@Override
    public void writeByteRange(boolean utf8String, int fieldNumber, byte[] value,
            int offset, int length, boolean repeated) throws IOException
    {
        final byte[] bytes = new byte[length];
        System.arraycopy(value, offset, bytes, 0, length);
        writeByteArray(fieldNumber, bytes, repeated);
    }
Returns the data written to this output as a single byte array.
protostuff-core/src/test/java/io/protostuff/DeferredOutput.java