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From ctubb...@apache.org
Subject [44/64] [abbrv] Merge branch '1.4.6-SNAPSHOT' into 1.5.2-SNAPSHOT
Date Wed, 09 Apr 2014 17:58:15 GMT
http://git-wip-us.apache.org/repos/asf/accumulo/blob/92613388/core/src/main/java/org/apache/accumulo/core/file/rfile/bcfile/TFile.java
----------------------------------------------------------------------
diff --cc core/src/main/java/org/apache/accumulo/core/file/rfile/bcfile/TFile.java
index f2cb326,0000000..b7a927b
mode 100644,000000..100644
--- a/core/src/main/java/org/apache/accumulo/core/file/rfile/bcfile/TFile.java
+++ b/core/src/main/java/org/apache/accumulo/core/file/rfile/bcfile/TFile.java
@@@ -1,2030 -1,0 +1,1986 @@@
 +/*
 + * 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.accumulo.core.file.rfile.bcfile;
 +
 +import java.io.ByteArrayInputStream;
 +import java.io.Closeable;
 +import java.io.DataInput;
 +import java.io.DataInputStream;
 +import java.io.DataOutput;
 +import java.io.DataOutputStream;
 +import java.io.EOFException;
 +import java.io.IOException;
 +import java.io.OutputStream;
 +import java.util.ArrayList;
 +import java.util.Comparator;
 +
 +import org.apache.accumulo.core.file.rfile.bcfile.BCFile.Reader.BlockReader;
 +import org.apache.accumulo.core.file.rfile.bcfile.BCFile.Writer.BlockAppender;
 +import org.apache.accumulo.core.file.rfile.bcfile.Chunk.ChunkDecoder;
 +import org.apache.accumulo.core.file.rfile.bcfile.Chunk.ChunkEncoder;
 +import org.apache.accumulo.core.file.rfile.bcfile.CompareUtils.BytesComparator;
 +import org.apache.accumulo.core.file.rfile.bcfile.CompareUtils.MemcmpRawComparator;
 +import org.apache.accumulo.core.file.rfile.bcfile.Utils.Version;
 +import org.apache.commons.logging.Log;
 +import org.apache.commons.logging.LogFactory;
 +import org.apache.hadoop.conf.Configuration;
 +import org.apache.hadoop.fs.FSDataInputStream;
 +import org.apache.hadoop.fs.FSDataOutputStream;
 +import org.apache.hadoop.io.BytesWritable;
 +import org.apache.hadoop.io.DataInputBuffer;
 +import org.apache.hadoop.io.DataOutputBuffer;
 +import org.apache.hadoop.io.IOUtils;
 +import org.apache.hadoop.io.RawComparator;
 +import org.apache.hadoop.io.WritableComparator;
 +import org.apache.hadoop.io.serializer.JavaSerializationComparator;
 +
 +/**
 + * A TFile is a container of key-value pairs. Both keys and values are type-less bytes. Keys are restricted to 64KB, value length is not restricted (practically
 + * limited to the available disk storage). TFile further provides the following features:
 + * <ul>
 + * <li>Block Compression.
 + * <li>Named meta data blocks.
 + * <li>Sorted or unsorted keys.
 + * <li>Seek by key or by file offset.
 + * </ul>
 + * The memory footprint of a TFile includes the following:
 + * <ul>
 + * <li>Some constant overhead of reading or writing a compressed block.
 + * <ul>
 + * <li>Each compressed block requires one compression/decompression codec for I/O.
 + * <li>Temporary space to buffer the key.
 + * <li>Temporary space to buffer the value (for TFile.Writer only). Values are chunk encoded, so that we buffer at most one chunk of user data. By default, the
 + * chunk buffer is 1MB. Reading chunked value does not require additional memory.
 + * </ul>
 + * <li>TFile index, which is proportional to the total number of Data Blocks. The total amount of memory needed to hold the index can be estimated as
 + * (56+AvgKeySize)*NumBlocks.
 + * <li>MetaBlock index, which is proportional to the total number of Meta Blocks.The total amount of memory needed to hold the index for Meta Blocks can be
 + * estimated as (40+AvgMetaBlockName)*NumMetaBlock.
 + * </ul>
 + * <p>
 + * The behavior of TFile can be customized by the following variables through Configuration:
 + * <ul>
 + * <li><b>tfile.io.chunk.size</b>: Value chunk size. Integer (in bytes). Default to 1MB. Values of the length less than the chunk size is guaranteed to have
 + * known value length in read time (See {@link TFile.Reader.Scanner.Entry#isValueLengthKnown()}).
 + * <li><b>tfile.fs.output.buffer.size</b>: Buffer size used for FSDataOutputStream. Integer (in bytes). Default to 256KB.
 + * <li><b>tfile.fs.input.buffer.size</b>: Buffer size used for FSDataInputStream. Integer (in bytes). Default to 256KB.
 + * </ul>
 + * <p>
 + * Suggestions on performance optimization.
 + * <ul>
 + * <li>Minimum block size. We recommend a setting of minimum block size between 256KB to 1MB for general usage. Larger block size is preferred if files are
 + * primarily for sequential access. However, it would lead to inefficient random access (because there are more data to decompress). Smaller blocks are good for
 + * random access, but require more memory to hold the block index, and may be slower to create (because we must flush the compressor stream at the conclusion of
 + * each data block, which leads to an FS I/O flush). Further, due to the internal caching in Compression codec, the smallest possible block size would be around
 + * 20KB-30KB.
 + * <li>The current implementation does not offer true multi-threading for reading. The implementation uses FSDataInputStream seek()+read(), which is shown to be
 + * much faster than positioned-read call in single thread mode. However, it also means that if multiple threads attempt to access the same TFile (using multiple
 + * scanners) simultaneously, the actual I/O is carried out sequentially even if they access different DFS blocks.
 + * <li>Compression codec. Use "none" if the data is not very compressable (by compressable, I mean a compression ratio at least 2:1). Generally, use "lzo" as
 + * the starting point for experimenting. "gz" overs slightly better compression ratio over "lzo" but requires 4x CPU to compress and 2x CPU to decompress,
 + * comparing to "lzo".
 + * <li>File system buffering, if the underlying FSDataInputStream and FSDataOutputStream is already adequately buffered; or if applications reads/writes keys
 + * and values in large buffers, we can reduce the sizes of input/output buffering in TFile layer by setting the configuration parameters
 + * "tfile.fs.input.buffer.size" and "tfile.fs.output.buffer.size".
 + * </ul>
 + * 
 + * Some design rationale behind TFile can be found at <a href=https://issues.apache.org/jira/browse/HADOOP-3315>Hadoop-3315</a>.
 + */
 +public class TFile {
 +  static final Log LOG = LogFactory.getLog(TFile.class);
 +  
 +  private static final String CHUNK_BUF_SIZE_ATTR = "tfile.io.chunk.size";
 +  private static final String FS_INPUT_BUF_SIZE_ATTR = "tfile.fs.input.buffer.size";
 +  private static final String FS_OUTPUT_BUF_SIZE_ATTR = "tfile.fs.output.buffer.size";
 +  
 +  static int getChunkBufferSize(Configuration conf) {
 +    int ret = conf.getInt(CHUNK_BUF_SIZE_ATTR, 1024 * 1024);
 +    return (ret > 0) ? ret : 1024 * 1024;
 +  }
 +  
 +  static int getFSInputBufferSize(Configuration conf) {
 +    return conf.getInt(FS_INPUT_BUF_SIZE_ATTR, 256 * 1024);
 +  }
 +  
 +  static int getFSOutputBufferSize(Configuration conf) {
 +    return conf.getInt(FS_OUTPUT_BUF_SIZE_ATTR, 256 * 1024);
 +  }
 +  
 +  private static final int MAX_KEY_SIZE = 64 * 1024; // 64KB
 +  static final Version API_VERSION = new Version((short) 1, (short) 0);
 +  
 +  /** snappy codec **/
 +  public static final String COMPRESSION_SNAPPY = "snappy";
 +
 +  /** compression: gzip */
 +  public static final String COMPRESSION_GZ = "gz";
 +  /** compression: lzo */
 +  public static final String COMPRESSION_LZO = "lzo";
 +  /** compression: none */
 +  public static final String COMPRESSION_NONE = "none";
 +  /** comparator: memcmp */
 +  public static final String COMPARATOR_MEMCMP = "memcmp";
 +  /** comparator prefix: java class */
 +  public static final String COMPARATOR_JCLASS = "jclass:";
 +  
 +  /**
 +   * Make a raw comparator from a string name.
 +   * 
 +   * @param name
 +   *          Comparator name
 +   * @return A RawComparable comparator.
 +   */
 +  static public Comparator<RawComparable> makeComparator(String name) {
 +    return TFileMeta.makeComparator(name);
 +  }
 +  
 +  // Prevent the instantiation of TFiles
 +  private TFile() {
 +    // nothing
 +  }
 +  
 +  /**
 +   * Get names of supported compression algorithms. The names are acceptable by TFile.Writer.
 +   * 
 +   * @return Array of strings, each represents a supported compression algorithm. Currently, the following compression algorithms are supported.
 +   *         <ul>
 +   *         <li>"none" - No compression.
 +   *         <li>"lzo" - LZO compression.
 +   *         <li>"gz" - GZIP compression.
