Added terminal/pty resize functionality and utility function to inherit size from master's pty to slave. Changes type winsize to make it accessible from outside the package. (#39)

Author: JonathanLogan

util.go

@@ -8,26 +8,53 @@ import (
 	"unsafe"
 )
 
+// InheritSize applies the terminal size of master to slave. This should be run
+// in a signal handler for syscall.SIGWINCH to automatically resize the slave when
+// the master receives a window size change notification.
+func InheritSize(master, slave *os.File) error {
+	size, err := GetsizeFull(master)
+	if err != nil {
+		return err
+	}
+	err = Setsize(slave, size)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// Setsize resizes t to s.
+func Setsize(t *os.File, ws *Winsize) error {
+	return windowRectCall(ws, t.Fd(), syscall.TIOCSWINSZ)
+}
+
+// GetsizeFull returns the full terminal size description.
+func GetsizeFull(t *os.File) (size *Winsize, err error) {
+	var ws Winsize
+	err = windowRectCall(&ws, t.Fd(), syscall.TIOCGWINSZ)
+	return &ws, err
+}
+
 // Getsize returns the number of rows (lines) and cols (positions
 // in each line) in terminal t.
 func Getsize(t *os.File) (rows, cols int, err error) {
-	var ws winsize
-	err = windowrect(&ws, t.Fd())
-	return int(ws.ws_row), int(ws.ws_col), err
+	ws, err := GetsizeFull(t)
+	return int(ws.Rows), int(ws.Cols), err
 }
 
-type winsize struct {
-	ws_row    uint16
-	ws_col    uint16
-	ws_xpixel uint16
-	ws_ypixel uint16
+// Winsize describes the terminal size.
+type Winsize struct {
+	Rows uint16 // ws_row: Number of rows (in cells)
+	Cols uint16 // ws_col: Number of columns (in cells)
+	X    uint16 // ws_xpixel: Width in pixels
+	Y    uint16 // ws_ypixel: Height in pixels
 }
 
-func windowrect(ws *winsize, fd uintptr) error {
+func windowRectCall(ws *Winsize, fd, a2 uintptr) error {
 	_, _, errno := syscall.Syscall(
 		syscall.SYS_IOCTL,
 		fd,
-		syscall.TIOCGWINSZ,
+		a2,
 		uintptr(unsafe.Pointer(ws)),
 	)
 	if errno != 0 {