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<!DOCTYPE html>
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<div class="atBigSexyLogoImageCont"><div class="atBigSexyLogoImage"></div></div>
<span class="atBigSexyLogoText">Athena</span>
<span class="atBigSexyLogoSubtext">Universal C++11 Data-Interchange System</span>
</div>
<div class="page-content">
<div class="wrapper">
<a id="core" class="anchor-target"></a>
<div class="atSection atCore">
<h1 class="atSectionTitle">Core I/O</h1>
<p>
Athena's primary taskflow involves use of <em>I/O stream objects</em> to convey
data to and from a binary medium. The stream objects are used to iteratively
read bytes from the data source and convert them into usable data-primitives
(i.e. integers, floats, SIMD vectors).
</p>
<h2>I/O Streaming</h2>
<p>
I/O streams have a common virtual interface in Athena, so code that consumes or
emits data is written against <a href="">athena::io::IStreamReader</a> and/or
<a href="">athena::io::IStreamWriter</a>. Projects may use type aliasing to
make Athena's namespacing more convenient for projects that use it heavily.
</p>
<p>Assume the following example data class:</p>
<div class="atIDE">
<h1>DemoRecord.hpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><span class="cp">#include <athena/IStreamReader.hpp></span>
<span class="cp">#include <athena/IStreamWriter.hpp></span>
<span class="k">using</span> <span class="n">ReadStream</span> <span class="o">=</span> <a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">IStreamReader</span></a><span class="p">;</span>
<span class="k">using</span> <span class="n">WriteStream</span> <span class="o">=</span> <a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">IStreamWriter</span></a><span class="p">;</span>
<span class="k">class</span> <span class="nc">MyDataRecord</span>
<span class="p">{</span>
<span class="n">atUint32</span> <span class="n">m_valTest</span><span class="p">;</span>
<span class="n">atUint32</span> <span class="n">m_valU32</span><span class="p">;</span>
<span class="kt">bool</span> <span class="n">m_valBool</span><span class="p">;</span>
<span class="n">std</span><span class="o">::</span><span class="n">string</span> <span class="n">m_string</span><span class="p">;</span>
<span class="k">public</span><span class="o">:</span>
<span class="kt">void</span> <span class="n">readData</span><span class="p">(</span><span class="n">ReadStream</span><span class="o">&</span> <span class="n">stream</span><span class="p">);</span>
<span class="kt">void</span> <span class="n">writeData</span><span class="p">(</span><span class="n">WriteStream</span><span class="o">&</span> <span class="n">stream</span><span class="p">)</span> <span class="k">const</span><span class="p">;</span>
<span class="p">};</span></code></pre></figure>
</div>
<p>The implementations for the I/O methods look like this:</p>
<div class="atIDE">
<div class="atReadLayer">
<h1>ReadDemo.cpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><span class="cp">#include "DemoRecord.hpp"</span>
<span class="kt">void</span> <span class="n">MyDataRecord</span><span class="o">::</span><span class="n">readData</span><span class="p">(</span><span class="n">ReadStream</span><span class="o">&</span> <span class="n">stream</span><span class="p">)</span>
<span class="p">{</span>
<span class="cm">/* Specify stream's default endianness as big for </span>
<span class="cm"> * this demo. All multi-byte numeric accesses will</span>
<span class="cm"> * adhere to this unless the 'Big' or 'Little' </span>
<span class="cm"> * read/write method suffix is used */</span>
<span class="n">stream</span><span class="p">.</span><span class="n">setEndian</span><span class="p">(</span><span class="n">athena</span><span class="o">::</span><span class="n">BigEndian</span><span class="p">);</span>