 +   *         <li>"snappy" - Snappy compression
 +   *         </ul>
 +   */
 +  public static String[] getSupportedCompressionAlgorithms() {
 +    return Compression.getSupportedAlgorithms();
 +  }
 +  
 +  /**
 +   * TFile Writer.
 +   */
 +  public static class Writer implements Closeable {
 +    // minimum compressed size for a block.
 +    private final int sizeMinBlock;
 +    
 +    // Meta blocks.
 +    final TFileIndex tfileIndex;
 +    final TFileMeta tfileMeta;
 +    
 +    // reference to the underlying BCFile.
 +    private BCFile.Writer writerBCF;
 +    
 +    // current data block appender.
 +    BlockAppender blkAppender;
 +    long blkRecordCount;
 +    
 +    // buffers for caching the key.
 +    BoundedByteArrayOutputStream currentKeyBufferOS;
 +    BoundedByteArrayOutputStream lastKeyBufferOS;
 +    
 +    // buffer used by chunk codec
 +    private byte[] valueBuffer;
 +    
 +    /**
 +     * Writer states. The state always transits in circles: READY -> IN_KEY -> END_KEY -> IN_VALUE -> READY.
 +     */
 +    private enum State {
 +      READY, // Ready to start a new key-value pair insertion.
 +      IN_KEY, // In the middle of key insertion.
 +      END_KEY, // Key insertion complete, ready to insert value.
 +      IN_VALUE, // In value insertion.
 +      // ERROR, // Error encountered, cannot continue.
 +      CLOSED, // TFile already closed.
 +    }
 +    
 +    // current state of Writer.
 +    State state = State.READY;
 +    Configuration conf;
 +    long errorCount = 0;
 +    
 +    /**
 +     * Constructor
 +     * 
 +     * @param fsdos
 +     *          output stream for writing. Must be at position 0.
 +     * @param minBlockSize
 +     *          Minimum compressed block size in bytes. A compression block will not be closed until it reaches this size except for the last block.
 +     * @param compressName
 +     *          Name of the compression algorithm. Must be one of the strings returned by {@link TFile#getSupportedCompressionAlgorithms()}.
 +     * @param comparator
 +     *          Leave comparator as null or empty string if TFile is not sorted. Otherwise, provide the string name for the comparison algorithm for keys. Two
 +     *          kinds of comparators are supported.
 +     *          <ul>
 +     *          <li>Algorithmic comparator: binary comparators that is language independent. Currently, only "memcmp" is supported.
 +     *          <li>Language-specific comparator: binary comparators that can only be constructed in specific language. For Java, the syntax is "jclass:",
 +     *          followed by the class name of the RawComparator. Currently, we only support RawComparators that can be constructed through the default
 +     *          constructor (with no parameters). Parameterized RawComparators such as {@link WritableComparator} or {@link JavaSerializationComparator} may not
 +     *          be directly used. One should write a wrapper class that inherits from such classes and use its default constructor to perform proper
 +     *          initialization.
 +     *          </ul>
 +     * @param conf
 +     *          The configuration object.
-      * @throws IOException
 +     */
 +    public Writer(FSDataOutputStream fsdos, int minBlockSize, String compressName, String comparator, Configuration conf) throws IOException {
 +      sizeMinBlock = minBlockSize;
 +      tfileMeta = new TFileMeta(comparator);
 +      tfileIndex = new TFileIndex(tfileMeta.getComparator());
 +      
 +      writerBCF = new BCFile.Writer(fsdos, compressName, conf, true);
 +      currentKeyBufferOS = new BoundedByteArrayOutputStream(MAX_KEY_SIZE);
 +      lastKeyBufferOS = new BoundedByteArrayOutputStream(MAX_KEY_SIZE);
 +      this.conf = conf;
 +    }
 +    
 +    /**
 +     * Close the Writer. Resources will be released regardless of the exceptions being thrown. Future close calls will have no effect.
 +     * 
 +     * The underlying FSDataOutputStream is not closed.
 +     */
 +    public void close() throws IOException {
 +      if ((state == State.CLOSED)) {
 +        return;
 +      }
 +      try {
 +        // First try the normal finish.
 +        // Terminate upon the first Exception.
 +        if (errorCount == 0) {
 +          if (state != State.READY) {
 +            throw new IllegalStateException("Cannot close TFile in the middle of key-value insertion.");
 +          }
 +          
 +          finishDataBlock(true);
 +          
 +          // first, write out data:TFile.meta
 +          BlockAppender outMeta = writerBCF.prepareMetaBlock(TFileMeta.BLOCK_NAME, COMPRESSION_NONE);
 +          try {
 +            tfileMeta.write(outMeta);
 +          } finally {
 +            outMeta.close();
 +          }
 +          
 +          // second, write out data:TFile.index
 +          BlockAppender outIndex = writerBCF.prepareMetaBlock(TFileIndex.BLOCK_NAME);
 +          try {
 +            tfileIndex.write(outIndex);
 +          } finally {
 +            outIndex.close();
 +          }
 +          
 +          writerBCF.close();
 +        }
 +      } finally {
 +        IOUtils.cleanup(LOG, blkAppender, writerBCF);
 +        blkAppender = null;
 +        writerBCF = null;
 +        state = State.CLOSED;
 +      }
 +    }
 +    
 +    /**
 +     * Adding a new key-value pair to the TFile. This is synonymous to append(key, 0, key.length, value, 0, value.length)
 +     * 
 +     * @param key
 +     *          Buffer for key.
 +     * @param value
 +     *          Buffer for value.
-      * @throws IOException
 +     */
 +    public void append(byte[] key, byte[] value) throws IOException {
 +      append(key, 0, key.length, value, 0, value.length);
 +    }
 +    
 +    /**
 +     * Adding a new key-value pair to TFile.
 +     * 
 +     * @param key
 +     *          buffer for key.
 +     * @param koff
 +     *          offset in key buffer.
 +     * @param klen
 +     *          length of key.
 +     * @param value
 +     *          buffer for value.
 +     * @param voff
 +     *          offset in value buffer.
 +     * @param vlen
 +     *          length of value.
 +     * @throws IOException
 +     *           Upon IO errors.
 +     *           <p>
 +     *           If an exception is thrown, the TFile will be in an inconsistent state. The only legitimate call after that would be close
 +     */
 +    public void append(byte[] key, int koff, int klen, byte[] value, int voff, int vlen) throws IOException {
 +      if ((koff | klen | (koff + klen) | (key.length - (koff + klen))) < 0) {
 +        throw new IndexOutOfBoundsException("Bad key buffer offset-length combination.");
 +      }
 +      
 +      if ((voff | vlen | (voff + vlen) | (value.length - (voff + vlen))) < 0) {
 +        throw new IndexOutOfBoundsException("Bad value buffer offset-length combination.");
 +      }
 +      
 +      try {
 +        DataOutputStream dosKey = prepareAppendKey(klen);
 +        try {
 +          ++errorCount;
 +          dosKey.write(key, koff, klen);
 +          --errorCount;
 +        } finally {
 +          dosKey.close();
 +        }
 +        
 +        DataOutputStream dosValue = prepareAppendValue(vlen);
 +        try {
 +          ++errorCount;
 +          dosValue.write(value, voff, vlen);
 +          --errorCount;
 +        } finally {
 +          dosValue.close();
 +        }
 +      } finally {
 +        state = State.READY;
 +      }
 +    }
 +    
 +    /**
 +     * Helper class to register key after close call on key append stream.
 +     */
 +    private class KeyRegister extends DataOutputStream {
 +      private final int expectedLength;
 +      private boolean closed = false;
 +      
 +      public KeyRegister(int len) {
 +        super(currentKeyBufferOS);
 +        if (len >= 0) {
 +          currentKeyBufferOS.reset(len);
 +        } else {
 +          currentKeyBufferOS.reset();
 +        }
 +        expectedLength = len;
 +      }
 +      
 +      @Override
 +      public void close() throws IOException {
 +        if (closed == true) {
 +          return;
 +        }
 +        
 +        try {
 +          ++errorCount;
 +          byte[] key = currentKeyBufferOS.getBuffer();
 +          int len = currentKeyBufferOS.size();
 +          /**
 +           * verify length.
 +           */
 +          if (expectedLength >= 0 && expectedLength != len) {
 +            throw new IOException("Incorrect key length: expected=" + expectedLength + " actual=" + len);
 +          }
 +          
 +          Utils.writeVInt(blkAppender, len);
 +          blkAppender.write(key, 0, len);
 +          if (tfileIndex.getFirstKey() == null) {
 +            tfileIndex.setFirstKey(key, 0, len);
 +          }
 +          
 +          if (tfileMeta.isSorted()) {
 +            byte[] lastKey = lastKeyBufferOS.getBuffer();
 +            int lastLen = lastKeyBufferOS.size();
 +            if (tfileMeta.getComparator().compare(key, 0, len, lastKey, 0, lastLen) < 0) {
 +              throw new IOException("Keys are not added in sorted order");
 +            }
 +          }
 +          
 +          BoundedByteArrayOutputStream tmp = currentKeyBufferOS;
 +          currentKeyBufferOS = lastKeyBufferOS;
 +          lastKeyBufferOS = tmp;
 +          --errorCount;
 +        } finally {
 +          closed = true;
 +          state = State.END_KEY;
 +        }
 +      }
 +    }
 +    
 +    /**
 +     * Helper class to register value after close call on value append stream.
