text: //  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).
  
  #pragma once
  
  #include <stddef.h>
  #include <stdint.h>
  #include <memory>
  #include <string>
  #include <vector>
  #include "rocksdb/options.h"
  #include "rocksdb/slice.h"
  #include "rocksdb/slice_transform.h"
  #include "db/dbformat.h"
  #include "util/hash.h"
  #include "table/filter_block.h"
  
  namespace rocksdb {
  
  class FilterPolicy;
  class FilterBitsBuilder;
  class FilterBitsReader;
  
  // A FullFilterBlockBuilder is used to construct a full filter for a
  // particular Table.  It generates a single string which is stored as
  // a special block in the Table.
  // The format of full filter block is:
  // +----------------------------------------------------------------+
  // |              full filter for all keys in sst file              |
  // +----------------------------------------------------------------+
  // The full filter can be very large. At the end of it, we put
  // num_probes: how many hash functions are used in bloom filter
  //
  class FullFilterBlockBuilder : public FilterBlockBuilder {
   public:
    explicit FullFilterBlockBuilder(const SliceTransform* prefix_extractor,
                                    bool whole_key_filtering,
                                    FilterBitsBuilder* filter_bits_builder);
    // bits_builder is created in filter_policy, it should be passed in here
    // directly. and be deleted here
    ~FullFilterBlockBuilder() {}
  
    virtual bool IsBlockBased() override { return false; }
    virtual void StartBlock(uint64_t /*block_offset*/) override {}
    virtual void Add(const Slice& key) override;
    virtual size_t NumAdded() const override { return num_added_; }
    virtual Slice Finish(const BlockHandle& tmp, Status* status) override;
    using FilterBlockBuilder::Finish;
  
   protected:
    virtual void AddKey(const Slice& key);
    std::unique_ptr<FilterBitsBuilder> filter_bits_builder_;
  
   private:
    // important: all of these might point to invalid addresses
    // at the time of destruction of this filter block. destructor
    // should NOT dereference them.
    const SliceTransform* prefix_extractor_;
    bool whole_key_filtering_;
    bool last_whole_key_recorded_;
    std::string last_whole_key_str_;
    bool last_prefix_recorded_;
    std::string last_prefix_str_;
  
    uint32_t num_added_;
    std::unique_ptr<const char[]> filter_data_;
  
    void AddPrefix(const Slice& key);
  
    // No copying allowed
    FullFilterBlockBuilder(const FullFilterBlockBuilder&);
    void operator=(const FullFilterBlockBuilder&);
  };
  
  // A FilterBlockReader is used to parse filter from SST table.
  // KeyMayMatch and PrefixMayMatch would trigger filter checking
  class FullFilterBlockReader : public FilterBlockReader {
   public:
    // REQUIRES: "contents" and filter_bits_reader must stay live
    // while *this is live.
    explicit FullFilterBlockReader(const SliceTransform* prefix_extractor,
                                   bool whole_key_filtering,
                                   const Slice& contents,
                                   FilterBitsReader* filter_bits_reader,
                                   Statistics* statistics);
    explicit FullFilterBlockReader(const SliceTransform* prefix_extractor,
                                   bool whole_key_filtering,
                                   BlockContents&& contents,
                                   FilterBitsReader* filter_bits_reader,
                                   Statistics* statistics);
  
    // bits_reader is created in filter_policy, it should be passed in here
    // directly. and be deleted here
    ~FullFilterBlockReader() {}
  
    virtual bool IsBlockBased() override { return false; }
    virtual bool KeyMayMatch(
        const Slice& key, uint64_t block_offset = kNotValid,
        const bool no_io = false,
        const Slice* const const_ikey_ptr = nullptr) override;
    virtual bool PrefixMayMatch(
        const Slice& prefix, uint64_t block_offset = kNotValid,
        const bool no_io = false,
        const Slice* const const_ikey_ptr = nullptr) override;
    virtual size_t ApproximateMemoryUsage() const override;
  
   private:
    const SliceTransform* prefix_extractor_;
    Slice contents_;
    std::unique_ptr<FilterBitsReader> filter_bits_reader_;
    BlockContents block_contents_;
    std::unique_ptr<const char[]> filter_data_;
  
    // No copying allowed
    FullFilterBlockReader(const FullFilterBlockReader&);
    bool MayMatch(const Slice& entry);
    void operator=(const FullFilterBlockReader&);
  };
  
  }  // namespace rocksdb
  