1 files changed, 359 insertions, 0 deletions
diff --git a/libgo/go/exp/terminal/shell.go b/libgo/go/exp/terminal/shell.go
new file mode 100644
index 00000000000..e3f584774e3
--- /dev/null
+++ b/libgo/go/exp/terminal/shell.go
@@ -0,0 +1,359 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package terminal
+
+import (
+	"os"
+	"io"
+)
+
+// Shell contains the state for running a VT100 terminal that is capable of
+// reading lines of input.
+type Shell struct {
+	c      io.ReadWriter
+	prompt string
+
+	// line is the current line being entered.
+	line []byte
+	// pos is the logical position of the cursor in line
+	pos int
+
+	// cursorX contains the current X value of the cursor where the left
+	// edge is 0. cursorY contains the row number where the first row of
+	// the current line is 0.
+	cursorX, cursorY int
+	// maxLine is the greatest value of cursorY so far.
+	maxLine int
+
+	termWidth, termHeight int
+
+	// outBuf contains the terminal data to be sent.
+	outBuf []byte
+	// remainder contains the remainder of any partial key sequences after
+	// a read. It aliases into inBuf.
+	remainder []byte
+	inBuf     [256]byte
+}
+
+// NewShell 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{
+		c:          c,
+		prompt:     prompt,
+		termWidth:  80,
+		termHeight: 24,
+	}
+}
+
+const (
+	keyCtrlD     = 4
+	keyEnter     = '\r'
+	keyEscape    = 27
+	keyBackspace = 127
+	keyUnknown   = 256 + iota
+	keyUp
+	keyDown
+	keyLeft
+	keyRight
+	keyAltLeft
+	keyAltRight
+)
+
+// bytesToKey tries to parse a key sequence from b. If successful, it returns
+// the key and the remainder of the input. Otherwise it returns -1.
+func bytesToKey(b []byte) (int, []byte) {
+	if len(b) == 0 {
+		return -1, nil
+	}
+
+	if b[0] != keyEscape {
+		return int(b[0]), b[1:]
+	}
+
+	if len(b) >= 3 && b[0] == keyEscape && b[1] == '[' {
+		switch b[2] {
+		case 'A':
+			return keyUp, b[3:]
+		case 'B':
+			return keyDown, b[3:]
+		case 'C':
+			return keyRight, b[3:]
+		case 'D':
+			return keyLeft, b[3:]
+		}
+	}
+
+	if len(b) >= 6 && b[0] == keyEscape && b[1] == '[' && b[2] == '1' && b[3] == ';' && b[4] == '3' {
+		switch b[5] {
+		case 'C':
+			return keyAltRight, b[6:]
+		case 'D':
+			return keyAltLeft, b[6:]
+		}
+	}
+
+	// If we get here then we have a key that we don't recognise, or a
+	// partial sequence. It's not clear how one should find the end of a
+	// sequence without knowing them all, but it seems that [a-zA-Z] only
+	// appears at the end of a sequence.
+	for i, c := range b[0:] {
+		if c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' {
+			return keyUnknown, b[i+1:]
+		}
+	}
+
+	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
+	}
+
+	oldLen := len(ss.outBuf)
+	ss.outBuf = ss.outBuf[:len(ss.outBuf)+len(data)]
+	copy(ss.outBuf[oldLen:], data)
+}
+
+var eraseUnderCursor = []byte{' ', keyEscape, '[', 'D'}
+
+func isPrintable(key int) bool {
+	return key >= 32 && key < 127
+}
+
+// moveCursorToPos appends data to ss.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
+
+	up := 0
+	if y < ss.cursorY {
+		up = ss.cursorY - y
+	}
+
+	down := 0
+	if y > ss.cursorY {
+		down = y - ss.cursorY
+	}
+
+	left := 0
+	if x < ss.cursorX {
+		left = ss.cursorX - x
+	}
+
+	right := 0
+	if x > ss.cursorX {
+		right = x - ss.cursorX
+	}
+
+	movement := make([]byte, 3*(up+down+left+right))
+	m := movement
+	for i := 0; i < up; i++ {
+		m[0] = keyEscape
+		m[1] = '['
+		m[2] = 'A'
+		m = m[3:]
+	}
+	for i := 0; i < down; i++ {
+		m[0] = keyEscape
+		m[1] = '['
+		m[2] = 'B'
+		m = m[3:]
+	}
+	for i := 0; i < left; i++ {
+		m[0] = keyEscape
+		m[1] = '['
+		m[2] = 'D'
+		m = m[3:]
+	}
+	for i := 0; i < right; i++ {
+		m[0] = keyEscape
+		m[1] = '['
+		m[2] = 'C'
+		m = m[3:]
+	}
+
+	ss.cursorX = x
+	ss.cursorY = y
+	ss.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) {
+	switch key {
+	case keyBackspace:
+		if ss.pos == 0 {
+			return
+		}
+		ss.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)
+	case keyAltLeft:
+		// move left by a word.
