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<!DOCTYPE html>
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<title>Exercise 34: Dynamic Array</title>
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<h1 class="title">Exercise 34: Dynamic Array</h1>
<p>This is an array that grows on its own and has most of the same features as a
linked list. It will usually take up less space, run faster, and has other
beneficial properties. This exercise will cover a few of the disadvantages
like very slow removal from the front, with a solution (just do it at the end).</p>
<p>A dynamic array is simply an array of <tt class="docutils literal">void **</tt> pointers that is pre-allocated
in one shot and that point at the data. In the linked list you had a full struct
that stored the <tt class="docutils literal">void *value</tt> pointer, but in a dynamic array there's just
a single array with all of them. This means you don't need any other pointers
for next and previous records since you can just index into it directly.</p>
<p>To start, I'll give you the header file you should type up for the implementation:</p>
<div class="highlight"><pre><a name="code--liblcthw--src--lcthw--darray.h-pyg.html-1"></a><span class="cp">#ifndef _DArray_h</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-2"></a><span class="cp">#define _DArray_h</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-3"></a><span class="cp">#include <stdlib.h></span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-4"></a><span class="cp">#include <assert.h></span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-5"></a><span class="cp">#include <lcthw/dbg.h></span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-6"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-7"></a><span class="k">typedef</span> <span class="k">struct</span> <span class="n">DArray</span> <span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-8"></a> <span class="kt">int</span> <span class="n">end</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-9"></a> <span class="kt">int</span> <span class="n">max</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-10"></a> <span class="kt">size_t</span> <span class="n">element_size</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-11"></a> <span class="kt">size_t</span> <span class="n">expand_rate</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-12"></a> <span class="kt">void</span> <span class="o">**</span><span class="n">contents</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-13"></a><span class="p">}</span> <span class="n">DArray</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-14"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-15"></a><span class="n">DArray</span> <span class="o">*</span><span class="nf">DArray_create</span><span class="p">(</span><span class="kt">size_t</span> <span class="n">element_size</span><span class="p">,</span> <span class="kt">size_t</span> <span class="n">initial_max</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-16"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-17"></a><span class="kt">void</span> <span class="nf">DArray_destroy</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-18"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-19"></a><span class="kt">void</span> <span class="nf">DArray_clear</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-20"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-21"></a><span class="kt">int</span> <span class="nf">DArray_expand</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-22"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-23"></a><span class="kt">int</span> <span class="nf">DArray_contract</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-24"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-25"></a><span class="kt">int</span> <span class="nf">DArray_push</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="kt">void</span> <span class="o">*</span><span class="n">el</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-26"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-27"></a><span class="kt">void</span> <span class="o">*</span><span class="nf">DArray_pop</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-28"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-29"></a><span class="kt">void</span> <span class="nf">DArray_clear_destroy</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-30"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-31"></a><span class="cp">#define DArray_last(A) ((A)->contents[(A)->end - 1])</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-32"></a><span class="cp">#define DArray_first(A) ((A)->contents[0])</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-33"></a><span class="cp">#define DArray_end(A) ((A)->end)</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-34"></a><span class="cp">#define DArray_count(A) DArray_end(A)</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-35"></a><span class="cp">#define DArray_max(A) ((A)->max)</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-36"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-37"></a><span class="cp">#define DEFAULT_EXPAND_RATE 300</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-38"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-39"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-40"></a><span class="k">static</span> <span class="kr">inline</span> <span class="kt">void</span> <span class="nf">DArray_set</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="kt">int</span> <span class="n">i</span><span class="p">,</span> <span class="kt">void</span> <span class="o">*</span><span class="n">el</span><span class="p">)</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-41"></a><span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-42"></a> <span class="n">check</span><span class="p">(</span><span class="n">i</span> <span class="o"><</span> <span class="n">array</span><span class="o">-></span><span class="n">max</span><span class="p">,</span> <span class="s">"darray attempt to set past max"</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-43"></a> <span class="k">if</span><span class="p">(</span><span class="n">i</span> <span class="o">></span> <span class="n">array</span><span class="o">-></span><span class="n">end</span><span class="p">)</span> <span class="n">array</span><span class="o">-></span><span class="n">end</span> <span class="o">=</span> <span class="n">i</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-44"></a> <span class="n">array</span><span class="o">-></span><span class="n">contents</span><span class="p">[</span><span class="n">i</span><span