SequenceFile.Reader (Hadoop 1.2.1 API)
Date: 2013-07-22

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## org.apache.hadoop.io
Class SequenceFile.Reader

    java.lang.Object
      org.apache.hadoop.io.SequenceFile.Reader

All Implemented Interfaces:
  Closeable

Enclosing class:
  SequenceFile

    public static class SequenceFile.Reader

extends Object
implements Closeable

Reads key/value pairs from a sequence-format file.

Constructor Summary
`SequenceFile.Reader(FileSystem fs, Path file, Configuration conf)` Open the named file.

Method Summary
`void` | `close()` Close the file.
`SequenceFile.ValueBytes` | `createValueBytes()`
`CompressionCodec` | `getCompressionCodec()` Returns the compression codec of data in this file.
`Object` | `getCurrentValue(Object val)` Get the 'value' corresponding to the last read 'key'.
`void` | `getCurrentValue(Writable val)` Get the 'value' corresponding to the last read 'key'.
`Class<?>` | `getKeyClass()` Returns the class of keys in this file.
`String` | `getKeyClassName()` Returns the name of the key class.
`SequenceFile.Metadata` | `getMetadata()` Returns the metadata object of the file
`long` | `getPosition()` Return the current byte position in the input file.
`Class<?>` | `getValueClass()` Returns the class of values in this file.
`String` | `getValueClassName()` Returns the name of the value class.
`boolean` | `isBlockCompressed()` Returns true if records are block-compressed.
`boolean` | `isCompressed()` Returns true if values are compressed.
`int` | `next(DataOutputBuffer buffer)` Deprecated. Call `nextRaw(DataOutputBuffer,SequenceFile.ValueBytes)`.
`Object` | `next(Object key)` Read the next key in the file, skipping its value.
`boolean` | `next(Writable key)` Read the next key in the file into `key`, skipping its value.
`boolean` | `next(Writable key, Writable val)` Read the next key/value pair in the file into `key` and `val`.
`int` | `nextRaw(DataOutputBuffer key, SequenceFile.ValueBytes val)` Read 'raw' records.
`int` | `nextRawKey(DataOutputBuffer key)` Read 'raw' keys.
`int` | `nextRawValue(SequenceFile.ValueBytes val)` Read 'raw' values.
`protected FSDataInputStream` | `openFile(FileSystem fs, Path file, int bufferSize, long length)` Override this method to specialize the type of `FSDataInputStream` returned.
`void` | `seek(long position)` Set the current byte position in the input file.
`void` | `sync(long position)` Seek to the next sync mark past a given position.
`boolean` | `syncSeen()` Returns true iff the previous call to next passed a sync mark.
`String` | `toString()` Returns the name of the file.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Constructor Detail

### SequenceFile.Reader

    public SequenceFile.Reader(FileSystem fs,
                               Path file,
                               Configuration conf)
                        throws IOException

  Open the named file.

  Throws:
    `IOException`

Method Detail

### openFile

    protected FSDataInputStream openFile(FileSystem fs,
                                         Path file,
                                         int bufferSize,
                                         long length)
                                  throws IOException

  Override this method to specialize the type of `FSDataInputStream` returned.

  Throws:
    `IOException`

### close

    public void close()
               throws IOException

  Close the file.

  Specified by:
    `close` in interface `Closeable`
  Throws:
    `IOException`

### getKeyClassName

    public String getKeyClassName()

  Returns the name of the key class.

### getKeyClass

    public Class<?> getKeyClass()

  Returns the class of keys in this file.

### getValueClassName

    public String getValueClassName()

  Returns the name of the value class.

### getValueClass

    public Class<?> getValueClass()

  Returns the class of values in this file.

### isCompressed

    public boolean isCompressed()

  Returns true if values are compressed.

### isBlockCompressed

    public boolean isBlockCompressed()

  Returns true if records are block-compressed.

### getCompressionCodec

    public CompressionCodec getCompressionCodec()

  Returns the compression codec of data in this file.

### getMetadata

    public SequenceFile.Metadata getMetadata()

  Returns the metadata object of the file

### getCurrentValue

    public void getCurrentValue(Writable val)
                         throws IOException

  Get the 'value' corresponding to the last read 'key'.

  Parameters:
    `val` - : The 'value' to be read.
  Throws:
    `IOException`

### getCurrentValue

    public Object getCurrentValue(Object val)
                           throws IOException

  Get the 'value' corresponding to the last read 'key'.

  Parameters:
    `val` - : The 'value' to be read.
  Throws:
    `IOException`

### next

    public boolean next(Writable key)
                 throws IOException

  Read the next key in the file into `key`, skipping its value. True if another entry exists, and false at end of file.

  Throws:
    `IOException`

### next

    public boolean next(Writable key,
                        Writable val)
                 throws IOException

  Read the next key/value pair in the file into `key` and `val`. Returns true if such a pair exists and false when at end of file

  Throws:
    `IOException`

### next

    public int next(DataOutputBuffer buffer)
             throws IOException

  Deprecated. Call `nextRaw(DataOutputBuffer,SequenceFile.ValueBytes)`.

  Throws:
    `IOException`

### createValueBytes

    public SequenceFile.ValueBytes createValueBytes()

### nextRaw

    public int nextRaw(DataOutputBuffer key,
                       SequenceFile.ValueBytes val)
                throws IOException

  Read 'raw' records.

  Parameters:
    `key` - - The buffer into which the key is read
    `val` - - The 'raw' value
  Returns:
    Returns the total record length or -1 for end of file
  Throws:
    `IOException`

### nextRawKey

    public int nextRawKey(DataOutputBuffer key)
                   throws IOException

  Read 'raw' keys.

  Parameters:
    `key` - - The buffer into which the key is read
  Returns:
    Returns the key length or -1 for end of file
  Throws:
    `IOException`

### next

    public Object next(Object key)
                throws IOException

  Read the next key in the file, skipping its value. Return null at end of file.

  Throws:
    `IOException`

### nextRawValue

    public int nextRawValue(SequenceFile.ValueBytes val)
                     throws IOException

  Read 'raw' values.

  Parameters:
    `val` - - The 'raw' value
  Returns:
    Returns the value length
  Throws:
    `IOException`

### seek

    public void seek(long position)
              throws IOException

  Set the current byte position in the input file.

  The position passed must be a position returned by `SequenceFile.Writer.getLength()` when writing this file. To seek to an arbitrary position, use `sync(long)`.

  Throws:
    `IOException`

### sync

    public void sync(long position)
              throws IOException

  Seek to the next sync mark past a given position.

  Throws:
    `IOException`

### syncSeen

    public boolean syncSeen()

  Returns true iff the previous call to next passed a sync mark.

### getPosition

    public long getPosition()
                     throws IOException

  Return the current byte position in the input file.

  Throws:
    `IOException`

### toString

    public String toString()

  Returns the name of the file.

  Overrides:
    `toString` in class `Object`

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