<span class="cm">/* A default-endian (Big here) read of 4-bytes (32-bits)</span>
<span class="cm"> * tightly packed in the binary stream */</span>
<span class="n">m_valTest</span> <span class="o">=</span> <span class="n">stream</span><span class="p">.</span><span class="n">readUint32</span><span class="p">();</span>
<span class="cm">/* Read 4-bytes and convert to 32-bit system word </span>
<span class="cm"> * (Little to host-endian; overriding the default Big) */</span>
<span class="n">m_valU32</span> <span class="o">=</span> <span class="n">stream</span><span class="p">.</span><a href=""><span class="n">readUint32Little</span></a><span class="p">();</span>
<span class="cm">/* Read 1-byte and convert to bool type */</span>
<span class="n">m_valBool</span> <span class="o">=</span> <span class="n">stream</span><span class="p">.</span><a href=""><span class="n">readBool</span></a><span class="p">();</span>
<span class="cm">/* Read null-terminated C-string (however long it is) </span>
<span class="cm"> * and construct std::string to contain it */</span>
<span class="n">m_string</span> <span class="o">=</span> <span class="n">stream</span><span class="p">.</span><a href=""><span class="n">readString</span></a><span class="p">(</span><span class="o">-</span><span class="mi">1</span><span class="p">);</span>
<span class="p">}</span></code></pre></figure>
</div>
<div class="atWriteLayer">
<h1>WriteDemo.cpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><span class="cp">#include "DemoRecord.hpp"</span>
<span class="kt">void</span> <span class="n">MyDataRecord</span><span class="o">::</span><span class="n">writeData</span><span class="p">(</span><span class="n">WriteStream</span><span class="o">&</span> <span class="n">stream</span><span class="p">)</span> <span class="k">const</span>
<span class="p">{</span>
<span class="cm">/* Specify stream's default endianness as big for </span>
<span class="cm"> * this demo. All multi-byte numeric accesses will</span>
<span class="cm"> * adhere to this unless the 'Big' or 'Little' </span>
<span class="cm"> * read/write method suffix is used */</span>
<span class="n">stream</span><span class="p">.</span><span class="n">setEndian</span><span class="p">(</span><span class="n">athena</span><span class="o">::</span><span class="n">BigEndian</span><span class="p">);</span>
<span class="cm">/* A default-endian (Big here) write of 4-bytes (32-bits)</span>
<span class="cm"> * tightly packed in the binary stream */</span>
<span class="n">stream</span><span class="p">.</span><span class="n">writeUint32</span><span class="p">(</span><span class="n">m_valTest</span><span class="p">);</span>
<span class="cm">/* Emit 4-bytes with binary 32-bit word </span>
<span class="cm"> * (host-endian to Little; overriding the default Big) */</span>
<span class="n">stream</span><span class="p">.</span><a href=""><span class="n">writeUint32Little</span></a><span class="p">(</span><span class="n">m_valU32</span><span class="p">);</span>
<span class="cm">/* Emit 1 byte with value 0 or 1 according to bool input */</span>
<span class="n">stream</span><span class="p">.</span><a href=""><span class="n">writeBool</span></a><span class="p">(</span><span class="n">m_valBool</span><span class="p">);</span>
<span class="cm">/* Write null-terminated C-string from input std::string */</span>
<span class="n">stream</span><span class="p">.</span><a href=""><span class="n">writeString</span></a><span class="p">(</span><span class="n">m_string</span><span class="p">);</span>
<span class="p">}</span></code></pre></figure>
</div>
</div>
<h2>Built-in Stream Backends</h2>
<p>
Athena ships with some useful streaming backends to get common
data interfaces up and going.
