Package com.tangosol.io

Class DelegatingWriteBuffer

  • All Implemented Interfaces:
    WriteBuffer
    public final class DelegatingWriteBuffer
extends AbstractWriteBuffer
    A DelegatingWriteBuffer is a WriteBuffer that writes through to an underlying (or "containing") WriteBuffer. Basically, it allows a process that is writing to a WriteBuffer to ask for a "protected" sub-portion of that WriteBuffer to hand to a second process, such that the second process can not affect (or even read from) the WriteBuffer outside of the portion that the first process explicitly designated as viewable and modifiable.

    This implementation is explicitly not thread-safe.

    Author:
    cp 2005.03.24 created

    • Field Detail

      • m_buf

        protected WriteBuffer m_buf
        The WriteBuffer to delegate to; the "containing" WriteBuffer.

      • m_ofStart

        protected int m_ofStart
        Offset into the containing WriteBuffer where this WriteBuffer starts.

      • m_cb

        protected int m_cb
        Length in bytes of this WriteBuffer.

      • m_cbMax

        protected int m_cbMax
        Maximum number of bytes in this WriteBuffer.

    • Constructor Detail

      • DelegatingWriteBuffer

        public DelegatingWriteBuffer​(WriteBuffer buf,
                             int of,
                             int cb)
        Construct a DelegatingWriteBuffer that will delegate to the containing WriteBuffer.
        Parameters:
        buf - the containing WriteBuffer
        of - the offset within the containing WriteBuffer that this WriteBuffer is starting at
        cb - the maximum capacity for this WriteBuffer

    • Method Detail

      • write

        public void write​(int ofDest,
                  byte b)
        Store the specified byte at the specified offset within the buffer.

        For purposes of side-effects and potential exceptions, this method is functionally equivalent to the following code: 

        
 byte[] abSrc = new byte[1];
 abSrc[0] = b;
 write(ofDest, abSrc, 0, abSrc.length);

        Specified by:
        write in interface WriteBuffer
        Specified by:
        write in class AbstractWriteBuffer
        Parameters:
        ofDest - the offset within this buffer to store the passed data
        b - the byte to store in this buffer

      • write

        public void write​(int ofDest,
                  ReadBuffer bufSrc,
                  int ofSrc,
                  int cbSrc)
        Store the specified portion of the contents of the specified ReadBuffer at the specified offset within this buffer.

        For purposes of side-effects and potential exceptions, this method is functionally equivalent to the following code: 

        
 byte[] abSrc = bufSrc.toByteArray(ofSrc, cbSrc);
 write(ofDest, abSrc, 0, abSrc.length);

        Specified by:
        write in interface WriteBuffer
        Overrides:
        write in class AbstractWriteBuffer
        Parameters:
        ofDest - the offset within this buffer to store the passed data
        bufSrc - the array of bytes to store in this buffer
        ofSrc - the offset within the passed ReadBuffer to copy from
        cbSrc - the number of bytes to copy from the passed ReadBuffer

      • write

        public void write​(int ofDest,
                  InputStreaming stream)
           throws IOException
        Store the remaining contents of the specified InputStreaming object at the specified offset within this buffer.

        For purposes of side-effects and potential exceptions, this method is functionally similar to the following code: 

        
 ByteArrayOutputStream streamOut = new ByteArrayOutputStream();
 int b;
 while ((b = stream.read()) >= 0)
     {
     streamOut.write(b);
     }
 byte[] abSrc = streamOut.toByteArray();
 write(ofDest, abSrc, 0, abSrc.length);

        Specified by:
        write in interface WriteBuffer
        Overrides:
        write in class AbstractWriteBuffer
        Parameters:
        ofDest - the offset within this buffer to store the passed data
        stream - the stream of bytes to read and store in this buffer
        Throws:
        IOException - if an IOException occurs reading from the passed stream

      • write

        public void write​(int ofDest,
                  InputStreaming stream,
                  int cbSrc)
           throws IOException
        Store the specified number of bytes from the specified InputStreaming object at the specified offset within this buffer.