+		if ss.pos == 0 {
+			return
+		}
+		ss.pos--
+		for ss.pos > 0 {
+			if ss.line[ss.pos] != ' ' {
+				break
+			}
+			ss.pos--
+		}
+		for ss.pos > 0 {
+			if ss.line[ss.pos] == ' ' {
+				ss.pos++
+				break
+			}
+			ss.pos--
+		}
+		ss.moveCursorToPos(ss.pos)
+	case keyAltRight:
+		// move right by a word.
+		for ss.pos < len(ss.line) {
+			if ss.line[ss.pos] == ' ' {
+				break
+			}
+			ss.pos++
+		}
+		for ss.pos < len(ss.line) {
+			if ss.line[ss.pos] != ' ' {
+				break
+			}
+			ss.pos++
+		}
+		ss.moveCursorToPos(ss.pos)
+	case keyLeft:
+		if ss.pos == 0 {
+			return
+		}
+		ss.pos--
+		ss.moveCursorToPos(ss.pos)
+	case keyRight:
+		if ss.pos == len(ss.line) {
+			return
+		}
+		ss.pos++
+		ss.moveCursorToPos(ss.pos)
+	case keyEnter:
+		ss.moveCursorToPos(len(ss.line))
+		ss.queue([]byte("\r\n"))
+		line = string(ss.line)
+		ok = true
+		ss.line = ss.line[:0]
+		ss.pos = 0
+		ss.cursorX = 0
+		ss.cursorY = 0
+		ss.maxLine = 0
+	default:
+		if !isPrintable(key) {
+			return
+		}
+		if len(ss.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
+		}
+		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)
+	}
+	return
+}
+
+func (ss *Shell) 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
+			}
+		}
+
+		remainingOnLine := ss.termWidth - ss.cursorX
+		todo := len(line)
+		if todo > remainingOnLine {
+			todo = remainingOnLine
+		}
+		ss.queue(line[:todo])
+		ss.cursorX += todo
+		line = line[todo:]
+	}
+}
+
+func (ss *Shell) Write(buf []byte) (n int, err os.Error) {
+	return ss.c.Write(buf)
+}
+
+// ReadLine returns a line of input from the terminal.
+func (ss *Shell) ReadLine() (line string, err os.Error) {
+	ss.writeLine([]byte(ss.prompt))
+	ss.c.Write(ss.outBuf)
+	ss.outBuf = ss.outBuf[:0]
+
+	for {
+		// ss.remainder is a slice at the beginning of ss.inBuf
+		// containing a partial key sequence
+		readBuf := ss.inBuf[len(ss.remainder):]
+		var n int
+		n, err = ss.c.Read(readBuf)
+		if err != nil {
+			return
+		}
+
+		if err == nil {
+			ss.remainder = ss.inBuf[:n+len(ss.remainder)]
+			rest := ss.remainder
+			lineOk := false
+			for !lineOk {
+				var key int
+				key, rest = bytesToKey(rest)
+				if key < 0 {
+					break
+				}
+				if key == keyCtrlD {
+					return "", os.EOF
+				}
+				line, lineOk = ss.handleKey(key)
+			}
+			if len(rest) > 0 {
+				n := copy(ss.inBuf[:], rest)
+				ss.remainder = ss.inBuf[:n]
+			} else {
+				ss.remainder = nil
+			}
+			ss.c.Write(ss.outBuf)
+			ss.outBuf = ss.outBuf[:0]
+			if lineOk {
+				return
+			}
+			continue
+		}
+	}
+	panic("unreachable")
+}