</p>
<h3>File Streams (with built-in memory buffering)</h3>
<div class="atIDE">
<div class="atReadLayer">
<h1>ReadDemoFile.cpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><span class="n">MyDataRecord</span> <span class="nf">ConstructAndRead</span><span class="p">(</span><span class="k">const</span> <span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="o">&</span> <span class="n">filePath</span><span class="p">)</span>
<span class="p">{</span>
<a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">FileReader</span></a> <span class="n">reader</span><span class="p">(</span><span class="n">filePath</span><span class="p">);</span>
<span class="n">MyDataRecord</span> <span class="n">dataObject</span><span class="p">;</span>
<span class="n">dataObject</span><span class="p">.</span><span class="n">readData</span><span class="p">(</span><span class="n">reader</span><span class="p">);</span>
<span class="k">return</span> <span class="n">dataObject</span><span class="p">;</span>
<span class="p">}</span></code></pre></figure>
</div>
<div class="atWriteLayer">
<h1>WriteDemoFile.cpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><span class="kt">void</span> <span class="nf">WriteExistingObject</span><span class="p">(</span><span class="k">const</span> <span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="o">&</span> <span class="n">filePath</span><span class="p">,</span> <span class="k">const</span> <span class="n">MyDataRecord</span><span class="o">&</span> <span class="n">obj</span><span class="p">)</span>
<span class="p">{</span>
<a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">FileWriter</span></a> <span class="n">writer</span><span class="p">(</span><span class="n">filePath</span><span class="p">);</span>
<span class="n">obj</span><span class="p">.</span><span class="n">writeData</span><span class="p">(</span><span class="n">writer</span><span class="p">);</span>
<span class="p">}</span></code></pre></figure>
</div>
</div>
<h3>Memory Streams (application-owned buffer)</h3>
<div class="atIDE">
<div class="atReadLayer">
<h1>ReadDemoMem.cpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><span class="n">MyDataRecord</span> <span class="nf">ConstructAndRead</span><span class="p">(</span><span class="kt">void</span><span class="o">*</span> <span class="n">buf</span><span class="p">,</span> <span class="n">atUint64</span> <span class="n">len</span><span class="p">)</span>
<span class="p">{</span>
<a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">MemoryReader</span></a> <span class="n">reader</span><span class="p">(</span><span class="n">buf</span><span class="p">,</span> <span class="n">len</span><span class="p">);</span>
<span class="n">MyDataRecord</span> <span class="n">dataObject</span><span class="p">;</span>
<span class="n">dataObject</span><span class="p">.</span><span class="n">readData</span><span class="p">(</span><span class="n">reader</span><span class="p">);</span>
<span class="k">return</span> <span class="n">dataObject</span><span class="p">;</span>
<span class="p">}</span></code></pre></figure>
</div>
<div class="atWriteLayer">
<h1>WriteDemoMem.cpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><span class="kt">void</span> <span class="nf">WriteExistingObject</span><span class="p">(</span><span class="kt">void</span><span class="o">*</span> <span class="n">buf</span><span class="p">,</span> <span class="n">atUint64</span> <span class="n">len</span><span class="p">,</span> <span class="k">const</span> <span class="n">MyDataRecord</span><span class="o">&</span> <span class="n">obj</span><span class="p">)</span>
<span class="p">{</span>
<a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">MemoryWriter</span></a> <span class="n">writer</span><span class="p">(</span><span class="n">buf</span><span class="p">,</span> <span class="n">len</span><span class="p">);</span>
<span class="n">obj</span><span class="p">.</span><span class="n">writeData</span><span class="p">(</span><span class="n">writer</span><span class="p">);</span>
<span class="p">}</span></code></pre></figure>
</div>
</div>
<h3>Memory Copy Streams (stream-owned copy buffer)</h3>
<div class="atIDE">
<div class="atReadLayer">
<h1>ReadDemoMemCopy.cpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">MemoryCopyReader</span></a> <span class="n">ConstructAndRead</span><span class="p">(</span><span class="kt">void</span><span class="o">*</span> <span class="n">buf</span><span class="p">,</span> <span class="n">atUint64</span> <span class="n">len</span><span class="p">,</span> <span class="n">MyDataRecord</span><span class="o">&</span> <span class="n">obj</span><span class="p">)</span>
<span class="p">{</span>
<span class="cm">/* Constructor performs buffer copy */</span>
<a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">MemoryCopyReader</span></a> <span class="n">reader</span><span class="p">(</span><span class="n">buf</span><span class="p">,</span> <span class="n">len</span><span class="p">);</span>
<span class="n">obj</span><span class="p">.</span><span class="n">readData</span><span class="p">(</span><span class="n">reader</span><span class="p">);</span>
<span class="cm">/* Raw data is still contained within reader for </span>
<span class="cm"> * continued lifetime without being clobbered */</span>
<span class="k">return</span> <span class="n">reader</span><span class="p">;</span>
<span class="p">}</span></code></pre></figure>
</div>
<div class="atWriteLayer">
<h1>WriteDemoMemCopy.cpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">MemoryCopyWriter</span></a> <span class="n">WriteExistingObject</span><span class="p">(</span><span class="kt">void</span><span class="o">*</span> <span class="n">buf</span><span class="p">,</span> <span class="n">atUint64</span> <span class="n">len</span><span class="p">,</span> <span class="k">const</span> <span class="n">MyDataRecord</span><span class="o">&</span> <span class="n">obj</span><span class="p">)</span>
<span class="p">{</span>
<span class="cm">/* Constructor performs buffer copy */</span>
<a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">MemoryCopyWriter</span></a> <span class="n">writer</span><span class="p">(</span><span class="n">buf</span><span class="p">,</span> <span class="n">len</span><span class="p">);</span>
<span class="n">obj</span><span class="p">.</span><span class="n">writeData</span><span class="p">(</span><span class="n">writer</span><span class="p">);</span>
<span class="cm">/* Raw data is still contained within writer for </span>
<span class="cm"> * continued lifetime without being clobbered */</span>
<span class="k">return</span> <span class="n">writer</span><span class="p">;</span>
<span class="p">}</span></code></pre></figure>
</div>
</div>
<h2>Custom Stream Backends</h2>
<p>
The actual data interfacing occurs via raw-byte transfers using
IStreamReader::readUBytesToBuf() and
IStreamWriter::writeUBytes(). Programs needing to interface
with custom data streams do so by inheriting IStreamReader/Writer and
implementing a few methods.
