652 lines
12 KiB
Go
652 lines
12 KiB
Go
// TOML lexer.
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//
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// Written using the principles developed by Rob Pike in
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// http://www.youtube.com/watch?v=HxaD_trXwRE
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package toml
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import (
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"bytes"
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"errors"
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"fmt"
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"regexp"
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"strconv"
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"strings"
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)
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var dateRegexp *regexp.Regexp
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// Define state functions
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type tomlLexStateFn func() tomlLexStateFn
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// Define lexer
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type tomlLexer struct {
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inputIdx int
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input []rune // Textual source
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currentTokenStart int
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currentTokenStop int
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tokens []token
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depth int
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line int
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col int
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endbufferLine int
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endbufferCol int
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}
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// Basic read operations on input
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func (l *tomlLexer) read() rune {
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r := l.peek()
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if r == '\n' {
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l.endbufferLine++
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l.endbufferCol = 1
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} else {
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l.endbufferCol++
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}
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l.inputIdx++
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return r
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}
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func (l *tomlLexer) next() rune {
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r := l.read()
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if r != eof {
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l.currentTokenStop++
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}
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return r
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}
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func (l *tomlLexer) ignore() {
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l.currentTokenStart = l.currentTokenStop
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l.line = l.endbufferLine
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l.col = l.endbufferCol
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}
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func (l *tomlLexer) skip() {
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l.next()
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l.ignore()
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}
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func (l *tomlLexer) fastForward(n int) {
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for i := 0; i < n; i++ {
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l.next()
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}
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}
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func (l *tomlLexer) emitWithValue(t tokenType, value string) {
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l.tokens = append(l.tokens, token{
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Position: Position{l.line, l.col},
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typ: t,
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val: value,
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})
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l.ignore()
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}
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func (l *tomlLexer) emit(t tokenType) {
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l.emitWithValue(t, string(l.input[l.currentTokenStart:l.currentTokenStop]))
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}
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func (l *tomlLexer) peek() rune {
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if l.inputIdx >= len(l.input) {
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return eof
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}
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return l.input[l.inputIdx]
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}
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func (l *tomlLexer) peekString(size int) string {
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maxIdx := len(l.input)
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upperIdx := l.inputIdx + size // FIXME: potential overflow
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if upperIdx > maxIdx {
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upperIdx = maxIdx
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}
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return string(l.input[l.inputIdx:upperIdx])
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}
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func (l *tomlLexer) follow(next string) bool {
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return next == l.peekString(len(next))
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}
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// Error management
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func (l *tomlLexer) errorf(format string, args ...interface{}) tomlLexStateFn {
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l.tokens = append(l.tokens, token{
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Position: Position{l.line, l.col},
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typ: tokenError,
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val: fmt.Sprintf(format, args...),
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})
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return nil
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}
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// State functions
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func (l *tomlLexer) lexVoid() tomlLexStateFn {
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for {
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next := l.peek()
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switch next {
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case '[':
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return l.lexTableKey
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case '#':
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return l.lexComment(l.lexVoid)
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case '=':
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return l.lexEqual
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case '\r':
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fallthrough
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case '\n':
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l.skip()
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continue
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}
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if isSpace(next) {
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l.skip()
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}
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if l.depth > 0 {
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return l.lexRvalue
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}
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if isKeyStartChar(next) {
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return l.lexKey
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}
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if next == eof {
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l.next()
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break
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}
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}
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l.emit(tokenEOF)
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return nil
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}
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func (l *tomlLexer) lexRvalue() tomlLexStateFn {
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for {
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next := l.peek()
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switch next {
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case '.':
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return l.errorf("cannot start float with a dot")
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case '=':
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return l.lexEqual
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case '[':
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l.depth++
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return l.lexLeftBracket
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case ']':
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l.depth--
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return l.lexRightBracket
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case '{':
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return l.lexLeftCurlyBrace
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case '}':
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return l.lexRightCurlyBrace
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case '#':
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return l.lexComment(l.lexRvalue)
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case '"':
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return l.lexString
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case '\'':
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return l.lexLiteralString
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case ',':
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return l.lexComma
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case '\r':
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fallthrough
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case '\n':
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l.skip()
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if l.depth == 0 {