 +     */
 +    private class ValueRegister extends DataOutputStream {
 +      private boolean closed = false;
 +      
 +      public ValueRegister(OutputStream os) {
 +        super(os);
 +      }
 +      
 +      // Avoiding flushing call to down stream.
 +      @Override
 +      public void flush() {
 +        // do nothing
 +      }
 +      
 +      @Override
 +      public void close() throws IOException {
 +        if (closed == true) {
 +          return;
 +        }
 +        
 +        try {
 +          ++errorCount;
 +          super.close();
 +          blkRecordCount++;
 +          // bump up the total record count in the whole file
 +          tfileMeta.incRecordCount();
 +          finishDataBlock(false);
 +          --errorCount;
 +        } finally {
 +          closed = true;
 +          state = State.READY;
 +        }
 +      }
 +    }
 +    
 +    /**
 +     * Obtain an output stream for writing a key into TFile. This may only be called when there is no active Key appending stream or value appending stream.
 +     * 
 +     * @param length
 +     *          The expected length of the key. If length of the key is not known, set length = -1. Otherwise, the application must write exactly as many bytes
 +     *          as specified here before calling close on the returned output stream.
 +     * @return The key appending output stream.
-      * @throws IOException
 +     * 
 +     */
 +    public DataOutputStream prepareAppendKey(int length) throws IOException {
 +      if (state != State.READY) {
 +        throw new IllegalStateException("Incorrect state to start a new key: " + state.name());
 +      }
 +      
 +      initDataBlock();
 +      DataOutputStream ret = new KeyRegister(length);
 +      state = State.IN_KEY;
 +      return ret;
 +    }
 +    
 +    /**
 +     * Obtain an output stream for writing a value into TFile. This may only be called right after a key appending operation (the key append stream must be
 +     * closed).
 +     * 
 +     * @param length
 +     *          The expected length of the value. If length of the value is not known, set length = -1. Otherwise, the application must write exactly as many
 +     *          bytes as specified here before calling close on the returned output stream. Advertising the value size up-front guarantees that the value is
 +     *          encoded in one chunk, and avoids intermediate chunk buffering.
-      * @throws IOException
-      * 
 +     */
 +    public DataOutputStream prepareAppendValue(int length) throws IOException {
 +      if (state != State.END_KEY) {
 +        throw new IllegalStateException("Incorrect state to start a new value: " + state.name());
 +      }
 +      
 +      DataOutputStream ret;
 +      
 +      // unknown length
 +      if (length < 0) {
 +        if (valueBuffer == null) {
 +          valueBuffer = new byte[getChunkBufferSize(conf)];
 +        }
 +        ret = new ValueRegister(new ChunkEncoder(blkAppender, valueBuffer));
 +      } else {
 +        ret = new ValueRegister(new Chunk.SingleChunkEncoder(blkAppender, length));
 +      }
 +      
 +      state = State.IN_VALUE;
 +      return ret;
 +    }
 +    
 +    /**
 +     * Obtain an output stream for creating a meta block. This function may not be called when there is a key append stream or value append stream active. No
 +     * more key-value insertion is allowed after a meta data block has been added to TFile.
 +     * 
 +     * @param name
 +     *          Name of the meta block.
 +     * @param compressName
 +     *          Name of the compression algorithm to be used. Must be one of the strings returned by {@link TFile#getSupportedCompressionAlgorithms()}.
 +     * @return A DataOutputStream that can be used to write Meta Block data. Closing the stream would signal the ending of the block.
-      * @throws IOException
 +     * @throws MetaBlockAlreadyExists
 +     *           the Meta Block with the same name already exists.
 +     */
 +    public DataOutputStream prepareMetaBlock(String name, String compressName) throws IOException, MetaBlockAlreadyExists {
 +      if (state != State.READY) {
 +        throw new IllegalStateException("Incorrect state to start a Meta Block: " + state.name());
 +      }
 +      
 +      finishDataBlock(true);
 +      DataOutputStream outputStream = writerBCF.prepareMetaBlock(name, compressName);
 +      return outputStream;
 +    }
 +    
 +    /**
 +     * Obtain an output stream for creating a meta block. This function may not be called when there is a key append stream or value append stream active. No
 +     * more key-value insertion is allowed after a meta data block has been added to TFile. Data will be compressed using the default compressor as defined in
 +     * Writer's constructor.
 +     * 
 +     * @param name
 +     *          Name of the meta block.
 +     * @return A DataOutputStream that can be used to write Meta Block data. Closing the stream would signal the ending of the block.
-      * @throws IOException
 +     * @throws MetaBlockAlreadyExists
 +     *           the Meta Block with the same name already exists.
 +     */
 +    public DataOutputStream prepareMetaBlock(String name) throws IOException, MetaBlockAlreadyExists {
 +      if (state != State.READY) {
 +        throw new IllegalStateException("Incorrect state to start a Meta Block: " + state.name());
 +      }
 +      
 +      finishDataBlock(true);
 +      return writerBCF.prepareMetaBlock(name);
 +    }
 +    
 +    /**
 +     * Check if we need to start a new data block.
 +     * 
 +     * @throws IOException
 +     */
 +    private void initDataBlock() throws IOException {
 +      // for each new block, get a new appender
 +      if (blkAppender == null) {
 +        blkAppender = writerBCF.prepareDataBlock();
 +      }
 +    }
 +    
 +    /**
 +     * Close the current data block if necessary.
 +     * 
 +     * @param bForceFinish
 +     *          Force the closure regardless of the block size.
 +     * @throws IOException
 +     */
 +    void finishDataBlock(boolean bForceFinish) throws IOException {
 +      if (blkAppender == null) {
 +        return;
 +      }
 +      
 +      // exceeded the size limit, do the compression and finish the block
 +      if (bForceFinish || blkAppender.getCompressedSize() >= sizeMinBlock) {
 +        // keep tracks of the last key of each data block, no padding
 +        // for now
 +        TFileIndexEntry keyLast = new TFileIndexEntry(lastKeyBufferOS.getBuffer(), 0, lastKeyBufferOS.size(), blkRecordCount);
 +        tfileIndex.addEntry(keyLast);
 +        // close the appender
 +        blkAppender.close();
 +        blkAppender = null;
 +        blkRecordCount = 0;
 +      }
 +    }
 +  }
 +  
 +  /**
 +   * TFile Reader. Users may only read TFiles by creating TFile.Reader.Scanner. objects. A scanner may scan the whole TFile ({@link Reader#createScanner()} ) ,
 +   * a portion of TFile based on byte offsets ( {@link Reader#createScanner(long, long)}), or a portion of TFile with keys fall in a certain key range (for
 +   * sorted TFile only, {@link Reader#createScanner(byte[], byte[])} or {@link Reader#createScanner(RawComparable, RawComparable)}).
 +   */
 +  public static class Reader implements Closeable {
 +    // The underlying BCFile reader.
 +    final BCFile.Reader readerBCF;
 +    
 +    // TFile index, it is loaded lazily.
 +    TFileIndex tfileIndex = null;
 +    final TFileMeta tfileMeta;
 +    final BytesComparator comparator;
 +    
 +    // global begin and end locations.
 +    private final Location begin;
 +    private final Location end;
 +    
 +    /**
 +     * Location representing a virtual position in the TFile.
 +     */
 +    static final class Location implements Comparable<Location>, Cloneable {
 +      private int blockIndex;
 +      // distance/offset from the beginning of the block
 +      private long recordIndex;
 +      
 +      Location(int blockIndex, long recordIndex) {
 +        set(blockIndex, recordIndex);
 +      }
 +      
 +      void incRecordIndex() {
 +        ++recordIndex;
 +      }
 +      
 +      Location(Location other) {
 +        set(other);
 +      }
 +      
 +      int getBlockIndex() {
 +        return blockIndex;
 +      }
 +      
 +      long getRecordIndex() {
 +        return recordIndex;
 +      }
 +      
 +      void set(int blockIndex, long recordIndex) {
 +        if ((blockIndex | recordIndex) < 0) {
 +          throw new IllegalArgumentException("Illegal parameter for BlockLocation.");
 +        }
 +        this.blockIndex = blockIndex;
 +        this.recordIndex = recordIndex;
 +      }
 +      
 +      void set(Location other) {
 +        set(other.blockIndex, other.recordIndex);
 +      }
 +      
 +      /**
 +       * @see java.lang.Comparable#compareTo(java.lang.Object)
 +       */
 +      @Override
 +      public int compareTo(Location other) {
 +        return compareTo(other.blockIndex, other.recordIndex);
 +      }
 +      
 +      int compareTo(int bid, long rid) {
 +        if (this.blockIndex == bid) {
 +          long ret = this.recordIndex - rid;
 +          if (ret > 0)
 +            return 1;
 +          if (ret < 0)
 +            return -1;
 +          return 0;
 +        }
 +        return this.blockIndex - bid;
 +      }
 +      
 +      /**
 +       * @see java.lang.Object#clone()
 +       */
 +      @Override
 +      protected Location clone() {
 +        return new Location(blockIndex, recordIndex);
 +      }
 +      
 +      /**
 +       * @see java.lang.Object#hashCode()
 +       */
 +      @Override
 +      public int hashCode() {
 +        final int prime = 31;
 +        int result = prime + blockIndex;
 +        result = (int) (prime * result + recordIndex);
 +        return result;
 +      }
 +      
 +      /**
 +       * @see java.lang.Object#equals(java.lang.Object)
 +       */
 +      @Override
 +      public boolean equals(Object obj) {
 +        if (this == obj)
 +          return true;
 +        if (obj == null)
 +          return false;
 +        if (getClass() != obj.getClass())
 +          return false;
 +        Location other = (Location) obj;
 +        if (blockIndex != other.blockIndex)
 +          return false;
 +        if (recordIndex != other.recordIndex)
 +          return false;
 +        return true;
 +      }
 +    }
 +    
 +    /**
 +     * Constructor
 +     * 
 +     * @param fsdis
 +     *          FS input stream of the TFile.
