org.apache.lucene.store
Class DataInput

java.lang.Object
  extended by org.apache.lucene.store.DataInput
All Implemented Interfaces:
Cloneable
Direct Known Subclasses:
ByteArrayDataInput, FST.BytesReader, IndexInput, InputStreamDataInput, PagedBytes.PagedBytesDataInput

public abstract class DataInput
extends Object
implements Cloneable

Abstract base class for performing read operations of Lucene's low-level data types.

DataInput 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 DataInput instance must be cloned before used in another thread. Subclasses must therefore implement clone(), returning a new DataInput which operates on the same underlying resource, but positioned independently.


Constructor Summary
DataInput()
           
 
Method Summary
 DataInput clone()
          Returns a clone of this stream.
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).
 int readInt()
          Reads four bytes and returns an int.
 long readLong()
          Reads eight bytes and returns a long.
 short readShort()
          Reads two bytes and returns a short.
 String readString()
          Reads a string.
 Set<String> readStringSet()
          Reads a Set<String> previously written with DataOutput.writeStringSet(Set).
 Map<String,String> readStringStringMap()
          Reads a Map<String,String> previously written with DataOutput.writeStringStringMap(Map).
 int readVInt()
          Reads an int stored in variable-length format.
 long readVLong()
          Reads a long stored in variable-length format.
 
Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

DataInput

public DataInput()
Method Detail

readByte

public abstract byte readByte()
                       throws IOException
Reads and returns a single byte.

Throws:
IOException
See Also:
DataOutput.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:
DataOutput.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:
DataOutput.writeBytes(byte[],int)

readShort

public short readShort()
                throws IOException
Reads two bytes and returns a short.

Throws:
IOException
See Also:
DataOutput.writeByte(byte)

readInt

public int readInt()
            throws IOException
Reads four bytes and returns an int.

Throws:
IOException
See Also:
DataOutput.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.

The format is described further in DataOutput.writeVInt(int).

Throws:
IOException
See Also:
DataOutput.writeVInt(int)

readLong

public long readLong()
              throws IOException
Reads eight bytes and returns a long.

Throws:
IOException
See Also:
DataOutput.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.

The format is described further in DataOutput.writeVInt(int).

Throws:
IOException
See Also:
DataOutput.writeVLong(long)

readString

public String readString()
                  throws IOException
Reads a string.

Throws:
IOException
See Also:
DataOutput.writeString(String)

clone

public DataInput 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
Reads a Map<String,String> previously written with DataOutput.writeStringStringMap(Map).

Throws:
IOException

readStringSet

public Set<String> readStringSet()
                          throws IOException
Reads a Set<String> previously written with DataOutput.writeStringSet(Set).

Throws:
IOException


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