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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.runtime.state;

import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.runtime.util.LongArrayList;
import org.apache.flink.util.CollectionUtil;

import java.io.IOException;
import java.util.Map;

/** Checkpoint output stream that allows to write raw operator state in a partitioned way. */
@PublicEvolving
public final class OperatorStateCheckpointOutputStream
        extends NonClosingCheckpointOutputStream {

    private LongArrayList partitionOffsets;
    private final long initialPosition;

    public OperatorStateCheckpointOutputStream(CheckpointStateOutputStream delegate)
            throws IOException {

        super(delegate);
        this.partitionOffsets = new LongArrayList(16);
        this.initialPosition = delegate.getPos();
    }

    /**
     * User code can call this method to signal that it begins to write a new partition of operator
     * state. Each previously written partition is considered final/immutable as soon as this method
     * is called again.
     */
    public void startNewPartition() throws IOException {
        partitionOffsets.add(delegate.getPos());
    }

    /** This method should not be public so as to not expose internals to user code. */
    @Override
    OperatorStateHandle closeAndGetHandle() throws IOException {
        StreamStateHandle streamStateHandle = super.closeAndGetHandleAfterLeasesReleased();

        if (null == streamStateHandle) {
            return null;
        }

        if (partitionOffsets.isEmpty() && delegate.getPos() > initialPosition) {
            startNewPartition();
        }

        Map offsetsMap =
                CollectionUtil.newHashMapWithExpectedSize(1);

        OperatorStateHandle.StateMetaInfo metaInfo =
                new OperatorStateHandle.StateMetaInfo(
                        partitionOffsets.toArray(), OperatorStateHandle.Mode.SPLIT_DISTRIBUTE);

        offsetsMap.put(DefaultOperatorStateBackend.DEFAULT_OPERATOR_STATE_NAME, metaInfo);

        return new OperatorStreamStateHandle(offsetsMap, streamStateHandle);
    }

    public int getNumberOfPartitions() {
        return partitionOffsets.size();
    }
}