 +     * @param fileLength
 +     *          The length of TFile. This is required because we have no easy way of knowing the actual size of the input file through the File input stream.
-      * @param conf
-      * @throws IOException
 +     */
 +    public Reader(FSDataInputStream fsdis, long fileLength, Configuration conf) throws IOException {
 +      readerBCF = new BCFile.Reader(fsdis, fileLength, conf);
 +      
 +      // first, read TFile meta
 +      BlockReader brMeta = readerBCF.getMetaBlock(TFileMeta.BLOCK_NAME);
 +      try {
 +        tfileMeta = new TFileMeta(brMeta);
 +      } finally {
 +        brMeta.close();
 +      }
 +      
 +      comparator = tfileMeta.getComparator();
 +      // Set begin and end locations.
 +      begin = new Location(0, 0);
 +      end = new Location(readerBCF.getBlockCount(), 0);
 +    }
 +    
 +    /**
 +     * Close the reader. The state of the Reader object is undefined after close. Calling close() for multiple times has no effect.
 +     */
 +    public void close() throws IOException {
 +      readerBCF.close();
 +    }
 +    
 +    /**
 +     * Get the begin location of the TFile.
 +     * 
 +     * @return If TFile is not empty, the location of the first key-value pair. Otherwise, it returns end().
 +     */
 +    Location begin() {
 +      return begin;
 +    }
 +    
 +    /**
 +     * Get the end location of the TFile.
 +     * 
 +     * @return The location right after the last key-value pair in TFile.
 +     */
 +    Location end() {
 +      return end;
 +    }
 +    
 +    /**
 +     * Get the string representation of the comparator.
 +     * 
 +     * @return If the TFile is not sorted by keys, an empty string will be returned. Otherwise, the actual comparator string that is provided during the TFile
 +     *         creation time will be returned.
 +     */
 +    public String getComparatorName() {
 +      return tfileMeta.getComparatorString();
 +    }
 +    
 +    /**
 +     * Is the TFile sorted?
 +     * 
 +     * @return true if TFile is sorted.
 +     */
 +    public boolean isSorted() {
 +      return tfileMeta.isSorted();
 +    }
 +    
 +    /**
 +     * Get the number of key-value pair entries in TFile.
 +     * 
 +     * @return the number of key-value pairs in TFile
 +     */
 +    public long getEntryCount() {
 +      return tfileMeta.getRecordCount();
 +    }
 +    
 +    /**
 +     * Lazily loading the TFile index.
 +     * 
 +     * @throws IOException
 +     */
 +    synchronized void checkTFileDataIndex() throws IOException {
 +      if (tfileIndex == null) {
 +        BlockReader brIndex = readerBCF.getMetaBlock(TFileIndex.BLOCK_NAME);
 +        try {
 +          tfileIndex = new TFileIndex(readerBCF.getBlockCount(), brIndex, tfileMeta.getComparator());
 +        } finally {
 +          brIndex.close();
 +        }
 +      }
 +    }
 +    
 +    /**
 +     * Get the first key in the TFile.
 +     * 
 +     * @return The first key in the TFile.
-      * @throws IOException
 +     */
 +    public RawComparable getFirstKey() throws IOException {
 +      checkTFileDataIndex();
 +      return tfileIndex.getFirstKey();
 +    }
 +    
 +    /**
 +     * Get the last key in the TFile.
 +     * 
 +     * @return The last key in the TFile.
-      * @throws IOException
 +     */
 +    public RawComparable getLastKey() throws IOException {
 +      checkTFileDataIndex();
 +      return tfileIndex.getLastKey();
 +    }
 +    
 +    /**
 +     * Get a Comparator object to compare Entries. It is useful when you want stores the entries in a collection (such as PriorityQueue) and perform sorting or
 +     * comparison among entries based on the keys without copying out the key.
 +     * 
 +     * @return An Entry Comparator..
 +     */
 +    public Comparator<Scanner.Entry> getEntryComparator() {
 +      if (!isSorted()) {
 +        throw new RuntimeException("Entries are not comparable for unsorted TFiles");
 +      }
 +      
 +      return new Comparator<Scanner.Entry>() {
 +        /**
 +         * Provide a customized comparator for Entries. This is useful if we have a collection of Entry objects. However, if the Entry objects come from
 +         * different TFiles, users must ensure that those TFiles share the same RawComparator.
 +         */
 +        @Override
 +        public int compare(Scanner.Entry o1, Scanner.Entry o2) {
 +          return comparator.compare(o1.getKeyBuffer(), 0, o1.getKeyLength(), o2.getKeyBuffer(), 0, o2.getKeyLength());
 +        }
 +      };
 +    }
 +    
 +    /**
 +     * Get an instance of the RawComparator that is constructed based on the string comparator representation.
 +     * 
 +     * @return a Comparator that can compare RawComparable's.
 +     */
 +    public Comparator<RawComparable> getComparator() {
 +      return comparator;
 +    }
 +    
 +    /**
 +     * Stream access to a meta block.``
 +     * 
 +     * @param name
 +     *          The name of the meta block.
 +     * @return The input stream.
 +     * @throws IOException
 +     *           on I/O error.
 +     * @throws MetaBlockDoesNotExist
 +     *           If the meta block with the name does not exist.
 +     */
 +    public DataInputStream getMetaBlock(String name) throws IOException, MetaBlockDoesNotExist {
 +      return readerBCF.getMetaBlock(name);
 +    }
 +    
 +    /**
 +     * if greater is true then returns the beginning location of the block containing the key strictly greater than input key. if greater is false then returns
 +     * the beginning location of the block greater than equal to the input key
 +     * 
 +     * @param key
 +     *          the input key
 +     * @param greater
 +     *          boolean flag
 +     * @throws IOException
 +     */
 +    Location getBlockContainsKey(RawComparable key, boolean greater) throws IOException {
 +      if (!isSorted()) {
 +        throw new RuntimeException("Seeking in unsorted TFile");
 +      }
 +      checkTFileDataIndex();
 +      int blkIndex = (greater) ? tfileIndex.upperBound(key) : tfileIndex.lowerBound(key);
 +      if (blkIndex < 0)
 +        return end;
 +      return new Location(blkIndex, 0);
 +    }
 +    
 +    int compareKeys(byte[] a, int o1, int l1, byte[] b, int o2, int l2) {
 +      if (!isSorted()) {
 +        throw new RuntimeException("Cannot compare keys for unsorted TFiles.");
 +      }
 +      return comparator.compare(a, o1, l1, b, o2, l2);
 +    }
 +    
 +    int compareKeys(RawComparable a, RawComparable b) {
 +      if (!isSorted()) {
 +        throw new RuntimeException("Cannot compare keys for unsorted TFiles.");
 +      }
 +      return comparator.compare(a, b);
 +    }
 +    
 +    /**
 +     * Get the location pointing to the beginning of the first key-value pair in a compressed block whose byte offset in the TFile is greater than or equal to
 +     * the specified offset.
 +     * 
 +     * @param offset
 +     *          the user supplied offset.
 +     * @return the location to the corresponding entry; or end() if no such entry exists.
 +     */
 +    Location getLocationNear(long offset) {
 +      int blockIndex = readerBCF.getBlockIndexNear(offset);
 +      if (blockIndex == -1)
 +        return end;
 +      return new Location(blockIndex, 0);
 +    }
 +    
 +    /**
 +     * Get a sample key that is within a block whose starting offset is greater than or equal to the specified offset.
 +     * 
 +     * @param offset
 +     *          The file offset.
 +     * @return the key that fits the requirement; or null if no such key exists (which could happen if the offset is close to the end of the TFile).
-      * @throws IOException
 +     */
 +    public RawComparable getKeyNear(long offset) throws IOException {
 +      int blockIndex = readerBCF.getBlockIndexNear(offset);
 +      if (blockIndex == -1)
 +        return null;
 +      checkTFileDataIndex();
 +      return new ByteArray(tfileIndex.getEntry(blockIndex).key);
 +    }
 +    
 +    /**
 +     * Get a scanner than can scan the whole TFile.
 +     * 
 +     * @return The scanner object. A valid Scanner is always returned even if the TFile is empty.
-      * @throws IOException
 +     */
 +    public Scanner createScanner() throws IOException {
 +      return new Scanner(this, begin, end);
 +    }
 +    
 +    /**
 +     * Get a scanner that covers a portion of TFile based on byte offsets.
 +     * 
 +     * @param offset
 +     *          The beginning byte offset in the TFile.
 +     * @param length
 +     *          The length of the region.
 +     * @return The actual coverage of the returned scanner tries to match the specified byte-region but always round up to the compression block boundaries. It
 +     *         is possible that the returned scanner contains zero key-value pairs even if length is positive.
-      * @throws IOException
 +     */
 +    public Scanner createScanner(long offset, long length) throws IOException {
 +      return new Scanner(this, offset, offset + length);
 +    }
 +    
 +    /**
 +     * Get a scanner that covers a portion of TFile based on keys.
