.. _P1:

.. raw:: html

   <script>ODSA.SETTINGS.DISP_MOD_COMP = true;ODSA.SETTINGS.MODULE_NAME = "P1";ODSA.SETTINGS.MODULE_LONG_NAME = "Project 1 Implementation Details";ODSA.SETTINGS.MODULE_CHAPTER = "Week 1"; ODSA.SETTINGS.BUILD_DATE = "2017-01-30 16:09:20"; ODSA.SETTINGS.BUILD_CMAP = false;JSAV_OPTIONS['lang']='en';JSAV_EXERCISE_OPTIONS['code']='java';</script>


.. |--| unicode:: U+2013   .. en dash
.. |---| unicode:: U+2014  .. em dash, trimming surrounding whitespace
   :trim:


.. This file is part of the OpenDSA eTextbook project. See
.. http://algoviz.org/OpenDSA for more details.
.. Copyright (c) 2012-2013 by the OpenDSA Project Contributors, and
.. distributed under an MIT open source license.

.. avmetadata::
   :author: Cliff Shaffer


================================
Project 1 Implementation Details
================================

Design Points
~~~~~~~~~~~~~
   * Normally for container classes we would want to detach the
     implementation from the data type. But since the hash function is
     tied to the key, we will just hard code them to store strings in
     P1.

   * A bad design: Main file (Memman.java) initializes program and
     implements the command processor. Calls hash tables to do main
     operations.

   * A better design:

     * Separate logical activities into separate classes (even if a
       couple of them end up small this time).
     * Main class only initializes the program
     * Syntax is done in separate command processor class
     * Semantics are handled in a separate "world" or "database"
       class. For P1, this has hash tables and memory manager.

Byte manipulation
~~~~~~~~~~~~~~~~~
   * System.arraycopy is useful for copying bytes.
   * String.getBytes will give you a byte array from a string.
   * Be careful about manipulating the 2-byte length field

   ::

     lenb = new byte[2];
     lenbb = ByteBuffer.wrap(lenb);
     int len = 25;
     lenbb.putShort(0, (short)len);     // Put into byte buffer
     int msgLength = lenbb.getShort(0); // Take it back out