class="p">]</span> <span class="o">=</span> <span class="n">el</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-45"></a><span class="nl">error:</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-46"></a> <span class="k">return</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-47"></a><span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-48"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-49"></a><span class="k">static</span> <span class="kr">inline</span> <span class="kt">void</span> <span class="o">*</span><span class="nf">DArray_get</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="kt">int</span> <span class="n">i</span><span class="p">)</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-50"></a><span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-51"></a> <span class="n">check</span><span class="p">(</span><span class="n">i</span> <span class="o"><</span> <span class="n">array</span><span class="o">-></span><span class="n">max</span><span class="p">,</span> <span class="s">"darray attempt to get past max"</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-52"></a> <span class="k">return</span> <span class="n">array</span><span class="o">-></span><span class="n">contents</span><span class="p">[</span><span class="n">i</span><span class="p">];</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-53"></a><span class="nl">error:</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-54"></a> <span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-55"></a><span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-56"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-57"></a><span class="k">static</span> <span class="kr">inline</span> <span class="kt">void</span> <span class="o">*</span><span class="nf">DArray_remove</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="kt">int</span> <span class="n">i</span><span class="p">)</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-58"></a><span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-59"></a> <span class="kt">void</span> <span class="o">*</span><span class="n">el</span> <span class="o">=</span> <span class="n">array</span><span class="o">-></span><span class="n">contents</span><span class="p">[</span><span class="n">i</span><span class="p">];</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-60"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-61"></a> <span class="n">array</span><span class="o">-></span><span class="n">contents</span><span class="p">[</span><span class="n">i</span><span class="p">]</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-62"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-63"></a> <span class="k">return</span> <span class="n">el</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-64"></a><span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-65"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-66"></a><span class="k">static</span> <span class="kr">inline</span> <span class="kt">void</span> <span class="o">*</span><span class="nf">DArray_new</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">)</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-67"></a><span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-68"></a> <span class="n">check</span><span class="p">(</span><span class="n">array</span><span class="o">-></span><span class="n">element_size</span> <span class="o">></span> <span class="mi">0</span><span class="p">,</span> <span class="s">"Can't use DArray_new on 0 size darrays."</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-69"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-70"></a> <span class="k">return</span> <span class="n">calloc</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="n">array</span><span class="o">-></span><span class="n">element_size</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-71"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-72"></a><span class="nl">error:</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-73"></a> <span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-74"></a><span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-75"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-76"></a><span class="cp">#define DArray_free(E) free((E))</span>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-77"></a>
<a name="code--liblcthw--src--lcthw--darray.h-pyg.html-78"></a><span class="cp">#endif</span>
</pre></div><p>This header file is showing you a new technique where I put <tt class="docutils literal">static inline</tt>
functions right in the header. These function definitions will work similar to
the <tt class="docutils literal">#define</tt> macros you've been making, but they're cleaner and easier to
write. If you need to create a block of code for a macro and you don't need
code generation, then use a <tt class="docutils literal">static inline</tt> function.</p>
<p>Compare this technique to the <tt class="docutils literal">LIST_FOREACH</tt> that <em>generates</em> a
proper for-loop for a list. This would be impossible to do with a <tt class="docutils literal">static inline</tt> function because it actually has to generate the inner block of code for
the loop. The only way to do that is with a callback function, but that's not
as fast and is harder to use.</p>
<p>I'll then change things up and have you create the unit test for <tt class="docutils literal">DArray</tt>:</p>
<div class="highlight"><pre><a name="code--liblcthw--tests--darray_tests.c-pyg.html-1"></a><span class="cp">#include "minunit.h"</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-2"></a><span class="cp">#include <lcthw/darray.h></span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-3"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-4"></a><span class="k">static</span> <span class="n">DArray</span> <span class="o">*</span><span class="n">array</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-5"></a><span class="k">static</span> <span class="kt">int</span> <span class="o">*</span><span class="n">val1</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-6"></a><span class="k">static</span> <span class="kt">int</span> <span class="o">*</span><span class="n">val2</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-7"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-8"></a><span class="kt">char</span> <span class="o">*</span><span class="nf">test_create</span><span class="p">()</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-9"></a><span class="p">{</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-10"></a> <span class="n">array</span> <span class="o">=</span> <span class="n">DArray_create</span><span class="p">(</span><span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">),</span> <span class="mi">100</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-11"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="n">array</span> <span class="o">!