 +     * 
 +     * @param beginKey
 +     *          Begin key of the scan (inclusive). If null, scan from the first key-value entry of the TFile.
 +     * @param endKey
 +     *          End key of the scan (exclusive). If null, scan up to the last key-value entry of the TFile.
 +     * @return The actual coverage of the returned scanner will cover all keys greater than or equal to the beginKey and less than the endKey.
-      * @throws IOException
 +     */
 +    public Scanner createScanner(byte[] beginKey, byte[] endKey) throws IOException {
 +      return createScanner((beginKey == null) ? null : new ByteArray(beginKey, 0, beginKey.length), (endKey == null) ? null : new ByteArray(endKey, 0,
 +          endKey.length));
 +    }
 +    
 +    /**
 +     * Get a scanner that covers a specific key range.
 +     * 
 +     * @param beginKey
 +     *          Begin key of the scan (inclusive). If null, scan from the first key-value entry of the TFile.
 +     * @param endKey
 +     *          End key of the scan (exclusive). If null, scan up to the last key-value entry of the TFile.
 +     * @return The actual coverage of the returned scanner will cover all keys greater than or equal to the beginKey and less than the endKey.
-      * @throws IOException
 +     */
 +    public Scanner createScanner(RawComparable beginKey, RawComparable endKey) throws IOException {
 +      if ((beginKey != null) && (endKey != null) && (compareKeys(beginKey, endKey) >= 0)) {
 +        return new Scanner(this, beginKey, beginKey);
 +      }
 +      return new Scanner(this, beginKey, endKey);
 +    }
 +    
 +    /**
 +     * The TFile Scanner. The Scanner has an implicit cursor, which, upon creation, points to the first key-value pair in the scan range. If the scan range is
 +     * empty, the cursor will point to the end of the scan range.
 +     * <p>
 +     * Use {@link Scanner#atEnd()} to test whether the cursor is at the end location of the scanner.
 +     * <p>
 +     * Use {@link Scanner#advance()} to move the cursor to the next key-value pair (or end if none exists). Use seekTo methods ( {@link Scanner#seekTo(byte[])}
 +     * or {@link Scanner#seekTo(byte[], int, int)}) to seek to any arbitrary location in the covered range (including backward seeking). Use
 +     * {@link Scanner#rewind()} to seek back to the beginning of the scanner. Use {@link Scanner#seekToEnd()} to seek to the end of the scanner.
 +     * <p>
 +     * Actual keys and values may be obtained through {@link Scanner.Entry} object, which is obtained through {@link Scanner#entry()}.
 +     */
 +    public static class Scanner implements Closeable {
 +      // The underlying TFile reader.
 +      final Reader reader;
 +      // current block (null if reaching end)
 +      private BlockReader blkReader;
 +      
 +      Location beginLocation;
 +      Location endLocation;
 +      Location currentLocation;
 +      
 +      // flag to ensure value is only examined once.
 +      boolean valueChecked = false;
 +      // reusable buffer for keys.
 +      final byte[] keyBuffer;
 +      // length of key, -1 means key is invalid.
 +      int klen = -1;
 +      
 +      static final int MAX_VAL_TRANSFER_BUF_SIZE = 128 * 1024;
 +      BytesWritable valTransferBuffer;
 +      
 +      DataInputBuffer keyDataInputStream;
 +      ChunkDecoder valueBufferInputStream;
 +      DataInputStream valueDataInputStream;
 +      // vlen == -1 if unknown.
 +      int vlen;
 +      
 +      /**
 +       * Constructor
 +       * 
 +       * @param reader
 +       *          The TFile reader object.
 +       * @param offBegin
 +       *          Begin byte-offset of the scan.
 +       * @param offEnd
 +       *          End byte-offset of the scan.
 +       * @throws IOException
 +       * 
 +       *           The offsets will be rounded to the beginning of a compressed block whose offset is greater than or equal to the specified offset.
 +       */
 +      protected Scanner(Reader reader, long offBegin, long offEnd) throws IOException {
 +        this(reader, reader.getLocationNear(offBegin), reader.getLocationNear(offEnd));
 +      }
 +      
 +      /**
 +       * Constructor
 +       * 
 +       * @param reader
 +       *          The TFile reader object.
 +       * @param begin
 +       *          Begin location of the scan.
 +       * @param end
 +       *          End location of the scan.
 +       * @throws IOException
 +       */
 +      Scanner(Reader reader, Location begin, Location end) throws IOException {
 +        this.reader = reader;
 +        // ensure the TFile index is loaded throughout the life of scanner.
 +        reader.checkTFileDataIndex();
 +        beginLocation = begin;
 +        endLocation = end;
 +        
 +        valTransferBuffer = new BytesWritable();
 +        keyBuffer = new byte[MAX_KEY_SIZE];
 +        keyDataInputStream = new DataInputBuffer();
 +        valueBufferInputStream = new ChunkDecoder();
 +        valueDataInputStream = new DataInputStream(valueBufferInputStream);
 +        
 +        if (beginLocation.compareTo(endLocation) >= 0) {
 +          currentLocation = new Location(endLocation);
 +        } else {
 +          currentLocation = new Location(0, 0);
 +          initBlock(beginLocation.getBlockIndex());
 +          inBlockAdvance(beginLocation.getRecordIndex());
 +        }
 +      }
 +      
 +      /**
 +       * Constructor
 +       * 
 +       * @param reader
 +       *          The TFile reader object.
 +       * @param beginKey
 +       *          Begin key of the scan. If null, scan from the first <K,V> entry of the TFile.
 +       * @param endKey
 +       *          End key of the scan. If null, scan up to the last <K, V> entry of the TFile.
-        * @throws IOException
 +       */
 +      protected Scanner(Reader reader, RawComparable beginKey, RawComparable endKey) throws IOException {
 +        this(reader, (beginKey == null) ? reader.begin() : reader.getBlockContainsKey(beginKey, false), reader.end());
 +        if (beginKey != null) {
 +          inBlockAdvance(beginKey, false);
 +          beginLocation.set(currentLocation);
 +        }
 +        if (endKey != null) {
 +          seekTo(endKey, false);
 +          endLocation.set(currentLocation);
 +          seekTo(beginLocation);
 +        }
 +      }
 +      
 +      /**
 +       * Move the cursor to the first entry whose key is greater than or equal to the input key. Synonymous to seekTo(key, 0, key.length). The entry returned by
 +       * the previous entry() call will be invalid.
 +       * 
 +       * @param key
 +       *          The input key
 +       * @return true if we find an equal key.
-        * @throws IOException
 +       */
 +      public boolean seekTo(byte[] key) throws IOException {
 +        return seekTo(key, 0, key.length);
 +      }
 +      
 +      /**
 +       * Move the cursor to the first entry whose key is greater than or equal to the input key. The entry returned by the previous entry() call will be
 +       * invalid.
 +       * 
 +       * @param key
 +       *          The input key
 +       * @param keyOffset
 +       *          offset in the key buffer.
 +       * @param keyLen
 +       *          key buffer length.
 +       * @return true if we find an equal key; false otherwise.
-        * @throws IOException
 +       */
 +      public boolean seekTo(byte[] key, int keyOffset, int keyLen) throws IOException {
 +        return seekTo(new ByteArray(key, keyOffset, keyLen), false);
 +      }
 +      
 +      private boolean seekTo(RawComparable key, boolean beyond) throws IOException {
 +        Location l = reader.getBlockContainsKey(key, beyond);
 +        if (l.compareTo(beginLocation) < 0) {
 +          l = beginLocation;
 +        } else if (l.compareTo(endLocation) >= 0) {
 +          seekTo(endLocation);
 +          return false;
 +        }
 +        
 +        // check if what we are seeking is in the later part of the current
 +        // block.
 +        if (atEnd() || (l.getBlockIndex() != currentLocation.getBlockIndex()) || (compareCursorKeyTo(key) >= 0)) {
 +          // sorry, we must seek to a different location first.
 +          seekTo(l);
 +        }
 +        
 +        return inBlockAdvance(key, beyond);
 +      }
 +      
 +      /**
 +       * Move the cursor to the new location. The entry returned by the previous entry() call will be invalid.
 +       * 
 +       * @param l
 +       *          new cursor location. It must fall between the begin and end location of the scanner.
 +       * @throws IOException
 +       */
 +      private void seekTo(Location l) throws IOException {
 +        if (l.compareTo(beginLocation) < 0) {
 +          throw new IllegalArgumentException("Attempt to seek before the begin location.");
 +        }
 +        
 +        if (l.compareTo(endLocation) > 0) {
 +          throw new IllegalArgumentException("Attempt to seek after the end location.");
 +        }
 +        
 +        if (l.compareTo(endLocation) == 0) {
 +          parkCursorAtEnd();
 +          return;
 +        }
 +        
 +        if (l.getBlockIndex() != currentLocation.getBlockIndex()) {
 +          // going to a totally different block
 +          initBlock(l.getBlockIndex());
 +        } else {
 +          if (valueChecked) {
 +            // may temporarily go beyond the last record in the block (in which
 +            // case the next if loop will always be true).
 +            inBlockAdvance(1);
 +          }
 +          if (l.getRecordIndex() < currentLocation.getRecordIndex()) {
 +            initBlock(l.getBlockIndex());
 +          }
 +        }
 +        
 +        inBlockAdvance(l.getRecordIndex() - currentLocation.getRecordIndex());
 +        
 +        return;
 +      }
 +      
 +      /**
 +       * Rewind to the first entry in the scanner. The entry returned by the previous entry() call will be invalid.
