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+// 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 "db/dbformat.h"
+#include "table/iterator_wrapper.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// When used with std::priority_queue, this comparison functor puts the
+// iterator with the max/largest key on top.
+class MaxIteratorComparator {
+ public:
+ MaxIteratorComparator(const InternalKeyComparator* comparator)
+ : comparator_(comparator) {}
+
+ bool operator()(IteratorWrapper* a, IteratorWrapper* b) const {
+ return comparator_->Compare(a->key(), b->key()) < 0;
+ }
+ private:
+ const InternalKeyComparator* comparator_;
+};
+
+// When used with std::priority_queue, this comparison functor puts the
+// iterator with the min/smallest key on top.
+class MinIteratorComparator {
+ public:
+ MinIteratorComparator(const InternalKeyComparator* comparator)
+ : comparator_(comparator) {}
+
+ bool operator()(IteratorWrapper* a, IteratorWrapper* b) const {
+ return comparator_->Compare(a->key(), b->key()) > 0;
+ }
+ private:
+ const InternalKeyComparator* comparator_;
+};
+
+} // namespace ROCKSDB_NAMESPACE