tidb iterator 代码
文件路径：/store/mockstore/unistore/lockstore/iterator.go
/ Copyright 2019-present 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,
/ 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 lockstore
/ Iterator iterates the entries in the MemStore.
type Iterator struct {
ls *MemStore
key []byte
val []byte
}
/ NewIterator returns a new Iterator for the lock store.
func (ls *MemStore) NewIterator() *Iterator {
return &Iterator{
ls: ls,
}
}
/ Valid returns true iff the iterator is positioned at a valid node.
func (it *Iterator) Valid() bool { return len(it.key) != 0 }
/ 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() {
e, _ := it.ls.findGreater(it.key, false)
it.setKeyValue(e)
}
/ Prev moves the iterator to the previous entry.
func (it *Iterator) Prev() {
e, _ := it.ls.findLess(it.key, false) / find <. No equality allowed.
it.setKeyValue(e)
}
/ Seek locates the iterator to the first entry with a key >= seekKey.
func (it *Iterator) Seek(seekKey []byte) {
e, _ := it.ls.findGreater(seekKey, true) / find >=.
it.setKeyValue(e)
}
/ SeekForPrev locates the iterator to the last entry with key <= target.
func (it *Iterator) SeekForPrev(target []byte) {
e, _ := it.ls.findLess(target, true) / find <=.
it.setKeyValue(e)
}
/ SeekForExclusivePrev locates the iterator to the last entry with key < target.
func (it *Iterator) SeekForExclusivePrev(target []byte) {
e, _ := it.ls.findLess(target, false)
it.setKeyValue(e)
}
/ SeekToFirst locates the iterator to the first entry.
func (it *Iterator) SeekToFirst() {
e := it.ls.getNext(it.ls.head, 0)
it.setKeyValue(e)
}
/ SeekToLast locates the iterator to the last entry.
func (it *Iterator) SeekToLast() {
e := it.ls.findLast()
it.setKeyValue(e)
}
func (it *Iterator) setKeyValue(e entry) {
it.key = append(it.key[:0], e.key...)
it.val = append(it.val[:0], e.getValue(it.ls.getArena())...)
}