Package uk.ac.starlink.fits

Class BlockInput

  • All Implemented Interfaces:
    BasicInput
    Direct Known Subclasses:
    BlockMappedInput, MultiByteBufferInput
    public abstract class BlockInput
extends java.lang.Object
implements BasicInput
    Partial random-access BasicInput implementation based on a set of ByteBuffers. These may be obtained eagerly or lazily, as defined by the implementation.
    Since:
    18 Mar 2021
    Author:
    Mark Taylor

    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      protected BlockInput​(int nblock)
      Constructor.

    • Method Summary

      All Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      protected abstract java.nio.ByteBuffer acquireBlock​(int iblock)
      Obtains a buffer corresponding to a named block of the stream.
      void close()
      Releases resources belonging to this object.
      int getBlockCount()
      Returns the number of mapped blocks used.
      abstract long getBlockOffset​(int iblock, int offsetInBlock)
      Returns the offset into this stream corresponding to a given block index and offset into that block.
      abstract int[] getBlockPos​(long offset)
      Returns the block location of a given byte offset.
      long getOffset()
      Returns the curent position in this stream (optional operation).
      boolean isRandom()
      Indicates whether this object supports random access.
      byte readByte()
      Reads a byte from the stream.
      void readBytes​(byte[] bbuf)
      Reads bytes into an array from the stream.
      double readDouble()
      Reads an 8-byte floating point value from the stream.
      float readFloat()
      Reads a 4-byte floating point value from the stream.
      int readInt()
      Reads a 4-byte integer from the stream.
      long readLong()
      Reads an 8-byte integer from the stream.
      short readShort()
      Reads a 2-byte integer from the stream.
      void seek​(long offset)
      Moves the current position of this stream to a given byte offset (optional operation).
      void skip​(long nbyte)
      Skips a given number of bytes forwards through the stream.

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • BlockInput

        protected BlockInput​(int nblock)
        Constructor.
        Parameters:
        nblock - number of buffers

    • Method Detail

      • readByte

        public byte readByte()
              throws java.io.IOException
        Description copied from interface: BasicInput
        Reads a byte from the stream. The current position is advanced.
        Specified by:
        readByte in interface BasicInput
        Returns:
        byte value
        Throws:
        java.io.IOException

      • readShort

        public short readShort()
                throws java.io.IOException
        Description copied from interface: BasicInput
        Reads a 2-byte integer from the stream. The current position is advanced.
        Specified by:
        readShort in interface BasicInput
        Returns:
        short value
        Throws:
        java.io.IOException

      • readInt

        public int readInt()
            throws java.io.IOException
        Description copied from interface: BasicInput
        Reads a 4-byte integer from the stream. The current position is advanced.
        Specified by:
        readInt in interface BasicInput
        Returns:
        int value
        Throws:
        java.io.IOException

      • readLong

        public long readLong()
              throws java.io.IOException
        Description copied from interface: BasicInput
        Reads an 8-byte integer from the stream. The current position is advanced.
        Specified by:
        readLong in interface BasicInput
        Returns:
        long value
        Throws:
        java.io.IOException

      • readFloat

        public float readFloat()
                throws java.io.IOException
        Description copied from interface: BasicInput
        Reads a 4-byte floating point value from the stream. The current position is advanced.
        Specified by:
        readFloat in interface BasicInput
        Returns:
        float value
        Throws:
        java.io.IOException

      • readDouble

        public double readDouble()
                  throws java.io.IOException
        Description copied from interface: BasicInput
        Reads an 8-byte floating point value from the stream. The current position is advanced.
        Specified by:
        readDouble in interface BasicInput
        Returns:
        double value
        Throws:
        java.io.IOException

      • readBytes

        public void readBytes​(byte[] bbuf)
               throws java.io.IOException
        Description copied from interface: BasicInput
        Reads bytes into an array from the stream. The current position is advanced.
        Specified by:
        readBytes in interface BasicInput
        Parameters:
        bbuf - array into which the bytes are read; the number of bytes read is the length of the array
        Throws:
        java.io.IOException

      • close

        public void close()
        Description copied from interface: BasicInput
        Releases resources belonging to this object. Attempts to use it after a call to this method result in undefined behaviour.
        Specified by:
        close in interface BasicInput

      • isRandom

        public boolean isRandom()
        Description copied from interface: BasicInput
        Indicates whether this object supports random access. The seek and getOffset methods may only be called if this method returns true.
        Specified by:
        isRandom in interface BasicInput
        Returns:
        true iff random access is supported

      • getBlockPos

        public abstract int[] getBlockPos​(long offset)
        Returns the block location of a given byte offset.

        This does the opposite of getBlockOffset.

        Parameters:
        offset - offset into this input stream
        Returns:
        2-element array giving [blockIndex, offsetInBlock]

      • getBlockOffset

        public abstract long getBlockOffset​(int iblock,
                                    int offsetInBlock)
        Returns the offset into this stream corresponding to a given block index and offset into that block.

        This does the opposite of getBlockPos.

        Parameters:
        iblock - block index
        offsetInBlock - offset into that block
        Returns:
        offset into stream

      • acquireBlock

        protected abstract java.nio.ByteBuffer acquireBlock​(int iblock)
                                             throws java.io.IOException
        Obtains a buffer corresponding to a named block of the stream. The buffer's position must be zero. This method is called whenever a buffer is required which is not the same as the most recently used one.
        Parameters:
        iblock - block index
        Returns:
        byte buffer for given block, positioned at start
        Throws:
        java.io.IOException

      • seek

        public void seek​(long offset)
          throws java.io.IOException
        Description copied from interface: BasicInput
        Moves the current position of this stream to a given byte offset (optional operation).
        Specified by:
        seek in interface BasicInput
        Throws:
        java.io.IOException

      • getOffset

        public long getOffset()
        Description copied from interface: BasicInput
        Returns the curent position in this stream (optional operation).
        Specified by:
        getOffset in interface BasicInput

      • skip

        public void skip​(long nbyte)
          throws java.io.IOException
        Description copied from interface: BasicInput
        Skips a given number of bytes forwards through the stream. An exception is thrown if there are not enough bytes left.
        Specified by:
        skip in interface BasicInput
        Parameters:
        nbyte - number of bytes to skip
        Throws:
        java.io.IOException

      • getBlockCount

        public int getBlockCount()
        Returns the number of mapped blocks used.
        Returns:
        block count