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states.go
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states.go
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package scanner
import (
"github.com/arnodel/golua/token"
)
func scanToken(l *Scanner) stateFn {
for {
switch c := l.next(); {
case c == '-':
if l.next() == '-' {
return scanComment
}
l.backup()
l.emit(token.SgMinus)
case c == '"' || c == '\'':
return scanShortString(c)
case isDec(c):
l.backup()
return scanNumber
case c == '[':
n := l.next()
if n == '[' || n == '=' {
l.backup()
return scanLongString
}
l.backup()
l.emit(token.SgOpenSquareBkt)
case isAlpha(c):
return scanIdent
case isSpace(c):
l.ignore()
default:
switch c {
case ';', '(', ')', ',', '|', '&', '+', '*', '%', '^', '#', ']', '{', '}':
case '=':
l.accept("=")
case ':':
l.accept(":")
case '.':
if accept(l, isDec, -1) > 0 {
return scanExp(l, isDec, "eE", token.NUMDEC)
}
if l.accept(".") {
l.accept(".")
}
case '<':
l.accept("=<")
case '>':
l.accept("=>")
case '~':
l.accept("=")
case '/':
l.accept("/")
case -1:
l.emit(token.EOF)
return nil
default:
return l.errorf(token.INVALID, "illegal character")
}
l.emit(sgType[string(l.lit())])
}
return scanToken
}
}
func scanComment(l *Scanner) stateFn {
c := l.next()
if c == '[' {
return scanLongComment
}
l.backup()
return scanShortComment
}
func scanShortComment(l *Scanner) stateFn {
for {
switch c := l.next(); c {
case '\n':
l.acceptRune('\r')
l.ignore()
return scanToken
case -1:
l.ignore()
l.emit(token.EOF)
return nil
}
}
}
func scanLongComment(l *Scanner) stateFn {
return scanLong(true)
}
func scanLong(comment bool) stateFn {
return func(l *Scanner) stateFn {
level := 0
OpeningLoop:
for {
switch c := l.next(); c {
case '=':
level++
case '[':
break OpeningLoop
default:
if comment {
l.ignore()
return scanShortComment
}
return l.errorf(token.INVALID, "expected opening long bracket")
}
}
closeLevel := -1
// -1 means we haven't starting closing a bracket
// 0 means we have processed the first ']'
// n > 0 means we have processed ']' + n*'='
for {
switch c := l.next(); c {
case ']':
if closeLevel == level {
if comment {
l.ignore()
} else {
l.emit(token.LONGSTRING)
}
return scanToken
}
closeLevel = 0
case '=':
if closeLevel >= 0 {
closeLevel++
}
case -1:
return l.errorf(token.UNFINISHED, "illegal <eof> in long bracket of level %d", level)
default:
closeLevel = -1
}
}
}
}
func scanShortString(q rune) stateFn {
return func(l *Scanner) stateFn {
for {
switch c := l.next(); c {
case q:
l.emit(token.STRING)
return scanToken
case '\\':
switch c := l.next(); {
case c == 'x':
if accept(l, isHex, 2) != 2 {
return l.errorf(token.INVALID, `\x must be followed by 2 hex digits`)
}
case isDec(c):
accept(l, isDec, 2)
case c == 'u':
if l.next() != '{' {
return l.errorf(token.INVALID, `\u must be followed by '{'`)
}
if accept(l, isHex, -1) == 0 {
return l.errorf(token.INVALID, "at least 1 hex digit required")
}
if l.next() != '}' {
return l.errorf(token.INVALID, "missing '}'")
}
case c == 'z':
accept(l, isSpace, -1)
default:
switch c {
case '\n':
// Nothing to do
case 'a', 'b', 'f', 'n', 'r', 't', 'v', 'z', '"', '\'', '\\':
break
default:
return l.errorf(token.INVALID, "illegal escaped character")
