/
ring.go
95 lines (73 loc) · 1.45 KB
/
ring.go
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package jsonc
import (
"fmt"
)
type ReadRune func() (r rune, size int, err error)
type Ring struct {
buf []rune
readRune ReadRune
minSize int
maxSize int
position int
absPosition int
}
func NewRing(maxSize int, minSize int, readRune ReadRune) (r *Ring, err error) {
if maxSize <= minSize {
return nil, fmt.Errorf("maxSize(%v) <= minSize(%v)", maxSize, minSize)
}
r = &Ring{readRune: readRune, minSize: minSize, maxSize: maxSize}
if readRune != nil {
err = r.fill()
}
return
}
func (r *Ring) Clear(rr ReadRune) (err error) {
r.readRune = rr
r.buf = nil
r.position = 0
r.absPosition = 0
err = r.fill()
return
}
func (r *Ring) Position() int {
return r.absPosition + r.position - len(r.buf)
}
func (r *Ring) Advance() error {
if r.position+1 >= len(r.buf) {
if len(r.buf) > r.maxSize {
r.buf = r.buf[r.maxSize-r.minSize:]
r.position -= (r.maxSize - r.minSize)
if r.position < 0 {
panic(fmt.Errorf("unexpected error"))
}
}
err := r.fill()
if err != nil {
return err
}
}
r.position += 1
return nil
}
func (r *Ring) fill() error {
ru, _, err := r.readRune()
if err != nil {
return err
}
r.buf = append(r.buf, ru)
r.absPosition += 1
return nil
}
func (r *Ring) Peek() rune {
return r.buf[r.position]
}
func (r *Ring) Pop() error {
if r.position == 0 && len(r.buf) == 0 {
return nil
}
if r.position == 0 {
return fmt.Errorf("buffer underrun")
}
r.position -= 1
return nil
}