68 lines
2.2 KiB
C++
68 lines
2.2 KiB
C++
// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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//
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// A filter block is stored near the end of a Table file. It contains
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// filters (e.g., bloom filters) for all data blocks in the table combined
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// into a single filter block.
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#ifndef STORAGE_LEVELDB_TABLE_FILTER_BLOCK_H_
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#define STORAGE_LEVELDB_TABLE_FILTER_BLOCK_H_
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#include <stddef.h>
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#include <stdint.h>
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#include <string>
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#include <vector>
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#include "leveldb/slice.h"
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#include "util/hash.h"
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namespace leveldb {
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class FilterPolicy;
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// A FilterBlockBuilder is used to construct all of the filters for a
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// particular Table. It generates a single string which is stored as
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// a special block in the Table.
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//
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// The sequence of calls to FilterBlockBuilder must match the regexp:
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// (StartBlock AddKey*)* Finish
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class FilterBlockBuilder {
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public:
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explicit FilterBlockBuilder(const FilterPolicy*);
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void StartBlock(uint64_t block_offset);
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void AddKey(const Slice& key);
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Slice Finish();
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private:
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void GenerateFilter();
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const FilterPolicy* policy_;
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std::string keys_; // Flattened key contents
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std::vector<size_t> start_; // Starting index in keys_ of each key
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std::string result_; // Filter data computed so far
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std::vector<Slice> tmp_keys_; // policy_->CreateFilter() argument
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std::vector<uint32_t> filter_offsets_;
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// No copying allowed
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FilterBlockBuilder(const FilterBlockBuilder&);
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void operator=(const FilterBlockBuilder&);
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};
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class FilterBlockReader {
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public:
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// REQUIRES: "contents" and *policy must stay live while *this is live.
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FilterBlockReader(const FilterPolicy* policy, const Slice& contents);
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bool KeyMayMatch(uint64_t block_offset, const Slice& key);
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private:
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const FilterPolicy* policy_;
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const char* data_; // Pointer to filter data (at block-start)
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const char* offset_; // Pointer to beginning of offset array (at block-end)
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size_t num_; // Number of entries in offset array
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size_t base_lg_; // Encoding parameter (see kFilterBaseLg in .cc file)
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};
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}
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#endif // STORAGE_LEVELDB_TABLE_FILTER_BLOCK_H_
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