add start to new scanner

scanner/position.go

@@ -0,0 +1,7 @@
+package scanner
+
+type Position struct {
+	Line   int
+	Column int
+	Char   rune
+}

scanner/scanner.go

@@ -0,0 +1,69 @@
+package scanner
+
+import (
+	"bufio"
+	"io"
+
+	"github.com/brettlangdon/gython/errorcode"
+	"github.com/brettlangdon/gython/token"
+)
+
+var EOF rune = 0
+var MAXINDENT int = 100
+
+type Scanner struct {
+	state           errorcode.ErrorCode
+	reader          *bufio.Reader
+	currentPosition *Position
+	positionBuffer  []*Position
+
+	currentLine   int
+	currentColumn int
+}
+
+func NewScanner(r io.Reader) *Scanner {
+	return &Scanner{
+		state:          errorcode.E_OK,
+		reader:         bufio.NewReader(r),
+		positionBuffer: make([]*Position, 0),
+		currentLine:    1,
+		currentColumn:  0,
+	}
+}
+
+func (scanner *Scanner) nextPosition() *Position {
+	if len(scanner.positionBuffer) > 0 {
+		last = len(scanner.positionBuffer) - 1
+		scanner.currentPosition = scanner.positionBuffer[last]
+		scanner.positionBuffer = scanner.positionBuffer[0:last]
+		return scanner.currentPosition
+	}
+
+	next, _, err := scanner.reader.ReadRune()
+	if err != nil {
+		scanner.state = errorcode.E_EOF
+		next = EOF
+	}
+
+	scanner.currentColumn++
+	if next == '\n' {
+		scanner.currentLine++
+		scanner.currentColumn = 0
+	}
+
+	return &Position{
+		Char:   next,
+		Line:   scanner.currentLine,
+		Column: scanner.currentColumn,
+	}
+}
+
+func (scanner *Scanner) unreadPosition(pos *Position) {
+	scanner.positionBuffer = append(scanner.positionBuffer, pos)
+}
+
+func (scanner *Scanner) NextToken() *token.Token {
+	return &Token{
+		ID: token.ENDMARKER,
+	}
+}