package lexer import "io" import "github.com/sashakoshka/arf/file" import "github.com/sashakoshka/arf/types" // LexingOperation holds information about an ongoing lexing operataion. type LexingOperation struct { file *file.File char rune tokens []Token } // Tokenize converts a file into a slice of tokens (lexemes). func Tokenize (file *file.File) (tokens []Token, err error) { lexer := LexingOperation { file: file } err = lexer.tokenize() tokens = lexer.tokens // if the lexing operation returned io.EOF, nothing went wrong so we // return nil for err. if err == io.EOF { err = nil } return } // tokenize converts a file into a slice of tokens (lexemes). It will always // return a non-nil error, but if nothing went wrong it will return io.EOF. func (lexer *LexingOperation) tokenize () (err error) { err = lexer.nextRune() if err != nil { return } for { lowercase := lexer.char >= 'a' && lexer.char <= 'z' uppercase := lexer.char >= 'A' && lexer.char <= 'Z' number := lexer.char >= '0' && lexer.char <= '9' if number { err = lexer.tokenizeNumberBeginning(false) if err != nil { return } } else if lowercase || uppercase { err = lexer.tokenizeAlphaBeginning() if err != nil { return } } else { err = lexer.tokenizeSymbolBeginning() if err != nil { return } } err = lexer.skipSpaces() if err != nil { return } } if lexer.tokens[len(lexer.tokens) - 1].kind != TokenKindNewline { lexer.addToken(Token { kind: TokenKindNewline }) } return } func (lexer *LexingOperation) tokenizeAlphaBeginning () (err error) { got := "" for { lowercase := lexer.char >= 'a' && lexer.char <= 'z' uppercase := lexer.char >= 'A' && lexer.char <= 'Z' number := lexer.char >= '0' && lexer.char <= '9' if !lowercase && !uppercase && !number { break } got += string(lexer.char) lexer.nextRune() } token := Token { kind: TokenKindName, value: got } if len(got) == 2 { firstValid := got[0] == 'n' || got[0] == 'r' || got[0] == 'w' secondValid := got[1] == 'n' || got[1] == 'r' || got[1] == 'w' if firstValid && secondValid { token.kind = TokenKindPermission token.value = types.PermissionFrom(got) } } lexer.addToken(token) return } func (lexer *LexingOperation) tokenizeSymbolBeginning () (err error) { switch lexer.char { case '#': // comment for lexer.char != '\n' { err = lexer.nextRune() if err != nil { return } } case '\t': // indent level previousToken := lexer.tokens[len(lexer.tokens) - 1] if !previousToken.Is(TokenKindNewline) || !previousToken.Is(TokenKindNewline) { file.NewError ( lexer.file.Location(), 1, "tab not used as indent", file.ErrorKindWarn) break } indentLevel := 0 for lexer.char == '\t' { indentLevel ++ err = lexer.nextRune() if err != nil { return } } lexer.addToken (Token { kind: TokenKindIndent, value: indentLevel, }) case '\n': // line break lastLineEmpty := true tokenIndex := len(lexer.tokens) - 1 for lexer.tokens[tokenIndex].kind != TokenKindNewline { if lexer.tokens[tokenIndex].kind != TokenKindIndent { lastLineEmpty = false break } tokenIndex -- } if lastLineEmpty { lexer.tokens = lexer.tokens[:tokenIndex] } // TODO: if last line was blank, (ony whitespace) discard. lexer.addToken (Token { kind: TokenKindNewline, }) err = lexer.nextRune() case '"': err = lexer.tokenizeString(false) case '\'': err = lexer.tokenizeString(true) case ':': lexer.addToken (Token { kind: TokenKindColon, }) err = lexer.nextRune() case '.': lexer.addToken (Token { kind: TokenKindDot, }) err = lexer.nextRune() case '[': lexer.addToken (Token { kind: TokenKindLBracket, }) err = lexer.nextRune() case ']': lexer.addToken (Token { kind: TokenKindRBracket, }) err = lexer.nextRune() case '{': lexer.addToken (Token { kind: TokenKindLBrace, }) err = lexer.nextRune() case '}': lexer.addToken (Token { kind: TokenKindRBrace, }) err = lexer.nextRune() case '+': err = lexer.nextRune() if err != nil { return } token := Token { kind: TokenKindPlus } if lexer.char == '+' { token.kind = TokenKindIncrement } lexer.addToken(token) err = lexer.nextRune() case '-': err = lexer.tokenizeDashBeginning() case '*': lexer.addToken (Token { kind: TokenKindAsterisk, }) err = lexer.nextRune() case '/': lexer.addToken (Token { kind: TokenKindSlash, }) err = lexer.nextRune() case '@': lexer.addToken (Token { kind: TokenKindAt, }) err = lexer.nextRune() case '!': lexer.addToken (Token { kind: TokenKindExclamation, }) err = lexer.nextRune() case '%': lexer.addToken (Token { kind: TokenKindPercent, }) err = lexer.nextRune() case '~': lexer.addToken (Token { kind: TokenKindTilde, }) err = lexer.nextRune() case '<': err = lexer.nextRune() if err != nil { return } token := Token { kind: TokenKindLessThan } if lexer.char == '<' { token.kind = TokenKindLShift } lexer.addToken(token) err = lexer.nextRune() case '>': err = lexer.nextRune() if err != nil { return } token := Token { kind: TokenKindGreaterThan } if lexer.char == '>' { token.kind = TokenKindRShift } lexer.addToken(token) err = lexer.nextRune() case '|': err = lexer.nextRune() if err != nil { return } token := Token { kind: TokenKindBinaryOr } if lexer.char == '|' { token.kind = TokenKindLogicalOr } lexer.addToken(token) err = lexer.nextRune() case '&': err = lexer.nextRune() if err != nil { return } token := Token { kind: TokenKindBinaryAnd } if lexer.char == '&' { token.kind = TokenKindLogicalAnd } lexer.addToken(token) err = lexer.nextRune() default: err = file.NewError ( lexer.file.Location(), 1, "unexpected symbol character " + string(lexer.char), file.ErrorKindError) return } return } func (lexer *LexingOperation) tokenizeDashBeginning () (err error) { err = lexer.nextRune() if err != nil { return } if lexer.char == '-' { token := Token { kind: TokenKindDecrement } err = lexer.nextRune() if err != nil { return } if lexer.char == '-' { token.kind = TokenKindSeparator lexer.nextRune() } lexer.addToken(token) } else if lexer.char == '>' { token := Token { kind: TokenKindReturnDirection } err = lexer.nextRune() if err != nil { return } lexer.addToken(token) } else if lexer.char >= '0' && lexer.char <= '9' { lexer.tokenizeNumberBeginning(true) } else { token := Token { kind: TokenKindMinus } lexer.addToken(token) } return } // addToken adds a new token to the lexer's token slice. func (lexer *LexingOperation) addToken (token Token) { lexer.tokens = append(lexer.tokens, token) } // skipSpaces skips all space characters (not tabs or newlines) func (lexer *LexingOperation) skipSpaces () (err error) { for lexer.char == ' ' { err = lexer.nextRune() if err != nil { return } } return } // nextRune advances the lexer to the next rune in the file. func (lexer *LexingOperation) nextRune () (err error) { lexer.char, _, err = lexer.file.ReadRune() if err != nil && err != io.EOF { return file.NewError ( lexer.file.Location(), 1, err.Error(), file.ErrorKindError) } return }