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661 lines
13 KiB
Go
661 lines
13 KiB
Go
package parser
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import (
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"fmt"
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"unicode"
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"unicode/utf8"
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"github.com/d5/tengo/v2/token"
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)
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// byte order mark
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const bom = 0xFEFF
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// ScanMode represents a scanner mode.
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type ScanMode int
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// List of scanner modes.
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const (
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ScanComments ScanMode = 1 << iota
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DontInsertSemis
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)
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// ScannerErrorHandler is an error handler for the scanner.
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type ScannerErrorHandler func(pos SourceFilePos, msg string)
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// Scanner reads the Tengo source text. It's based on Go's scanner
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// implementation.
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type Scanner struct {
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file *SourceFile // source file handle
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src []byte // source
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ch rune // current character
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offset int // character offset
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readOffset int // reading offset (position after current character)
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lineOffset int // current line offset
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insertSemi bool // insert a semicolon before next newline
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errorHandler ScannerErrorHandler // error reporting; or nil
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errorCount int // number of errors encountered
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mode ScanMode
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}
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// NewScanner creates a Scanner.
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func NewScanner(
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file *SourceFile,
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src []byte,
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errorHandler ScannerErrorHandler,
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mode ScanMode,
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) *Scanner {
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if file.Size != len(src) {
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panic(fmt.Sprintf("file size (%d) does not match src len (%d)",
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file.Size, len(src)))
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}
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s := &Scanner{
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file: file,
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src: src,
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errorHandler: errorHandler,
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ch: ' ',
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mode: mode,
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}
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s.next()
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if s.ch == bom {
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s.next() // ignore BOM at file beginning
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}
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return s
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}
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// ErrorCount returns the number of errors.
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func (s *Scanner) ErrorCount() int {
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return s.errorCount
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}
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// Scan returns a token, token literal and its position.
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func (s *Scanner) Scan() (
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tok token.Token,
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literal string,
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pos Pos,
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) {
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s.skipWhitespace()
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pos = s.file.FileSetPos(s.offset)
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insertSemi := false
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// determine token value
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switch ch := s.ch; {
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case isLetter(ch):
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literal = s.scanIdentifier()
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tok = token.Lookup(literal)
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switch tok {
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case token.Ident, token.Break, token.Continue, token.Return,
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token.Export, token.True, token.False, token.Undefined:
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insertSemi = true
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}
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case ('0' <= ch && ch <= '9') || (ch == '.' && '0' <= s.peek() && s.peek() <= '9'):
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insertSemi = true
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tok, literal = s.scanNumber()
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default:
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s.next() // always make progress
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switch ch {
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case -1: // EOF
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if s.insertSemi {
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s.insertSemi = false // EOF consumed
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return token.Semicolon, "\n", pos
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}
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tok = token.EOF
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case '\n':
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// we only reach here if s.insertSemi was set in the first place
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s.insertSemi = false // newline consumed
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return token.Semicolon, "\n", pos
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case '"':
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insertSemi = true
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tok = token.String
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literal = s.scanString()
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case '\'':
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insertSemi = true
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tok = token.Char
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literal = s.scanRune()
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case '`':
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insertSemi = true
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tok = token.String
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literal = s.scanRawString()
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case ':':
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tok = s.switch2(token.Colon, token.Define)
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case '.':
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tok = token.Period
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if s.ch == '.' && s.peek() == '.' {
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s.next()
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s.next() // consume last '.'
