//  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 "table/block_based/index_reader_common.h"

namespace ROCKSDB_NAMESPACE {

// Index that leverages an internal hash table to quicken the lookup for a given

// key.

class HashIndexReader : public BlockBasedTable::IndexReaderCommon {

 public:

  static Status Create(const BlockBasedTable* table, const ReadOptions& ro,

                       FilePrefetchBuffer* prefetch_buffer,

                       InternalIterator* meta_index_iter, bool use_cache,

                       bool prefetch, bool pin,

                       BlockCacheLookupContext* lookup_context,

                       std::unique_ptr<IndexReader>* index_reader);

  InternalIteratorBase<IndexValue>* NewIterator(

      const ReadOptions& read_options, bool disable_prefix_seek,

      IndexBlockIter* iter, GetContext* get_context,

      BlockCacheLookupContext* lookup_context) override;

  size_t ApproximateMemoryUsage() const override {

    size_t usage = ApproximateIndexBlockMemoryUsage();

#ifdef ROCKSDB_MALLOC_USABLE_SIZE

    usage += malloc_usable_size(const_cast<HashIndexReader*>(this));

#else

    if (prefix_index_) {

      usage += prefix_index_->ApproximateMemoryUsage();

    }

    usage += sizeof(*this);

#endif  // ROCKSDB_MALLOC_USABLE_SIZE

    return usage;

  }

 private:

  HashIndexReader(const BlockBasedTable* t, CachableEntry<Block>&& index_block)

      : IndexReaderCommon(t, std::move(index_block)) {}

  std::unique_ptr<BlockPrefixIndex> prefix_index_;

};

}  // namespace ROCKSDB_NAMESPACE