1 files changed, 119 insertions, 0 deletions
diff --git a/wl/conn.go b/wl/conn.go
new file mode 100644
index 00000000..a04845cf
--- /dev/null
+++ b/wl/conn.go
@@ -0,0 +1,119 @@
+package wl
+
+import (
+	"errors"
+	"net"
+	"os"
+	"runtime"
+	"sync"
+	"syscall"
+)
+
+type Conn struct {
+	conn *net.UnixConn
+
+	done     chan struct{}
+	doneOnce sync.Once
+
+	mu sync.Mutex
+}
+
+// Attach connects Conn to a wayland socket.
+func (c *Conn) Attach(p string) (err error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.conn != nil {
+		return errors.New("attached")
+	}
+
+	c.conn, err = net.DialUnix("unix", nil, &net.UnixAddr{Name: p, Net: "unix"})
+	return
+}
+
+// Close releases resources and closes the connection to the wayland compositor.
+func (c *Conn) Close() error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.done == nil {
+		return errors.New("no socket bound")
+	}
+
+	c.doneOnce.Do(func() {
+		c.done <- struct{}{}
+		<-c.done
+	})
+
+	// closed by wayland
+	runtime.SetFinalizer(c.conn, nil)
+	return nil
+}
+
+func (c *Conn) Bind(p, appID, instanceID string) (*os.File, error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.conn == nil {
+		return nil, errors.New("not attached")
+	}
+	if c.done != nil {
+		return nil, errors.New("bound")
+	}
+
+	if rc, err := c.conn.SyscallConn(); err != nil {
+		// unreachable
+		return nil, err
+	} else {
+		c.done = make(chan struct{})
+		return bindRawConn(c.done, rc, p, appID, instanceID)
+	}
+}
+
+func bindRawConn(done chan struct{}, rc syscall.RawConn, p, appID, instanceID string) (*os.File, error) {
+	var syncPipe [2]*os.File
+
+	if r, w, err := os.Pipe(); err != nil {
+		return nil, err
+	} else {
+		syncPipe[0] = r
+		syncPipe[1] = w
+	}
+
+	setupDone := make(chan error, 1) // does not block with c.done
+
+	go func() {
+		if err := rc.Control(func(fd uintptr) {
+			// prevent runtime from closing the read end of sync fd
+			runtime.SetFinalizer(syncPipe[0], nil)
+
+			// allow the Bind method to return after setup
+			setupDone <- bind(fd, p, appID, instanceID, syncPipe[0].Fd())
+			close(setupDone)
+
+			// keep socket alive until done is requested
+			<-done
+		}); err != nil {
+			setupDone <- err
+		}
+
+		// notify Close that rc.Control has returned
+		close(done)
+	}()
+
+	// return write end of the pipe
+	return syncPipe[1], <-setupDone
+}
+
+func bind(fd uintptr, p, appID, instanceID string, syncFD uintptr) error {
+	// ensure p is available
+	if f, err := os.Create(p); err != nil {
+		return err
+	} else if err = f.Close(); err != nil {
+		return err
+	} else if err = os.Remove(p); err != nil {
+		return err
+	}
+
+	return bindWaylandFd(p, fd, appID, instanceID, syncFD)
+}