=</span> <span class="nb">NULL</span><span class="p">,</span> <span class="s">"DArray_create failed."</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-12"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="n">array</span><span class="o">-></span><span class="n">contents</span> <span class="o">!=</span> <span class="nb">NULL</span><span class="p">,</span> <span class="s">"contents are wrong in darray"</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-13"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="n">array</span><span class="o">-></span><span class="n">end</span> <span class="o">==</span> <span class="mi">0</span><span class="p">,</span> <span class="s">"end isn't at the right spot"</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-14"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="n">array</span><span class="o">-></span><span class="n">element_size</span> <span class="o">==</span> <span class="k">sizeof</span><span class="p">(</span><span class="kt">int</span><span class="p">),</span> <span class="s">"element size is wrong."</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-15"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="n">array</span><span class="o">-></span><span class="n">max</span> <span class="o">==</span> <span class="mi">100</span><span class="p">,</span> <span class="s">"wrong max length on initial size"</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-16"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-17"></a> <span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-18"></a><span class="p">}</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-19"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-20"></a><span class="kt">char</span> <span class="o">*</span><span class="nf">test_destroy</span><span class="p">()</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-21"></a><span class="p">{</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-22"></a> <span class="n">DArray_destroy</span><span class="p">(</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-23"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-24"></a> <span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-25"></a><span class="p">}</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-26"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-27"></a><span class="kt">char</span> <span class="o">*</span><span class="nf">test_new</span><span class="p">()</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-28"></a><span class="p">{</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-29"></a> <span class="n">val1</span> <span class="o">=</span> <span class="n">DArray_new</span><span class="p">(</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-30"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="n">val1</span> <span class="o">!=</span> <span class="nb">NULL</span><span class="p">,</span> <span class="s">"failed to make a new element"</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-31"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-32"></a> <span class="n">val2</span> <span class="o">=</span> <span class="n">DArray_new</span><span class="p">(</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-33"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="n">val2</span> <span class="o">!=</span> <span class="nb">NULL</span><span class="p">,</span> <span class="s">"failed to make a new element"</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-34"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-35"></a> <span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-36"></a><span class="p">}</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-37"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-38"></a><span class="kt">char</span> <span class="o">*</span><span class="nf">test_set</span><span class="p">()</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-39"></a><span class="p">{</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-40"></a> <span class="n">DArray_set</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="n">val1</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-41"></a> <span class="n">DArray_set</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="n">val2</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-42"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-43"></a> <span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-44"></a><span class="p">}</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-45"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-46"></a><span class="kt">char</span> <span class="o">*</span><span class="nf">test_get</span><span class="p">()</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-47"></a><span class="p">{</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-48"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="n">DArray_get</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span> <span class="o">==</span> <span class="n">val1</span><span class="p">,</span> <span class="s">"Wrong first value."</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-49"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="n">DArray_get</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span> <span class="o">==</span> <span class="n">val2</span><span class="p">,</span> <span class="s">"Wrong second value."</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-50"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-51"></a> <span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-52"></a><span class="p">}</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-53"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-54"></a><span class="kt">char</span> <span class="o">*</span><span class="nf">test_remove</span><span class="p">()</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-55"></a><span class="p">{</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-56"></a> <span class="kt">int</span> <span class="o">*</span><span class="n">val_check</span> <span class="o">=</span> <span class="n">DArray_remove</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="mi">0</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-57"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="n">val_check</span> <span class="o">!=</span> <span class="nb">NULL</span><span class="p">,</span> <span class="s">"Should not get NULL."