Class FileBuffer

  • All Implemented Interfaces:
    Buffer

    class FileBuffer
    extends java.lang.Object
    implements Buffer
    The FileBuffer object is used to create a buffer which will write the appended data to an underlying file. This is typically used for buffers that are too large for to allocate in memory. Data appended to the buffer can be retrieved at a later stage by acquiring the InputStream for the underlying file. To ensure that excessive file system space is not occupied the buffer files are cleaned every five minutes.
    See Also:
    FileAllocator
    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      private class  FileBuffer.Range
      The Range object is used to provide a stream that can read a range of bytes from a provided input stream.
      private class  FileBuffer.Segment
      The Segment object is used to create a segment of the parent buffer.
    • Field Summary

      Fields 
      Modifier and Type Field Description
      private java.io.OutputStream buffer
      This is the file output stream used for this buffer object.
      private boolean closed
      This is used to determine if this buffer has been closed.
      private long count
      This is the number of bytes currently appended to the buffer.
      private java.io.File file
      This is the path for the file that this buffer appends to.
      private FileBuffer.Segment segment
      This represents the last file segment that has been created.
    • Constructor Summary

      Constructors 
      Constructor Description
      FileBuffer​(java.io.File file)
      Constructor for the FileBuffer object.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      Buffer allocate()
      This is used to allocate a segment within this buffer.
      Buffer append​(byte[] array)
      This is used to append the specified data to the underlying file.
      Buffer append​(byte[] array, int off, int size)
      This is used to append the specified data to the underlying file.
      void clear()
      This will clear all data from the buffer.
      void close()
      This method is used to ensure the buffer can be closed.
      private java.lang.String convert​(java.io.InputStream source, java.lang.String charset, int count)
      This method is used to acquire the buffered bytes as a string.
      java.lang.String encode()
      This method is used to acquire the buffered bytes as a string.
      java.lang.String encode​(java.lang.String charset)
      This method is used to acquire the buffered bytes as a string.
      long length()
      This is used to provide the number of bytes that have been written to the buffer.
      java.io.InputStream open()
      This method is used so that a buffer can be represented as a stream of bytes.
      private java.io.InputStream open​(java.io.File file)
      This method is used so that a buffer can be represented as a stream of bytes.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Field Detail

      • buffer

        private java.io.OutputStream buffer
        This is the file output stream used for this buffer object.
      • segment

        private FileBuffer.Segment segment
        This represents the last file segment that has been created.
      • file

        private java.io.File file
        This is the path for the file that this buffer appends to.
      • count

        private long count
        This is the number of bytes currently appended to the buffer.
      • closed

        private boolean closed
        This is used to determine if this buffer has been closed.
    • Constructor Detail

      • FileBuffer

        public FileBuffer​(java.io.File file)
                   throws java.io.IOException
        Constructor for the FileBuffer object. This will create a buffer using the provided file. All data appended to this buffer will effectively written to the underlying file. If the appended data needs to be retrieved at a later stage then it can be acquired using the buffers input stream.
        Parameters:
        file - this is the file used for the file buffer
        Throws:
        java.io.IOException
    • Method Detail

      • allocate

        public Buffer allocate()
                        throws java.io.IOException
        This is used to allocate a segment within this buffer. If the buffer is closed this will throw an exception, if however the buffer is still open then a segment is created which will write all appended data to this buffer. However it can be treated as an independent source of data.
        Specified by:
        allocate in interface Buffer
        Returns:
        this returns a buffer which is a segment of this
        Throws:
        java.io.IOException
      • append

        public Buffer append​(byte[] array)
                      throws java.io.IOException
        This is used to append the specified data to the underlying file. All bytes appended to the file can be consumed at a later stage by acquiring the InputStream from this buffer. Also if require the data can be encoded as a string object in a required character set.
        Specified by:
        append in interface Buffer
        Parameters:
        array - this is the array to write the the file
        Returns:
        this returns this buffer for further operations
        Throws:
        java.io.IOException
      • append

        public Buffer append​(byte[] array,
                             int off,
                             int size)
                      throws java.io.IOException
        This is used to append the specified data to the underlying file. All bytes appended to the file can be consumed at a later stage by acquiring the InputStream from this buffer. Also if require the data can be encoded as a string object in a required character set.
        Specified by:
        append in interface Buffer
        Parameters:
        array - this is the array to write the the file
        off - this is the offset within the array to write
        size - this is the number of bytes to be appended
        Returns:
        this returns this buffer for further operations
        Throws:
        java.io.IOException
      • encode

        public java.lang.String encode()
                                throws java.io.IOException
        This method is used to acquire the buffered bytes as a string. This is useful if the contents need to be manipulated as a string or transferred into another encoding. If the UTF-8 content encoding is not supported the platform default is used, however this is unlikely as UTF-8 should be supported.
        Specified by:
        encode in interface Buffer
        Returns:
        this returns a UTF-8 encoding of the buffer contents
        Throws:
        java.io.IOException
      • encode

        public java.lang.String encode​(java.lang.String charset)
                                throws java.io.IOException
        This method is used to acquire the buffered bytes as a string. This is useful if the contents need to be manipulated as a string or transferred into another encoding. This will convert the bytes using the specified character encoding format.
        Specified by:
        encode in interface Buffer
        Parameters:
        charset - this is the charset to encode the data with
        Returns:
        this returns the encoding of the buffer contents
        Throws:
        java.io.IOException
      • convert

        private java.lang.String convert​(java.io.InputStream source,
                                         java.lang.String charset,
                                         int count)
                                  throws java.io.IOException
        This method is used to acquire the buffered bytes as a string. This is useful if the contents need to be manipulated as a string or transferred into another encoding. This will convert the bytes using the specified character encoding format.
        Parameters:
        source - this is the source stream that is to be encoded
        charset - this is the charset to encode the data with
        count - this is the number of bytes to be encoded
        Returns:
        this returns the encoding of the buffer contents
        Throws:
        java.io.IOException
      • open

        public java.io.InputStream open()
                                 throws java.io.IOException
        This method is used so that a buffer can be represented as a stream of bytes. This provides a quick means to access the data that has been written to the buffer. It wraps the buffer within an input stream so that it can be read directly.
        Specified by:
        open in interface Buffer
        Returns:
        a stream that can be used to read the buffered bytes
        Throws:
        java.io.IOException
      • open

        private java.io.InputStream open​(java.io.File file)
                                  throws java.io.IOException
        This method is used so that a buffer can be represented as a stream of bytes. This provides a quick means to access the data that has been written to the buffer. It wraps the buffer within an input stream so that it can be read directly.
        Parameters:
        file - this is the file used to create the input stream
        Returns:
        a stream that can be used to read the buffered bytes
        Throws:
        java.io.IOException
      • clear

        public void clear()
                   throws java.io.IOException
        This will clear all data from the buffer. This simply sets the count to be zero, it will not clear the memory occupied by the instance as the internal buffer will remain. This allows the memory occupied to be reused as many times as is required.
        Specified by:
        clear in interface Buffer
        Throws:
        java.io.IOException
      • close

        public void close()
                   throws java.io.IOException
        This method is used to ensure the buffer can be closed. Once the buffer is closed it is an immutable collection of bytes and can not longer be modified. This ensures that it can be passed by value without the risk of modification of the bytes.
        Specified by:
        close in interface Buffer
        Throws:
        java.io.IOException
      • length

        public long length()
        This is used to provide the number of bytes that have been written to the buffer. This increases as bytes are appended to the buffer. if the buffer is cleared this resets to zero.
        Specified by:
        length in interface Buffer
        Returns:
        this returns the number of bytes within the buffer