//  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/block_based_table_reader.h"

#include "table/block_based/reader_common.h"

namespace ROCKSDB_NAMESPACE {

// Encapsulates common functionality for the various index reader

// implementations. Provides access to the index block regardless of whether

// it is owned by the reader or stored in the cache, or whether it is pinned

// in the cache or not.

class BlockBasedTable::IndexReaderCommon : public BlockBasedTable::IndexReader {

 public:

  IndexReaderCommon(const BlockBasedTable* t,

                    CachableEntry<Block>&& index_block)

      : table_(t), index_block_(std::move(index_block)) {

    assert(table_ != nullptr);

  }

  void EraseFromCacheBeforeDestruction(

      uint32_t /*uncache_aggressiveness*/) override;

 protected:

  static Status ReadIndexBlock(const BlockBasedTable* table,

                               FilePrefetchBuffer* prefetch_buffer,

                               const ReadOptions& read_options, bool use_cache,

                               GetContext* get_context,

                               BlockCacheLookupContext* lookup_context,

                               CachableEntry<Block>* index_block);

  const BlockBasedTable* table() const { return table_; }

  const InternalKeyComparator* internal_comparator() const {

    assert(table_ != nullptr);

    assert(table_->get_rep() != nullptr);

    return &table_->get_rep()->internal_comparator;

  }

  bool index_has_first_key() const {

    assert(table_ != nullptr);

    assert(table_->get_rep() != nullptr);

    return table_->get_rep()->index_has_first_key;

  }

  bool index_key_includes_seq() const {

    assert(table_ != nullptr);

    assert(table_->get_rep() != nullptr);

    return table_->get_rep()->index_key_includes_seq;

  }

  bool index_value_is_full() const {

    assert(table_ != nullptr);

    assert(table_->get_rep() != nullptr);

    return table_->get_rep()->index_value_is_full;

  }

  bool cache_index_blocks() const {

    assert(table_ != nullptr);

    assert(table_->get_rep() != nullptr);

    return table_->get_rep()->table_options.cache_index_and_filter_blocks;

  }

  bool user_defined_timestamps_persisted() const {

    assert(table_ != nullptr);

    assert(table_->get_rep() != nullptr);

    return table_->get_rep()->user_defined_timestamps_persisted;

  }

  Status GetOrReadIndexBlock(GetContext* get_context,

                             BlockCacheLookupContext* lookup_context,

                             CachableEntry<Block>* index_block,

                             const ReadOptions& read_options) const;

  size_t ApproximateIndexBlockMemoryUsage() const {

    assert(!index_block_.GetOwnValue() || index_block_.GetValue() != nullptr);

    return index_block_.GetOwnValue()

               ? index_block_.GetValue()->ApproximateMemoryUsage()

               : 0;

  }

 private:

  const BlockBasedTable* table_;

  CachableEntry<Block> index_block_;

};

}  // namespace ROCKSDB_NAMESPACE