Merge lp:~sergiusens/go-dbus/sequential_writes into lp:go-dbus/v1

[Sergio Schvezov]

Making message writing sequential to avoid multiple messages writing to the bus at the same time

[John Lenton (chipaca)]

LGTM.

review: Approve

[Roberto Alsina (ralsina)]

Needs fixing because "doesn't not need" is not a reasonable comment :-)

[lp:~sergiusens/go-dbus/sequential_writes]

130. By Sergio Schvezov on 2014-10-22

Fixing double negation

[Roberto Alsina (ralsina)]

There's still a couple double negations, lines 17, 26 of the diff.

=== modified file 'auth.go'
--- auth.go	2013-03-09 04:13:25 +0000
+++ auth.go	2014-10-22 21:48:46 +0000
@@ -115,6 +115,8 @@
 	}
 
 	// The authentication process starts by writing a nul byte
+	// writing at this point does not need to be synced as the connection
+	// is not shared at this point.
 	if _, err := conn.Write([]byte{0}); err != nil {
 		return err
 	}
@@ -122,6 +124,8 @@
 	inStream := bufio.NewReader(conn)
 	send := func(command ...[]byte) ([][]byte, error) {
 		msg := bytes.Join(command, []byte(" "))
+		// writing at this point doesn't not need to be synced as the connection
+		// is not shared at this point.
 		_, err := conn.Write(append(msg, []byte("\r\n")...))
 		if err != nil {
 			return nil, err
@@ -178,6 +182,8 @@
 		return errors.New("Could not authenticate with any mechanism")
 	}
 	// XXX: UNIX FD negotiation would go here.
+	// writing at this point doesn't not need to be synced as the connection
+	// is not shared at this point.
 	if _, err := conn.Write([]byte("BEGIN\r\n")); err != nil {
 		return err
 	}
 
=== modified file 'message.go'
--- message.go	2013-03-12 07:20:42 +0000
+++ message.go	2014-10-22 21:48:46 +0000
@@ -4,6 +4,7 @@
 	"encoding/binary"
 	"errors"
 	"io"
+	"sync"
 )
 
 // See the D-Bus tutorial for information about message types.
@@ -26,6 +27,8 @@
 	TypeError:        "error",
 }
 
+var writeMutex sync.Mutex
+
 func (t MessageType) String() string { return messageTypeString[t] }
 
 type MessageFlag uint8
@@ -319,6 +322,10 @@
 
 // WriteTo serialises the message and writes it to the given writer.
 func (p *Message) WriteTo(w io.Writer) (int64, error) {
+	// message writing needs to be sequential
+	writeMutex.Lock()
+	defer writeMutex.Unlock()
+
 	fields := make([]headerField, 0, 10)
 	if p.Path != "" {
 		fields = append(fields, headerField{1, Variant{p.Path}})
 
=== modified file 'transport.go'
--- transport.go	2013-03-09 04:13:25 +0000
+++ transport.go	2014-10-22 21:48:46 +0000
@@ -102,6 +102,8 @@
 		return nil, err
 	}
 	// Write the nonce data to the socket
+	// writing at this point does not need to be synced as the connection
+	// is not shared at this point.
 	if _, err := conn.Write(data); err != nil {
 		conn.Close()
 		return nil, err