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// Copyright (c) 2015 Couchbase, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package gtreap provides an in-memory implementation of the
// KVStore interfaces using the gtreap balanced-binary treap,
// copy-on-write data structure.
package gtreap
import (
"bytes"
"sync"
"github.com/steveyen/gtreap"
)
type Iterator struct {
t *gtreap.Treap
m sync.Mutex
cancelCh chan struct{}
nextCh chan *Item
curr *Item
currOk bool
prefix []byte
start []byte
end []byte
}
func (w *Iterator) Seek(k []byte) {
if w.start != nil && bytes.Compare(k, w.start) < 0 {
k = w.start
}
if w.prefix != nil && !bytes.HasPrefix(k, w.prefix) {
if bytes.Compare(k, w.prefix) < 0 {
k = w.prefix
} else {
var end []byte
for i := len(w.prefix) - 1; i >= 0; i-- {
c := w.prefix[i]
if c < 0xff {
end = make([]byte, i+1)
copy(end, w.prefix)
end[i] = c + 1
break
}
}
k = end
}
}
w.restart(&Item{k: k})
}
func (w *Iterator) restart(start *Item) *Iterator {
cancelCh := make(chan struct{})
nextCh := make(chan *Item, 1)
w.m.Lock()
if w.cancelCh != nil {
close(w.cancelCh)
}
w.cancelCh = cancelCh
w.nextCh = nextCh
w.curr = nil
w.currOk = false
w.m.Unlock()
go func() {
if start != nil {
w.t.VisitAscend(start, func(itm gtreap.Item) bool {
select {
case <-cancelCh:
return false
case nextCh <- itm.(*Item):
return true
}
})
}
close(nextCh)
}()
w.Next()
return w
}
func (w *Iterator) Next() {
w.m.Lock()
nextCh := w.nextCh
w.m.Unlock()
w.curr, w.currOk = <-nextCh
}
func (w *Iterator) Current() ([]byte, []byte, bool) {
w.m.Lock()
defer w.m.Unlock()
if !w.currOk || w.curr == nil {
return nil, nil, false
}
if w.prefix != nil && !bytes.HasPrefix(w.curr.k, w.prefix) {
return nil, nil, false
} else if w.end != nil && bytes.Compare(w.curr.k, w.end) >= 0 {
return nil, nil, false
}
return w.curr.k, w.curr.v, w.currOk
}
func (w *Iterator) Key() []byte {
k, _, ok := w.Current()
if !ok {
return nil
}
return k
}
func (w *Iterator) Value() []byte {
_, v, ok := w.Current()
if !ok {
return nil
}
return v
}
func (w *Iterator) Valid() bool {
_, _, ok := w.Current()
return ok
}
func (w *Iterator) Close() error {
w.m.Lock()
if w.cancelCh != nil {
close(w.cancelCh)
}
w.cancelCh = nil
w.nextCh = nil
w.curr = nil
w.currOk = false
w.m.Unlock()
return nil
}
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