unix: unify Ioctl* functions

Unify Ioctl* functions common across the different UNIX OSs.

Change-Id: I2376d97a7162e7e6518f75faf9317ffc87962411
Reviewed-on: https://go-review.googlesource.com/c/sys/+/192358
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>

unix/ioctl.go

@@ -6,7 +6,19 @@
 
 package unix
 
-import "runtime"
+import (
+	"runtime"
+	"unsafe"
+)
+
+// ioctl itself should not be exposed directly, but additional get/set
+// functions for specific types are permissible.
+
+// IoctlSetInt performs an ioctl operation which sets an integer value
+// on fd, using the specified request number.
+func IoctlSetInt(fd int, req uint, value int) error {
+	return ioctl(fd, req, uintptr(value))
+}
 
 // IoctlSetWinsize performs an ioctl on fd with a *Winsize argument.
 //
@@ -14,7 +26,7 @@ import "runtime"
 func IoctlSetWinsize(fd int, req uint, value *Winsize) error {
 	// TODO: if we get the chance, remove the req parameter and
 	// hardcode TIOCSWINSZ.
-	err := ioctlSetWinsize(fd, req, value)
+	err := ioctl(fd, req, uintptr(unsafe.Pointer(value)))
 	runtime.KeepAlive(value)
 	return err
 }
@@ -24,7 +36,27 @@ func IoctlSetWinsize(fd int, req uint, value *Winsize) error {
 // The req value will usually be TCSETA or TIOCSETA.
 func IoctlSetTermios(fd int, req uint, value *Termios) error {
 	// TODO: if we get the chance, remove the req parameter.
-	err := ioctlSetTermios(fd, req, value)
+	err := ioctl(fd, req, uintptr(unsafe.Pointer(value)))
 	runtime.KeepAlive(value)
 	return err
 }
+
+// IoctlGetInt performs an ioctl operation which gets an integer value
+// from fd, using the specified request number.
+func IoctlGetInt(fd int, req uint) (int, error) {
+	var value int
+	err := ioctl(fd, req, uintptr(unsafe.Pointer(&value)))
+	return value, err
+}
+
+func IoctlGetWinsize(fd int, req uint) (*Winsize, error) {
+	var value Winsize
+	err := ioctl(fd, req, uintptr(unsafe.Pointer(&value)))
+	return &value, err
+}
+
+func IoctlGetTermios(fd int, req uint) (*Termios, error) {
+	var value Termios
+	err := ioctl(fd, req, uintptr(unsafe.Pointer(&value)))
+	return &value, err
+}