</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-58"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="o">*</span><span class="n">val_check</span> <span class="o">==</span> <span class="o">*</span><span class="n">val1</span><span class="p">,</span> <span class="s">"Should get the first value."</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-59"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="n">DArray_get</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span> <span class="o">==</span> <span class="nb">NULL</span><span class="p">,</span> <span class="s">"Should be gone."</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-60"></a> <span class="n">DArray_free</span><span class="p">(</span><span class="n">val_check</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-61"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-62"></a> <span class="n">val_check</span> <span class="o">=</span> <span class="n">DArray_remove</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-63"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="n">val_check</span> <span class="o">!=</span> <span class="nb">NULL</span><span class="p">,</span> <span class="s">"Should not get NULL."</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-64"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="o">*</span><span class="n">val_check</span> <span class="o">==</span> <span class="o">*</span><span class="n">val2</span><span class="p">,</span> <span class="s">"Should get the first value."</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-65"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="n">DArray_get</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span> <span class="o">==</span> <span class="nb">NULL</span><span class="p">,</span> <span class="s">"Should be gone."</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-66"></a> <span class="n">DArray_free</span><span class="p">(</span><span class="n">val_check</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-67"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-68"></a> <span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-69"></a><span class="p">}</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-70"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-71"></a><span class="kt">char</span> <span class="o">*</span><span class="nf">test_expand_contract</span><span class="p">()</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-72"></a><span class="p">{</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-73"></a> <span class="kt">int</span> <span class="n">old_max</span> <span class="o">=</span> <span class="n">array</span><span class="o">-></span><span class="n">max</span><span class="p">;</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-74"></a> <span class="n">DArray_expand</span><span class="p">(</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-75"></a> <span class="n">mu_assert</span><span class="p">((</span><span class="kt">unsigned</span> <span class="kt">int</span><span class="p">)</span><span class="n">array</span><span class="o">-></span><span class="n">max</span> <span class="o">==</span> <span class="n">old_max</span> <span class="o">+</span> <span class="n">array</span><span class="o">-></span><span class="n">expand_rate</span><span class="p">,</span> <span class="s">"Wrong size after expand."</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-76"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-77"></a> <span class="n">DArray_contract</span><span class="p">(</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-78"></a> <span class="n">mu_assert</span><span class="p">((</span><span class="kt">unsigned</span> <span class="kt">int</span><span class="p">)</span><span class="n">array</span><span class="o">-></span><span class="n">max</span> <span class="o">==</span> <span class="n">array</span><span class="o">-></span><span class="n">expand_rate</span> <span class="o">+</span> <span class="mi">1</span><span class="p">,</span> <span class="s">"Should stay at the expand_rate at least."</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-79"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-80"></a> <span class="n">DArray_contract</span><span class="p">(</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-81"></a> <span class="n">mu_assert</span><span class="p">((</span><span class="kt">unsigned</span> <span class="kt">int</span><span class="p">)</span><span class="n">array</span><span class="o">-></span><span class="n">max</span> <span class="o">==</span> <span class="n">array</span><span class="o">-></span><span class="n">expand_rate</span> <span class="o">+</span> <span class="mi">1</span><span class="p">,</span> <span class="s">"Should stay at the expand_rate at least."</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-82"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-83"></a> <span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-84"></a><span class="p">}</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-85"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-86"></a><span class="kt">char</span> <span class="o">*</span><span class="nf">test_push_pop</span><span class="p">()</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-87"></a><span class="p">{</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-88"></a> <span class="kt">int</span> <span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-89"></a> <span class="k">for</span><span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="mi">1000</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-90"></a> <span class="kt">int</span> <span class="o">*</span><span class="n">val</span> <span class="o">=</span> <span class="n">DArray_new</span><span class="p">(</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-91"></a> <span class="o">*</span><span class="n">val</span> <span class="o">=</span> <span class="n">i</span> <span class="o">*</span> <span class="mi">333</span><span class="p">;</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-92"></a> <span class="n">DArray_push</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="n">val</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-93"></a> <span class="p">}</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-94"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-95"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="n">array</span><span class="o">-></span><span class="n">max</span> <span class="o">==</span> <span class="mi">1201</span><span class="p">,</span> <span class="s">"Wrong max size."