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isolating-run-sequence.go
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isolating-run-sequence.go
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package bidih
import (
"github.com/apaxa-go/helper/unicodeh/bidih/internal/bidi"
)
type runSequence struct {
sos, eos bidi.Class
ranges []struct{ from, to int } // [from; to)
rangeI, runeI int // for iteration over sequence
}
func makeRunSequence(from, to int) runSequence {
return runSequence{ranges: []struct{ from, to int }{{from, to}}}
}
func (s *runSequence) start() {
s.rangeI = 0
s.runeI = s.ranges[0].from
}
func (s *runSequence) end() {
s.rangeI = len(s.ranges) - 1
s.runeI = s.ranges[s.rangeI].to - 1
}
func (s *runSequence) next() {
if s.isEnd() {
return
}
s.runeI++
if s.runeI >= s.ranges[s.rangeI].to && s.rangeI < len(s.ranges)-1 {
s.rangeI++
s.runeI = s.ranges[s.rangeI].from
}
}
func (s *runSequence) prev() {
if s.isStart() {
return
}
s.runeI--
if s.runeI < s.ranges[s.rangeI].from && s.rangeI > 0 {
s.rangeI--
s.runeI = s.ranges[s.rangeI].to - 1
}
}
func (s *runSequence) isEnd() bool {
return s.runeI >= s.ranges[len(s.ranges)-1].to
}
func (s *runSequence) isStart() bool {
return s.runeI < s.ranges[0].from
}
type sequenceState struct {
rangeI, runeI int
}
func (s *runSequence) saveState() sequenceState {
return sequenceState{s.rangeI, s.runeI}
}
func (s *runSequence) loadState(state sequenceState) {
s.rangeI = state.rangeI
s.runeI = state.runeI
}