</p>
<div class="atIDE">
<div class="atReadLayer">
<h1>MyReadBackend.hpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><span class="cp">#include <athena/IStreamReader.hpp></span>
<span class="k">class</span> <span class="nc">MyReadBackend</span> <span class="o">:</span> <span class="k">public</span> <a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">IStreamReader</span></a>
<span class="p">{</span>
<span class="n">MyReadSource</span><span class="o">&</span> <span class="n">m_source</span>
<span class="n">atUint64</span> <span class="n">m_curPos</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
<span class="k">public</span><span class="o">:</span>
<span class="n">MyReadBackend</span><span class="p">(</span><span class="n">MyReadSource</span><span class="o">&</span> <span class="n">source</span><span class="p">)</span>
<span class="o">:</span> <span class="n">m_source</span><span class="p">(</span><span class="n">source</span><span class="p">)</span> <span class="p">{}</span>
<span class="cm">/* Some applications (like this demo) may not</span>
<span class="cm"> * require random-access; leave this implementation as a stub */</span>
<span class="kt">void</span> <span class="n">seek</span><span class="p">(</span><span class="n">atInt64</span> <span class="n">pos</span><span class="p">,</span> <span class="n">SeekOrigin</span> <span class="n">origin</span><span class="p">)</span>
<span class="p">{}</span>
<span class="cm">/* Identifies current stream-position (byte index to be read next) */</span>
<span class="n">atUint64</span> <span class="n">position</span><span class="p">()</span> <span class="k">const</span>
<span class="p">{</span>
<span class="k">return</span> <span class="n">m_curPos</span><span class="p">;</span>
<span class="p">}</span>
<span class="cm">/* Identifies source length */</span>
<span class="n">atUint64</span> <span class="n">length</span><span class="p">()</span> <span class="k">const</span>
<span class="p">{</span>
<span class="k">return</span> <span class="n">m_source</span><span class="p">.</span><span class="n">getLength</span><span class="p">();</span>
<span class="p">}</span>
<span class="cm">/* Performs read to provided buffer </span>
<span class="cm"> * (automatically called by data-primitive methods like readUint32) */</span>
<span class="n">atUint64</span> <span class="n">readUBytesToBuf</span><span class="p">(</span><span class="kt">void</span><span class="o">*</span> <span class="n">buf</span><span class="p">,</span> <span class="n">atUint64</span> <span class="n">len</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">atUint64</span> <span class="n">rLen</span> <span class="o">=</span> <span class="n">m_source</span><span class="p">.</span><span class="n">readData</span><span class="p">(</span><span class="n">buf</span><span class="p">,</span> <span class="n">len</span><span class="p">);</span>
<span class="n">m_curPos</span> <span class="o">+=</span> <span class="n">rLen</span><span class="p">;</span>
<span class="k">return</span> <span class="n">rLen</span><span class="p">;</span>
<span class="p">}</span>
<span class="p">};</span></code></pre></figure>
</div>
<div class="atWriteLayer">
<h1>MyWriteBackend.hpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><span class="cp">#include <athena/IStreamWriter.hpp></span>
<span class="k">class</span> <span class="nc">MyWriteBackend</span> <span class="o">:</span> <span class="k">public</span> <a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">IStreamWriter</span></a>
<span class="p">{</span>
<span class="n">MyWriteDestination</span><span class="o">&</span> <span class="n">m_dest</span><span class="p">;</span>
<span class="n">atUint64</span> <span class="n">m_curPos</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
