org.apache.hadoop.fs

Class FSInputStream

java.lang.Object

java.io.InputStream

org.apache.hadoop.fs.FSInputStream

All Implemented Interfaces:

Closeable, AutoCloseable, PositionedReadable, Seekable

@InterfaceAudience.Public
 @InterfaceStability.Evolving
public abstract class FSInputStream
extends InputStream
implements Seekable, PositionedReadable

FSInputStream is a generic old InputStream with a little bit of RAF-style seek ability.

Constructor Summary

Constructors

Constructor and Description
FSInputStream()

Method Summary

Modifier and Type	Method and Description
abstract long	getPos() Return the current offset from the start of the file
int	read(long position, byte[] buffer, int offset, int length) Read up to the specified number of bytes, from a given position within a file, and return the number of bytes read.
void	readFully(long position, byte[] buffer) Read number of bytes equal to the length of the buffer, from a given position within a file.
void	readFully(long position, byte[] buffer, int offset, int length) Read the specified number of bytes, from a given position within a file.
abstract void	seek(long pos) Seek to the given offset from the start of the file.
abstract boolean	seekToNewSource(long targetPos) Seeks a different copy of the data.
String	toString() toString method returns the superclass toString, but if the subclass implements IOStatisticsSource then those statistics are extracted and included in the output.
protected void	validatePositionedReadArgs(long position, byte[] buffer, int offset, int length) Validation code, available for use in subclasses.

Methods inherited from class java.io.InputStream

available, close, mark, markSupported, read, read, read, reset, skip

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

FSInputStream

public FSInputStream()

Method Detail

seek

public abstract void seek(long pos)
                   throws IOException

Seek to the given offset from the start of the file. The next read() will be from that location. Can't seek past the end of the file.

Specified by:

seek in interface Seekable

Throws:

IOException

getPos

public abstract long getPos()
                     throws IOException

Return the current offset from the start of the file

Specified by:

getPos in interface Seekable

Throws:

IOException

seekToNewSource

public abstract boolean seekToNewSource(long targetPos)
                                 throws IOException

Seeks a different copy of the data. Returns true if found a new source, false otherwise.

Throws:

IOException

read

public int read(long position,
                byte[] buffer,
                int offset,
                int length)
         throws IOException

Description copied from interface: PositionedReadable

Read up to the specified number of bytes, from a given position within a file, and return the number of bytes read. This does not change the current offset of a file, and is thread-safe. Warning: Not all filesystems satisfy the thread-safety requirement.

Specified by:

read in interface PositionedReadable

Parameters:

position - position within file

buffer - destination buffer

offset - offset in the buffer

length - number of bytes to read

Returns:

actual number of bytes read; -1 means "none"

Throws:

IOException - IO problems.

validatePositionedReadArgs

protected void validatePositionedReadArgs(long position,
                                          byte[] buffer,
                                          int offset,
                                          int length)
                                   throws EOFException

Validation code, available for use in subclasses.

Parameters:

position - position: if negative an EOF exception is raised

buffer - destination buffer

offset - offset within the buffer

length - length of bytes to read

Throws:

EOFException - if the position is negative

IndexOutOfBoundsException - if there isn't space for the amount of data requested.

IllegalArgumentException - other arguments are invalid.

readFully

public void readFully(long position,
                      byte[] buffer,
                      int offset,
                      int length)
               throws IOException

Description copied from interface: PositionedReadable

Read the specified number of bytes, from a given position within a file. This does not change the current offset of a file, and is thread-safe. Warning: Not all filesystems satisfy the thread-safety requirement.

Specified by:

readFully in interface PositionedReadable

Parameters:

position - position within file

buffer - destination buffer

offset - offset in the buffer

length - number of bytes to read

Throws:

IOException - IO problems.

EOFException - the end of the data was reached before the read operation completed

readFully

public void readFully(long position,
                      byte[] buffer)
               throws IOException

Description copied from interface: PositionedReadable

Read number of bytes equal to the length of the buffer, from a given position within a file. This does not change the current offset of a file, and is thread-safe. Warning: Not all filesystems satisfy the thread-safety requirement.

Specified by:

readFully in interface PositionedReadable

Parameters:

position - position within file

buffer - destination buffer

Throws:

IOException - IO problems.

EOFException - the end of the data was reached before the read operation completed

toString

public String toString()

toString method returns the superclass toString, but if the subclass implements IOStatisticsSource then those statistics are extracted and included in the output. That is: statistics of subclasses are automatically reported.

Overrides:

toString in class Object

Returns:

a string value.