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tok = token.Ellipsis
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}
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case ',':
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tok = token.Comma
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case '?':
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tok = token.Question
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case ';':
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tok = token.Semicolon
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literal = ";"
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case '(':
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tok = token.LParen
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case ')':
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insertSemi = true
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tok = token.RParen
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case '[':
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tok = token.LBrack
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case ']':
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insertSemi = true
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tok = token.RBrack
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case '{':
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tok = token.LBrace
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case '}':
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insertSemi = true
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tok = token.RBrace
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case '+':
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tok = s.switch3(token.Add, token.AddAssign, '+', token.Inc)
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if tok == token.Inc {
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insertSemi = true
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}
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case '-':
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tok = s.switch3(token.Sub, token.SubAssign, '-', token.Dec)
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if tok == token.Dec {
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insertSemi = true
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}
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case '*':
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tok = s.switch2(token.Mul, token.MulAssign)
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case '/':
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if s.ch == '/' || s.ch == '*' {
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// comment
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if s.insertSemi && s.findLineEnd() {
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// reset position to the beginning of the comment
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s.ch = '/'
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s.offset = s.file.Offset(pos)
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s.readOffset = s.offset + 1
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s.insertSemi = false // newline consumed
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return token.Semicolon, "\n", pos
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}
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comment := s.scanComment()
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if s.mode&ScanComments == 0 {
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// skip comment
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s.insertSemi = false // newline consumed
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return s.Scan()
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}
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tok = token.Comment
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literal = comment
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} else {
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tok = s.switch2(token.Quo, token.QuoAssign)
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}
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case '%':
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tok = s.switch2(token.Rem, token.RemAssign)
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case '^':
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tok = s.switch2(token.Xor, token.XorAssign)
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case '<':
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tok = s.switch4(token.Less, token.LessEq, '<',
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token.Shl, token.ShlAssign)
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case '>':
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tok = s.switch4(token.Greater, token.GreaterEq, '>',
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token.Shr, token.ShrAssign)
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case '=':
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tok = s.switch2(token.Assign, token.Equal)
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case '!':
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tok = s.switch2(token.Not, token.NotEqual)
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case '&':
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if s.ch == '^' {
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s.next()
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tok = s.switch2(token.AndNot, token.AndNotAssign)
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} else {
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tok = s.switch3(token.And, token.AndAssign, '&', token.LAnd)
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}
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case '|':
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tok = s.switch3(token.Or, token.OrAssign, '|', token.LOr)
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default:
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// next reports unexpected BOMs - don't repeat
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if ch != bom {
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s.error(s.file.Offset(pos),
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fmt.Sprintf("illegal character %#U", ch))
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}
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insertSemi = s.insertSemi // preserve insertSemi info
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tok = token.Illegal
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literal = string(ch)
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}
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}
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if s.mode&DontInsertSemis == 0 {
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s.insertSemi = insertSemi
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}
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return
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}
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func (s *Scanner) next() {
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if s.readOffset < len(s.src) {
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s.offset = s.readOffset
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if s.ch == '\n' {
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s.lineOffset = s.offset
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s.file.AddLine(s.offset)
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}
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r, w := rune(s.src[s.readOffset]), 1
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switch {
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case r == 0:
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s.error(s.offset, "illegal character NUL")
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case r >= utf8.RuneSelf:
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// not ASCII
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r, w = utf8.DecodeRune(s.src[s.readOffset:])
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if r == utf8.RuneError && w == 1 {
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s.error(s.offset, "illegal UTF-8 encoding")
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} else if r == bom && s.offset > 0 {
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s.error(s.offset, "illegal byte order mark")
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}
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}
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s.readOffset += w
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s.ch = r
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} else {
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s.offset = len(s.src)
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if s.ch == '\n' {
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s.lineOffset = s.offset
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s.file.AddLine(s.offset)
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}
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s.ch = -1 // eof
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}
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}
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func (s *Scanner) peek() byte {
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if s.readOffset < len(s.src) {
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return s.src[s.readOffset]
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}
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return 0
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}
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func (s *Scanner) error(offset int, msg string) {
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if s.errorHandler != nil {
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s.errorHandler(s.file.Position(s.file.FileSetPos(offset)), msg)
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}
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s.errorCount++
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}
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func (s *Scanner) scanComment() string {
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// initial '/' already consumed; s.ch == '/' || s.ch == '*'
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offs := s.offset - 1 // position of initial '/'
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var numCR int
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if s.ch == '/' {
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//-style comment
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// (the final '\n' is not considered part of the comment)
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s.next()
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for s.ch != '\n' && s.ch >= 0 {
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if s.ch == '\r' {
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numCR++
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}
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s.next()
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}
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goto exit
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}
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/*-style comment */
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s.next()
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for s.ch >= 0 {
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ch := s.ch
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if ch == '\r' {
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numCR++
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}
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s.next()
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if ch == '*' && s.ch == '/' {
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s.next()
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goto exit
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}
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}
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s.error(offs, "comment not terminated")
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exit:
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lit := s.src[offs:s.offset]
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// On Windows, a (//-comment) line may end in "\r\n".
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// Remove the final '\r' before analyzing the text for line directives (matching the compiler).
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// Remove any other '\r' afterwards (matching the pre-existing behavior of the scanner).