</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-96"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-97"></a> <span class="k">for</span><span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">999</span><span class="p">;</span> <span class="n">i</span> <span class="o">>=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span><span class="o">--</span><span class="p">)</span> <span class="p">{</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-98"></a> <span class="kt">int</span> <span class="o">*</span><span class="n">val</span> <span class="o">=</span> <span class="n">DArray_pop</span><span class="p">(</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-99"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="n">val</span> <span class="o">!=</span> <span class="nb">NULL</span><span class="p">,</span> <span class="s">"Shouldn't get a NULL."</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-100"></a> <span class="n">mu_assert</span><span class="p">(</span><span class="o">*</span><span class="n">val</span> <span class="o">==</span> <span class="n">i</span> <span class="o">*</span> <span class="mi">333</span><span class="p">,</span> <span class="s">"Wrong value."</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-101"></a> <span class="n">DArray_free</span><span class="p">(</span><span class="n">val</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-102"></a> <span class="p">}</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-103"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-104"></a> <span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-105"></a><span class="p">}</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-106"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-107"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-108"></a><span class="kt">char</span> <span class="o">*</span> <span class="nf">all_tests</span><span class="p">()</span> <span class="p">{</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-109"></a> <span class="n">mu_suite_start</span><span class="p">();</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-110"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-111"></a> <span class="n">mu_run_test</span><span class="p">(</span><span class="n">test_create</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-112"></a> <span class="n">mu_run_test</span><span class="p">(</span><span class="n">test_new</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-113"></a> <span class="n">mu_run_test</span><span class="p">(</span><span class="n">test_set</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-114"></a> <span class="n">mu_run_test</span><span class="p">(</span><span class="n">test_get</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-115"></a> <span class="n">mu_run_test</span><span class="p">(</span><span class="n">test_remove</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-116"></a> <span class="n">mu_run_test</span><span class="p">(</span><span class="n">test_expand_contract</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-117"></a> <span class="n">mu_run_test</span><span class="p">(</span><span class="n">test_push_pop</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-118"></a> <span class="n">mu_run_test</span><span class="p">(</span><span class="n">test_destroy</span><span class="p">);</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-119"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-120"></a> <span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-121"></a><span class="p">}</span>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-122"></a>
<a name="code--liblcthw--tests--darray_tests.c-pyg.html-123"></a><span class="n">RUN_TESTS</span><span class="p">(</span><span class="n">all_tests</span><span class="p">);</span>
</pre></div><p>This shows you how all of the operations are used, which then makes implementing
the <tt class="docutils literal">DArray</tt> much easier:</p>
<div class="highlight"><pre><a name="code--liblcthw--src--lcthw--darray.c-pyg.html-1"></a><span class="cp">#include <lcthw/darray.h></span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-2"></a><span class="cp">#include <assert.h></span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-3"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-4"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-5"></a><span class="n">DArray</span> <span class="o">*</span><span class="nf">DArray_create</span><span class="p">(</span><span class="kt">size_t</span> <span class="n">element_size</span><span class="p">,</span> <span class="kt">size_t</span> <span class="n">initial_max</span><span class="p">)</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-6"></a><span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-7"></a> <span class="n">DArray</span> <span class="o">*</span><span class="n">array</span> <span class="o">=</span> <span class="n">malloc</span><span class="p">(</span><span class="k">sizeof</span><span class="p">(</span><span class="n">DArray</span><span class="p">));</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-8"></a> <span class="n">check_mem</span><span class="p">(</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-9"></a> <span class="n">array</span><span class="o">-></span><span class="n">max</span> <span class="o">=</span> <span class="n">initial_max</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-10"></a> <span class="n">check</span><span class="p">(</span><span class="n">array</span><span class="o">-></span><span class="n">max</span> <span class="o">></span> <span class="mi">0</span><span class="p">,</span> <span class="s">"You must set an initial_max > 0."</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-11"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-12"></a> <span class="n">array</span><span class="o">-></span><span class="n">contents</span> <span class="o">=</span> <span class="n">calloc</span><span class="p">(</span><span class="n">initial_max</span><span class="p">,</span> <span class="k">sizeof</span><span class="p">(</span><span class="kt">void</span> <span class="o">*</span><span class="p">));</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-13"></a> <span class="n">check_mem</span><span class="p">(</span><span class="n">array</span><span class="o">-></span><span class="n">contents</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-14"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-15"></a> <span class="n">array</span><span class="o">-></span><span class="n">end</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-16"></a> <span class="n">array</span><span class="o">-></span><span class="n">element_size</span> <span class="o">=</span> <span class="n">element_size</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-17"></a> <span