Class BlockInput

java.lang.Object
uk.ac.starlink.fits.BlockInput
All Implemented Interfaces:
BasicInput
Direct Known Subclasses:
BlockMappedInput, MultiByteBufferInput
public abstract class BlockInput extends 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

    Modifier and Type
    Method
    Description
    protected abstract 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 Object

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

  • Constructor Details

    • BlockInput

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

  • Method Details

    • readByte

      public byte readByte() throws 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:
      IOException

    • readShort

      public short readShort() throws 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:
      IOException

    • readInt

      public int readInt() throws 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:
      IOException

    • readLong

      public long readLong() throws 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:
      IOException

    • readFloat

      public float readFloat() throws 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:
      IOException

    • readDouble

      public double readDouble() throws 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:
      IOException

    • readBytes

      public void readBytes(byte[] bbuf) throws 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:
      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 ByteBuffer acquireBlock(int iblock) throws 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:
      IOException

    • seek

      public void seek(long offset) throws 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:
      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 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:
      IOException

    • getBlockCount

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

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