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if numCR > 0 && len(lit) >= 2 && lit[1] == '/' && lit[len(lit)-1] == '\r' {
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lit = lit[:len(lit)-1]
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numCR--
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}
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if numCR > 0 {
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lit = StripCR(lit, lit[1] == '*')
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}
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return string(lit)
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}
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func (s *Scanner) findLineEnd() bool {
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// initial '/' already consumed
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defer func(offs int) {
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// reset scanner state to where it was upon calling findLineEnd
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s.ch = '/'
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s.offset = offs
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s.readOffset = offs + 1
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s.next() // consume initial '/' again
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}(s.offset - 1)
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// read ahead until a newline, EOF, or non-comment tok is found
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for s.ch == '/' || s.ch == '*' {
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if s.ch == '/' {
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//-style comment always contains a newline
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return true
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}
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/*-style comment: look for newline */
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s.next()
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for s.ch >= 0 {
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ch := s.ch
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if ch == '\n' {
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return true
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}
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s.next()
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if ch == '*' && s.ch == '/' {
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s.next()
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break
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}
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}
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s.skipWhitespace() // s.insertSemi is set
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if s.ch < 0 || s.ch == '\n' {
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return true
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}
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if s.ch != '/' {
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// non-comment tok
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return false
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}
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s.next() // consume '/'
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}
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return false
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}
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func (s *Scanner) scanIdentifier() string {
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offs := s.offset
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for isLetter(s.ch) || isDigit(s.ch) {
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s.next()
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}
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return string(s.src[offs:s.offset])
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}
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func (s *Scanner) scanDigits(base int) {
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for s.ch == '_' || digitVal(s.ch) < base {
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s.next()
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}
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}
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func (s *Scanner) scanNumber() (token.Token, string) {
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offs := s.offset
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tok := token.Int
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base := 10
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// Determine base
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switch {
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case s.ch == '0' && lower(s.peek()) == 'b':
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base = 2
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s.next()
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s.next()
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case s.ch == '0' && lower(s.peek()) == 'o':
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base = 8
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s.next()
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s.next()
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case s.ch == '0' && lower(s.peek()) == 'x':
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base = 16
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s.next()
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s.next()
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}
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// Scan whole number
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s.scanDigits(base)
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// Scan fractional part
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if s.ch == '.' && (base == 10 || base == 16) {
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tok = token.Float
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s.next()
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s.scanDigits(base)
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}
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// Scan exponent
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if s.ch == 'e' || s.ch == 'E' || s.ch == 'p' || s.ch == 'P' {
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tok = token.Float
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s.next()
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if s.ch == '-' || s.ch == '+' {
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s.next()
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}
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offs := s.offset
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s.scanDigits(10)
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if offs == s.offset {
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s.error(offs, "exponent has no digits")
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}
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}
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return tok, string(s.src[offs:s.offset])
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}
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func (s *Scanner) scanEscape(quote rune) bool {
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offs := s.offset
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var n int
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var base, max uint32
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switch s.ch {
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case 'a', 'b', 'f', 'n', 'r', 't', 'v', '\\', quote:
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s.next()
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return true
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case '0', '1', '2', '3', '4', '5', '6', '7':
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n, base, max = 3, 8, 255
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case 'x':
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s.next()
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n, base, max = 2, 16, 255
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case 'u':
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s.next()
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n, base, max = 4, 16, unicode.MaxRune
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case 'U':
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s.next()
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n, base, max = 8, 16, unicode.MaxRune
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default:
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msg := "unknown escape sequence"
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if s.ch < 0 {
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msg = "escape sequence not terminated"
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}
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s.error(offs, msg)
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return false
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}
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var x uint32
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for n > 0 {
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d := uint32(digitVal(s.ch))
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if d >= base {
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msg := fmt.Sprintf(
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"illegal character %#U in escape sequence", s.ch)
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if s.ch < 0 {
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msg = "escape sequence not terminated"
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}
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s.error(s.offset, msg)
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return false
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}
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x = x*base + d
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s.next()
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n--
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}
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if x > max || 0xD800 <= x && x < 0xE000 {
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s.error(offs, "escape sequence is invalid Unicode code point")
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return false
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}
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return true
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}
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func (s *Scanner) scanRune() string {
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offs := s.offset - 1 // '\'' opening already consumed
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valid := true
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n := 0
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for {
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ch := s.ch
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if ch == '\n' || ch < 0 {
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// only report error if we don't have one already
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if valid {
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s.error(offs, "rune literal not terminated")
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valid = false
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}
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break
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}
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s.next()
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if ch == '\'' {
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break
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}
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n++
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if ch == '\\' {
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if !s.scanEscape('\'') {
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valid = false
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}
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// continue to read to closing quote
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}
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}
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if valid && n != 1 {
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s.error(offs, "illegal rune literal")
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}
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return string(s.src[offs:s.offset])
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}
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|
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func (s *Scanner) scanString() string {
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offs := s.offset - 1 // '"' opening already consumed
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for {
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ch := s.ch
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if ch == '\n' || ch < 0 {
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s.error(offs, "string literal not terminated")
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break
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}
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s.next()
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if ch == '"' {
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break
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}
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if ch == '\\' {
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s.scanEscape('"')
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}
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}
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return string(s.src[offs:s.offset])
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}
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func (s *Scanner) scanRawString() string {
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offs := s.offset - 1 // '`' opening already consumed
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hasCR := false
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for {
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ch := s.ch
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if ch < 0 {
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s.error(offs, "raw string literal not terminated")
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break
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}
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s.next()
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if ch == '`' {
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break
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}
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if ch == '\r' {
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hasCR = true
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}
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}
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lit := s.src[offs:s.offset]
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if hasCR {
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lit = StripCR(lit, false)
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}
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return string(lit)
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}
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|
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// StripCR removes carriage return characters.