class="n">array</span><span class="o">-></span><span class="n">expand_rate</span> <span class="o">=</span> <span class="n">DEFAULT_EXPAND_RATE</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-18"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-19"></a> <span class="k">return</span> <span class="n">array</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-20"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-21"></a><span class="nl">error:</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-22"></a> <span class="k">if</span><span class="p">(</span><span class="n">array</span><span class="p">)</span> <span class="n">free</span><span class="p">(</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-23"></a> <span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-24"></a><span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-25"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-26"></a><span class="kt">void</span> <span class="nf">DArray_clear</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">)</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-27"></a><span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-28"></a> <span class="kt">int</span> <span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-29"></a> <span class="k">if</span><span class="p">(</span><span class="n">array</span><span class="o">-></span><span class="n">element_size</span> <span class="o">></span> <span class="mi">0</span><span class="p">)</span> <span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-30"></a> <span class="k">for</span><span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">array</span><span class="o">-></span><span class="n">max</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-31"></a> <span class="k">if</span><span class="p">(</span><span class="n">array</span><span class="o">-></span><span class="n">contents</span><span class="p">[</span><span class="n">i</span><span class="p">]</span> <span class="o">!=</span> <span class="nb">NULL</span><span class="p">)</span> <span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-32"></a> <span class="n">free</span><span class="p">(</span><span class="n">array</span><span class="o">-></span><span class="n">contents</span><span class="p">[</span><span class="n">i</span><span class="p">]);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-33"></a> <span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-34"></a> <span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-35"></a> <span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-36"></a><span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-37"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-38"></a><span class="k">static</span> <span class="kr">inline</span> <span class="kt">int</span> <span class="nf">DArray_resize</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="kt">size_t</span> <span class="n">newsize</span><span class="p">)</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-39"></a><span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-40"></a> <span class="n">array</span><span class="o">-></span><span class="n">max</span> <span class="o">=</span> <span class="n">newsize</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-41"></a> <span class="n">check</span><span class="p">(</span><span class="n">array</span><span class="o">-></span><span class="n">max</span> <span class="o">></span> <span class="mi">0</span><span class="p">,</span> <span class="s">"The newsize must be > 0."</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-42"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-43"></a> <span class="kt">void</span> <span class="o">*</span><span class="n">contents</span> <span class="o">=</span> <span class="n">realloc</span><span class="p">(</span><span class="n">array</span><span class="o">-></span><span class="n">contents</span><span class="p">,</span> <span class="n">array</span><span class="o">-></span><span class="n">max</span> <span class="o">*</span> <span class="k">sizeof</span><span class="p">(</span><span class="kt">void</span> <span class="o">*</span><span class="p">));</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-44"></a> <span class="c1">// check contents and assume realloc doesn't harm the original on error</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-45"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-46"></a> <span class="n">check_mem</span><span class="p">(</span><span class="n">contents</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-47"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-48"></a> <span class="n">array</span><span class="o">-></span><span class="n">contents</span> <span class="o">=</span> <span class="n">contents</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-49"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-50"></a> <span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-51"></a><span class="nl">error:</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-52"></a> <span class="k">return</span> <span class="o">-</span><span class="mi">1</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-53"></a><span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-54"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-55"></a><span class="kt">int</span> <span class="nf">DArray_expand</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">)</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-56"></a><span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-57"></a> <span class="kt">size_t</span> <span class="n">old_max</span> <span class="o">=</span> <span class="n">array</span><span class="o">-></span><span class="n">max</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-58"></a> <span class="n">check</span><span class="p">(</span><span class="n">DArray_resize</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="n">array</span><span class="o">-></span><span class="n">max</span> <span class="o">+</span> <span class="n">array</span><span class="o">-></span><span class="n">expand_rate</span><span class="p">)</span> <span class="o">==</span> <span class="mi">0</span><span class="p">,</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-59"></a> <span class="s">"Failed to expand array to new size: %d"</span><span class="p">,</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-60"></a> <span class="n">array</span><span class="o">-></span><span class="n">max</span> <span class="o">+</span> <span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="n">array</span><span class="o">-></span><span class="n">expand_rate</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-61"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-62"></a> <span