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package bechars
import (
"src.userspace.com.au/felix/lexer"
)
const (
_ lexer.TokenType = iota
tBREStart
tBREEnd
tRangeStart
tRangeDash
tRangeEnd
tCharacter
tClass
tNot
)
func startState(l *lexer.Lexer) lexer.StateFunc {
l.SkipWhitespace()
r := l.Next()
if r != '[' {
return l.Error("expecting [")
}
l.Emit(tBREStart)
return beFirstState
}
// Handle the first characters of the BRE.
func beFirstState(l *lexer.Lexer) lexer.StateFunc {
switch l.Next() {
case '^':
l.Emit(tNot)
// - or ] After ^ is literal
if l.Accept("-]") {
l.Emit(tCharacter)
}
return beState
case ']':
// Check for empty BRE
if l.Peek() == lexer.EOFRune {
l.Emit(tBREEnd)
return nil
}
l.Emit(tCharacter)
return beState
case '-':
l.Emit(tCharacter)
return beState
default:
l.Backup()
return beState
}
}
func beState(l *lexer.Lexer) lexer.StateFunc {
switch r := l.Next(); {
case r == ']':
l.Emit(tBREEnd)
return nil
case r == ':':
return classState
case r == '-':
return l.Error("parse error, unexpected '-'")
case r == '\\':
if l.Accept("ux") {
return unicodeState
}
l.Emit(tCharacter)
return beState
case r == lexer.EOFRune:
return l.Error("parse error, unexpected EOF")
default:
if l.Peek() == '-' {
l.Emit(tRangeStart)
l.Accept("-")
l.Emit(tRangeDash)
if l.Accept("-][^") {
return l.Error("parse error, invalid range end")
}
l.Next()
l.Emit(tRangeEnd)
} else {
l.Emit(tCharacter)
}
return beState
}
}
func classState(l *lexer.Lexer) lexer.StateFunc {
// TODO
l.AcceptRun("abcdefghijklmnopqrstuvwxyz")
if !l.Accept(":") {
return l.Error("parse error, expecting ':'")
}
l.Emit(tClass)
return beState
}
func unicodeState(l *lexer.Lexer) lexer.StateFunc {
// TODO valid code point
if n := l.AcceptRun("0123456789abcdef"); n > 0 {
l.Emit(tCharacter)
}
return beState
}
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