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func StripCR(b []byte, comment bool) []byte {
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c := make([]byte, len(b))
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i := 0
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for j, ch := range b {
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// In a /*-style comment, don't strip \r from *\r/ (incl. sequences of
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// \r from *\r\r...\r/) since the resulting */ would terminate the
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// comment too early unless the \r is immediately following the opening
|
|
// /* in which case it's ok because /*/ is not closed yet.
|
|
if ch != '\r' || comment && i > len("/*") && c[i-1] == '*' &&
|
|
j+1 < len(b) && b[j+1] == '/' {
|
|
c[i] = ch
|
|
i++
|
|
}
|
|
}
|
|
return c[:i]
|
|
}
|
|
|
|
func (s *Scanner) skipWhitespace() {
|
|
for s.ch == ' ' || s.ch == '\t' || s.ch == '\n' && !s.insertSemi ||
|
|
s.ch == '\r' {
|
|
s.next()
|
|
}
|
|
}
|
|
|
|
func (s *Scanner) switch2(tok0, tok1 token.Token) token.Token {
|
|
if s.ch == '=' {
|
|
s.next()
|
|
return tok1
|
|
}
|
|
return tok0
|
|
}
|
|
|
|
func (s *Scanner) switch3(
|
|
tok0, tok1 token.Token,
|
|
ch2 rune,
|
|
tok2 token.Token,
|
|
) token.Token {
|
|
if s.ch == '=' {
|
|
s.next()
|
|
return tok1
|
|
}
|
|
if s.ch == ch2 {
|
|
s.next()
|
|
return tok2
|
|
}
|
|
return tok0
|
|
}
|
|
|
|
func (s *Scanner) switch4(
|
|
tok0, tok1 token.Token,
|
|
ch2 rune,
|
|
tok2, tok3 token.Token,
|
|
) token.Token {
|
|
if s.ch == '=' {
|
|
s.next()
|
|
return tok1
|
|
}
|
|
if s.ch == ch2 {
|
|
s.next()
|
|
if s.ch == '=' {
|
|
s.next()
|
|
return tok3
|
|
}
|
|
return tok2
|
|
}
|
|
return tok0
|
|
}
|
|
|
|
func isLetter(ch rune) bool {
|
|
return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch == '_' ||
|
|
ch >= utf8.RuneSelf && unicode.IsLetter(ch)
|
|
}
|
|
|
|
func isDigit(ch rune) bool {
|
|
return '0' <= ch && ch <= '9' ||
|
|
ch >= utf8.RuneSelf && unicode.IsDigit(ch)
|
|
}
|
|
|
|
func digitVal(ch rune) int {
|
|
switch {
|
|
case '0' <= ch && ch <= '9':
|
|
return int(ch - '0')
|
|
case 'a' <= ch && ch <= 'f':
|
|
return int(ch - 'a' + 10)
|
|
case 'A' <= ch && ch <= 'F':
|
|
return int(ch - 'A' + 10)
|
|
}
|
|
return 16 // larger than any legal digit val
|
|
}
|
|
|
|
func lower(c byte) byte {
|
|
return c | ('x' - 'X')
|
|
}
|