org.apache.hadoop.io
Class SequenceFile.Reader

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

Enclosing class:

SequenceFile

public static class SequenceFile.Reader
extends Object

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.
void	getCurrentValue(Writable val) Get the 'value' corresponding to the last read 'key'.
Class	getKeyClass() Returns the class of keys in this file.
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.
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).
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.
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

close

public void close()
           throws IOException

Close the file.

Throws:

IOException

getKeyClass

public Class getKeyClass()

Returns the class of keys in this file.

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

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

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

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