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return l.lexVoid
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}
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return l.lexRvalue
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case '_':
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return l.errorf("cannot start number with underscore")
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}
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if l.follow("true") {
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return l.lexTrue
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}
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if l.follow("false") {
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return l.lexFalse
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}
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if isSpace(next) {
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l.skip()
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continue
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}
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if next == eof {
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l.next()
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break
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}
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possibleDate := l.peekString(35)
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dateMatch := dateRegexp.FindString(possibleDate)
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if dateMatch != "" {
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l.fastForward(len(dateMatch))
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return l.lexDate
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}
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if next == '+' || next == '-' || isDigit(next) {
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return l.lexNumber
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}
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if isAlphanumeric(next) {
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return l.lexKey
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}
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return l.errorf("no value can start with %c", next)
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}
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l.emit(tokenEOF)
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return nil
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}
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func (l *tomlLexer) lexLeftCurlyBrace() tomlLexStateFn {
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l.next()
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l.emit(tokenLeftCurlyBrace)
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return l.lexRvalue
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}
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func (l *tomlLexer) lexRightCurlyBrace() tomlLexStateFn {
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l.next()
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l.emit(tokenRightCurlyBrace)
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return l.lexRvalue
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}
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func (l *tomlLexer) lexDate() tomlLexStateFn {
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l.emit(tokenDate)
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return l.lexRvalue
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}
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func (l *tomlLexer) lexTrue() tomlLexStateFn {
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l.fastForward(4)
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l.emit(tokenTrue)
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return l.lexRvalue
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}
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func (l *tomlLexer) lexFalse() tomlLexStateFn {
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l.fastForward(5)
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l.emit(tokenFalse)
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return l.lexRvalue
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}
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func (l *tomlLexer) lexEqual() tomlLexStateFn {
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l.next()
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l.emit(tokenEqual)
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return l.lexRvalue
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}
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func (l *tomlLexer) lexComma() tomlLexStateFn {
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l.next()
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l.emit(tokenComma)
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return l.lexRvalue
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}
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func (l *tomlLexer) lexKey() tomlLexStateFn {
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growingString := ""
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for r := l.peek(); isKeyChar(r) || r == '\n' || r == '\r'; r = l.peek() {
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if r == '"' {
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l.next()
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str, err := l.lexStringAsString(`"`, false, true)
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if err != nil {
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return l.errorf(err.Error())
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}
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growingString += `"` + str + `"`
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l.next()
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continue
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} else if r == '\n' {
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return l.errorf("keys cannot contain new lines")
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} else if isSpace(r) {
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break
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} else if !isValidBareChar(r) {
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return l.errorf("keys cannot contain %c character", r)
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}
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growingString += string(r)
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l.next()
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}
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l.emitWithValue(tokenKey, growingString)
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return l.lexVoid
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}
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func (l *tomlLexer) lexComment(previousState tomlLexStateFn) tomlLexStateFn {
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return func() tomlLexStateFn {
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for next := l.peek(); next != '\n' && next != eof; next = l.peek() {
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if next == '\r' && l.follow("\r\n") {
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break
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}
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l.next()
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}
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l.ignore()
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return previousState
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}
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}
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func (l *tomlLexer) lexLeftBracket() tomlLexStateFn {
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l.next()
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l.emit(tokenLeftBracket)
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return l.lexRvalue
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}
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func (l *tomlLexer) lexLiteralStringAsString(terminator string, discardLeadingNewLine bool) (string, error) {
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growingString := ""
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if discardLeadingNewLine {
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if l.follow("\r\n") {
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l.skip()
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l.skip()
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} else if l.peek() == '\n' {
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l.skip()
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}
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}
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// find end of string
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for {
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if l.follow(terminator) {
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return growingString, nil
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}
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next := l.peek()
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if next == eof {
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break
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}
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growingString += string(l.next())
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}
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return "", errors.New("unclosed string")
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}
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func (l *tomlLexer) lexLiteralString() tomlLexStateFn {
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l.skip()
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// handle special case for triple-quote
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terminator := "'"
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discardLeadingNewLine := false
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if l.follow("''") {
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l.skip()
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l.skip()
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terminator = "'''"
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discardLeadingNewLine = true
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}
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str, err := l.lexLiteralStringAsString(terminator, discardLeadingNewLine)
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if err != nil {
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return l.errorf(err.Error())
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}
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l.emitWithValue(tokenString, str)
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l.fastForward(len(terminator))
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l.ignore()
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return l.lexRvalue
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}
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// Lex a string and return the results as a string.
