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

go.mod

@@ -6,7 +6,7 @@ require (
 	github.com/mattn/go-isatty v0.0.12
 	github.com/xiaq/persistent v0.0.0-20200820214153-3175cfb92e14
 	go.etcd.io/bbolt v1.3.5
-	golang.org/x/sys v0.0.0-20200820212457-1fb795427249
+	golang.org/x/sys v0.0.0-20200824131525-c12d262b63d8
 )
 
 go 1.14

go.sum

@@ -13,3 +13,5 @@ golang.org/x/sys v0.0.0-20200202164722-d101bd2416d5 h1:LfCXLvNmTYH9kEmVgqbnsWfru
 golang.org/x/sys v0.0.0-20200202164722-d101bd2416d5/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200820212457-1fb795427249 h1:tKP05IMsVLZ4VeeCEFmrIUmxAAx6UD8IBdPtYlYNa8g=
 golang.org/x/sys v0.0.0-20200820212457-1fb795427249/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200824131525-c12d262b63d8 h1:AvbQYmiaaaza3cW3QXRyPo5kYgpFIzOAfeAAN7m3qQ4=
+golang.org/x/sys v0.0.0-20200824131525-c12d262b63d8/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

pkg/cli/term/setup_unix.go

@@ -11,14 +11,12 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-const flushInputDuringSetup = false
-
 func setup(in, out *os.File) (func() error, error) {
 	// On Unix, use input file for changing termios. All fds pointing to the
 	// 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)
 	}
@@ -40,14 +38,6 @@ func setup(in, out *os.File) (func() error, error) {
 		return nil, fmt.Errorf("can't set up terminal attribute: %s", err)
 	}
 
-	var errFlushInput error
-	if flushInputDuringSetup {
-		err = sys.FlushInput(fd)
-		if err != nil {
-			errFlushInput = fmt.Errorf("can't flush input: %s", err)
-		}
-	}
-
 	var errSetupVT error
 	err = setupVT(out)
 	if err != nil {
@@ -58,7 +48,7 @@ func setup(in, out *os.File) (func() error, error) {
 		return util.Errors(savedTermios.ApplyToFd(fd), restoreVT(out))
 	}
 
-	return restore, util.Errors(errFlushInput, errSetupVT)
+	return restore, errSetupVT
 }
 
 func setupGlobal() func() {

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.IoctlSetPointerInt(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.
@@ -65,8 +62,3 @@ func (term *Termios) SetEcho(v bool) {
 func (term *Termios) SetICRNL(v bool) {
 	setFlag(&term.Iflag, unix.ICRNL, v)
 }
-
-// FlushInput discards data written to a file descriptor but not read.
-func FlushInput(fd int) error {
-	return Ioctl(fd, flushIOCTL, uintptr(unix.TCIFLUSH))
-}