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rocksdb/table/internal_iterator.h

99 lines
3.7 KiB

// Copyright (c) 2011-present, 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
#include <string>
#include "rocksdb/iterator.h"
#include "rocksdb/status.h"
namespace rocksdb {
class PinnedIteratorsManager;
class InternalIterator : public Cleanable {
public:
InternalIterator() {}
virtual ~InternalIterator() {}
// An iterator is either positioned at a key/value pair, or
// not valid. This method returns true iff the iterator is valid.
virtual bool Valid() const = 0;
// Position at the first key in the source. The iterator is Valid()
// after this call iff the source is not empty.
virtual void SeekToFirst() = 0;
// Position at the last key in the source. The iterator is
// Valid() after this call iff the source is not empty.
virtual void SeekToLast() = 0;
// Position at the first key in the source that at or past target
// The iterator is Valid() after this call iff the source contains
// an entry that comes at or past target.
virtual void Seek(const Slice& target) = 0;
// Moves to the next entry in the source. After this call, Valid() is
// true iff the iterator was not positioned at the last entry in the source.
// REQUIRES: Valid()
virtual void Next() = 0;
// Moves to the previous entry in the source. After this call, Valid() is
// true iff the iterator was not positioned at the first entry in source.
// REQUIRES: Valid()
virtual void Prev() = 0;
// Return the key for the current entry. The underlying storage for
// the returned slice is valid only until the next modification of
// the iterator.
// REQUIRES: Valid()
virtual Slice key() const = 0;
// Return the value for the current entry. The underlying storage for
// the returned slice is valid only until the next modification of
// the iterator.
// REQUIRES: !AtEnd() && !AtStart()
virtual Slice value() const = 0;
// If an error has occurred, return it. Else return an ok status.
// If non-blocking IO is requested and this operation cannot be
// satisfied without doing some IO, then this returns Status::Incomplete().
virtual Status status() const = 0;
// Pass the PinnedIteratorsManager to the Iterator, most Iterators dont
// communicate with PinnedIteratorsManager so default implementation is no-op
// but for Iterators that need to communicate with PinnedIteratorsManager
// they will implement this function and use the passed pointer to communicate
// with PinnedIteratorsManager.
virtual void SetPinnedItersMgr(PinnedIteratorsManager* pinned_iters_mgr) {}
// If true, this means that the Slice returned by key() is valid as long as
// PinnedIteratorsManager::ReleasePinnedIterators is not called and the
// Iterator is not deleted.
//
// IsKeyPinned() is guaranteed to always return true if
// - Iterator is created with ReadOptions::pin_data = true
// - DB tables were created with BlockBasedTableOptions::use_delta_encoding
// set to false.
virtual bool IsKeyPinned() const { return false; }
virtual Status GetProperty(std::string prop_name, std::string* prop) {
return Status::NotSupported("");
}
private:
// No copying allowed
InternalIterator(const InternalIterator&) = delete;
InternalIterator& operator=(const InternalIterator&) = delete;
};
// Return an empty iterator (yields nothing).
extern InternalIterator* NewEmptyInternalIterator();
// Return an empty iterator with the specified status.
extern InternalIterator* NewErrorInternalIterator(const Status& status);
} // namespace rocksdb