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// Copyright 2020 PingCAP, 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package memdb
import (
"unsafe"
)
// Iterator iterates the entries in the DB.
type Iterator struct {
sb *Sandbox
curr *node
key []byte
val []byte
}
// NewIterator returns a new Iterator for the lock store.
func (sb *Sandbox) NewIterator() Iterator {
return Iterator{
sb: sb,
}
}
// Valid returns true if the iterator is positioned at a valid node.
func (it *Iterator) Valid() bool { return it.curr != nil }
// Key returns the key at the current position.
func (it *Iterator) Key() []byte {
return it.key
}
// Value returns value.
func (it *Iterator) Value() []byte {
return it.val
}
// Next moves the iterator to the next entry.
func (it *Iterator) Next() {
it.changeToAddr(it.curr.nexts(0))
}
// Prev moves the iterator to the previous entry.
func (it *Iterator) Prev() {
it.changeToAddr(it.curr.prev)
}
// Seek locates the iterator to the first entry with a key >= seekKey.
func (it *Iterator) Seek(seekKey []byte) {
node, nodeData, _ := it.sb.findGreaterEqual(seekKey) // find >=.
it.updateState(node, nodeData)
}
// SeekForPrev locates the iterator to the last entry with key <= target.
func (it *Iterator) SeekForPrev(target []byte) {
node, nodeData, _ := it.sb.findLess(target, true) // find <=.
it.updateState(node, nodeData)
}
// SeekForExclusivePrev locates the iterator to the last entry with key < target.
func (it *Iterator) SeekForExclusivePrev(target []byte) {
node, nodeData, _ := it.sb.findLess(target, false)
it.updateState(node, nodeData)
}
// SeekToFirst locates the iterator to the first entry.
func (it *Iterator) SeekToFirst() {
head := it.sb.getHead()
node, nodeData := head.getNext(it.sb.arena, 0)
it.updateState(node, nodeData)
}
// SeekToLast locates the iterator to the last entry.
func (it *Iterator) SeekToLast() {
node, nodeData := it.sb.findLast()
it.updateState(node, nodeData)
}
func (it *Iterator) updateState(node *node, nodeData []byte) {
it.curr = node
if node != nil {
it.key = node.getKey(nodeData)
it.val = node.getValue(nodeData)
}
}
func (it *Iterator) changeToAddr(addr arenaAddr) {
var data []byte
var n *node
if !addr.isNull() {
data = it.sb.arena.getFrom(addr)
n = (*node)(unsafe.Pointer(&data[0]))
}
it.updateState(n, data)
}