        For purposes of side-effects and potential exceptions, this method is functionally similar to the following code: 

        
 DataInputStream streamData = new DataInputStream(
         new WrapperInputStream(stream));
 byte[] abSrc = new byte[cbSrc];
 streamData.readFully(abSrc);
 write(ofDest, abSrc, 0, abSrc.length);

        Specified by:
        write in interface WriteBuffer
        Overrides:
        write in class AbstractWriteBuffer
        Parameters:
        ofDest - the offset within this buffer to store the passed data
        stream - the stream of bytes to read and store in this buffer
        cbSrc - the exact number of bytes to read from the stream and put in this buffer
        Throws:
        IOException - if an IOException occurs reading from the passed stream

      • length

        public int length()
        Determine the length of the data that is in the buffer. This is the actual number of bytes of data that have been written to the buffer, not the capacity of the buffer.
        Specified by:
        length in interface WriteBuffer
        Specified by:
        length in class AbstractWriteBuffer
        Returns:
        the number of bytes of data represented by this WriteBuffer

      • retain

        public void retain​(int of,
                   int cb)
        Starting with the byte at offset of, retain cb bytes in this WriteBuffer, such that the byte at offset of is shifted to offset 0, the byte at offset of + 1 is shifted to offset 1, and so on up to the byte at offset of + cb - 1, which is shifted to offset cb - 1. After this method, the length of the buffer as indicated by the WriteBuffer.length() method will be equal to cb.

        Legal values for the offset of the first byte to retain of are (of >= 0 && of <= WriteBuffer.length()). Legal values for the number of bytes to retain cb are (cb >= 0 && cb <= WriteBuffer.length()), such that (of + cb <= WriteBuffer.length()).

        If cb is zero, then this method will have the same effect as clear. If of is zero, then this method will have the effect of truncating the data in the buffer, but no bytes will be shifted within the buffer.

        The effect on the capacity of the buffer is implementation-specific; some implementations are expected to retain the same capacity while others are expected to shrink accordingly.

        Specified by:
        retain in interface WriteBuffer
        Specified by:
        retain in class AbstractWriteBuffer
        Parameters:
        of - the offset of the first byte within the WriteBuffer that will be retained
        cb - the number of bytes to retain

      • clear

        public void clear()
        Set the length of the buffer as indicated by the WriteBuffer.length() method to zero.

        The effect on the capacity of the buffer is implementation-specific; some implementations are expected to retain the same capacity while others are expected to shrink accordingly.

        Specified by:
        clear in interface WriteBuffer
        Overrides:
        clear in class AbstractWriteBuffer

      • getCapacity

        public int getCapacity()
        Determine the number of bytes that the buffer can hold without resizing itself. In other words, a WriteBuffer has getCapacity() - WriteBuffer.length() bytes that can be written to it without overflowing the current underlying buffer allocation. Since the buffer is an abstract concept, the actual mechanism for the underlying buffer is not known, but it could be a Java NIO buffer, or a byte array, etc.

        Note that if the maximum size returned by WriteBuffer.getMaximumCapacity() is greater than the current size returned by this method, then the WriteBuffer will automatically resize itself to allocate more space when the amount of data written to it passes the current size.

        Specified by:
        getCapacity in interface WriteBuffer
        Specified by:
        getCapacity in class AbstractWriteBuffer
        Returns:
        the number of bytes of data that this WriteBuffer can hold without resizing its underlying buffer

      • getMaximumCapacity

        public int getMaximumCapacity()
        Determine the maximum number of bytes that the buffer can hold. If the maximum size is greater than the current size, then the buffer is expected to resize itself as necessary up to the maximum size in order to contain the data given to it.
        Specified by:
        getMaximumCapacity in interface WriteBuffer
        Overrides:
        getMaximumCapacity in class AbstractWriteBuffer
        Returns:
        the maximum number of bytes of data that the WriteBuffer can hold

      • getBufferOutput

        public WriteBuffer.BufferOutput getBufferOutput​(int of)
        Get a BufferOutput object to write data to this buffer starting at a particular offset.

