129 lines
2.0 KiB
Go
129 lines
2.0 KiB
Go
package lexer
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import "strings"
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func lexInitial(l *Lexer) stateFn {
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loop:
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for {
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switch r := l.next(); r {
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case ' ', '\t':
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return lexSpace(l)
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case '\n':
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l.lineNum++
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case 'n':
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l.backup()
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return lexNull(l)
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case 't', 'f':
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l.backup()
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return lexBool(l)
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case '1', '2', '3', '4', '5', '6', '7', '8', '9', '0':
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l.backup()
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return lexNumber(l)
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case '"':
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return lexString(l)
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case '[':
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l.emit(itemBracketOpen)
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case ']':
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l.emit(itemBracketClose)
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case '{':
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l.emit(itemBraceOpen)
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case '}':
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l.emit(itemBraceClose)
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case ':':
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l.emit(itemColon)
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case ',':
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l.emit(itemComma)
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case EOF:
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break loop
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default:
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panic("Unexpected symbol: " + string(r))
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}
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}
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// Correctly reached EOF.
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l.emit(itemEOF)
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return nil
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}
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// Skip all spaces
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// One space has already been seen
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func lexSpace(l *Lexer) stateFn {
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for isSpace(l.peek()) {
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l.next()
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}
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l.ignore()
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return lexInitial
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}
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func lexNull(l *Lexer) stateFn {
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if l.acceptString("null") {
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l.emit(itemNull)
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} else {
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return l.errorf("Unexpected token")
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}
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return lexInitial
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}
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func lexBool(l *Lexer) stateFn {
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if l.acceptString("true") || l.acceptString("false") {
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l.emit(itemBool)
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}
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return lexInitial
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}
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func lexNumber(l *Lexer) stateFn {
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hasDot := false
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for {
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if r := l.peek(); isDigit(r) {
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l.next()
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} else if r == '.' {
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if hasDot {
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return l.errorf("Invalid number")
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} else {
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hasDot = true
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l.next()
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}
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} else {
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break
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}
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}
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l.emit(itemNumber)
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return lexInitial
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}
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func lexString(l *Lexer) stateFn {
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escaped := false
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loop:
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for {
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switch r := l.next(); r {
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case '\\':
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escaped = true
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case '"':
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if escaped {
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escaped = false
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} else {
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l.emit(itemString)
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break loop
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}
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case '\n':
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l.lineNum++
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case EOF:
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return l.errorf("String hits EOF")
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default:
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escaped = false
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}
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}
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return lexInitial
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}
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func isSpace(r rune) bool {
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return r == ' ' || r == '\t'
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}
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func isDigit(r rune) bool {
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return strings.IndexRune("1234567890", r) > -1
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}
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