rocksdb/table/cuckoo_table_factory.h

// Copyright (c) 2014, 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.

#pragma once
#ifndef ROCKSDB_LITE

#include <string>
#include "rocksdb/table.h"
#include "util/murmurhash.h"
#include "rocksdb/options.h"

namespace rocksdb {

const uint32_t kCuckooMurmurSeedMultiplier = 816922183;
static inline uint64_t CuckooHash(
    const Slice& user_key, uint32_t hash_cnt, bool use_module_hash,
    uint64_t table_size_, bool identity_as_first_hash,
    uint64_t (*get_slice_hash)(const Slice&, uint32_t, uint64_t)) {
#if !defined NDEBUG || defined OS_WIN
  // This part is used only in unit tests but we have to keep it for Windows
  // build as we run test in both debug and release modes under Windows.
  if (get_slice_hash != nullptr) {
    return get_slice_hash(user_key, hash_cnt, table_size_);
  }
#endif

  uint64_t value = 0;
  if (hash_cnt == 0 && identity_as_first_hash) {
    value = (*reinterpret_cast<const int64_t*>(user_key.data()));
  } else {
    value = MurmurHash(user_key.data(), static_cast<int>(user_key.size()),
                       kCuckooMurmurSeedMultiplier * hash_cnt);
  }
  if (use_module_hash) {
    return value % table_size_;
  } else {
    return value & (table_size_ - 1);
  }
}

// Cuckoo Table is designed for applications that require fast point lookups
// but not fast range scans.
//
// Some assumptions:
// - Key length and Value length are fixed.
// - Does not support Snapshot.
// - Does not support Merge operations.
class CuckooTableFactory : public TableFactory {
 public:
  explicit CuckooTableFactory(const CuckooTableOptions& table_options)
    : table_options_(table_options) {}
  ~CuckooTableFactory() {}

  const char* Name() const override { return "CuckooTable"; }

  Status NewTableReader(const ImmutableCFOptions& ioptions,
                        const EnvOptions& env_options,
                        const InternalKeyComparator& internal_comparator,
                        unique_ptr<RandomAccessFileReader>&& file,
                        uint64_t file_size,
                        unique_ptr<TableReader>* table) const override;

  TableBuilder* NewTableBuilder(
      const TableBuilderOptions& table_builder_options,
      WritableFileWriter* file) const override;

  // Sanitizes the specified DB Options.
  Status SanitizeOptions(const DBOptions& db_opts,
                         const ColumnFamilyOptions& cf_opts) const override {
    return Status::OK();
  }

  std::string GetPrintableTableOptions() const override;

 private:
  const CuckooTableOptions table_options_;
};

}  // namespace rocksdb
#endif  // ROCKSDB_LITE