Eliminate sys.Ioctl

I started by writing tests for sys.Ioctl but after I had 100% coverage
of that function it occurred to me the function could be eliminated.

Related #1062

pkg/cli/term/setup_unix.go

@@ -18,7 +18,7 @@ func setup(in, out *os.File) (func() error, error) {
 	// same terminal are equivalent.
 
 	fd := int(in.Fd())
-	term, err := sys.NewTermiosFromFd(fd)
+	term, err := sys.TermiosForFd(fd)
 	if err != nil {
 		return nil, fmt.Errorf("can't get terminal attribute: %s", err)
 	}

pkg/cli/term/setup_unix_test.go

@@ -22,5 +22,5 @@ func TestSetupTerminal(t *testing.T) {
 	}
 	// TODO(xiaq): Test whether the interesting flags in the termios were indeed
 	// set.
-	// termios, err := sys.NewTermiosFromFd(int(tty.Fd()))
+	// termios, err := sys.TermiosForFd(int(tty.Fd()))
 }

pkg/sys/ioctl.go

@@ -1,19 +0,0 @@
-// +build !windows,!plan9
-
-package sys
-
-import (
-	"os"
-
-	"golang.org/x/sys/unix"
-)
-
-// Ioctl wraps the ioctl syscall.
-func Ioctl(fd int, req uintptr, arg uintptr) error {
-	_, _, e := unix.Syscall(
-		unix.SYS_IOCTL, uintptr(fd), req, arg)
-	if e != 0 {
-		return os.NewSyscallError("ioctl", e)
-	}
-	return nil
-}

pkg/sys/isatty_unix.go

@@ -4,12 +4,10 @@ package sys
 
 import (
 	"os"
-	"unsafe"
 )
 
 // IsATTY returns true if the given file is a terminal.
 func IsATTY(file *os.File) bool {
-	var term Termios
-	err := Ioctl(int(file.Fd()), getAttrIOCTL, uintptr(unsafe.Pointer(&term)))
+	_, err := TermiosForFd(int(file.Fd()))
 	return err == nil
 }

pkg/sys/tc.go

@@ -3,20 +3,9 @@
 package sys
 
 import (
-	"unsafe"
-
 	"golang.org/x/sys/unix"
 )
 
-func Tcgetpgrp(fd int) (int, error) {
-	var pid int
-	errno := Ioctl(fd, unix.TIOCGPGRP, uintptr(unsafe.Pointer(&pid)))
-	if errno == nil {
-		return pid, nil
-	}
-	return -1, errno
-}
-
 func Tcsetpgrp(fd int, pid int) error {
-	return Ioctl(fd, unix.TIOCSPGRP, uintptr(unsafe.Pointer(&pid)))
+	return unix.IoctlSetInt(fd, unix.TIOCSPGRP, pid)
 }

pkg/sys/termios.go

@@ -15,19 +15,16 @@ import (
 // Termios represents terminal attributes.
 type Termios unix.Termios
 
-// NewTermiosFromFd extracts the terminal attribute of the given file
-// descriptor.
-func NewTermiosFromFd(fd int) (*Termios, error) {
-	var term Termios
-	if err := Ioctl(fd, getAttrIOCTL, uintptr(unsafe.Pointer(&term))); err != nil {
-		return nil, err
-	}
-	return &term, nil
+// TermiosForFd returns a pointer to a Termios structure if the file
+// descriptor is open on a terminal device.
+func TermiosForFd(fd int) (*Termios, error) {
+	term, err := unix.IoctlGetTermios(fd, getAttrIOCTL)
+	return (*Termios)(term), err
 }
 
 // ApplyToFd applies term to the given file descriptor.
 func (term *Termios) ApplyToFd(fd int) error {
-	return Ioctl(fd, setAttrNowIOCTL, uintptr(unsafe.Pointer(term)))
+	return unix.IoctlSetTermios(fd, setAttrNowIOCTL, (*unix.Termios)(unsafe.Pointer(term)))
 }
 
 // Copy returns a copy of term.
@@ -68,5 +65,5 @@ func (term *Termios) SetICRNL(v bool) {
 
 // FlushInput discards data written to a file descriptor but not read.
 func FlushInput(fd int) error {
-	return Ioctl(fd, flushIOCTL, uintptr(unix.TCIFLUSH))
+	return unix.IoctlSetInt(fd, flushIOCTL, unix.TCIFLUSH)
 }