class="n">memset</span><span class="p">(</span><span class="n">array</span><span class="o">-></span><span class="n">contents</span> <span class="o">+</span> <span class="n">old_max</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="n">array</span><span class="o">-></span><span class="n">expand_rate</span> <span class="o">+</span> <span class="mi">1</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-63"></a> <span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-64"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-65"></a><span class="nl">error:</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-66"></a> <span class="k">return</span> <span class="o">-</span><span class="mi">1</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-67"></a><span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-68"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-69"></a><span class="kt">int</span> <span class="nf">DArray_contract</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">)</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-70"></a><span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-71"></a> <span class="kt">int</span> <span class="n">new_size</span> <span class="o">=</span> <span class="n">array</span><span class="o">-></span><span class="n">end</span> <span class="o"><</span> <span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="n">array</span><span class="o">-></span><span class="n">expand_rate</span> <span class="o">?</span> <span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="n">array</span><span class="o">-></span><span class="n">expand_rate</span> <span class="o">:</span> <span class="n">array</span><span class="o">-></span><span class="n">end</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-72"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-73"></a> <span class="k">return</span> <span class="n">DArray_resize</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="n">new_size</span> <span class="o">+</span> <span class="mi">1</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-74"></a><span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-75"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-76"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-77"></a><span class="kt">void</span> <span class="nf">DArray_destroy</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">)</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-78"></a><span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-79"></a> <span class="k">if</span><span class="p">(</span><span class="n">array</span><span class="p">)</span> <span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-80"></a> <span class="k">if</span><span class="p">(</span><span class="n">array</span><span class="o">-></span><span class="n">contents</span><span class="p">)</span> <span class="n">free</span><span class="p">(</span><span class="n">array</span><span class="o">-></span><span class="n">contents</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-81"></a> <span class="n">free</span><span class="p">(</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-82"></a> <span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-83"></a><span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-84"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-85"></a><span class="kt">void</span> <span class="nf">DArray_clear_destroy</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">)</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-86"></a><span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-87"></a> <span class="n">DArray_clear</span><span class="p">(</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-88"></a> <span class="n">DArray_destroy</span><span class="p">(</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-89"></a><span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-90"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-91"></a><span class="kt">int</span> <span class="nf">DArray_push</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="kt">void</span> <span class="o">*</span><span class="n">el</span><span class="p">)</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-92"></a><span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-93"></a> <span class="n">array</span><span class="o">-></span><span class="n">contents</span><span class="p">[</span><span class="n">array</span><span class="o">-></span><span class="n">end</span><span class="p">]</span> <span class="o">=</span> <span class="n">el</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-94"></a> <span class="n">array</span><span class="o">-></span><span class="n">end</span><span class="o">++</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-95"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-96"></a> <span class="k">if</span><span class="p">(</span><span class="n">DArray_end</span><span class="p">(</span><span class="n">array</span><span class="p">)</span> <span class="o">>=</span> <span class="n">DArray_max</span><span class="p">(</span><span class="n">array</span><span class="p">))</span> <span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-97"></a> <span class="k">return</span> <span class="n">DArray_expand</span><span class="p">(</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-98"></a> <span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-99"></a> <span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-100"></a> <span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-101"></a><span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-102"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-103"></a><span class="kt">void</span> <span class="o">*</span><span class="nf">DArray_pop</span><span class="p">(</span><span class="n">DArray</span> <span class="o">*</span><span class="n">array</span><span class="p">)</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-104"></a><span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-105"></a> <span class="n">check</span><span class="p">(</span><span class="n">array</span><span class="o">-></span><span class="n">end</span> <span class="o">-</span> <span class="mi">1</span> <span class="o">>=</span> <span class="mi">0</span><span class="p">,</span> <span class="s">"Attempt to pop from empty array."