org.apache.lucene.store
Class IndexInput

java.lang.Object
  extended by org.apache.lucene.store.IndexInput
All Implemented Interfaces:
Closeable, Cloneable
Direct Known Subclasses:
BufferedIndexInput, ChecksumIndexInput

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

Constructor Summary
IndexInput()
           
 
Method Summary
 Object 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.
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
 

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

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

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


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