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rocksdb/table/iterator_wrapper.h

106 lines
3.2 KiB

// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
//
// 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.
#pragma once
#include <set>
#include "table/internal_iterator.h"
namespace rocksdb {
// 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(InternalIterator* _iter) : iter_(nullptr) {
Set(_iter);
}
~IteratorWrapper() {}
InternalIterator* iter() const { return iter_; }
// Set the underlying Iterator to _iter and return
// previous underlying Iterator.
InternalIterator* Set(InternalIterator* _iter) {
InternalIterator* old_iter = iter_;
iter_ = _iter;
if (iter_ == nullptr) {
valid_ = false;
} else {
Update();
}
return old_iter;
}
void DeleteIter(bool is_arena_mode) {
if (iter_) {
if (!is_arena_mode) {
delete iter_;
} else {
iter_->~InternalIterator();
}
}
}
// 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 SeekForPrev(const Slice& k) {
assert(iter_);
iter_->SeekForPrev(k);
Update();
}
void SeekToFirst() { assert(iter_); iter_->SeekToFirst(); Update(); }
void SeekToLast() { assert(iter_); iter_->SeekToLast(); Update(); }
void SetPinnedItersMgr(PinnedIteratorsManager* pinned_iters_mgr) {
assert(iter_);
iter_->SetPinnedItersMgr(pinned_iters_mgr);
}
bool IsKeyPinned() const {
assert(Valid());
return iter_->IsKeyPinned();
}
bool IsValuePinned() const {
assert(Valid());
return iter_->IsValuePinned();
}
private:
void Update() {
valid_ = iter_->Valid();
if (valid_) {
key_ = iter_->key();
}
}
InternalIterator* iter_;
bool valid_;
Slice key_;
};
class Arena;
// Return an empty iterator (yields nothing) allocated from arena.
extern InternalIterator* NewEmptyInternalIterator(Arena* arena);
// Return an empty iterator with the specified status, allocated arena.
extern InternalIterator* NewErrorInternalIterator(const Status& status,
Arena* arena);
} // namespace rocksdb