25개 이상의 토픽을 선택하실 수 없습니다.
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
92 lines
2.1 KiB
92 lines
2.1 KiB
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style license that can be
|
|
// found in the LICENSE file. See the AUTHORS file for names of contributors.
|
|
|
|
#ifndef STORAGE_LEVELDB_TABLE_ITERATOR_WRAPPER_H_
|
|
#define STORAGE_LEVELDB_TABLE_ITERATOR_WRAPPER_H_
|
|
|
|
#include "leveldb/iterator.h"
|
|
#include "leveldb/slice.h"
|
|
|
|
namespace leveldb {
|
|
|
|
// A internal wrapper class with an interface similar to Iterator that
|
|
// caches the valid() and key() results for an underlying iterator.
|
|
// This can help avoid virtual function calls and also gives better
|
|
// cache locality.
|
|
class IteratorWrapper {
|
|
public:
|
|
IteratorWrapper() : iter_(nullptr), valid_(false) {}
|
|
explicit IteratorWrapper(Iterator* iter) : iter_(nullptr) { Set(iter); }
|
|
~IteratorWrapper() { delete iter_; }
|
|
Iterator* iter() const { return iter_; }
|
|
|
|
// Takes ownership of "iter" and will delete it when destroyed, or
|
|
// when Set() is invoked again.
|
|
void Set(Iterator* iter) {
|
|
delete iter_;
|
|
iter_ = iter;
|
|
if (iter_ == nullptr) {
|
|
valid_ = false;
|
|
} else {
|
|
Update();
|
|
}
|
|
}
|
|
|
|
// Iterator interface methods
|
|
bool Valid() const { return valid_; }
|
|
Slice key() const {
|
|
assert(Valid());
|
|
return key_;
|
|
}
|
|
Slice value() const {
|
|
assert(Valid());
|
|
return iter_->value();
|
|
}
|
|
// Methods below require iter() != nullptr
|
|
Status status() const {
|
|
assert(iter_);
|
|
return iter_->status();
|
|
}
|
|
void Next() {
|
|
assert(iter_);
|
|
iter_->Next();
|
|
Update();
|
|
}
|
|
void Prev() {
|
|
assert(iter_);
|
|
iter_->Prev();
|
|
Update();
|
|
}
|
|
void Seek(const Slice& k) {
|
|
assert(iter_);
|
|
iter_->Seek(k);
|
|
Update();
|
|
}
|
|
void SeekToFirst() {
|
|
assert(iter_);
|
|
iter_->SeekToFirst();
|
|
Update();
|
|
}
|
|
void SeekToLast() {
|
|
assert(iter_);
|
|
iter_->SeekToLast();
|
|
Update();
|
|
}
|
|
|
|
private:
|
|
void Update() {
|
|
valid_ = iter_->Valid();
|
|
if (valid_) {
|
|
key_ = iter_->key();
|
|
}
|
|
}
|
|
|
|
Iterator* iter_;
|
|
bool valid_;
|
|
Slice key_;
|
|
};
|
|
|
|
} // namespace leveldb
|
|
|
|
#endif // STORAGE_LEVELDB_TABLE_ITERATOR_WRAPPER_H_
|