Move windows console specific implementation in sub package

Signed-off-by: Sachin Joshi <sachin_jayant_joshi@hotmail.com>

term/winconsole/term_emulator.go

@@ -0,0 +1,216 @@
+package winconsole
+
+import (
+	"io"
+	"strconv"
+	"strings"
+)
+
+// http://manpages.ubuntu.com/manpages/intrepid/man4/console_codes.4.html
+const (
+	ANSI_ESCAPE_PRIMARY   = 0x1B
+	ANSI_ESCAPE_SECONDARY = 0x5B
+	ANSI_COMMAND_FIRST    = 0x40
+	ANSI_COMMAND_LAST     = 0x7E
+	ANSI_PARAMETER_SEP    = ";"
+	ANSI_CMD_G0           = '('
+	ANSI_CMD_G1           = ')'
+	ANSI_CMD_G2           = '*'
+	ANSI_CMD_G3           = '+'
+	ANSI_CMD_DECPNM       = '>'
+	ANSI_CMD_DECPAM       = '='
+	ANSI_CMD_OSC          = ']'
+	ANSI_CMD_STR_TERM     = '\\'
+	ANSI_BEL              = 0x07
+	KEY_EVENT             = 1
+)
+
+// Interface that implements terminal handling
+type terminalEmulator interface {
+	HandleOutputCommand(command []byte) (n int, err error)
+	HandleInputSequence(command []byte) (n int, err error)
+	WriteChars(w io.Writer, p []byte) (n int, err error)
+	ReadChars(w io.Reader, p []byte) (n int, err error)
+}
+
+type terminalWriter struct {
+	wrappedWriter io.Writer
+	emulator      terminalEmulator
+	command       []byte
+	inSequence    bool
+}
+
+type terminalReader struct {
+	wrappedReader io.ReadCloser
+	emulator      terminalEmulator
+	command       []byte
+	inSequence    bool
+}
+
+// http://manpages.ubuntu.com/manpages/intrepid/man4/console_codes.4.html
+func isAnsiCommandChar(b byte) bool {
+	switch {
+	case ANSI_COMMAND_FIRST <= b && b <= ANSI_COMMAND_LAST && b != ANSI_ESCAPE_SECONDARY:
+		return true
+	case b == ANSI_CMD_G1 || b == ANSI_CMD_OSC || b == ANSI_CMD_DECPAM || b == ANSI_CMD_DECPNM:
+		// non-CSI escape sequence terminator
+		return true
+	case b == ANSI_CMD_STR_TERM || b == ANSI_BEL:
+		// String escape sequence terminator
+		return true
+	}
+	return false
+}
+
+func isCharacterSelectionCmdChar(b byte) bool {
+	return (b == ANSI_CMD_G0 || b == ANSI_CMD_G1 || b == ANSI_CMD_G2 || b == ANSI_CMD_G3)
+}
+
+func isXtermOscSequence(command []byte, current byte) bool {
+	return (len(command) >= 2 && command[0] == ANSI_ESCAPE_PRIMARY && command[1] == ANSI_CMD_OSC && current != ANSI_BEL)
+}
+
+// Write writes len(p) bytes from p to the underlying data stream.
+// http://golang.org/pkg/io/#Writer
+func (tw *terminalWriter) Write(p []byte) (n int, err error) {
+	if len(p) == 0 {
+		return 0, nil
+	}
+	if tw.emulator == nil {
+		return tw.wrappedWriter.Write(p)
+	}
+	// Emulate terminal by extracting commands and executing them
+	totalWritten := 0
+	start := 0 // indicates start of the next chunk
+	end := len(p)
+	for current := 0; current < end; current++ {
+		if tw.inSequence {
+			// inside escape sequence
+			tw.command = append(tw.command, p[current])
+			if isAnsiCommandChar(p[current]) {
+				if !isXtermOscSequence(tw.command, p[current]) {
+					// found the last command character.
+					// Now we have a complete command.
+					nchar, err := tw.emulator.HandleOutputCommand(tw.command)
+					totalWritten += nchar
+					if err != nil {
+						return totalWritten, err
+					}
+
+					// clear the command
+					// don't include current character again