-        * 
-        * @throws IOException
 +       */
 +      public void rewind() throws IOException {
 +        seekTo(beginLocation);
 +      }
 +      
 +      /**
 +       * Seek to the end of the scanner. The entry returned by the previous entry() call will be invalid.
-        * 
-        * @throws IOException
 +       */
 +      public void seekToEnd() throws IOException {
 +        parkCursorAtEnd();
 +      }
 +      
 +      /**
 +       * Move the cursor to the first entry whose key is greater than or equal to the input key. Synonymous to lowerBound(key, 0, key.length). The entry
 +       * returned by the previous entry() call will be invalid.
 +       * 
 +       * @param key
 +       *          The input key
-        * @throws IOException
 +       */
 +      public void lowerBound(byte[] key) throws IOException {
 +        lowerBound(key, 0, key.length);
 +      }
 +      
 +      /**
 +       * Move the cursor to the first entry whose key is greater than or equal to the input key. The entry returned by the previous entry() call will be
 +       * invalid.
 +       * 
 +       * @param key
 +       *          The input key
 +       * @param keyOffset
 +       *          offset in the key buffer.
 +       * @param keyLen
 +       *          key buffer length.
-        * @throws IOException
 +       */
 +      public void lowerBound(byte[] key, int keyOffset, int keyLen) throws IOException {
 +        seekTo(new ByteArray(key, keyOffset, keyLen), false);
 +      }
 +      
 +      /**
 +       * Move the cursor to the first entry whose key is strictly greater than the input key. Synonymous to upperBound(key, 0, key.length). The entry returned
 +       * by the previous entry() call will be invalid.
 +       * 
 +       * @param key
 +       *          The input key
-        * @throws IOException
 +       */
 +      public void upperBound(byte[] key) throws IOException {
 +        upperBound(key, 0, key.length);
 +      }
 +      
 +      /**
 +       * Move the cursor to the first entry whose key is strictly greater than the input key. The entry returned by the previous entry() call will be invalid.
 +       * 
 +       * @param key
 +       *          The input key
 +       * @param keyOffset
 +       *          offset in the key buffer.
 +       * @param keyLen
 +       *          key buffer length.
-        * @throws IOException
 +       */
 +      public void upperBound(byte[] key, int keyOffset, int keyLen) throws IOException {
 +        seekTo(new ByteArray(key, keyOffset, keyLen), true);
 +      }
 +      
 +      /**
 +       * Move the cursor to the next key-value pair. The entry returned by the previous entry() call will be invalid.
 +       * 
 +       * @return true if the cursor successfully moves. False when cursor is already at the end location and cannot be advanced.
-        * @throws IOException
 +       */
 +      public boolean advance() throws IOException {
 +        if (atEnd()) {
 +          return false;
 +        }
 +        
 +        int curBid = currentLocation.getBlockIndex();
 +        long curRid = currentLocation.getRecordIndex();
 +        long entriesInBlock = reader.getBlockEntryCount(curBid);
 +        if (curRid + 1 >= entriesInBlock) {
 +          if (endLocation.compareTo(curBid + 1, 0) <= 0) {
 +            // last entry in TFile.
 +            parkCursorAtEnd();
 +          } else {
 +            // last entry in Block.
 +            initBlock(curBid + 1);
 +          }
 +        } else {
 +          inBlockAdvance(1);
 +        }
 +        return true;
 +      }
 +      
 +      /**
 +       * Load a compressed block for reading. Expecting blockIndex is valid.
 +       * 
 +       * @throws IOException
 +       */
 +      private void initBlock(int blockIndex) throws IOException {
 +        klen = -1;
 +        if (blkReader != null) {
 +          try {
 +            blkReader.close();
 +          } finally {
 +            blkReader = null;
 +          }
 +        }
 +        blkReader = reader.getBlockReader(blockIndex);
 +        currentLocation.set(blockIndex, 0);
 +      }
 +      
 +      private void parkCursorAtEnd() throws IOException {
 +        klen = -1;
 +        currentLocation.set(endLocation);
 +        if (blkReader != null) {
 +          try {
 +            blkReader.close();
 +          } finally {
 +            blkReader = null;
 +          }
 +        }
 +      }
 +      
 +      /**
 +       * Close the scanner. Release all resources. The behavior of using the scanner after calling close is not defined. The entry returned by the previous
 +       * entry() call will be invalid.
 +       */
 +      public void close() throws IOException {
 +        parkCursorAtEnd();
 +      }
 +      
 +      /**
 +       * Is cursor at the end location?
 +       * 
 +       * @return true if the cursor is at the end location.
 +       */
 +      public boolean atEnd() {
 +        return (currentLocation.compareTo(endLocation) >= 0);
 +      }
 +      
 +      /**
 +       * check whether we have already successfully obtained the key. It also initializes the valueInputStream.
 +       */
 +      void checkKey() throws IOException {
 +        if (klen >= 0)
 +          return;
 +        if (atEnd()) {
 +          throw new EOFException("No key-value to read");
 +        }
 +        klen = -1;
 +        vlen = -1;
 +        valueChecked = false;
 +        
 +        klen = Utils.readVInt(blkReader);
 +        blkReader.readFully(keyBuffer, 0, klen);
 +        valueBufferInputStream.reset(blkReader);
 +        if (valueBufferInputStream.isLastChunk()) {
 +          vlen = valueBufferInputStream.getRemain();
 +        }
 +      }
 +      
 +      /**
 +       * Get an entry to access the key and value.
 +       * 
 +       * @return The Entry object to access the key and value.
-        * @throws IOException
 +       */
 +      public Entry entry() throws IOException {
 +        checkKey();
 +        return new Entry();
 +      }
 +      
 +      /**
 +       * Internal API. Comparing the key at cursor to user-specified key.
 +       * 
 +       * @param other
 +       *          user-specified key.
 +       * @return negative if key at cursor is smaller than user key; 0 if equal; and positive if key at cursor greater than user key.
 +       * @throws IOException
 +       */
 +      int compareCursorKeyTo(RawComparable other) throws IOException {
 +        checkKey();
 +        return reader.compareKeys(keyBuffer, 0, klen, other.buffer(), other.offset(), other.size());
 +      }
 +      
 +      /**
 +       * Entry to a &lt;Key, Value&gt; pair.
 +       */
 +      public class Entry implements Comparable<RawComparable> {
 +        /**
 +         * Get the length of the key.
 +         * 
 +         * @return the length of the key.
 +         */
 +        public int getKeyLength() {
 +          return klen;
 +        }
 +        
 +        byte[] getKeyBuffer() {
 +          return keyBuffer;
 +        }
 +        
 +        /**
 +         * Copy the key and value in one shot into BytesWritables. This is equivalent to getKey(key); getValue(value);
 +         * 
 +         * @param key
 +         *          BytesWritable to hold key.
 +         * @param value
 +         *          BytesWritable to hold value
-          * @throws IOException
 +         */
 +        public void get(BytesWritable key, BytesWritable value) throws IOException {
 +          getKey(key);
 +          getValue(value);
 +        }
 +        
 +        /**
 +         * Copy the key into BytesWritable. The input BytesWritable will be automatically resized to the actual key size.
 +         * 
 +         * @param key
 +         *          BytesWritable to hold the key.
-          * @throws IOException
 +         */
 +        public int getKey(BytesWritable key) throws IOException {
 +          key.setSize(getKeyLength());
 +          getKey(key.getBytes());
 +          return key.getLength();
 +        }
 +        
 +        /**
 +         * Copy the value into BytesWritable. The input BytesWritable will be automatically resized to the actual value size. The implementation directly uses
 +         * the buffer inside BytesWritable for storing the value. The call does not require the value length to be known.
-          * 
-          * @param value
-          * @throws IOException
 +         */
 +        public long getValue(BytesWritable value) throws IOException {
 +          DataInputStream dis = getValueStream();
 +          int size = 0;
 +          try {
 +            int remain;
 +            while ((remain = valueBufferInputStream.getRemain()) > 0) {
 +              value.setSize(size + remain);
 +              dis.readFully(value.getBytes(), size, remain);
 +              size += remain;
 +            }
 +            return value.getLength();
 +          } finally {
 +            dis.close();
 +          }
 +        }
 +        
 +        /**
 +         * Writing the key to the output stream. This method avoids copying key buffer from Scanner into user buffer, then writing to the output stream.
 +         * 
 +         * @param out
 +         *          The output stream
 +         * @return the length of the key.
-          * @throws IOException
 +         */
 +        public int writeKey(OutputStream out) throws IOException {
 +          out.write(keyBuffer, 0, klen);
 +          return klen;
 +        }
 +        
 +        /**
 +         * Writing the value to the output stream. This method avoids copying value data from Scanner into user buffer, then writing to the output stream. It
 +         * does not require the value length to be known.
