Initial commit

lex.go

@@ -0,0 +1,16 @@
+package main
+
+import (
+	"io/ioutil"
+	"os"
+
+	"github.com/localhots/punk/lexer"
+)
+
+func main() {
+	f, _ := os.Open("test.json")
+	b, _ := ioutil.ReadAll(f)
+
+	lex := lexer.New("foo", string(b))
+	lex.Run()
+}

lexer/lexer.go

@@ -0,0 +1,230 @@
+package lexer
+
+import (
+	"fmt"
+	"strings"
+	"unicode/utf8"
+)
+
+type (
+	// lexer holds the state of the scanner.
+	Lexer struct {
+		input      string    // the string being scanned
+		state      stateFn   // the next lexing function to enter
+		pos        Pos       // current position in the input
+		start      Pos       // start position of this item
+		width      Pos       // width of last rune read from input
+		lastPos    Pos       // position of most recent item returned by nextItem
+		items      chan item // channel of scanned items
+		parenDepth int       // nesting depth of ( ) exprs
+	}
+	Pos int
+
+	// stateFn represents the state of the scanner as a function that returns the next state.
+	stateFn func(*Lexer) stateFn
+
+	// item represents a token or text string returned from the scanner.
+	item struct {
+		typ itemType // The type of this item.
+		pos Pos      // The starting position, in bytes, of this item in the input string.
+		val string   // The value of this item.
+	}
+
+	// itemType identifies the type of lex items.
+	itemType int
+)
+
+const (
+	// Special
+	itemError itemType = iota // error occurred; value is text of error
+	itemEOF
+	itemSpace
+
+	// Symbols
+	itemBraceOpen    // {
+	itemBraceClose   // }
+	itemBracketOpen  // [
+	itemBracketClose // [
+	itemQuote        // "
+	itemColon        // :
+	itemComma        // ,
+
+	// Types
+	itemNull   // null
+	itemBool   // true, false
+	itemNumber // 0, 2.5
+	itemString // "foo"
+	itemArray  // [1, 2, 3]
+	itemObject // {"a": 1, "b": 2}
+)
+
+const (
+	EOF = -1
+)
+
+var (
+	itemMap = map[string]itemType{
+		"null":  itemNull,
+		"true":  itemBool,
+		"false": itemBool,
+	}
+)
+
+// lex creates a new scanner for the input string.
+func New(name, input string) *Lexer {
+	l := &Lexer{
+		input: input,
+		items: make(chan item),
+	}
+	return l
+}
+
+// run runs the state machine for the lexer.
+func (l *Lexer) Run() {
+	for l.state = lexInitial; l.state != nil; {
+		l.state = l.state(l)
+	}
+}
+
+//
+// States
+//
+
+func lexInitial(l *Lexer) stateFn {
+	for {
+		switch l.next() {
+		case EOF:
+			break
+		default:
+			panic("Unexpected symbol!")
+		}
+	}
+
+	// Correctly reached EOF.
+	l.emit(itemEOF)
+
+	return nil
+}
+
+func lexNumber(l *Lexer) stateFn {
+	return lexInitial
+}
+
+func lexString(l *Lexer) stateFn {
+	return lexInitial
+}
+
+func lexArray(l *Lexer) stateFn {
+	return lexInitial
+}
+
+func lexObject(l *Lexer) stateFn {
+	return lexInitial
+}
+
+// lexSpace scans a run of space characters.
+// One space has already been seen.
+func lexSpace(l *Lexer) stateFn {
+	for isSpace(l.peek()) {
+		l.next()
+	}
+	l.emit(itemSpace)
+	return lexInitial
+}
+
+//
+// Lexer stuff
+//
+
+func (i item) String() string {
+	switch {
+	case i.typ == itemEOF:
+		return "EOF"
+	case i.typ == itemError:
+		return i.val
+	case len(i.val) > 10:
+		return fmt.Sprintf("%.10q...", i.val)
+	}
+	return fmt.Sprintf("%q", i.val)
+}
+
+// next returns the next rune in the input.
+func (l *Lexer) next() rune {
+	if int(l.pos) >= len(l.input) {
+		l.width = 0
+		return EOF
+	}
+	r, w := utf8.DecodeRuneInString(l.input[l.pos:])
+	l.width = Pos(w)
+	l.pos += l.width
+	return r
+}
+
+// peek returns but does not consume the next rune in the input.
+func (l *Lexer) peek() rune {
+	r := l.next()
+	l.backup()
+	return r
+}
+
+// backup steps back one rune. Can only be called once per call of next.
+func (l *Lexer) backup() {
+	l.pos -= l.width
+}
+
+// emit passes an item back to the client.
+func (l *Lexer) emit(t itemType) {
+	l.items <- item{t, l.start, l.input[l.start:l.pos]}
+	l.start = l.pos
+}
+
+// ignore skips over the pending input before this point.
+func (l *Lexer) ignore() {
+	l.start = l.pos
+}
+
+// accept consumes the next rune if it's from the valid set.
+func (l *Lexer) accept(valid string) bool {
+	if strings.IndexRune(valid, l.next()) >= 0 {
+		return true
+	}
+	l.backup()
+	return false
+}
+
+// acceptRun consumes a run of runes from the valid set.
+func (l *Lexer) acceptRun(valid string) {
+	for strings.IndexRune(valid, l.next()) >= 0 {
+	}
+	l.backup()
+}
+
+// lineNumber reports which line we're on, based on the position of
+// the previous item returned by nextItem. Doing it this way
+// means we don't have to worry about peek double counting.
+func (l *Lexer) lineNumber() int {
+	return 1 + strings.Count(l.input[:l.lastPos], "\n")
+}
+
+// errorf returns an error token and terminates the scan by passing
+// back a nil pointer that will be the next state, terminating l.nextItem.
+func (l *Lexer) errorf(format string, args ...interface{}) stateFn {
+	l.items <- item{itemError, l.start, fmt.Sprintf(format, args...)}
+	return nil
+}
+
+// nextItem returns the next item from the input.
+func (l *Lexer) nextItem() item {
+	item := <-l.items
+	l.lastPos = item.pos
+	return item
+}
+
+//
+// Helpers
+//
+
+// isSpace reports whether r is a space character.
+func isSpace(r rune) bool {
+	return r == ' ' || r == '\t'
+}

test.json

@@ -0,0 +1,12 @@
+{
+    "prices": {
+        "apple": 25,
+        "banana": 10,
+        "peach": 40
+    },
+    "bananas": [
+        {"length": 13, "weight": 5},
+        {"length": 18, "weight": 8},
+        {"length": 13, "weight": 4}
+    ]
+}