youtubebeat/vendor/github.com/gobwas/glob/syntax/lexer/lexer.go

273 lines
4.4 KiB
Go

package lexer
import (
"bytes"
"fmt"
"github.com/gobwas/glob/util/runes"
"unicode/utf8"
)
const (
char_any = '*'
char_comma = ','
char_single = '?'
char_escape = '\\'
char_range_open = '['
char_range_close = ']'
char_terms_open = '{'
char_terms_close = '}'
char_range_not = '!'
char_range_between = '-'
)
var specials = []byte{
char_any,
char_single,
char_escape,
char_range_open,
char_range_close,
char_terms_open,
char_terms_close,
}
func Special(c byte) bool {
return bytes.IndexByte(specials, c) != -1
}
type tokens []Token
func (i *tokens) shift() (ret Token) {
ret = (*i)[0]
copy(*i, (*i)[1:])
*i = (*i)[:len(*i)-1]
return
}
func (i *tokens) push(v Token) {
*i = append(*i, v)
}
func (i *tokens) empty() bool {
return len(*i) == 0
}
var eof rune = 0
type lexer struct {
data string
pos int
err error
tokens tokens
termsLevel int
lastRune rune
lastRuneSize int
hasRune bool
}
func NewLexer(source string) *lexer {
l := &lexer{
data: source,
tokens: tokens(make([]Token, 0, 4)),
}
return l
}
func (l *lexer) Next() Token {
if l.err != nil {
return Token{Error, l.err.Error()}
}
if !l.tokens.empty() {
return l.tokens.shift()
}
l.fetchItem()
return l.Next()
}
func (l *lexer) peek() (r rune, w int) {
if l.pos == len(l.data) {
return eof, 0
}
r, w = utf8.DecodeRuneInString(l.data[l.pos:])
if r == utf8.RuneError {
l.errorf("could not read rune")
r = eof
w = 0
}
return
}
func (l *lexer) read() rune {
if l.hasRune {
l.hasRune = false
l.seek(l.lastRuneSize)
return l.lastRune
}
r, s := l.peek()
l.seek(s)
l.lastRune = r
l.lastRuneSize = s
return r
}
func (l *lexer) seek(w int) {
l.pos += w
}
func (l *lexer) unread() {
if l.hasRune {
l.errorf("could not unread rune")
return
}
l.seek(-l.lastRuneSize)
l.hasRune = true
}
func (l *lexer) errorf(f string, v ...interface{}) {
l.err = fmt.Errorf(f, v...)
}
func (l *lexer) inTerms() bool {
return l.termsLevel > 0
}
func (l *lexer) termsEnter() {
l.termsLevel++
}
func (l *lexer) termsLeave() {
l.termsLevel--
}
var inTextBreakers = []rune{char_single, char_any, char_range_open, char_terms_open}
var inTermsBreakers = append(inTextBreakers, char_terms_close, char_comma)
func (l *lexer) fetchItem() {
r := l.read()
switch {
case r == eof:
l.tokens.push(Token{EOF, ""})
case r == char_terms_open:
l.termsEnter()
l.tokens.push(Token{TermsOpen, string(r)})
case r == char_comma && l.inTerms():
l.tokens.push(Token{Separator, string(r)})
case r == char_terms_close && l.inTerms():
l.tokens.push(Token{TermsClose, string(r)})
l.termsLeave()
case r == char_range_open:
l.tokens.push(Token{RangeOpen, string(r)})
l.fetchRange()
case r == char_single:
l.tokens.push(Token{Single, string(r)})
case r == char_any:
if l.read() == char_any {
l.tokens.push(Token{Super, string(r) + string(r)})
} else {
l.unread()
l.tokens.push(Token{Any, string(r)})
}
default:
l.unread()
var breakers []rune
if l.inTerms() {
breakers = inTermsBreakers
} else {
breakers = inTextBreakers
}
l.fetchText(breakers)
}
}
func (l *lexer) fetchRange() {
var wantHi bool
var wantClose bool
var seenNot bool
for {
r := l.read()
if r == eof {
l.errorf("unexpected end of input")
return
}
if wantClose {
if r != char_range_close {
l.errorf("expected close range character")
} else {
l.tokens.push(Token{RangeClose, string(r)})
}
return
}
if wantHi {
l.tokens.push(Token{RangeHi, string(r)})
wantClose = true
continue
}
if !seenNot && r == char_range_not {
l.tokens.push(Token{Not, string(r)})
seenNot = true
continue
}
if n, w := l.peek(); n == char_range_between {
l.seek(w)
l.tokens.push(Token{RangeLo, string(r)})
l.tokens.push(Token{RangeBetween, string(n)})
wantHi = true
continue
}
l.unread() // unread first peek and fetch as text
l.fetchText([]rune{char_range_close})
wantClose = true
}
}
func (l *lexer) fetchText(breakers []rune) {
var data []rune
var escaped bool
reading:
for {
r := l.read()
if r == eof {
break
}
if !escaped {
if r == char_escape {
escaped = true
continue
}
if runes.IndexRune(breakers, r) != -1 {
l.unread()
break reading
}
}
escaped = false
data = append(data, r)
}
if len(data) > 0 {
l.tokens.push(Token{Text, string(data)})
}
}