 +         * 
 +         * @param out
 +         *          The output stream
 +         * @return the length of the value
-          * @throws IOException
 +         */
 +        public long writeValue(OutputStream out) throws IOException {
 +          DataInputStream dis = getValueStream();
 +          long size = 0;
 +          try {
 +            int chunkSize;
 +            while ((chunkSize = valueBufferInputStream.getRemain()) > 0) {
 +              chunkSize = Math.min(chunkSize, MAX_VAL_TRANSFER_BUF_SIZE);
 +              valTransferBuffer.setSize(chunkSize);
 +              dis.readFully(valTransferBuffer.getBytes(), 0, chunkSize);
 +              out.write(valTransferBuffer.getBytes(), 0, chunkSize);
 +              size += chunkSize;
 +            }
 +            return size;
 +          } finally {
 +            dis.close();
 +          }
 +        }
 +        
 +        /**
 +         * Copy the key into user supplied buffer.
 +         * 
 +         * @param buf
 +         *          The buffer supplied by user. The length of the buffer must not be shorter than the key length.
 +         * @return The length of the key.
-          * 
-          * @throws IOException
 +         */
 +        public int getKey(byte[] buf) throws IOException {
 +          return getKey(buf, 0);
 +        }
 +        
 +        /**
 +         * Copy the key into user supplied buffer.
 +         * 
 +         * @param buf
 +         *          The buffer supplied by user.
 +         * @param offset
 +         *          The starting offset of the user buffer where we should copy the key into. Requiring the key-length + offset no greater than the buffer
 +         *          length.
 +         * @return The length of the key.
-          * @throws IOException
 +         */
 +        public int getKey(byte[] buf, int offset) throws IOException {
 +          if ((offset | (buf.length - offset - klen)) < 0) {
 +            throw new IndexOutOfBoundsException("Bufer not enough to store the key");
 +          }
 +          System.arraycopy(keyBuffer, 0, buf, offset, klen);
 +          return klen;
 +        }
 +        
 +        /**
 +         * Streaming access to the key. Useful for desrializing the key into user objects.
 +         * 
 +         * @return The input stream.
 +         */
 +        public DataInputStream getKeyStream() {
 +          keyDataInputStream.reset(keyBuffer, klen);
 +          return keyDataInputStream;
 +        }
 +        
 +        /**
 +         * Get the length of the value. isValueLengthKnown() must be tested true.
 +         * 
 +         * @return the length of the value.
 +         */
 +        public int getValueLength() {
 +          if (vlen >= 0) {
 +            return vlen;
 +          }
 +          
 +          throw new RuntimeException("Value length unknown.");
 +        }
 +        
 +        /**
 +         * Copy value into user-supplied buffer. User supplied buffer must be large enough to hold the whole value. The value part of the key-value pair pointed
 +         * by the current cursor is not cached and can only be examined once. Calling any of the following functions more than once without moving the cursor
 +         * will result in exception: {@link #getValue(byte[])}, {@link #getValue(byte[], int)}, {@link #getValueStream}.
 +         * 
 +         * @return the length of the value. Does not require isValueLengthKnown() to be true.
-          * @throws IOException
 +         * 
 +         */
 +        public int getValue(byte[] buf) throws IOException {
 +          return getValue(buf, 0);
 +        }
 +        
 +        /**
 +         * Copy value into user-supplied buffer. User supplied buffer must be large enough to hold the whole value (starting from the offset). The value part of
 +         * the key-value pair pointed by the current cursor is not cached and can only be examined once. Calling any of the following functions more than once
 +         * without moving the cursor will result in exception: {@link #getValue(byte[])}, {@link #getValue(byte[], int)}, {@link #getValueStream}.
 +         * 
 +         * @return the length of the value. Does not require isValueLengthKnown() to be true.
-          * @throws IOException
 +         */
 +        public int getValue(byte[] buf, int offset) throws IOException {
 +          DataInputStream dis = getValueStream();
 +          try {
 +            if (isValueLengthKnown()) {
 +              if ((offset | (buf.length - offset - vlen)) < 0) {
 +                throw new IndexOutOfBoundsException("Buffer too small to hold value");
 +              }
 +              dis.readFully(buf, offset, vlen);
 +              return vlen;
 +            }
 +            
 +            int nextOffset = offset;
 +            while (nextOffset < buf.length) {
 +              int n = dis.read(buf, nextOffset, buf.length - nextOffset);
 +              if (n < 0) {
 +                break;
 +              }
 +              nextOffset += n;
 +            }
 +            if (dis.read() >= 0) {
 +              // attempt to read one more byte to determine whether we reached
 +              // the
 +              // end or not.
 +              throw new IndexOutOfBoundsException("Buffer too small to hold value");
 +            }
 +            return nextOffset - offset;
 +          } finally {
 +            dis.close();
 +          }
 +        }
 +        
 +        /**
 +         * Stream access to value. The value part of the key-value pair pointed by the current cursor is not cached and can only be examined once. Calling any
 +         * of the following functions more than once without moving the cursor will result in exception: {@link #getValue(byte[])},
 +         * {@link #getValue(byte[], int)}, {@link #getValueStream}.
 +         * 
 +         * @return The input stream for reading the value.
-          * @throws IOException
 +         */
 +        public DataInputStream getValueStream() throws IOException {
 +          if (valueChecked == true) {
 +            throw new IllegalStateException("Attempt to examine value multiple times.");
 +          }
 +          valueChecked = true;
 +          return valueDataInputStream;
 +        }
 +        
 +        /**
 +         * Check whether it is safe to call getValueLength().
 +         * 
 +         * @return true if value length is known before hand. Values less than the chunk size will always have their lengths known before hand. Values that are
 +         *         written out as a whole (with advertised length up-front) will always have their lengths known in read.
 +         */
 +        public boolean isValueLengthKnown() {
 +          return (vlen >= 0);
 +        }
 +        
 +        /**
 +         * Compare the entry key to another key. Synonymous to compareTo(key, 0, key.length).
 +         * 
 +         * @param buf
 +         *          The key buffer.
 +         * @return comparison result between the entry key with the input key.
 +         */
 +        public int compareTo(byte[] buf) {
 +          return compareTo(buf, 0, buf.length);
 +        }
 +        
 +        /**
 +         * Compare the entry key to another key. Synonymous to compareTo(new ByteArray(buf, offset, length)
 +         * 
 +         * @param buf
 +         *          The key buffer
 +         * @param offset
 +         *          offset into the key buffer.
 +         * @param length
 +         *          the length of the key.
 +         * @return comparison result between the entry key with the input key.
 +         */
 +        public int compareTo(byte[] buf, int offset, int length) {
 +          return compareTo(new ByteArray(buf, offset, length));
 +        }
 +        
 +        /**
 +         * Compare an entry with a RawComparable object. This is useful when Entries are stored in a collection, and we want to compare a user supplied key.
 +         */
 +        @Override
 +        public int compareTo(RawComparable key) {
 +          return reader.compareKeys(keyBuffer, 0, getKeyLength(), key.buffer(), key.offset(), key.size());
 +        }
 +        
 +        /**
 +         * Compare whether this and other points to the same key value.
 +         */
 +        @Override
 +        public boolean equals(Object other) {
 +          if (this == other)
 +            return true;
 +          if (!(other instanceof Entry))
 +            return false;
 +          return ((Entry) other).compareTo(keyBuffer, 0, getKeyLength()) == 0;
 +        }
 +        
 +        @Override
 +        public int hashCode() {
 +          return WritableComparator.hashBytes(keyBuffer, getKeyLength());
 +        }
 +      }
 +      
 +      /**
 +       * Advance cursor by n positions within the block.
 +       * 
 +       * @param n
 +       *          Number of key-value pairs to skip in block.
 +       * @throws IOException
 +       */
 +      private void inBlockAdvance(long n) throws IOException {
 +        for (long i = 0; i < n; ++i) {
 +          checkKey();
 +          if (!valueBufferInputStream.isClosed()) {
 +            valueBufferInputStream.close();
 +          }
 +          klen = -1;
 +          currentLocation.incRecordIndex();
 +        }
 +      }
 +      
 +      /**
 +       * Advance cursor in block until we find a key that is greater than or equal to the input key.
 +       * 
 +       * @param key
 +       *          Key to compare.
 +       * @param greater
 +       *          advance until we find a key greater than the input key.
 +       * @return true if we find a equal key.
 +       * @throws IOException
 +       */
 +      private boolean inBlockAdvance(RawComparable key, boolean greater) throws IOException {
 +        int curBid = currentLocation.getBlockIndex();
 +        long entryInBlock = reader.getBlockEntryCount(curBid);
 +        if (curBid == endLocation.getBlockIndex()) {
 +          entryInBlock = endLocation.getRecordIndex();
 +        }
 +        
 +        while (currentLocation.getRecordIndex() < entryInBlock) {
 +          int cmp = compareCursorKeyTo(key);
 +          if (cmp > 0)
 +            return false;
 +          if (cmp == 0 && !greater)
 +            return true;
 +          if (!valueBufferInputStream.isClosed()) {
 +            valueBufferInputStream.close();
 +          }
 +          klen = -1;
 +          currentLocation.incRecordIndex();
 +        }
 +        
 +        throw new RuntimeException("Cannot find matching key in block.");
 +      }
 +    }
 +    
 +    long getBlockEntryCount(int curBid) {
 +      return tfileIndex.getEntry(curBid).entries();
 +    }
 +    
 +    BlockReader getBlockReader(int blockIndex) throws IOException {
 +      return readerBCF.getDataBlock(blockIndex);
 +    }
 +  }
 +  
 +  /**
 +   * Data structure representing "TFile.meta" meta block.