</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-106"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-107"></a> <span class="kt">void</span> <span class="o">*</span><span class="n">el</span> <span class="o">=</span> <span class="n">DArray_remove</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="n">array</span><span class="o">-></span><span class="n">end</span> <span class="o">-</span> <span class="mi">1</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-108"></a> <span class="n">array</span><span class="o">-></span><span class="n">end</span><span class="o">--</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-109"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-110"></a> <span class="k">if</span><span class="p">(</span><span class="n">DArray_end</span><span class="p">(</span><span class="n">array</span><span class="p">)</span> <span class="o">></span> <span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="n">array</span><span class="o">-></span><span class="n">expand_rate</span> <span class="o">&&</span> <span class="n">DArray_end</span><span class="p">(</span><span class="n">array</span><span class="p">)</span> <span class="o">%</span> <span class="n">array</span><span class="o">-></span><span class="n">expand_rate</span><span class="p">)</span> <span class="p">{</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-111"></a> <span class="n">DArray_contract</span><span class="p">(</span><span class="n">array</span><span class="p">);</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-112"></a> <span class="p">}</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-113"></a>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-114"></a> <span class="k">return</span> <span class="n">el</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-115"></a><span class="nl">error:</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-116"></a> <span class="k">return</span> <span class="nb">NULL</span><span class="p">;</span>
<a name="code--liblcthw--src--lcthw--darray.c-pyg.html-117"></a><span class="p">}</span>
</pre></div><p>This shows you another way to tackle complex code. Instead of diving right
into the <tt class="docutils literal">.c</tt> implementation, look at the header file, then read the
unit test. This gives you an "abstract to concrete" understanding how the
pieces work together and making it easier to remember.</p>
<div class="section" id="advantages-and-disadvantages">
<h1>Advantages And Disadvantages</h1>
<p>A <tt class="docutils literal">DArray</tt> is better when you need to optimize these operations:</p>
<ul class="simple">
<li>Iteration. You can just use a basic for-loop and <tt class="docutils literal">DArray_count</tt>
with <tt class="docutils literal">DArray_get</tt> and you're done. No special macros needed, and
it's faster because you aren't walking pointers.</li>
<li>Indexing. You can use <tt class="docutils literal">DArray_get</tt> and <tt class="docutils literal">DArray_set</tt> to
access any element at random, but with a <tt class="docutils literal">List</tt> you have to go
through N elements to get to N+1.</li>
<li>Destroying. You just free the struct and the <tt class="docutils literal">contents</tt> in
two operations. A <tt class="docutils literal">List</tt> requires a series of <tt class="docutils literal">free</tt> calls
and also walking every element.</li>
<li>Cloning. You can also clone it in just two operations (plus whatever
it's storing) by copying the struct and <tt class="docutils literal">contents</tt>. A list
again requires walking the whole thing and copying every <tt class="docutils literal">ListNode</tt>
plus its value.</li>
<li>Sorting. As you saw, <tt class="docutils literal">List</tt> is horrible if you need to keep the
data sorted. A <tt class="docutils literal">DArray</tt> opens up a whole class of great sorting
algorithms because now you can access elements randomly.</li>
<li>Large Data. If you need to keep around a lot of data, then a <tt class="docutils literal">DArray</tt>
wins since it's base <tt class="docutils literal">contents</tt> takes up less memory than the same
number of <tt class="docutils literal">ListNode</tt> structs.</li>
</ul>
<p>The <tt class="docutils literal">List</tt> however wins on these operations:</p>
<ul class="simple">
<li>Insert and remove on the front (what I called shift). A <tt class="docutils literal">DArray</tt>
needs special treatment to be able to do this efficiently, and usually
has to do some copying.</li>
<li>Splitting or joining. A <tt class="docutils literal">List</tt> can just copy some pointers and
it's done, but with a <tt class="docutils literal">DArray</tt> you have to do copying of the
arrays involved.</li>
<li>Small Data. If you only need to store a few elements, then typically the
storage will be less in a <tt class="docutils literal">List</tt> than a generic <tt class="docutils literal">DArray</tt> because
the <tt class="docutils literal">DArray</tt> needs to expand the backing store to accommodate future
inserts, but a <tt class="docutils literal">List</tt> only makes what it needs.</li>
</ul>
<p>With this, I prefer to use a <tt class="docutils literal">DArray</tt> for most of the things you see
other people use a <tt class="docutils literal">List</tt>. I reserve using <tt class="docutils literal">List</tt> for any
data structure that requires small number of nodes that are inserted and
removed from either end. I'll show you two similar data structures
called a <tt class="docutils literal">Stack</tt> and <tt class="docutils literal">Queue</tt> where this is important.</p>
</div>
<div class="section" id="how-to-improve-it">
<h1>How To Improve It</h1>
<p>As usual, go through each function and operation and add the defensive programming
checks, pre-conditions, invariants, and anything else you can find to make the
implementation more bulletproof.</p>
</div>
<div class="section" id="extra-credit">
<h1>Extra Credit</h1>
<ul class="simple">
<li>Improve the unit tests to cover more of the operations and test that
using a for-loop to iterate works.</li>
<li>Research what it would take to implement bubble sort and merge sort
for DArray, but don't do it yet. I'll be implementing DArray algorithms
next and you'll do this then.</li>
<li>Write some performance tests for common operations and compare them
to the same operations in <tt class="docutils literal">List</tt>. You did some of this, but this
time, write a unit test that repeatedly does the operation in question,
then in the main runner do the timing.</li>
<li>Look at how the <tt class="docutils literal">DArray_expand</tt> is implemented using a constant increase (size + 300).
Typically dynamic arrays are implemented with a multiplicative increase (size * 2), but I've
found this to cost needless memory for no real performance gain. Test my assertion
and see when you'd want a multiplied increase instead of a constant increase.</li>
</ul>
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