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// Terminator is the substring indicating the end of the token.
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// The resulting string does not include the terminator.
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func (l *tomlLexer) lexStringAsString(terminator string, discardLeadingNewLine, acceptNewLines bool) (string, error) {
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growingString := ""
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if discardLeadingNewLine {
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if l.follow("\r\n") {
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l.skip()
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l.skip()
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} else if l.peek() == '\n' {
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l.skip()
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}
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}
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for {
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if l.follow(terminator) {
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return growingString, nil
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}
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if l.follow("\\") {
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l.next()
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switch l.peek() {
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case '\r':
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fallthrough
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case '\n':
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fallthrough
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case '\t':
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fallthrough
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case ' ':
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// skip all whitespace chars following backslash
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for strings.ContainsRune("\r\n\t ", l.peek()) {
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l.next()
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}
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case '"':
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growingString += "\""
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l.next()
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case 'n':
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growingString += "\n"
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l.next()
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case 'b':
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growingString += "\b"
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l.next()
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case 'f':
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growingString += "\f"
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l.next()
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case '/':
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growingString += "/"
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l.next()
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case 't':
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growingString += "\t"
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l.next()
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case 'r':
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growingString += "\r"
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l.next()
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case '\\':
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growingString += "\\"
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l.next()
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case 'u':
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l.next()
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code := ""
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for i := 0; i < 4; i++ {
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c := l.peek()
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if !isHexDigit(c) {
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return "", errors.New("unfinished unicode escape")
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}
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l.next()
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code = code + string(c)
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}
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intcode, err := strconv.ParseInt(code, 16, 32)
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if err != nil {
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return "", errors.New("invalid unicode escape: \\u" + code)
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}
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growingString += string(rune(intcode))
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case 'U':
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l.next()
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code := ""
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for i := 0; i < 8; i++ {
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c := l.peek()
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if !isHexDigit(c) {
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return "", errors.New("unfinished unicode escape")
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}
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l.next()
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code = code + string(c)
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}
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intcode, err := strconv.ParseInt(code, 16, 64)
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if err != nil {
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return "", errors.New("invalid unicode escape: \\U" + code)
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}
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growingString += string(rune(intcode))
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default:
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return "", errors.New("invalid escape sequence: \\" + string(l.peek()))
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}
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} else {
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r := l.peek()
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if 0x00 <= r && r <= 0x1F && !(acceptNewLines && (r == '\n' || r == '\r')) {
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return "", fmt.Errorf("unescaped control character %U", r)
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}
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l.next()
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growingString += string(r)
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}
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if l.peek() == eof {
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break
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}
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}
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return "", errors.New("unclosed string")
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}
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func (l *tomlLexer) lexString() tomlLexStateFn {
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l.skip()
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// handle special case for triple-quote
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terminator := `"`
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discardLeadingNewLine := false
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acceptNewLines := false
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if l.follow(`""`) {
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l.skip()
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l.skip()