<span class="k">public</span><span class="o">:</span>
<span class="n">MyWriteBackend</span><span class="p">(</span><span class="n">MyWriteDestination</span><span class="o">&</span> <span class="n">dest</span><span class="p">)</span>
<span class="o">:</span> <span class="n">m_dest</span><span class="p">(</span><span class="n">dest</span><span class="p">)</span> <span class="p">{}</span>
<span class="cm">/* Some applications (like this demo) may not</span>
<span class="cm"> * require random-access; leave this implementation as a stub */</span>
<span class="kt">void</span> <span class="n">seek</span><span class="p">(</span><span class="n">atInt64</span> <span class="n">pos</span><span class="p">,</span> <span class="n">SeekOrigin</span> <span class="n">origin</span><span class="p">)</span>
<span class="p">{}</span>
<span class="cm">/* Identifies current stream-position (byte index to be written next) */</span>
<span class="n">atUint64</span> <span class="n">position</span><span class="p">()</span> <span class="k">const</span>
<span class="p">{</span>
<span class="k">return</span> <span class="n">m_curPos</span><span class="p">;</span>
<span class="p">}</span>
<span class="cm">/* Identifies destination capacity */</span>
<span class="n">atUint64</span> <span class="n">length</span><span class="p">()</span> <span class="k">const</span>
<span class="p">{</span>
<span class="k">return</span> <span class="n">m_dest</span><span class="p">.</span><span class="n">getCapacity</span><span class="p">();</span>
<span class="p">}</span>
<span class="cm">/* Performs write using provided buffer </span>
<span class="cm"> * (automatically called by data-primitive methods like writeUint32) */</span>
<span class="n">atUint64</span> <span class="n">writeUBytes</span><span class="p">(</span><span class="kt">void</span><span class="o">*</span> <span class="n">buf</span><span class="p">,</span> <span class="n">atUint64</span> <span class="n">len</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">atUint64</span> <span class="n">wLen</span> <span class="o">=</span> <span class="n">m_dest</span><span class="p">.</span><span class="n">writeData</span><span class="p">(</span><span class="n">buf</span><span class="p">,</span> <span class="n">len</span><span class="p">);</span>
<span class="n">m_curPos</span> <span class="o">+=</span> <span class="n">wLen</span><span class="p">;</span>
<span class="k">return</span> <span class="n">wLen</span><span class="p">;</span>
<span class="p">}</span>
<span class="p">};</span></code></pre></figure>
</div>
</div>
</div>
<a id="dna" class="anchor-target"></a>
<div class="atSection atDNA">
<h1 class="atSectionTitle">DNA</h1>
<p>
Loading data field-by-field with Athena's Core has some benefits: It provides
a sensible place to convert endian (byte-order) for numeric types.
It can be made to handle compound types. The backing buffer is
tightly-packed for compact storage (no need to worry about
SIMD-alignment once read).
</p>
<p>
The major drawback is inconvenience; code needs to be written to
map the data structure's fields to segments in the streamed buffer.
</p>
<h2>ATDNA: Athena's Copilot</h2>
<p>
Athena ships with a build-tool inspired by
<a href="http://wiki.blender.org/index.php/Dev:2.5/Source/Architecture/RNA">Blender's build system</a>
called <code>atdna</code>. This tool transforms C++ record
declarations (i.e. structs, classes, unions) into reader/writer implementations
<em>automatically</em>. When properly integrated into a project's build system,
changes made to the C++ records will trigger these implementations to update
along with the project.
</p>
<p>
Special template types are provided by <a href="">athena::io::DNA</a> to
produce a well-defined <em>DNA Record</em>.
