http: add Pending method to ServerConn, ClientConn

R=rsc
CC=golang-dev
https://golang.org/cl/216052

src/pkg/http/persist.go

@@ -45,6 +45,8 @@ func NewServerConn(c net.Conn, r *bufio.Reader) *ServerConn {
 // called before Read has signaled the end of the keep-alive logic. The user
 // should not call Close while Read or Write is in progress.
 func (sc *ServerConn) Close() (c net.Conn, r *bufio.Reader) {
+	sc.lk.Lock()
+	defer sc.lk.Unlock()
 	c = sc.c
 	r = sc.r
 	sc.c = nil
@@ -111,6 +113,14 @@ func (sc *ServerConn) Read() (req *Request, err os.Error) {
 	return
 }
 
+// Pending returns the number of unanswered requests
+// that have been received on the connection.
+func (sc *ServerConn) Pending() int {
+	sc.lk.Lock()
+	defer sc.lk.Unlock()
+	return sc.nread - sc.nwritten
+}
+
 // Write writes a repsonse. To close the connection gracefully, set the
 // Response.Close field to true. Write should be considered operational until
 // it returns an error, regardless of any errors returned on the Read side.
@@ -176,11 +186,11 @@ func NewClientConn(c net.Conn, r *bufio.Reader) *ClientConn {
 // called before the user or Read have signaled the end of the keep-alive
 // logic. The user should not call Close while Read or Write is in progress.
 func (cc *ClientConn) Close() (c net.Conn, r *bufio.Reader) {
+	cc.lk.Lock()
 	c = cc.c
 	r = cc.r
 	cc.c = nil
 	cc.r = nil
-	cc.lk.Lock()
 	cc.reqm.Init()
 	cc.lk.Unlock()
 	return
@@ -228,6 +238,14 @@ func (cc *ClientConn) Write(req *Request) os.Error {
 	return nil
 }
 
+// Pending returns the number of unanswered requests
+// that have been sent on the connection.
+func (cc *ClientConn) Pending() int {
+	cc.lk.Lock()
+	defer cc.lk.Unlock()
+	return cc.nwritten - cc.nread
+}
+
 // Read reads the next response from the wire. A valid response might be
 // returned together with an ErrPersistEOF, which means that the remote
 // requested that this be the last request serviced. Read can be called