribeToken:
+			token.setError(fmt.Errorf("connection lost before Unsubscribe completed"))
+		case nil:
+			continue
+		}
+		token.flowComplete()
+	}
+	mids.index = make(map[uint16]tokenCompletor)
+	mids.Unlock()
+	DEBUG.Println(MID, "cleaned up")
+}
+
+func (mids *messageIds) freeID(id uint16) {
+	mids.Lock()
+	delete(mids.index, id)
+	mids.Unlock()
+}
+
+func (mids *messageIds) claimID(token tokenCompletor, id uint16) {
+	mids.Lock()
+	defer mids.Unlock()
+	if _, ok := mids.index[id]; !ok {
+		mids.index[id] = token
+	} else {
+		old := mids.index[id]
+		old.flowComplete()
+		mids.index[id] = token
+	}
+	if id > mids.lastIssuedID {
+		mids.lastIssuedID = id
+	}
+}
+
+// getID will return an available id or 0 if none available
+// The id will generally be the previous id + 1 (because this makes tracing messages a bit simpler)
+func (mids *messageIds) getID(t tokenCompletor) uint16 {
+	mids.Lock()
+	defer mids.Unlock()
+	i := mids.lastIssuedID // note: the only situation where lastIssuedID is 0 the map will be empty
+	looped := false        // uint16 will loop from 65535->0
+	for {
+		i++
+		if i == 0 { // skip 0 because its not a valid id (Control Packets MUST contain a non-zero 16-bit Packet Identifier [MQTT-2.3.1-1])
+			i++
+			looped = true
+		}
+		if _, ok := mids.index[i]; !ok {
+			mids.index[i] = t
+			mids.lastIssuedID = i
+			return i
+		}
+		if (looped && i == mids.lastIssuedID) || (mids.lastIssuedID == 0 && i == midMax) { // lastIssuedID will be 0 at startup
+			return 0 // no free ids
+		}
+	}
+}
+
+func (mids *messageIds) getToken(id uint16) tokenCompletor {
+	mids.RLock()
+	defer mids.RUnlock()
+	if token, ok := mids.index[id]; ok {
+		return token
+	}
+	return &DummyToken{id: id}
+}
+
+type DummyToken struct {
+	id uint16
+}
+
+// Wait implements the Token Wait method.
+func (d *DummyToken) Wait() bool {
+	return true
+}
+
+// WaitTimeout implements the Token WaitTimeout method.
+func (d *DummyToken) WaitTimeout(t time.Duration) bool {
+	return true
+}
+
+// Done implements the Token Done method.
+func (d *DummyToken) Done() <-chan struct{} {
+	ch := make(chan struct{})
+	close(ch)
+	return ch
+}
+
+func (d *DummyToken) flowComplete() {
+	ERROR.Printf("A lookup for token %d returned nil\n", d.id)
+}
+
+func (d *DummyToken) Error() error {
+	return nil
+}
+
+func (d *DummyToken) setError(e error) {}
+
+// PlaceHolderToken does nothing and was implemented to allow a messageid to be reserved
+// it differs from DummyToken in that calling flowComplete does not generate an error (it
+// is expected that flowComplete will be called when the token is overwritten with a real token)
+type PlaceHolderToken struct {
+	id uint16
+}
+
+// Wait implements the Token Wait method.
+func (p *PlaceHolderToken) Wait() bool {
+	return true
+}
+
+// WaitTimeout implements the Token WaitTimeout method.
+func (p *PlaceHolderToken) WaitTimeout(t time.Duration) bool {
+	return true
+}
+
+// Done implements the Token Done method.
+func (p *PlaceHolderToken) Done() <-chan struct{} {
+	ch := make(chan struct{})
+	close(ch)
+	return ch
+}
+
+func (p *PlaceHolderToken) flowComplete() {
+}
+
+func (p *PlaceHolderToken) Error() error {
+	return nil
+}
+
+func (p *PlaceHolderToken) setError(e error) {}