exp/terminal: rename shell to terminal and add SetSize

It was never really a shell, but the name carried
over from SSH's ServerShell.

Two small functional changes:

Add SetSize, which allows the size of the terminal
to be changed in response, say, to an SSH message.

Don't write the prompt if there's already something
on the current line.

R=rsc
CC=golang-dev
https://golang.org/cl/5376066

src/pkg/exp/terminal/Makefile

@@ -6,7 +6,7 @@ include ../../../Make.inc
 
 TARG=exp/terminal
 GOFILES=\
-	shell.go\
+	terminal.go\
 
 ifneq ($(GOOS),windows)
 GOFILES+=util.go

src/pkg/exp/terminal/terminal.go

@@ -6,9 +6,9 @@ package terminal
 
 import "io"
 
-// Shell contains the state for running a VT100 terminal that is capable of
+// Terminal contains the state for running a VT100 terminal that is capable of
 // reading lines of input.
-type Shell struct {
+type Terminal struct {
 	c      io.ReadWriter
 	prompt string
 
@@ -34,12 +34,12 @@ type Shell struct {
 	inBuf     [256]byte
 }
 
-// NewShell runs a VT100 terminal on the given ReadWriter. If the ReadWriter is
+// NewTerminal runs a VT100 terminal on the given ReadWriter. If the ReadWriter is
 // a local terminal, that terminal must first have been put into raw mode.
 // prompt is a string that is written at the start of each input line (i.e.
 // "> ").
-func NewShell(c io.ReadWriter, prompt string) *Shell {
-	return &Shell{
+func NewTerminal(c io.ReadWriter, prompt string) *Terminal {
+	return &Terminal{
 		c:          c,
 		prompt:     prompt,
 		termWidth:  80,
@@ -107,17 +107,17 @@ func bytesToKey(b []byte) (int, []byte) {
 	return -1, b
 }
 
-// queue appends data to the end of ss.outBuf
-func (ss *Shell) queue(data []byte) {
-	if len(ss.outBuf)+len(data) > cap(ss.outBuf) {
-		newOutBuf := make([]byte, len(ss.outBuf), 2*(len(ss.outBuf)+len(data)))
-		copy(newOutBuf, ss.outBuf)
-		ss.outBuf = newOutBuf
+// queue appends data to the end of t.outBuf
+func (t *Terminal) queue(data []byte) {
+	if len(t.outBuf)+len(data) > cap(t.outBuf) {
+		newOutBuf := make([]byte, len(t.outBuf), 2*(len(t.outBuf)+len(data)))
+		copy(newOutBuf, t.outBuf)
+		t.outBuf = newOutBuf
 	}
 
-	oldLen := len(ss.outBuf)
-	ss.outBuf = ss.outBuf[:len(ss.outBuf)+len(data)]
-	copy(ss.outBuf[oldLen:], data)
+	oldLen := len(t.outBuf)
+	t.outBuf = t.outBuf[:len(t.outBuf)+len(data)]
+	copy(t.outBuf[oldLen:], data)
 }
 
 var eraseUnderCursor = []byte{' ', keyEscape, '[', 'D'}
@@ -126,31 +126,31 @@ func isPrintable(key int) bool {
 	return key >= 32 && key < 127
 }
 
-// moveCursorToPos appends data to ss.outBuf which will move the cursor to the
+// moveCursorToPos appends data to t.outBuf which will move the cursor to the
 // given, logical position in the text.
-func (ss *Shell) moveCursorToPos(pos int) {
-	x := len(ss.prompt) + pos
-	y := x / ss.termWidth
-	x = x % ss.termWidth
+func (t *Terminal) moveCursorToPos(pos int) {
+	x := len(t.prompt) + pos
+	y := x / t.termWidth
+	x = x % t.termWidth
 
 	up := 0
-	if y < ss.cursorY {
-		up = ss.cursorY - y
+	if y < t.cursorY {
+		up = t.cursorY - y
 	}
 
 	down := 0
-	if y > ss.cursorY {
-		down = y - ss.cursorY
+	if y > t.cursorY {
+		down = y - t.cursorY
 	}
 
 	left := 0
-	if x < ss.cursorX {
-		left = ss.cursorX - x
+	if x < t.cursorX {
+		left = t.cursorX - x
 	}
 
 	right := 0
-	if x > ss.cursorX {
-		right = x - ss.cursorX
+	if x > t.cursorX {
+		right = x - t.cursorX
 	}
 
 	movement := make([]byte, 3*(up+down+left+right))
@@ -180,152 +180,154 @@ func (ss *Shell) moveCursorToPos(pos int) {
 		m = m[3:]
 	}
 
