YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.

//  This source code is licensed under the BSD-style license found in the

//  LICENSE file in the root directory of this source tree. An additional grant

//  of patent rights can be found in the PATENTS file in the same directory.

//

// The following only applies to changes made to this file as part of YugaByte development.

//

// Portions Copyright (c) YugaByte, 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.

//

// 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 "yb/rocksdb/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), iters_pinned_(false), valid_(false) {}

  explicit IteratorWrapper(InternalIterator* _iter)

      : iter_(nullptr), iters_pinned_(false) {

    Set(_iter);

  }

  ~IteratorWrapper() {}

  InternalIterator* iter() const { return iter_; }

  // Takes the ownership of "_iter" and will delete it when destroyed.

  // Next call to Set() will destroy "_iter" except if PinData() was called.

  void Set(InternalIterator* _iter) {

    if (iters_pinned_ && iter_) {

      // keep old iterator until ReleasePinnedData() is called

      pinned_iters_.insert(iter_);

    } else {

      delete iter_;

    }

    iter_ = _iter;

    if (iter_ == nullptr) {

      valid_ = false;

    } else {

      Update();

      if (iters_pinned_) {

        // Pin new iterator

        Status s = iter_->PinData();

        assert(s.ok());

      }

    }

  }

  Status PinData() {

    Status s;

    if (iters_pinned_) {

      return s;

    }

    if (iter_) {

      s = iter_->PinData();

    }

    if (s.ok()) {

      iters_pinned_ = true;

    }

    return s;

  }

  Status ReleasePinnedData() {

    Status s;

    if (!iters_pinned_) {

      return s;

    }

    if (iter_) {

      s = iter_->ReleasePinnedData();

    }

    if (s.ok()) {

      iters_pinned_ = false;

      // No need to call ReleasePinnedData() for pinned_iters_

      // since we will delete them

      DeletePinnedIterators(false);

    }

    return s;

  }

  bool IsKeyPinned() const {

    assert(iter_);

    return iters_pinned_ && iter_->IsKeyPinned();

  }

  void DeleteIter(bool is_arena_mode) {

    if (iter_ && pinned_iters_.find(iter_) == pinned_iters_.end()) {

      DestroyIterator(iter_, is_arena_mode);

    }

    DeletePinnedIterators(is_arena_mode);

  }

  // 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();

    }

  }

  void DeletePinnedIterators(bool is_arena_mode) {

    for (auto it : pinned_iters_) {

      DestroyIterator(it, is_arena_mode);

    }

    pinned_iters_.clear();

  }

  inline void DestroyIterator(InternalIterator* it, bool is_arena_mode) {

    if (!is_arena_mode) {

      delete it;

    } else {

      it->~InternalIterator();

    }

  }

  InternalIterator* iter_;

  // If set to true, current and future iterators wont be deleted.

  bool iters_pinned_;

  // List of past iterators that are pinned and wont be deleted as long as

  // iters_pinned_ is true. When we are pinning iterators this set will contain

  // iterators of previous data blocks to keep them from being deleted.

  std::set<InternalIterator*> pinned_iters_;

  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