}
}
case '\n', '\r':
return l.errorf(token.INVALID, "illegal new line in string literal")
case -1:
return l.errorf(token.INVALID, "illegal <eof> in string literal")
}
}
}
}
// For scanning numbers e.g. in files
func scanNumberPrefix(l *Scanner) stateFn {
accept(l, isSpace, -1)
l.accept("+-")
return scanNumber
}
func scanNumber(l *Scanner) stateFn {
isDigit := isDec
exp := "eE"
tp := token.NUMDEC
leading0 := l.accept("0")
dcount := 0
if leading0 && l.accept("xX") {
isDigit = isHex
exp = "pP"
tp = token.NUMHEX
} else if leading0 {
dcount++
}
dcount += accept(l, isDigit, -1)
if l.accept(".") {
dcount += accept(l, isDigit, -1)
}
if dcount == 0 {
return l.errorf(token.INVALID, "no digits in mantissa")
}
return scanExp(l, isDigit, exp, tp)
}
func scanExp(l *Scanner, isDigit func(rune) bool, exp string, tp token.Type) stateFn {
if l.accept(exp) {
l.accept("+-")
if accept(l, isDec, -1) == 0 {
return l.errorf(token.INVALID, "digit required after exponent")
}
}
l.emit(tp)
if isAlpha(l.peek()) {
l.next()
return l.errorf(token.INVALID, "illegal character following number")
}
return scanToken
}
func scanLongString(l *Scanner) stateFn {
return scanLong(false)
}
var kwType = map[string]token.Type{
"break": token.KwBreak,
"goto": token.KwGoto,
"do": token.KwDo,
"while": token.KwWhile,
"end": token.KwEnd,
"repeat": token.KwRepeat,
"until": token.KwUntil,
"then": token.KwThen,
"else": token.KwElse,
"elseif": token.KwElseIf,
"if": token.KwIf,
"for": token.KwFor,
"in": token.KwIn,
"function": token.KwFunction,
"local": token.KwLocal,
"and": token.KwAnd,
"or": token.KwOr,
"not": token.KwNot,
"nil": token.KwNil,
"true": token.KwTrue,
"false": token.KwFalse,
"return": token.KwReturn,
}
var sgType = map[string]token.Type{
"-": token.SgMinus,
"+": token.SgPlus,
"*": token.SgStar,
"/": token.SgSlash,
"//": token.SgSlashSlash,
"%": token.SgPct,
"|": token.SgPipe,
"&": token.SgAmpersand,
"^": token.SgHat,
">>": token.SgShiftRight,
"<<": token.SgShiftLeft,
"..": token.SgConcat,
"==": token.SgEqual,
"~=": token.SgNotEqual,
"<": token.SgLess,
"<=": token.SgLessEqual,
">": token.SgGreater,
">=": token.SgGreaterEqual,
"...": token.SgEtc,
"[": token.SgOpenSquareBkt,
"]": token.SgCloseSquareBkt,
"(": token.SgOpenBkt,
")": token.SgCloseBkt,
"{": token.SgOpenBrace,
"}": token.SgCloseBrace,
";": token.SgSemicolon,
",": token.SgComma,
".": token.SgDot,
":": token.SgColon,
"::": token.SgDoubleColon,
"=": token.SgAssign,
"#": token.SgHash,
"~": token.SgTilde,
}
func scanIdent(l *Scanner) stateFn {
accept(l, isAlnum, -1)
tp, ok := kwType[string(l.lit())]
if !ok {
tp = token.IDENT
}
l.emit(tp)
return scanToken
}
func isDec(x rune) bool {
return '0' <= x && x <= '9'
}
func isAlpha(x rune) bool {
return x >= 'a' && x <= 'z' || x >= 'A' && x <= 'Z' || x == '_'
}
func isAlnum(x rune) bool {
return isDec(x) || isAlpha(x)
}
func isHex(x rune) bool {
return isDec(x) || 'a' <= x && x <= 'f' || 'A' <= x && x <= 'F'
}
func isSpace(x rune) bool {
return x == ' ' || x == '\n' || x == '\r' || x == '\t' || x == '\v' || x == '\f'
}
type runePredicate func(rune) bool
func accept(l *Scanner, p runePredicate, max int) int {
for i := 0; i != max; i++ {
if !p(l.next()) {
l.backup()
return i
}
}
return max
}