66 lines
1.9 KiB
C
66 lines
1.9 KiB
C
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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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//
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// Copyright (c) 2011 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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#pragma once
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#include <string>
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#include <utility>
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#include "rocksdb/db.h"
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#include "rocksdb/slice.h"
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#include "rocksdb/types.h"
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namespace rocksdb {
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// A helper class useful for DBImpl::Get()
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class LookupKey {
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public:
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// Initialize *this for looking up user_key at a snapshot with
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// the specified sequence number.
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LookupKey(const Slice& _user_key, SequenceNumber sequence);
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~LookupKey();
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// Return a key suitable for lookup in a MemTable.
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Slice memtable_key() const {
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return Slice(start_, static_cast<size_t>(end_ - start_));
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}
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// Return an internal key (suitable for passing to an internal iterator)
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Slice internal_key() const {
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return Slice(kstart_, static_cast<size_t>(end_ - kstart_));
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}
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// Return the user key
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Slice user_key() const {
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return Slice(kstart_, static_cast<size_t>(end_ - kstart_ - 8));
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}
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private:
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// We construct a char array of the form:
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// klength varint32 <-- start_
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// userkey char[klength] <-- kstart_
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// tag uint64
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// <-- end_
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// The array is a suitable MemTable key.
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// The suffix starting with "userkey" can be used as an InternalKey.
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const char* start_;
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const char* kstart_;
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const char* end_;
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char space_[200]; // Avoid allocation for short keys
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// No copying allowed
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LookupKey(const LookupKey&);
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void operator=(const LookupKey&);
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};
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inline LookupKey::~LookupKey() {
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if (start_ != space_) delete[] start_;
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}
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} // namespace rocksdb
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