+					tw.command = tw.command[:0]
+					start = current + 1
+					tw.inSequence = false
+				}
+			}
+		} else {
+			if p[current] == ANSI_ESCAPE_PRIMARY {
+				// entering escape sequnce
+				tw.inSequence = true
+				// indicates end of "normal sequence", write whatever you have so far
+				if len(p[start:current]) > 0 {
+					nw, err := tw.emulator.WriteChars(tw.wrappedWriter, p[start:current])
+					totalWritten += nw
+					if err != nil {
+						return totalWritten, err
+					}
+				}
+				// include the current character as part of the next sequence
+				tw.command = append(tw.command, p[current])
+			}
+		}
+	}
+	// note that so far, start of the escape sequence triggers writing out of bytes to console.
+	// For the part _after_ the end of last escape sequence, it is not written out yet. So write it out
+	if !tw.inSequence {
+		// assumption is that we can't be inside sequence and therefore command should be empty
+		if len(p[start:]) > 0 {
+			nw, err := tw.emulator.WriteChars(tw.wrappedWriter, p[start:])
+			totalWritten += nw
+			if err != nil {
+				return totalWritten, err
+			}
+		}
+	}
+	return totalWritten, nil
+
+}
+
+// Read reads up to len(p) bytes into p.
+// http://golang.org/pkg/io/#Reader
+func (tr *terminalReader) Read(p []byte) (n int, err error) {
+	//Implementations of Read are discouraged from returning a zero byte count
+	// with a nil error, except when len(p) == 0.
+	if len(p) == 0 {
+		return 0, nil
+	}
+	if nil == tr.emulator {
+		return tr.readFromWrappedReader(p)
+	}
+	return tr.emulator.ReadChars(tr.wrappedReader, p)
+}
+
+// Close the underlying stream
+func (tr *terminalReader) Close() (err error) {
+	return tr.wrappedReader.Close()
+}
+
+func (tr *terminalReader) readFromWrappedReader(p []byte) (n int, err error) {
+	return tr.wrappedReader.Read(p)
+}
+
+type ansiCommand struct {
+	CommandBytes []byte
+	Command      string
+	Parameters   []string
+	IsSpecial    bool
+}
+
+func parseAnsiCommand(command []byte) *ansiCommand {
+	if isCharacterSelectionCmdChar(command[1]) {
+		// Is Character Set Selection commands
+		return &ansiCommand{
+			CommandBytes: command,
+			Command:      string(command),
+			IsSpecial:    true,
+		}
+	}
+	// last char is command character
+	lastCharIndex := len(command) - 1
+
+	retValue := &ansiCommand{
+		CommandBytes: command,
+		Command:      string(command[lastCharIndex]),
+		IsSpecial:    false,
+	}
+	// more than a single escape
+	if lastCharIndex != 0 {
+		start := 1
+		// skip if double char escape sequence
+		if command[0] == ANSI_ESCAPE_PRIMARY && command[1] == ANSI_ESCAPE_SECONDARY {
+			start++
+		}
+		// convert this to GetNextParam method
+		retValue.Parameters = strings.Split(string(command[start:lastCharIndex]), ANSI_PARAMETER_SEP)
+	}
+	return retValue
+}
+
+func (c *ansiCommand) getParam(index int) string {
+	if len(c.Parameters) > index {
+		return c.Parameters[index]
+	}
+	return ""
+}
+
+func parseInt16OrDefault(s string, defaultValue int16) (n int16, err error) {
+	if s == "" {
+		return defaultValue, nil
+	}
+	parsedValue, err := strconv.ParseInt(s, 10, 16)
+	if nil != err {
+		return defaultValue, err
+	}
+	return int16(parsedValue), nil
+}