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diff --git a/src/mongo/db/pipeline/change_stream_split_event_helpers.h b/src/mongo/db/pipeline/change_stream_split_event_helpers.h
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+/**
+ *    Copyright (C) 2023-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include <queue>
+
+#include "mongo/db/exec/document_value/document.h"
+
+namespace mongo {
+namespace change_stream_split_event {
+
+constexpr auto kIdField = "_id"_sd;
+constexpr auto kSplitEventField = "splitEvent"_sd;
+constexpr auto kFragmentNumberField = "fragment"_sd;
+constexpr auto kTotalFragmentsField = "of"_sd;
+
+/**
+ * Calculates BSON size by serializing the event to BSON. Ensures that the serialization is
+ * re-usable. The parameter 'withMetadata' desides whether the metadata is counted.
+ * Also returns a new document optimized for later serialization by PlanExecutorPipeline.
+ */
+std::pair<Document, size_t> processChangeEventBeforeSplit(const Document& event, bool withMetadata);
+
+/**
+ * Splits the given change stream 'event' to several sub-events, called fragments. The size of BSON
+ * serialization of each fragment does not exceed the given maximum fragment size. Each fragment
+ * carries additionally fragment's ordinal number and the total number of fragments. Each fragment
+ * has its own resume token as its '_id' and the sort key. In the resume scenario, the
+ * 'skipFirstFragments' parameter indicates how many fragments were already received by the client
+ * and can be skipped. For example, the following change event
+ *     {_id: "RESUMETOKEN1", fullDocument: ..., fullDocumentBeforeChange: ..., ...}
+ * can be split into the following fragments
+ *     {_id: "RESUMETOKEN2", splitEvent{fragment: 1, of: 2}, fullDocumentBeforeChange: ...}
+ *     {_id: "RESUMETOKEN3", splitEvent{fragment: 2, of: 2}, fullDocument: ...}
+ */
+std::queue<Document> splitChangeEvent(const Document& event,
+                                      size_t maxFragmentBsonSize,
+                                      size_t skipFirstFragments = 0);
+
+}  // namespace change_stream_split_event
+}  // namespace mongo