-	ss.cursorX = x
-	ss.cursorY = y
-	ss.queue(movement)
+	t.cursorX = x
+	t.cursorY = y
+	t.queue(movement)
 }
 
 const maxLineLength = 4096
 
 // handleKey processes the given key and, optionally, returns a line of text
 // that the user has entered.
-func (ss *Shell) handleKey(key int) (line string, ok bool) {
+func (t *Terminal) handleKey(key int) (line string, ok bool) {
 	switch key {
 	case keyBackspace:
-		if ss.pos == 0 {
+		if t.pos == 0 {
 			return
 		}
-		ss.pos--
+		t.pos--
 
-		copy(ss.line[ss.pos:], ss.line[1+ss.pos:])
-		ss.line = ss.line[:len(ss.line)-1]
-		ss.writeLine(ss.line[ss.pos:])
-		ss.moveCursorToPos(ss.pos)
-		ss.queue(eraseUnderCursor)
+		copy(t.line[t.pos:], t.line[1+t.pos:])
+		t.line = t.line[:len(t.line)-1]
+		t.writeLine(t.line[t.pos:])
+		t.moveCursorToPos(t.pos)
+		t.queue(eraseUnderCursor)
 	case keyAltLeft:
 		// move left by a word.
-		if ss.pos == 0 {
+		if t.pos == 0 {
 			return
 		}
-		ss.pos--
-		for ss.pos > 0 {
-			if ss.line[ss.pos] != ' ' {
+		t.pos--
+		for t.pos > 0 {
+			if t.line[t.pos] != ' ' {
 				break
 			}
-			ss.pos--
+			t.pos--
 		}
-		for ss.pos > 0 {
-			if ss.line[ss.pos] == ' ' {
-				ss.pos++
+		for t.pos > 0 {
+			if t.line[t.pos] == ' ' {
+				t.pos++
 				break
 			}
-			ss.pos--
+			t.pos--
 		}
-		ss.moveCursorToPos(ss.pos)
+		t.moveCursorToPos(t.pos)
 	case keyAltRight:
 		// move right by a word.
-		for ss.pos < len(ss.line) {
-			if ss.line[ss.pos] == ' ' {
+		for t.pos < len(t.line) {
+			if t.line[t.pos] == ' ' {
 				break
 			}
-			ss.pos++
+			t.pos++
 		}
-		for ss.pos < len(ss.line) {
-			if ss.line[ss.pos] != ' ' {
+		for t.pos < len(t.line) {
+			if t.line[t.pos] != ' ' {
 				break
 			}
-			ss.pos++
+			t.pos++
 		}
-		ss.moveCursorToPos(ss.pos)
+		t.moveCursorToPos(t.pos)
 	case keyLeft:
-		if ss.pos == 0 {
+		if t.pos == 0 {
 			return
 		}
-		ss.pos--
-		ss.moveCursorToPos(ss.pos)
+		t.pos--
+		t.moveCursorToPos(t.pos)
 	case keyRight:
-		if ss.pos == len(ss.line) {
+		if t.pos == len(t.line) {
 			return
 		}
-		ss.pos++
-		ss.moveCursorToPos(ss.pos)
+		t.pos++
+		t.moveCursorToPos(t.pos)
 	case keyEnter:
-		ss.moveCursorToPos(len(ss.line))
-		ss.queue([]byte("\r\n"))
-		line = string(ss.line)
+		t.moveCursorToPos(len(t.line))
+		t.queue([]byte("\r\n"))
+		line = string(t.line)
 		ok = true
-		ss.line = ss.line[:0]
-		ss.pos = 0
-		ss.cursorX = 0
-		ss.cursorY = 0
-		ss.maxLine = 0
+		t.line = t.line[:0]
+		t.pos = 0
+		t.cursorX = 0
+		t.cursorY = 0
+		t.maxLine = 0
 	default:
 		if !isPrintable(key) {
 			return
 		}
-		if len(ss.line) == maxLineLength {
+		if len(t.line) == maxLineLength {
 			return
 		}
-		if len(ss.line) == cap(ss.line) {
-			newLine := make([]byte, len(ss.line), 2*(1+len(ss.line)))
-			copy(newLine, ss.line)
-			ss.line = newLine
+		if len(t.line) == cap(t.line) {
+			newLine := make([]byte, len(t.line), 2*(1+len(t.line)))
+			copy(newLine, t.line)
+			t.line = newLine
 		}
-		ss.line = ss.line[:len(ss.line)+1]
-		copy(ss.line[ss.pos+1:], ss.line[ss.pos:])
-		ss.line[ss.pos] = byte(key)
-		ss.writeLine(ss.line[ss.pos:])
-		ss.pos++
-		ss.moveCursorToPos(ss.pos)
+		t.line = t.line[:len(t.line)+1]
+		copy(t.line[t.pos+1:], t.line[t.pos:])
+		t.line[t.pos] = byte(key)
+		t.writeLine(t.line[t.pos:])
+		t.pos++
+		t.moveCursorToPos(t.pos)
 	}
 	return
 }
 
