From 768a7d5052cbcd22844d1300d5bc5626e995ee09 Mon Sep 17 00:00:00 2001
From: Jakob Borg <jakob@nym.se>
Date: Sun, 15 Dec 2013 15:58:27 +0100
Subject: [PATCH] Simplify async results

---
 protocol/protocol.go | 62 ++++++++++++++++++++++----------------------
 1 file changed, 31 insertions(+), 31 deletions(-)

diff --git a/protocol/protocol.go b/protocol/protocol.go
index 7eca8428a..20a605f93 100644
--- a/protocol/protocol.go
+++ b/protocol/protocol.go
@@ -18,8 +18,6 @@ const (
 	messageTypePong
 )
 
-var ErrClosed = errors.New("Connection closed")
-
 type FileInfo struct {
 	Name     string
 	Flags    uint32
@@ -50,11 +48,18 @@ type Connection struct {
 	wLock      sync.RWMutex
 	closed     bool
 	closedLock sync.RWMutex
-	awaiting   map[int]chan interface{}
+	awaiting   map[int]chan asyncResult
 	nextId     int
 	ID         string
 }
 
+var ErrClosed = errors.New("Connection closed")
+
+type asyncResult struct {
+	val []byte
+	err error
+}
+
 func NewConnection(nodeID string, reader io.Reader, writer io.Writer, receiver Model) *Connection {
 	flrd := flate.NewReader(reader)
 	flwr, err := flate.NewWriter(writer, flate.BestSpeed)
@@ -68,7 +73,7 @@ func NewConnection(nodeID string, reader io.Reader, writer io.Writer, receiver M
 		mreader:  &marshalReader{flrd, 0, nil},
 		writer:   flwr,
 		mwriter:  &marshalWriter{flwr, 0, nil},
-		awaiting: make(map[int]chan interface{}),
+		awaiting: make(map[int]chan asyncResult),
 		ID:       nodeID,
 	}
 
@@ -91,7 +96,7 @@ func (c *Connection) Index(idx []FileInfo) {
 // Request returns the bytes for the specified block after fetching them from the connected peer.
 func (c *Connection) Request(name string, offset uint64, size uint32, hash []byte) ([]byte, error) {
 	c.wLock.Lock()
-	rc := make(chan interface{})
+	rc := make(chan asyncResult)
 	c.awaiting[c.nextId] = rc
 	c.mwriter.writeHeader(header{0, c.nextId, messageTypeRequest})
 	c.mwriter.writeRequest(request{name, offset, size, hash})
@@ -99,30 +104,16 @@ func (c *Connection) Request(name string, offset uint64, size uint32, hash []byt
 	c.nextId = (c.nextId + 1) & 0xfff
 	c.wLock.Unlock()
 
-	// Reading something that might be nil from a possibly closed channel...
-	// r0<~
-
-	var data []byte
-	i, ok := <-rc
-	if ok {
-		if d, ok := i.([]byte); ok {
-			data = d
-		}
+	res, ok := <-rc
+	if !ok {
+		return nil, ErrClosed
 	}
-
-	var err error
-	i, ok = <-rc
-	if ok {
-		if e, ok := i.(error); ok {
-			err = e
-		}
-	}
-	return data, err
+	return res.val, res.err
 }
 
 func (c *Connection) Ping() bool {
 	c.wLock.Lock()
-	rc := make(chan interface{})
+	rc := make(chan asyncResult)
 	c.awaiting[c.nextId] = rc
 	c.mwriter.writeHeader(header{0, c.nextId, messageTypePing})
 	c.flush()
@@ -150,12 +141,14 @@ func (c *Connection) close() {
 	c.closedLock.Lock()
 	c.closed = true
 	c.closedLock.Unlock()
+
 	c.wLock.Lock()
 	for _, ch := range c.awaiting {
 		close(ch)
 	}
 	c.awaiting = nil
 	c.wLock.Unlock()
+
 	c.receiver.Close(c.ID)
 }
 
@@ -196,10 +189,12 @@ func (c *Connection) readerLoop() {
 				c.wLock.RUnlock()
 
 				if ok {
-					rc <- data
-					rc <- c.mreader.err
-					delete(c.awaiting, hdr.msgID)
+					rc <- asyncResult{data, c.mreader.err}
 					close(rc)
+
+					c.wLock.Lock()
+					delete(c.awaiting, hdr.msgID)
+					c.wLock.Unlock()
 				}
 			}
 
@@ -210,13 +205,18 @@ func (c *Connection) readerLoop() {
 			c.wLock.Unlock()
 
 		case messageTypePong:
-			c.wLock.Lock()
-			if rc, ok := c.awaiting[hdr.msgID]; ok {
-				rc <- true
+			c.wLock.RLock()
+			rc, ok := c.awaiting[hdr.msgID]
+			c.wLock.RUnlock()
+
+			if ok {
+				rc <- asyncResult{}
 				close(rc)
+
+				c.wLock.Lock()
 				delete(c.awaiting, hdr.msgID)
+				c.wLock.Unlock()
 			}
-			c.wLock.Unlock()
 		}
 	}
 }