rpc: add new client, use it everywhere

The new client implementation supports concurrent requests,
subscriptions and replaces the various ad hoc RPC clients
throughout go-ethereum.

rpc/ipc_windows.go

@@ -22,16 +22,27 @@ import (
 	"net"
 	"time"
 
+	"golang.org/x/net/context"
 	"gopkg.in/natefinch/npipe.v2"
 )
 
+// This is used if the dialing context has no deadline. It is much smaller than the
+// defaultDialTimeout because named pipes are local and there is no need to wait so long.
+const defaultPipeDialTimeout = 2 * time.Second
+
 // ipcListen will create a named pipe on the given endpoint.
 func ipcListen(endpoint string) (net.Listener, error) {
 	return npipe.Listen(endpoint)
 }
 
 // newIPCConnection will connect to a named pipe with the given endpoint as name.
-func newIPCConnection(endpoint string) (net.Conn, error) {
-	timeout := 5 * time.Second
+func newIPCConnection(ctx context.Context, endpoint string) (net.Conn, error) {
+	timeout := defaultPipeDialTimeout
+	if deadline, ok := ctx.Deadline(); ok {
+		timeout = deadline.Sub(time.Now())
+		if timeout < 0 {
+			timeout = 0
+		}
+	}
 	return npipe.DialTimeout(endpoint, timeout)
 }