</p>
<div class="atIDE">
<h1>DNADemo.hpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><span class="cp">#include <athena/DNA.hpp></span>
<span class="k">using</span> <span class="n">BigDNA</span> <span class="o">=</span> <a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">DNA</span></a><span class="o"><</span><span class="n">athena</span><span class="o">::</span><span class="n">BigEndian</span><span class="o">></span><span class="p">;</span>
<span class="k">struct</span> <span class="nl">MyDNARecord</span> <span class="p">:</span> <span class="n">BigDNA</span>
<span class="p">{</span>
<span class="cm">/* This macro declares required member functions implementing the </span>
<span class="cm"> * DNA record (generated by ATDNA and linked as a separate .cpp file) */</span>
<span class="n">DECL_DNA</span>
<span class="cm">/* Value<T> template passes T though to the compiler and </span>
<span class="cm"> * exposes the field to ATDNA. Primitive fields without Value<T></span>
<span class="cm"> * are ignored by ATDNA. */</span>
<span class="n">Value</span><span class="o"><</span><span class="n">atUint32</span><span class="o">></span> <span class="n">m_val1</span><span class="p">;</span>
<span class="n">Value</span><span class="o"><</span><span class="kt">float</span><span class="o">></span> <span class="n">m_val2</span><span class="p">;</span>
<span class="n">Value</span><span class="o"><</span><span class="n">atVec3f</span><span class="o">></span> <span class="n">m_val3</span><span class="p">;</span>
<span class="cm">/* Nested record declartions are also processed by ATDNA, </span>
<span class="cm"> * assisting multi-level nested reads/writes */</span>
<span class="k">struct</span> <span class="nl">MyDNASubRecord</span> <span class="p">:</span> <span class="n">BigDNA</span>
<span class="p">{</span>
<span class="n">DECL_DNA</span>
<span class="n">Value</span><span class="o"><</span><span class="n">atUint32</span><span class="o">></span> <span class="n">m_subVal</span><span class="p">;</span>
<span class="p">};</span>
<span class="cm">/* Vector<T,DNA_COUNT(N)> template wraps a std::vector containing </span>
<span class="cm"> * N elements of type T. N is captured as a full C++ expression by the </span>
<span class="cm"> * DNA_COUNT macro and pasted within the DNA record implementation. */</span>
<span class="n">Value</span><span class="o"><</span><span class="n">atUint32</span><span class="o">></span> <span class="n">m_subCount</span><span class="p">;</span>
<span class="n">Vector</span><span class="o"><</span><span class="n">MyDNASubRecord</span><span class="p">,</span> <span class="n">DNA_COUNT</span><span class="p">(</span><span class="n">m_subCount</span><span class="p">)</span><span class="o">></span> <span class="n">m_subObjs</span><span class="p">;</span>
<span class="p">};</span></code></pre></figure>
</div>
<p>
Once the record has been defined in a header file, the header is passed
to <code>atdna</code> whenever it changes. It uses
<a href="http://clang.llvm.org/docs/Tooling.html">libclang</a>
to decompose the header into C++ declarations and emits the appropriate
read/write functions according to the field types.
</p>
<h2>ATDNA + CMake</h2>
<p>
Currently, ATDNA is easiest to integrate using <a href="http://www.cmake.org/">CMake</a>.
Projects may define DNA targets using the <code>atdna(<out> <in>)</code> macro, and
connecting the output file to a library or executable target.
</p>
<p>
CMake integrates with several build environments including <em>make</em>, <em>Visual Studio</em>,
and <em>Xcode</em>. Please see <a href="http://www.cmake.org/documentation/">CMake's documentation</a>
for details.