        Note that each call to this method will return a new BufferOutput object, with the possible exception being that a zero-length non-resizing WriteBuffer could always return the same instance (since it is not writable).

        This is functionally equivalent to: 

        
 BufferOutput bufout = getBufferOutput();
 bufout.setOffset(of);
 return bufout;

        Specified by:
        getBufferOutput in interface WriteBuffer
        Overrides:
        getBufferOutput in class AbstractWriteBuffer
        Parameters:
        of - the offset of the first byte of this buffer that the BufferOutput will write to
        Returns:
        a BufferOutput that will write to this buffer

      • getReadBuffer

        public ReadBuffer getReadBuffer()
        Get a ReadBuffer object that is a snapshot of this WriteBuffer's data.

        This method is functionally equivalent to the following code: 

        
 ReadBuffer buf = getUnsafeReadBuffer();
 byte[] ab = buf.toByteArray();
 return new ByteArrayReadBuffer(ab);

        Specified by:
        getReadBuffer in interface WriteBuffer
        Overrides:
        getReadBuffer in class AbstractWriteBuffer
        Returns:
        a ReadBuffer that reflects the point-in-time contents of this WriteBuffer

      • getUnsafeReadBuffer

        public ReadBuffer getUnsafeReadBuffer()
        Get a ReadBuffer object to read data from this buffer. This method is not guaranteed to return a snapshot of this buffer's data, nor is it guaranteed to return a live view of this buffer, which means that subsequent changes to this WriteBuffer may or may not affect the contents and / or the length of the returned ReadBuffer.

        To get a snapshot, use the WriteBuffer.getReadBuffer() method.

        Specified by:
        getUnsafeReadBuffer in interface WriteBuffer
        Specified by:
        getUnsafeReadBuffer in class AbstractWriteBuffer
        Returns:
        a ReadBuffer that reflects the contents of this WriteBuffer but whose behavior is undefined if the WriteBuffer is modified

      • toByteArray

        public byte[] toByteArray()
        Returns a new byte array that holds the complete contents of this WriteBuffer.

        This method is functionally equivalent to the following code: 

        
 return getUnsafeReadBuffer().toByteArray();

        Specified by:
        toByteArray in interface WriteBuffer
        Overrides:
        toByteArray in class AbstractWriteBuffer
        Returns:
        the contents of this WriteBuffer as a byte[]

      • toBinary

        public Binary toBinary()
        Returns a new Binary object that holds the complete contents of this WriteBuffer.

        This method is functionally equivalent to the following code: 

        
 return getUnsafeReadBuffer().toBinary();

        Specified by:
        toBinary in interface WriteBuffer
        Overrides:
        toBinary in class AbstractWriteBuffer
        Returns:
        the contents of this WriteBuffer as a Binary object

      • checkBounds

        protected void checkBounds​(int of,
                           int cb)
        Test an offset and length of data to write to see if it can be written to this buffer.
        Parameters:
        of - offset to write data at
        cb - length in bytes of data

      • updateLength

        protected void updateLength​(int cb)
        Update the length if the passed length is greater than the current buffer length.
        Parameters:
        cb - the possible new length

      • copyStream

        protected int copyStream​(int ofDest,
                         InputStreaming stream,
                         int cbMax)
                  throws IOException
        Store the remaining contents of the specified InputStreaming object at the specified offset within this buffer.
        Overrides:
        copyStream in class AbstractWriteBuffer
        Parameters:
        ofDest - the offset within this buffer to store the passed data
        stream - the stream of bytes to read and store in this buffer
        cbMax - the maximum number of bytes to copy
        Returns:
        the actual number of bytes read from the InputStreaming object and written to this buffer
        Throws:
        IOException - if an IOException occurs reading from the passed stream or if the limit is reached without emptying the source stream