Module org.apache.lucene.core

Package org.apache.lucene.store

Class IndexInput

java.lang.Object

org.apache.lucene.store.DataInput

org.apache.lucene.store.IndexInput

All Implemented Interfaces:

Closeable, AutoCloseable, Cloneable

Direct Known Subclasses:

BufferedIndexInput, ByteBufferIndexInput, ByteBuffersIndexInput, ChecksumIndexInput, DirectIODirectory.DirectIOIndexInput, FilterIndexInput

public abstract class IndexInput
extends DataInput
implements Closeable

Abstract base class for input from a file in a Directory. A random-access input stream. Used for all Lucene index input operations.

IndexInput may only be used from one thread, because it is not thread safe (it keeps internal state like file position). To allow multithreaded use, every IndexInput instance must be cloned before it is used in another thread. Subclasses must therefore implement clone(), returning a new IndexInput which operates on the same underlying resource, but positioned independently.

Warning: Lucene never closes cloned IndexInputs, it will only call close() on the original object.

If you access the cloned IndexInput after closing the original object, any readXXX methods will throw AlreadyClosedException.

See Also:

• Directory

Field Summary

Fields

Modifier and Type	Field	Description
private final String	resourceDescription

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	IndexInput(String resourceDescription)	resourceDescription should be a non-null, opaque string describing this resource; it's returned from toString().

Method Summary

Modifier and Type	Method	Description
IndexInput	clone()	Returns a clone of this stream.
abstract void	close()	Closes the stream to further operations.
abstract long	getFilePointer()	Returns the current position in this file, where the next read will occur.
protected String	getFullSliceDescription(String sliceDescription)	Subclasses call this to get the String for resourceDescription of a slice of this IndexInput.
abstract long	length()	The number of bytes in the file.
RandomAccessInput	randomAccessSlice(long offset, long length)	Creates a random-access slice of this index input, with the given offset and length.
abstract void	seek(long pos)	Sets current position in this file, where the next read will occur.
void	skipBytes(long numBytes)	Skip over numBytes bytes.
abstract IndexInput	slice(String sliceDescription, long offset, long length)	Creates a slice of this index input, with the given description, offset, and length.
String	toString()

Methods inherited from class org.apache.lucene.store.DataInput

readByte, readBytes, readBytes, readFloats, readGroupVInt, readGroupVInts, readInt, readInts, readLong, readLongs, readMapOfStrings, readSetOfStrings, readShort, readString, readVInt, readVLong, readZInt, readZLong

Methods inherited from class java.lang.Object

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

Field Details

resourceDescription

private final String resourceDescription

Constructor Details

IndexInput

protected IndexInput(String resourceDescription)

resourceDescription should be a non-null, opaque string describing this resource; it's returned from toString().

Method Details

close

public abstract void close()
                    throws IOException

Closes the stream to further operations.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Throws:

IOException

getFilePointer

public abstract long getFilePointer()

Returns the current position in this file, where the next read will occur.

See Also:

• seek(long)

seek

public abstract void seek(long pos)
                   throws IOException

Sets current position in this file, where the next read will occur. If this is beyond the end of the file then this will throw EOFException and then the stream is in an undetermined state.

Throws:

IOException

See Also:

• getFilePointer()

skipBytes

public void skipBytes(long numBytes)
               throws IOException

Skip over numBytes bytes. This method may skip bytes in whatever way is most optimal, and may not have the same behavior as reading the skipped bytes. In general, negative numBytes are not supported.

Behavior is functionally equivalent to seeking to getFilePointer() + numBytes.

Specified by:

skipBytes in class DataInput

Throws:

IOException

See Also:

• getFilePointer()
• seek(long)

length

public abstract long length()

The number of bytes in the file.

toString

public String toString()

Overrides:

toString in class Object

clone

public IndexInput clone()

Returns a clone of this stream.

Clones of a stream access the same data, and are positioned at the same point as the stream they were cloned from.

Expert: Subclasses must ensure that clones may be positioned at different points in the input from each other and from the stream they were cloned from.

Warning: Lucene never closes cloned IndexInputs, it will only call close() on the original object.

If you access the cloned IndexInput after closing the original object, any readXXX methods will throw AlreadyClosedException.

This method is NOT thread safe, so if the current IndexInput is being used by one thread while clone is called by another, disaster could strike.

Overrides:

clone in class DataInput

slice

public abstract IndexInput slice(String sliceDescription,
 long offset,
 long length)
                          throws IOException

Creates a slice of this index input, with the given description, offset, and length. The slice is sought to the beginning.

Throws:

IOException

getFullSliceDescription

protected String getFullSliceDescription(String sliceDescription)

Subclasses call this to get the String for resourceDescription of a slice of this IndexInput.

randomAccessSlice

public RandomAccessInput randomAccessSlice(long offset,
 long length)
                                    throws IOException

Creates a random-access slice of this index input, with the given offset and length.

The default implementation calls slice(java.lang.String, long, long), and it doesn't support random access, it implements absolute reads as seek+read.

Throws:

IOException