io.druid.common.guava.MoreSequences.java Source code

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Here is the source code for io.druid.common.guava.MoreSequences.java

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/*
 * Licensed to Metamarkets Group Inc. (Metamarkets) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. Metamarkets 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 io.druid.common.guava;

import com.google.common.base.Preconditions;
import com.metamx.common.guava.Accumulator;
import com.metamx.common.guava.Sequence;
import com.metamx.common.guava.Yielder;
import com.metamx.common.guava.YieldingAccumulator;

import java.io.Closeable;
import java.io.IOException;

public final class MoreSequences {
    /**
     * Fixed version of {@link com.metamx.common.guava.Sequences#withBaggage(Sequence, Closeable)}, closes the baggage
     * after the yielder of the wrapped sequence.
     */
    public static <T> Sequence<T> withBaggage(Sequence<T> sequence, final Closeable baggage) {
        Preconditions.checkNotNull(baggage, "baggage");
        return wrap(sequence, new SequenceWrapper() {
            @Override
            public void open() {
                // do nothing
            }

            @Override
            public void close() {
                try {
                    baggage.close();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
        });
    }

    public static <T> Sequence<T> wrap(final Sequence<T> sequence, final SequenceWrapper wrapper) {
        Preconditions.checkNotNull(wrapper, "wrapper");
        return new Sequence<T>() {
            @Override
            public <OutType> OutType accumulate(OutType outType, Accumulator<OutType, T> accumulator) {
                wrapper.open();
                //noinspection unused
                try (SequenceWrapper toClose = wrapper) {
                    return sequence.accumulate(outType, accumulator);
                }
            }

            @Override
            public <OutType> Yielder<OutType> toYielder(OutType initValue,
                    YieldingAccumulator<OutType, T> accumulator) {
                wrapper.open();
                try {
                    return makeYielder(sequence.toYielder(initValue, accumulator));
                } catch (Throwable throwable) {
                    try {
                        wrapper.close();
                    } catch (Throwable t) {
                        throwable.addSuppressed(t);
                    }
                    throw throwable;
                }
            }

            private <OutType> Yielder<OutType> makeYielder(final Yielder<OutType> yielder) {
                return new Yielder<OutType>() {
                    @Override
                    public OutType get() {
                        return yielder.get();
                    }

                    @Override
                    public Yielder<OutType> next(OutType initValue) {
                        return makeYielder(yielder.next(initValue));
                    }

                    @Override
                    public boolean isDone() {
                        return yielder.isDone();
                    }

                    @Override
                    public void close() throws IOException {
                        //noinspection unused
                        try (SequenceWrapper toClose = wrapper) {
                            yielder.close();
                        }
                    }
                };
            }
        };

    }
}