org.apache.lucene.store
Class IndexInput

java.lang.Object
  org.apache.lucene.store.IndexInput

All Implemented Interfaces:

Closeable, Cloneable

Direct Known Subclasses:

BufferedIndexInput, ChecksumIndexInput, DbIndexInput, JEIndexInput

public abstract class IndexInput
extends Object
implements Cloneable, Closeable

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

See Also:

Directory

Field Summary

protected byte[]

copyBuf

Constructor Summary

IndexInput()

Method Summary

Object	clone() Returns a clone of this stream.
abstract void	close() Closes the stream to further operations.
void	copyBytes(IndexOutput out, long numBytes) Copies numBytes bytes to the given IndexOutput.
abstract long	getFilePointer() Returns the current position in this file, where the next read will occur.
abstract long	length() The number of bytes in the file.
abstract byte	readByte() Reads and returns a single byte.
abstract void	readBytes(byte[] b, int offset, int len) Reads a specified number of bytes into an array at the specified offset.
void	readBytes(byte[] b, int offset, int len, boolean useBuffer) Reads a specified number of bytes into an array at the specified offset with control over whether the read should be buffered (callers who have their own buffer should pass in "false" for useBuffer).
void	readChars(char[] buffer, int start, int length) Deprecated. -- please use readString or readBytes instead, and construct the string from those utf8 bytes
int	readInt() Reads four bytes and returns an int.
long	readLong() Reads eight bytes and returns a long.
String	readString() Reads a string.
Map<String,String>	readStringStringMap()
int	readVInt() Reads an int stored in variable-length format.
long	readVLong() Reads a long stored in variable-length format.
abstract void	seek(long pos) Sets current position in this file, where the next read will occur.
void	setModifiedUTF8StringsMode() Call this if readString should read characters stored in the old modified UTF8 format (length in java chars and java's modified UTF8 encoding).
void	skipChars(int length) Deprecated. this method operates on old "modified utf8" encoded strings

Methods inherited from class java.lang.Object

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

Field Detail

copyBuf

protected byte[] copyBuf

Constructor Detail

IndexInput

public IndexInput()

Method Detail

readByte

public abstract byte readByte()
                       throws IOException

Reads and returns a single byte.

Throws:

IOException

See Also:

IndexOutput.writeByte(byte)

readBytes

public abstract void readBytes(byte[] b,
                               int offset,
                               int len)
                        throws IOException

Reads a specified number of bytes into an array at the specified offset.

Parameters:

b - the array to read bytes into

offset - the offset in the array to start storing bytes

len - the number of bytes to read

Throws:

IOException

See Also:

IndexOutput.writeBytes(byte[],int)

readBytes

public void readBytes(byte[] b,
                      int offset,
                      int len,
                      boolean useBuffer)
               throws IOException

Reads a specified number of bytes into an array at the specified offset with control over whether the read should be buffered (callers who have their own buffer should pass in "false" for useBuffer). Currently only BufferedIndexInput respects this parameter.

Parameters:

b - the array to read bytes into

offset - the offset in the array to start storing bytes

len - the number of bytes to read

useBuffer - set to false if the caller will handle buffering.

Throws:

IOException

See Also:

IndexOutput.writeBytes(byte[],int)

readInt

public int readInt()
            throws IOException

Reads four bytes and returns an int.

Throws:

IOException

See Also:

IndexOutput.writeInt(int)

readVInt

public int readVInt()
             throws IOException

Reads an int stored in variable-length format. Reads between one and five bytes. Smaller values take fewer bytes. Negative numbers are not supported.

Throws:

IOException

See Also:

IndexOutput.writeVInt(int)

readLong

public long readLong()
              throws IOException

Reads eight bytes and returns a long.

Throws:

IOException

See Also:

IndexOutput.writeLong(long)

readVLong

public long readVLong()
               throws IOException

Reads a long stored in variable-length format. Reads between one and nine bytes. Smaller values take fewer bytes. Negative numbers are not supported.

Throws:

IOException

setModifiedUTF8StringsMode

public void setModifiedUTF8StringsMode()

Call this if readString should read characters stored in the old modified UTF8 format (length in java chars and java's modified UTF8 encoding). This is used for indices written pre-2.4 See LUCENE-510 for details.

readString

public String readString()
                  throws IOException

Reads a string.

Throws:

IOException

See Also:

IndexOutput.writeString(String)

readChars

@Deprecated
public void readChars(char[] buffer,
                                 int start,
                                 int length)
               throws IOException

Deprecated. -- please use readString or readBytes instead, and construct the string from those utf8 bytes

Reads Lucene's old "modified UTF-8" encoded characters into an array.

Parameters:

buffer - the array to read characters into

start - the offset in the array to start storing characters

length - the number of characters to read

Throws:

IOException

See Also:

IndexOutput.writeChars(String,int,int)

skipChars

@Deprecated
public void skipChars(int length)
               throws IOException

Deprecated. this method operates on old "modified utf8" encoded strings

Expert Similar to readChars(char[], int, int) but does not do any conversion operations on the bytes it is reading in. It still has to invoke readByte() just as readChars(char[], int, int) does, but it does not need a buffer to store anything and it does not have to do any of the bitwise operations, since we don't actually care what is in the byte except to determine how many more bytes to read

Parameters:

length - The number of chars to read

Throws:

IOException

close

public abstract void close()
                    throws IOException

Closes the stream to further operations.

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.

Throws:

IOException

See Also:

getFilePointer()

length

public abstract long length()

The number of bytes in the file.

clone

public Object 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.

Overrides:

clone in class Object

readStringStringMap

public Map<String,String> readStringStringMap()
                                       throws IOException

Throws:

IOException

copyBytes

public void copyBytes(IndexOutput out,
                      long numBytes)
               throws IOException

Copies numBytes bytes to the given IndexOutput.

NOTE: this method uses an intermediate buffer to copy the bytes. Consider overriding it in your implementation, if you can make a better, optimized copy.

NOTE ensure that there are enough bytes in the input to copy to output. Otherwise, different exceptions may be thrown, depending on the implementation.

Throws:

IOException