fork of https://github.com/oxigraph/rocksdb and https://github.com/facebook/rocksdb for nextgraph and oxigraph
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125 lines
4.6 KiB
125 lines
4.6 KiB
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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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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//
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// An iterator yields a sequence of key/value pairs from a source.
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// The following class defines the interface. Multiple implementations
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// are provided by this library. In particular, iterators are provided
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// to access the contents of a Table or a DB.
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//
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// Multiple threads can invoke const methods on an Iterator without
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// external synchronization, but if any of the threads may call a
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// non-const method, all threads accessing the same Iterator must use
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// external synchronization.
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#ifndef STORAGE_ROCKSDB_INCLUDE_ITERATOR_H_
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#define STORAGE_ROCKSDB_INCLUDE_ITERATOR_H_
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#include <string>
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#include "rocksdb/slice.h"
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#include "rocksdb/status.h"
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namespace rocksdb {
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class Cleanable {
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public:
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Cleanable();
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~Cleanable();
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// Clients are allowed to register function/arg1/arg2 triples that
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// will be invoked when this iterator is destroyed.
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//
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// Note that unlike all of the preceding methods, this method is
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// not abstract and therefore clients should not override it.
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typedef void (*CleanupFunction)(void* arg1, void* arg2);
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void RegisterCleanup(CleanupFunction function, void* arg1, void* arg2);
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protected:
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struct Cleanup {
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CleanupFunction function;
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void* arg1;
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void* arg2;
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Cleanup* next;
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};
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Cleanup cleanup_;
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};
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class Iterator : public Cleanable {
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public:
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Iterator() {}
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virtual ~Iterator() {}
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// An iterator is either positioned at a key/value pair, or
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// not valid. This method returns true iff the iterator is valid.
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virtual bool Valid() const = 0;
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// Position at the first key in the source. The iterator is Valid()
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// after this call iff the source is not empty.
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virtual void SeekToFirst() = 0;
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// Position at the last key in the source. The iterator is
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// Valid() after this call iff the source is not empty.
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virtual void SeekToLast() = 0;
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// Position at the first key in the source that at or past target
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// The iterator is Valid() after this call iff the source contains
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// an entry that comes at or past target.
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virtual void Seek(const Slice& target) = 0;
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// Moves to the next entry in the source. After this call, Valid() is
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// true iff the iterator was not positioned at the last entry in the source.
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// REQUIRES: Valid()
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virtual void Next() = 0;
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// Moves to the previous entry in the source. After this call, Valid() is
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// true iff the iterator was not positioned at the first entry in source.
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// REQUIRES: Valid()
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virtual void Prev() = 0;
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// Return the key for the current entry. The underlying storage for
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// the returned slice is valid only until the next modification of
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// the iterator.
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// REQUIRES: Valid()
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virtual Slice key() const = 0;
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// Return the value for the current entry. The underlying storage for
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// the returned slice is valid only until the next modification of
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// the iterator.
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// REQUIRES: !AtEnd() && !AtStart()
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virtual Slice value() const = 0;
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// If an error has occurred, return it. Else return an ok status.
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// If non-blocking IO is requested and this operation cannot be
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// satisfied without doing some IO, then this returns Status::Incomplete().
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virtual Status status() const = 0;
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// Property "rocksdb.iterator.is-key-pinned":
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// If returning "1", this means that the Slice returned by key() is valid
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// as long as the iterator is not deleted.
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// It is guaranteed to always return "1" if
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// - Iterator created with ReadOptions::pin_data = true
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// - DB tables were created with
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// BlockBasedTableOptions::use_delta_encoding = false.
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// Property "rocksdb.iterator.super-version-number":
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// LSM version used by the iterator. The same format as DB Property
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// kCurrentSuperVersionNumber. See its comment for more information.
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virtual Status GetProperty(std::string prop_name, std::string* prop);
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private:
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// No copying allowed
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Iterator(const Iterator&);
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void operator=(const Iterator&);
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};
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// Return an empty iterator (yields nothing).
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extern Iterator* NewEmptyIterator();
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// Return an empty iterator with the specified status.
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extern Iterator* NewErrorIterator(const Status& status);
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} // namespace rocksdb
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#endif // STORAGE_ROCKSDB_INCLUDE_ITERATOR_H_
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