Interface ByteCursor

  • All Known Implementing Classes:
    TransportCursor

    public interface ByteCursor
    The ByteCursor object is used to acquire bytes from a given source. This provides a cursor style reading of bytes from a stream in that it will allow the reader to move the cursor back if the amount of bytes read is too much. Allowing the cursor to move ensures that excess bytes back be placed back in the stream.

    This is used when parsing input from a stream as it ensures that on arrival at a terminal token any excess bytes can be placed back in to the stream. This allows data to be read efficiently in large chunks from blocking streams such as sockets.

    Author:
    Niall Gallagher
    See Also:
    TransportCursor
    • Method Summary

      All Methods Instance Methods Abstract Methods 
      Modifier and Type Method Description
      boolean isOpen()
      Determines whether the cursor is still open.
      boolean isReady()
      Determines whether the cursor is ready for reading.
      void push​(byte[] data)
      Pushes the provided data on to the cursor.
      void push​(byte[] data, int off, int len)
      Pushes the provided data on to the cursor.
      int read​(byte[] data)
      Reads a block of bytes from the underlying stream.
      int read​(byte[] data, int off, int len)
      Reads a block of bytes from the underlying stream.
      int ready()
      Provides the number of bytes that can be read from the stream without blocking.
      int reset​(int len)
      Moves the cursor backward within the stream.
    • Method Detail

      • isOpen

        boolean isOpen()
                throws java.io.IOException
        Determines whether the cursor is still open. The cursor is considered open if there are still bytes to read. If there is still bytes buffered and the underlying transport is closed then the cursor is still considered open.
        Returns:
        true if the read method does not return a -1 value
        Throws:
        java.io.IOException
      • isReady

        boolean isReady()
                 throws java.io.IOException
        Determines whether the cursor is ready for reading. When the cursor is ready then it guarantees that some amount of bytes can be read from the underlying stream without blocking.
        Returns:
        true if some data can be read without blocking
        Throws:
        java.io.IOException
      • ready

        int ready()
           throws java.io.IOException
        Provides the number of bytes that can be read from the stream without blocking. This is typically the number of buffered or available bytes within the stream. When this reaches zero then the cursor may perform a blocking read.
        Returns:
        the number of bytes that can be read without blocking
        Throws:
        java.io.IOException
      • read

        int read​(byte[] data)
          throws java.io.IOException
        Reads a block of bytes from the underlying stream. This will read up to the requested number of bytes from the underlying stream. If there are no ready bytes on the stream this can return zero, representing the fact that nothing was read.
        Parameters:
        data - this is the array to read the bytes in to
        Returns:
        this returns the number of bytes read from the stream
        Throws:
        java.io.IOException
      • read

        int read​(byte[] data,
                 int off,
                 int len)
          throws java.io.IOException
        Reads a block of bytes from the underlying stream. This will read up to the requested number of bytes from the underlying stream. If there are no ready bytes on the stream this can return zero, representing the fact that nothing was read.
        Parameters:
        data - this is the array to read the bytes in to
        off - this is the offset to begin writing the bytes to
        len - this is the number of bytes that are requested
        Returns:
        this returns the number of bytes read from the stream
        Throws:
        java.io.IOException
      • push

        void push​(byte[] data)
           throws java.io.IOException
        Pushes the provided data on to the cursor. Data pushed on to the cursor will be the next data read from the cursor. This complements the reset method which will reset the cursors position on a stream. Allowing data to be pushed on to the cursor allows more flexibility.
        Parameters:
        data - this is the data to be pushed on to the cursor
        Throws:
        java.io.IOException
      • push

        void push​(byte[] data,
                  int off,
                  int len)
           throws java.io.IOException
        Pushes the provided data on to the cursor. Data pushed on to the cursor will be the next data read from the cursor. This complements the reset method which will reset the cursors position on a stream. Allowing data to be pushed on to the cursor allows more flexibility.
        Parameters:
        data - this is the data to be pushed on to the cursor
        off - this is the offset to begin reading the bytes
        len - this is the number of bytes that are to be used
        Throws:
        java.io.IOException
      • reset

        int reset​(int len)
           throws java.io.IOException
        Moves the cursor backward within the stream. This ensures that any bytes read from the last read can be pushed back in to the stream so that they can be read again. This will throw an exception if the reset can not be performed.
        Parameters:
        len - this is the number of bytes to reset back
        Returns:
        this is the number of bytes that have been reset
        Throws:
        java.io.IOException