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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.cassandra.io.util;

import java.io.File;
import java.io.IOException;

import org.apache.cassandra.io.compress.BufferType;
import org.apache.cassandra.io.util.DataIntegrityMetadata.ChecksumValidator;
import org.apache.cassandra.utils.ByteBufferUtil;
import org.apache.cassandra.utils.ChecksumType;

public class ChecksummedRandomAccessReader
{
    @SuppressWarnings("serial")
    public static class CorruptFileException extends RuntimeException
    {
        public final String filePath;

        public CorruptFileException(Exception cause, String filePath)
        {
            super(cause);
            this.filePath = filePath;
        }
    }

    static class ChecksummedRebufferer extends BufferManagingRebufferer
    {
        private final DataIntegrityMetadata.ChecksumValidator validator;

        public ChecksummedRebufferer(ChannelProxy channel, ChecksumValidator validator)
        {
            super(new SimpleChunkReader(channel, channel.size(), BufferType.ON_HEAP, validator.chunkSize));
            this.validator = validator;
        }

        @Override
        public BufferHolder rebuffer(long desiredPosition)
        {
            if (desiredPosition != offset + buffer.position())
                validator.seek(desiredPosition);

            // align with buffer size, as checksums were computed in chunks of buffer size each.
            offset = alignedPosition(desiredPosition);
            source.readChunk(offset, buffer);

            try
            {
                validator.validate(ByteBufferUtil.getArray(buffer), 0, buffer.remaining());
            }
            catch (IOException e)
            {
                throw new CorruptFileException(e, channel().filePath());
            }

            return this;
        }

        @Override
        public void close()
        {
            try
            {
                source.close();
            }
            finally
            {
                validator.close();
            }
        }

        @Override
        long alignedPosition(long desiredPosition)
        {
            return (desiredPosition / buffer.capacity()) * buffer.capacity();
        }
    }

    public static final class Builder extends RandomAccessReader.Builder
    {
        private final DataIntegrityMetadata.ChecksumValidator validator;

        @SuppressWarnings("resource")
        public Builder(File file, File crcFile) throws IOException
        {
            super(new ChannelProxy(file));
            this.validator = new DataIntegrityMetadata.ChecksumValidator(ChecksumType.CRC32,
                                                                         RandomAccessReader.open(crcFile),
                                                                         file.getPath());
        }

        @Override
        protected Rebufferer createRebufferer()
        {
            return new ChecksummedRebufferer(channel, validator);
        }

        @Override
        public RandomAccessReader build()
        {
            // Always own and close the channel.
            return buildWithChannel();
        }
    }
}