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