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terminator = `"""`
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discardLeadingNewLine = true
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acceptNewLines = true
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}
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str, err := l.lexStringAsString(terminator, discardLeadingNewLine, acceptNewLines)
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if err != nil {
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return l.errorf(err.Error())
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}
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l.emitWithValue(tokenString, str)
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l.fastForward(len(terminator))
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l.ignore()
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return l.lexRvalue
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}
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func (l *tomlLexer) lexTableKey() tomlLexStateFn {
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l.next()
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if l.peek() == '[' {
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// token '[[' signifies an array of tables
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l.next()
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l.emit(tokenDoubleLeftBracket)
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return l.lexInsideTableArrayKey
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}
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// vanilla table key
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l.emit(tokenLeftBracket)
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return l.lexInsideTableKey
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}
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func (l *tomlLexer) lexInsideTableArrayKey() tomlLexStateFn {
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for r := l.peek(); r != eof; r = l.peek() {
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switch r {
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case ']':
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if l.currentTokenStop > l.currentTokenStart {
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l.emit(tokenKeyGroupArray)
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}
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l.next()
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if l.peek() != ']' {
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break
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}
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l.next()
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l.emit(tokenDoubleRightBracket)
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return l.lexVoid
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case '[':
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return l.errorf("table array key cannot contain ']'")
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default:
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l.next()
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}
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}
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return l.errorf("unclosed table array key")
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}
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func (l *tomlLexer) lexInsideTableKey() tomlLexStateFn {
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for r := l.peek(); r != eof; r = l.peek() {
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switch r {
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case ']':
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if l.currentTokenStop > l.currentTokenStart {
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l.emit(tokenKeyGroup)
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}
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l.next()
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l.emit(tokenRightBracket)
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return l.lexVoid
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case '[':
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return l.errorf("table key cannot contain ']'")
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default:
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l.next()
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}
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}
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return l.errorf("unclosed table key")
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}
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func (l *tomlLexer) lexRightBracket() tomlLexStateFn {
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l.next()
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l.emit(tokenRightBracket)
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return l.lexRvalue
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}
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func (l *tomlLexer) lexNumber() tomlLexStateFn {
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r := l.peek()
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if r == '+' || r == '-' {
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l.next()
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}
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pointSeen := false
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expSeen := false
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digitSeen := false
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for {
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next := l.peek()
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if next == '.' {
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if pointSeen {
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return l.errorf("cannot have two dots in one float")
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}
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l.next()
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if !isDigit(l.peek()) {
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return l.errorf("float cannot end with a dot")
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}
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pointSeen = true
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} else if next == 'e' || next == 'E' {
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expSeen = true
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l.next()
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r := l.peek()
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if r == '+' || r == '-' {
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l.next()
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}
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} else if isDigit(next) {
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digitSeen = true
|
|
l.next()
|
|
} else if next == '_' {
|
|
l.next()
|
|
} else {
|
|
break
|
|
}
|
|
if pointSeen && !digitSeen {
|
|
return l.errorf("cannot start float with a dot")
|
|
}
|
|
}
|
|
|
|
if !digitSeen {
|
|
return l.errorf("no digit in that number")
|
|
}
|
|
if pointSeen || expSeen {
|
|
l.emit(tokenFloat)
|
|
} else {
|
|
l.emit(tokenInteger)
|
|
}
|
|
return l.lexRvalue
|
|
}
|
|
|
|
func (l *tomlLexer) run() {
|
|
for state := l.lexVoid; state != nil; {
|
|
state = state()
|
|
}
|
|
}
|
|
|
|
func init() {
|
|
dateRegexp = regexp.MustCompile(`^\d{1,4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(\.\d{1,9})?(Z|[+-]\d{2}:\d{2})`)
|
|
}
|
|
|
|
// Entry point
|
|
func lexToml(inputBytes []byte) []token {
|
|
runes := bytes.Runes(inputBytes)
|
|
l := &tomlLexer{
|
|
input: runes,
|
|
tokens: make([]token, 0, 256),
|
|
line: 1,
|
|
col: 1,
|
|
endbufferLine: 1,
|
|
endbufferCol: 1,
|
|
}
|
|
l.run()
|
|
return l.tokens
|
|
}
|