-func (ss *Shell) writeLine(line []byte) {
+func (t *Terminal) writeLine(line []byte) {
 	for len(line) != 0 {
-		if ss.cursorX == ss.termWidth {
-			ss.queue([]byte("\r\n"))
-			ss.cursorX = 0
-			ss.cursorY++
-			if ss.cursorY > ss.maxLine {
-				ss.maxLine = ss.cursorY
+		if t.cursorX == t.termWidth {
+			t.queue([]byte("\r\n"))
+			t.cursorX = 0
+			t.cursorY++
+			if t.cursorY > t.maxLine {
+				t.maxLine = t.cursorY
 			}
 		}
 
-		remainingOnLine := ss.termWidth - ss.cursorX
+		remainingOnLine := t.termWidth - t.cursorX
 		todo := len(line)
 		if todo > remainingOnLine {
 			todo = remainingOnLine
 		}
-		ss.queue(line[:todo])
-		ss.cursorX += todo
+		t.queue(line[:todo])
+		t.cursorX += todo
 		line = line[todo:]
 	}
 }
 
-func (ss *Shell) Write(buf []byte) (n int, err error) {
-	return ss.c.Write(buf)
+func (t *Terminal) Write(buf []byte) (n int, err error) {
+	return t.c.Write(buf)
 }
 
 // ReadLine returns a line of input from the terminal.
-func (ss *Shell) ReadLine() (line string, err error) {
-	ss.writeLine([]byte(ss.prompt))
-	ss.c.Write(ss.outBuf)
-	ss.outBuf = ss.outBuf[:0]
+func (t *Terminal) ReadLine() (line string, err error) {
+	if t.cursorX == 0 {
+		t.writeLine([]byte(t.prompt))
+		t.c.Write(t.outBuf)
+		t.outBuf = t.outBuf[:0]
+	}
 
 	for {
-		// ss.remainder is a slice at the beginning of ss.inBuf
+		// t.remainder is a slice at the beginning of t.inBuf
 		// containing a partial key sequence
-		readBuf := ss.inBuf[len(ss.remainder):]
+		readBuf := t.inBuf[len(t.remainder):]
 		var n int
-		n, err = ss.c.Read(readBuf)
+		n, err = t.c.Read(readBuf)
 		if err != nil {
 			return
 		}
 
 		if err == nil {
-			ss.remainder = ss.inBuf[:n+len(ss.remainder)]
-			rest := ss.remainder
+			t.remainder = t.inBuf[:n+len(t.remainder)]
+			rest := t.remainder
 			lineOk := false
 			for !lineOk {
 				var key int
@@ -336,16 +338,16 @@ func (ss *Shell) ReadLine() (line string, err error) {
 				if key == keyCtrlD {
 					return "", io.EOF
 				}
-				line, lineOk = ss.handleKey(key)
+				line, lineOk = t.handleKey(key)
 			}
 			if len(rest) > 0 {
-				n := copy(ss.inBuf[:], rest)
-				ss.remainder = ss.inBuf[:n]
+				n := copy(t.inBuf[:], rest)
+				t.remainder = t.inBuf[:n]
 			} else {
-				ss.remainder = nil
+				t.remainder = nil
 			}
-			ss.c.Write(ss.outBuf)
-			ss.outBuf = ss.outBuf[:0]
+			t.c.Write(t.outBuf)
+			t.outBuf = t.outBuf[:0]
 			if lineOk {
 				return
 			}
@@ -354,3 +356,7 @@ func (ss *Shell) ReadLine() (line string, err error) {
 	}
 	panic("unreachable")
 }
+
+func (t *Terminal) SetSize(width, height int) {
+	t.termWidth, t.termHeight = width, height
+}

src/pkg/exp/terminal/terminal_test.go

@@ -41,7 +41,7 @@ func (c *MockTerminal) Write(data []byte) (n int, err error) {
 
 func TestClose(t *testing.T) {
 	c := &MockTerminal{}
-	ss := NewShell(c, "> ")
+	ss := NewTerminal(c, "> ")
 	line, err := ss.ReadLine()
 	if line != "" {
 		t.Errorf("Expected empty line but got: %s", line)
@@ -95,7 +95,7 @@ func TestKeyPresses(t *testing.T) {
 				toSend:       []byte(test.in),
 				bytesPerRead: j,
 			}
-			ss := NewShell(c, "> ")
+			ss := NewTerminal(c, "> ")
 			line, err := ss.ReadLine()
 			if line != test.line {
 				t.Errorf("Line resulting from test %d (%d bytes per read) was '%s', expected '%s'", i, j, line, test.line)