Package org.apache.lucene.store

Class DataInput

  • All Implemented Interfaces:
    java.lang.Cloneable
    Direct Known Subclasses:
    ByteArrayDataInput, FST.BytesReader, IndexInput, InputStreamDataInput, PagedBytes.PagedBytesDataInput
    public abstract class DataInput
extends java.lang.Object
implements java.lang.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

      Constructors 
      Constructor Description
      DataInput()  

    • Method Summary

      All Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      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.
      java.lang.String readString()
      Reads a string.
      java.util.Set<java.lang.String> readStringSet()
      Reads a Set<String> previously written with DataOutput.writeStringSet(Set).
      java.util.Map<java.lang.String,​java.lang.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, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

      • DataInput

        public DataInput()

    • Method Detail

      • readByte

        public abstract byte readByte()
                       throws java.io.IOException
        Reads and returns a single byte.
        Throws:
        java.io.IOException
        See Also:
        DataOutput.writeByte(byte)

      • readBytes

        public abstract void readBytes​(byte[] b,
                               int offset,
                               int len)
                        throws java.io.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:
        java.io.IOException
        See Also:
        DataOutput.writeBytes(byte[],int)

      • readBytes

        public void readBytes​(byte[] b,
                      int offset,
                      int len,
                      boolean useBuffer)
               throws java.io.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:
        java.io.IOException
        See Also:
        DataOutput.writeBytes(byte[],int)

      • readShort

        public short readShort()
                throws java.io.IOException
        Reads two bytes and returns a short.
        Throws:
        java.io.IOException
        See Also:
        DataOutput.writeByte(byte)

      • readInt

        public int readInt()
            throws java.io.IOException
        Reads four bytes and returns an int.
        Throws:
        java.io.IOException
        See Also:
        DataOutput.writeInt(int)

      • readVInt

        public int readVInt()
             throws java.io.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:
        java.io.IOException
        See Also:
        DataOutput.writeVInt(int)

      • readLong

        public long readLong()
              throws java.io.IOException
        Reads eight bytes and returns a long.
        Throws:
        java.io.IOException
        See Also:
        DataOutput.writeLong(long)

      • readVLong

        public long readVLong()
               throws java.io.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:
        java.io.IOException
        See Also:
        DataOutput.writeVLong(long)

      • readString

        public java.lang.String readString()
                            throws java.io.IOException
        Reads a string.
        Throws:
        java.io.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.

      • readStringStringMap

        public java.util.Map<java.lang.String,​java.lang.String> readStringStringMap()
                                                                           throws java.io.IOException
        Reads a Map<String,String> previously written with DataOutput.writeStringStringMap(Map).
        Throws:
        java.io.IOException

      • readStringSet

        public java.util.Set<java.lang.String> readStringSet()
                                              throws java.io.IOException
        Reads a Set<String> previously written with DataOutput.writeStringSet(Set).
        Throws:
        java.io.IOException