 +   */
 +  static final class TFileMeta {
 +    final static String BLOCK_NAME = "TFile.meta";
 +    final Version version;
 +    private long recordCount;
 +    private final String strComparator;
 +    private final BytesComparator comparator;
 +    
 +    // ctor for writes
 +    public TFileMeta(String comparator) {
 +      // set fileVersion to API version when we create it.
 +      version = TFile.API_VERSION;
 +      recordCount = 0;
 +      strComparator = (comparator == null) ? "" : comparator;
 +      this.comparator = makeComparator(strComparator);
 +    }
 +    
 +    // ctor for reads
 +    public TFileMeta(DataInput in) throws IOException {
 +      version = new Version(in);
 +      if (!version.compatibleWith(TFile.API_VERSION)) {
 +        throw new RuntimeException("Incompatible TFile fileVersion.");
 +      }
 +      recordCount = Utils.readVLong(in);
 +      strComparator = Utils.readString(in);
 +      comparator = makeComparator(strComparator);
 +    }
 +    
 +    @SuppressWarnings({"rawtypes", "unchecked"})
 +    static BytesComparator makeComparator(String comparator) {
 +      if (comparator.length() == 0) {
 +        // unsorted keys
 +        return null;
 +      }
 +      if (comparator.equals(COMPARATOR_MEMCMP)) {
 +        // default comparator
 +        return new BytesComparator(new MemcmpRawComparator());
 +      } else if (comparator.startsWith(COMPARATOR_JCLASS)) {
 +        String compClassName = comparator.substring(COMPARATOR_JCLASS.length()).trim();
 +        try {
 +          Class compClass = Class.forName(compClassName);
 +          // use its default ctor to create an instance
 +          return new BytesComparator((RawComparator<Object>) compClass.newInstance());
 +        } catch (Exception e) {
 +          throw new IllegalArgumentException("Failed to instantiate comparator: " + comparator + "(" + e.toString() + ")");
 +        }
 +      } else {
 +        throw new IllegalArgumentException("Unsupported comparator: " + comparator);
 +      }
 +    }
 +    
 +    public void write(DataOutput out) throws IOException {
 +      TFile.API_VERSION.write(out);
 +      Utils.writeVLong(out, recordCount);
 +      Utils.writeString(out, strComparator);
 +    }
 +    
 +    public long getRecordCount() {
 +      return recordCount;
 +    }
 +    
 +    public void incRecordCount() {
 +      ++recordCount;
 +    }
 +    
 +    public boolean isSorted() {
 +      return !strComparator.equals("");
 +    }
 +    
 +    public String getComparatorString() {
 +      return strComparator;
 +    }
 +    
 +    public BytesComparator getComparator() {
 +      return comparator;
 +    }
 +    
 +    public Version getVersion() {
 +      return version;
 +    }
 +  } // END: class MetaTFileMeta
 +  
 +  /**
 +   * Data structure representing "TFile.index" meta block.
 +   */
 +  static class TFileIndex {
 +    final static String BLOCK_NAME = "TFile.index";
 +    private ByteArray firstKey;
 +    private final ArrayList<TFileIndexEntry> index;
 +    private final BytesComparator comparator;
 +    
 +    /**
 +     * For reading from file.
-      * 
-      * @throws IOException
 +     */
 +    public TFileIndex(int entryCount, DataInput in, BytesComparator comparator) throws IOException {
 +      index = new ArrayList<TFileIndexEntry>(entryCount);
 +      int size = Utils.readVInt(in); // size for the first key entry.
 +      if (size > 0) {
 +        byte[] buffer = new byte[size];
 +        in.readFully(buffer);
 +        DataInputStream firstKeyInputStream = new DataInputStream(new ByteArrayInputStream(buffer, 0, size));
 +        
 +        int firstKeyLength = Utils.readVInt(firstKeyInputStream);
 +        firstKey = new ByteArray(new byte[firstKeyLength]);
 +        firstKeyInputStream.readFully(firstKey.buffer());
 +        
 +        for (int i = 0; i < entryCount; i++) {
 +          size = Utils.readVInt(in);
 +          if (buffer.length < size) {
 +            buffer = new byte[size];
 +          }
 +          in.readFully(buffer, 0, size);
 +          TFileIndexEntry idx = new TFileIndexEntry(new DataInputStream(new ByteArrayInputStream(buffer, 0, size)));
 +          index.add(idx);
 +        }
 +      } else {
 +        if (entryCount != 0) {
 +          throw new RuntimeException("Internal error");
 +        }
 +      }
 +      this.comparator = comparator;
 +    }
 +    
 +    /**
 +     * @param key
 +     *          input key.
 +     * @return the ID of the first block that contains key >= input key. Or -1 if no such block exists.
 +     */
 +    public int lowerBound(RawComparable key) {
 +      if (comparator == null) {
 +        throw new RuntimeException("Cannot search in unsorted TFile");
 +      }
 +      
 +      if (firstKey == null) {
 +        return -1; // not found
 +      }
 +      
 +      int ret = Utils.lowerBound(index, key, comparator);
 +      if (ret == index.size()) {
 +        return -1;
 +      }
 +      return ret;
 +    }
 +    
 +    public int upperBound(RawComparable key) {
 +      if (comparator == null) {
 +        throw new RuntimeException("Cannot search in unsorted TFile");
 +      }
 +      
 +      if (firstKey == null) {
 +        return -1; // not found
 +      }
 +      
 +      int ret = Utils.upperBound(index, key, comparator);
 +      if (ret == index.size()) {
 +        return -1;
 +      }
 +      return ret;
 +    }
 +    
 +    /**
 +     * For writing to file.
 +     */
 +    public TFileIndex(BytesComparator comparator) {
 +      index = new ArrayList<TFileIndexEntry>();
 +      this.comparator = comparator;
 +    }
 +    
 +    public RawComparable getFirstKey() {
 +      return firstKey;
 +    }
 +    
 +    public void setFirstKey(byte[] key, int offset, int length) {
 +      firstKey = new ByteArray(new byte[length]);
 +      System.arraycopy(key, offset, firstKey.buffer(), 0, length);
 +    }
 +    
 +    public RawComparable getLastKey() {
 +      if (index.size() == 0) {
 +        return null;
 +      }
 +      return new ByteArray(index.get(index.size() - 1).buffer());
 +    }
 +    
 +    public void addEntry(TFileIndexEntry keyEntry) {
 +      index.add(keyEntry);
 +    }
 +    
 +    public TFileIndexEntry getEntry(int bid) {
 +      return index.get(bid);
 +    }
 +    
 +    public void write(DataOutput out) throws IOException {
 +      if (firstKey == null) {
 +        Utils.writeVInt(out, 0);
 +        return;
 +      }
 +      
 +      DataOutputBuffer dob = new DataOutputBuffer();
 +      Utils.writeVInt(dob, firstKey.size());
 +      dob.write(firstKey.buffer());
 +      Utils.writeVInt(out, dob.size());
 +      out.write(dob.getData(), 0, dob.getLength());
 +      
 +      for (TFileIndexEntry entry : index) {
 +        dob.reset();
 +        entry.write(dob);
 +        Utils.writeVInt(out, dob.getLength());
 +        out.write(dob.getData(), 0, dob.getLength());
 +      }
 +    }
 +  }
 +  
 +  /**
 +   * TFile Data Index entry. We should try to make the memory footprint of each index entry as small as possible.
 +   */
 +  static final class TFileIndexEntry implements RawComparable {
 +    final byte[] key;
 +    // count of <key, value> entries in the block.
 +    final long kvEntries;
 +    
 +    public TFileIndexEntry(DataInput in) throws IOException {
 +      int len = Utils.readVInt(in);
 +      key = new byte[len];
 +      in.readFully(key, 0, len);
 +      kvEntries = Utils.readVLong(in);
 +    }
 +    
 +    // default entry, without any padding
 +    public TFileIndexEntry(byte[] newkey, int offset, int len, long entries) {
 +      key = new byte[len];
 +      System.arraycopy(newkey, offset, key, 0, len);
 +      this.kvEntries = entries;
 +    }
 +    
 +    @Override
 +    public byte[] buffer() {
 +      return key;
 +    }
 +    
 +    @Override
 +    public int offset() {
 +      return 0;
 +    }
 +    
 +    @Override
 +    public int size() {
 +      return key.length;
 +    }
 +    
 +    long entries() {
 +      return kvEntries;
 +    }
 +    
 +    public void write(DataOutput out) throws IOException {
 +      Utils.writeVInt(out, key.length);
 +      out.write(key, 0, key.length);
 +      Utils.writeVLong(out, kvEntries);
 +    }
 +  }
 +  
 +  /**
 +   * Dumping the TFile information.
 +   * 
 +   * @param args
 +   *          A list of TFile paths.
 +   */
 +  public static void main(String[] args) {
 +    System.out.printf("TFile Dumper (TFile %s, BCFile %s)%n", TFile.API_VERSION.toString(), BCFile.API_VERSION.toString());
 +    if (args.length == 0) {
 +      System.out.println("Usage: java ... org.apache.hadoop.io.file.tfile.TFile tfile-path [tfile-path ...]");
 +      System.exit(0);
 +    }
 +    Configuration conf = new Configuration();
 +    
 +    for (String file : args) {
 +      System.out.println("===" + file + "===");
 +      try {
 +        TFileDumper.dumpInfo(file, System.out, conf);
 +      } catch (IOException e) {
 +        e.printStackTrace(System.err);
 +      }
 +    }
 +  }
 +}


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