// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package asm
import (
"fmt"
"os"
"strings"
"unicode"
"unicode/utf8"
)
// stateFn is used through the lifetime of the
// lexer to parse the different values at the
// current state.
type stateFn func(*lexer) stateFn
// token is emitted when the lexer has discovered
// a new parsable token. These are delivered over
// the tokens channels of the lexer
type token struct {
typ tokenType
lineno int
text string
}
// tokenType are the different types the lexer
// is able to parse and return.
type tokenType int
const (
eof tokenType = iota // end of file
lineStart // emitted when a line starts
lineEnd // emitted when a line ends
invalidStatement // any invalid statement
element // any element during element parsing
label // label is emitted when a labal is found
labelDef // label definition is emitted when a new label is found
number // number is emitted when a number is found
stringValue // stringValue is emitted when a string has been found
Numbers = "1234567890" // characters representing any decimal number
HexadecimalNumbers = Numbers + "aAbBcCdDeEfF" // characters representing any hexadecimal
Alpha = "abcdefghijklmnopqrstuwvxyzABCDEFGHIJKLMNOPQRSTUWVXYZ" // characters representing alphanumeric
)
// String implements stringer
func (it tokenType) String() string {
if int(it) > len(stringtokenTypes) {
return "invalid"
}
return stringtokenTypes[it]
}
var stringtokenTypes = []string{
eof: "EOF",
invalidStatement: "invalid statement",
element: "element",
lineEnd: "end of line",
lineStart: "new line",
label: "label",
labelDef: "label definition",
number: "number",
stringValue: "string",
}
// lexer is the basic construct for parsing
// source code and turning them in to tokens.
// Tokens are interpreted by the compiler.
type lexer struct {
input string // input contains the source code of the program
tokens chan token // tokens is used to deliver tokens to the listener
state stateFn // the current state function
lineno int // current line number in the source file
start, pos, width int // positions for lexing and returning value
debug bool // flag for triggering debug output
}
// lex lexes the program by name with the given source. It returns a
// channel on which the tokens are delivered.
func Lex(name string, source []byte, debug bool) <-chan token {
ch := make(chan token)
l := &lexer{
input: string(source),
tokens: ch,
state: lexLine,
debug: debug,
}
go func() {
l.emit(lineStart)
for l.state != nil {
l.state = l.state(l)
}
l.emit(eof)
close(l.tokens)
}()
return ch
}
// next returns the next rune in the program's source.
func (l *lexer) next() (rune rune) {
if l.pos >= len(l.input) {
l.width = 0
return 0
}
rune, l.width = utf8.DecodeRuneInString(l.input[l.pos:])
l.pos += l.width
return rune
}
// backup backsup the last parsed element (multi-character)
func (l *lexer) backup() {
l.pos -= l.width
}
// peek returns the next rune but does not advance the seeker
func (l *lexer) peek() rune {
r := l.next()
l.backup()
return r
}
// ignore advances the seeker and ignores the value
func (l *lexer) ignore() {
l.start = l.pos
}
// Accepts checks whether the given input matches the next rune
func (l *lexer) accept(valid string) bool {
if strings.IndexRune(valid, l.next()) >= 0 {
return true
}
l.backup()
return false
}
// acceptRun will continue to advance the seeker until valid
// can no longer be met.
func (l *lexer) acceptRun(valid string) {
for strings.IndexRune(valid, l.next()) >= 0 {
}
l.backup()
}
// acceptRunUntil is the inverse of acceptRun and will continue
// to advance the seeker until the rune has been found.
func (l *lexer) acceptRunUntil(until rune) bool {
// Continues running until a rune is found
for i := l.next(); strings.IndexRune(string(until), i) == -1; i = l.next() {
if i == 0 {
return false
}
}
return true
}
// blob returns the current value
func (l *lexer) blob() string {
return l.input[l.start:l.pos]
}
// Emits a new token on to token channel for processing
func (l *lexer) emit(t tokenType) {
token := token{t, l.lineno, l.blob()}
if l.debug {
fmt.Fprintf(os.Stderr, "%04d: (%-20v) %s\n", token.lineno, token.typ, token.text)
}
l.tokens <- token
l.start = l.pos
}
// lexLine is state function for lexing lines
func lexLine(l *lexer) stateFn {
for {
switch r := l.next(); {
case r == '\n':
l.emit(lineEnd)
l.ignore()
l.lineno++
l.emit(lineStart)
case r == ';' && l.peek() == ';':
return lexComment
case isSpace(r):
l.ignore()
case isAlphaNumeric(r) || r == '_':
return lexElement
case isNumber(r):
return lexNumber
case r == '@':
l.ignore()
return lexLabel
case r == '"':
return lexInsideString
default:
return nil
}
}
}
// lexComment parses the current position until the end
// of the line and discards the text.
func lexComment(l *lexer) stateFn {
l.acceptRunUntil('\n')
l.ignore()
return lexLine
}
// lexLabel parses the current label, emits and returns
// the lex text state function to advance the parsing
// process.
func lexLabel(l *lexer) stateFn {
l.acceptRun(Alpha + "_")
l.emit(label)
return lexLine
}
// lexInsideString lexes the inside of a string until
// until the state function finds the closing quote.
// It returns the lex text state function.
func lexInsideString(l *lexer) stateFn {
if l.acceptRunUntil('"') {
l.emit(stringValue)
}
return lexLine
}
func lexNumber(l *lexer) stateFn {
acceptance := Numbers
if l.accept("0") || l.accept("xX") {
acceptance = HexadecimalNumbers
}
l.acceptRun(acceptance)
l.emit(number)
return lexLine
}
func lexElement(l *lexer) stateFn {
l.acceptRun(Alpha + "_" + Numbers)
if l.peek() == ':' {
l.emit(labelDef)
l.accept(":")
l.ignore()
} else {
l.emit(element)
}
return lexLine
}
func isAlphaNumeric(t rune) bool {
return unicode.IsLetter(t)
}
func isSpace(t rune) bool {
return unicode.IsSpace(t)
}
func isNumber(t rune) bool {
return unicode.IsNumber(t)
}
