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// 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 allows binary search lookup for the first key of each block.
// This class can be viewed as a thin wrapper for `Block` class which already
// supports binary search.
class BinarySearchIndexReader : public BlockBasedTable::IndexReaderCommon {
public:
// Read index from the file and create an intance for
// `BinarySearchIndexReader`.
// On success, index_reader will be populated; otherwise it will remain
// unmodified.
static Status Create(const BlockBasedTable* table, const ReadOptions& ro,
FilePrefetchBuffer* prefetch_buffer, 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<BinarySearchIndexReader*>(this));
#else
usage += sizeof(*this);
#endif // ROCKSDB_MALLOC_USABLE_SIZE
return usage;
}
private:
BinarySearchIndexReader(const BlockBasedTable* t,
CachableEntry<Block>&& index_block)
: IndexReaderCommon(t, std::move(index_block)) {}
};
} // namespace ROCKSDB_NAMESPACE
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