103 lines
2.6 KiB
Go
103 lines
2.6 KiB
Go
// Copyright 2019 PingCAP, 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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// See the License for the specific language governing permissions and
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// limitations under the License.
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package memdb
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import "unsafe"
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// Iterator iterates the entries in the DB.
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type Iterator struct {
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db *DB
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curr *node
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key []byte
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val []byte
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}
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// NewIterator returns a new Iterator for the lock store.
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func (db *DB) NewIterator() Iterator {
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return Iterator{
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db: db,
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}
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}
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// Valid returns true if the iterator is positioned at a valid node.
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func (it *Iterator) Valid() bool { return it.curr != nil }
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// Key returns the key at the current position.
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func (it *Iterator) Key() []byte {
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return it.key
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}
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// Value returns value.
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func (it *Iterator) Value() []byte {
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return it.val
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}
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// Next moves the iterator to the next entry.
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func (it *Iterator) Next() {
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it.changeToAddr(it.curr.nexts[0])
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}
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// Prev moves the iterator to the previous entry.
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func (it *Iterator) Prev() {
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it.changeToAddr(it.curr.prev)
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}
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// Seek locates the iterator to the first entry with a key >= seekKey.
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func (it *Iterator) Seek(seekKey []byte) {
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node, nodeData, _ := it.db.findGreaterEqual(seekKey) // find >=.
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it.updateState(node, nodeData)
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}
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// SeekForPrev locates the iterator to the last entry with key <= target.
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func (it *Iterator) SeekForPrev(target []byte) {
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node, nodeData, _ := it.db.findLess(target, true) // find <=.
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it.updateState(node, nodeData)
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}
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// SeekForExclusivePrev locates the iterator to the last entry with key < target.
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func (it *Iterator) SeekForExclusivePrev(target []byte) {
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node, nodeData, _ := it.db.findLess(target, false)
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it.updateState(node, nodeData)
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}
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// SeekToFirst locates the iterator to the first entry.
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func (it *Iterator) SeekToFirst() {
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node, nodeData := it.db.getNext(it.db.head.node, 0)
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it.updateState(node, nodeData)
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}
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// SeekToLast locates the iterator to the last entry.
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func (it *Iterator) SeekToLast() {
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node, nodeData := it.db.findLast()
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it.updateState(node, nodeData)
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}
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func (it *Iterator) updateState(node *node, nodeData []byte) {
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it.curr = node
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if node != nil {
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it.key = node.getKey(nodeData)
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it.val = node.getValue(nodeData)
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}
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}
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func (it *Iterator) changeToAddr(addr arenaAddr) {
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var data []byte
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var n *node
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if !addr.isNull() {
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data = it.db.arena.getFrom(addr)
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n = (*node)(unsafe.Pointer(&data[0]))
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}
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it.updateState(n, data)
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}
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