</p>
<div class="atIDE">
<h1>CMakeLists.txt</h1>
<figure class="highlight"><pre><code class="language-cmake" data-lang="cmake"><span class="nb">cmake_minimum_required</span><span class="p">(</span><span class="s">VERSION</span> <span class="s">3.0</span><span class="p">)</span>
<span class="nb">project</span><span class="p">(</span><span class="s">ATDNADemo</span><span class="p">)</span>
<span class="c"># When Athena's codebase is built/installed on the local system,</span>
<span class="c"># this package is visible from any project.</span>
<span class="nb">find_package</span><span class="p">(</span><span class="s">atdna</span> <span class="s">REQUIRED</span><span class="p">)</span>
<span class="c"># Defines the build rule to generate 'DNADemo.cpp' whenever </span>
<span class="c"># 'DNADemo.hpp' changes</span>
<span class="nb">atdna</span><span class="p">(</span><span class="s">DNADemo.cpp</span> <span class="s">DNADemo.hpp</span><span class="p">)</span>
<span class="c"># Defines the executable to compile</span>
<span class="nb">add_executable</span><span class="p">(</span><span class="s">ATDNADemo</span> <span class="s">main.cpp</span> <span class="s">DNADemo.cpp</span> <span class="s">DNADemo.hpp</span><span class="p">)</span></code></pre></figure>
</div>
<p>
When built, a file like the following is generated:
</p>
<div class="atIDE">
<h1>DNADemo.cpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><span class="cm">/* Auto generated atdna implementation */</span>
<span class="cp">#include <athena/Global.hpp></span>
<span class="cp">#include <athena/IStreamReader.hpp></span>
<span class="cp">#include <athena/IStreamWriter.hpp></span>
<span class="cp">#include "DNADemo.hpp"</span>
<span class="kt">void</span> <span class="n">MyDNARecord</span><span class="o">::</span><span class="n">read</span><span class="p">(</span><a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">IStreamReader</span></a><span class="o">&</span> <span class="n">__dna_reader</span><span class="p">)</span>
<span class="p">{</span>
<span class="cm">/* m_val1 */</span>
<span class="n">m_val1</span> <span class="o">=</span> <span class="n">__dna_reader</span><span class="p">.</span><span class="n">readUint32Big</span><span class="p">();</span>
<span class="cm">/* m_val2 */</span>
<span class="n">m_val2</span> <span class="o">=</span> <span class="n">__dna_reader</span><span class="p">.</span><span class="n">readFloatBig</span><span class="p">();</span>
<span class="cm">/* m_val3 */</span>
<span class="n">m_val3</span> <span class="o">=</span> <span class="n">__dna_reader</span><span class="p">.</span><span class="n">readVec3fBig</span><span class="p">();</span>
<span class="cm">/* m_subCount */</span>
<span class="n">m_subCount</span> <span class="o">=</span> <span class="n">__dna_reader</span><span class="p">.</span><span class="n">readUint32Big</span><span class="p">();</span>
<span class="cm">/* m_subObjs */</span>
<span class="n">__dna_reader</span><span class="p">.</span><span class="n">enumerate</span><span class="p">(</span><span class="n">m_subObjs</span><span class="p">,</span> <span class="n">m_subCount</span><span class="p">);</span>
<span class="p">}</span>
<span class="kt">void</span> <span class="n">MyDNARecord</span><span class="o">::</span><span class="n">write</span><span class="p">(</span><a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">IStreamWriter</span></a><span class="o">&</span> <span class="n">__dna_writer</span><span class="p">)</span> <span class="k">const</span>
<span class="p">{</span>
<span class="cm">/* m_val1 */</span>
<span class="n">__dna_writer</span><span class="p">.</span><span class="n">writeUint32Big</span><span class="p">(</span><span class="n">m_val1</span><span class="p">);</span>
<span class="cm">/* m_val2 */</span>
<span class="n">__dna_writer</span><span class="p">.</span><span class="n">writeFloatBig</span><span class="p">(</span><span class="n">m_val2</span><span class="p">);</span>
<span class="cm">/* m_val3 */</span>
<span class="n">__dna_writer</span><span class="p">.</span><span class="n">writeVec3fBig</span><span class="p">(</span><span class="n">m_val3</span><span class="p">);</span>
<span class="cm">/* m_subCount */</span>
<span class="n">__dna_writer</span><span class="p">.</span><span class="n">writeUint32Big</span><span class="p">(</span><span class="n">m_subCount</span><span class="p">);</span>
<span class="cm">/* m_subObjs */</span>
<span class="n">__dna_writer</span><span class="p">.</span><span class="n">enumerate</span><span class="p">(</span><span class="n">m_subObjs</span><span class="p">);</span>
<span class="p">}</span>
<span class="kt">void</span> <span class="n">MyDNARecord</span><span class="o">::</span><span class="n">MyDNASubRecord</span><span class="o">::</span><span class="n">read</span><span class="p">(</span><a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">IStreamReader</span></a><span class="o">&</span> <span class="n">__dna_reader</span><span class="p">)</span>
<span class="p">{</span>
<span class="cm">/* m_subVal */</span>
<span class="n">m_subVal</span> <span class="o">=</span> <span class="n">__dna_reader</span><span class="p">.</span><span class="n">readUint32Big</span><span class="p">();</span>
<span class="p">}</span>
<span class="kt">void</span> <span class="n">MyDNARecord</span><span class="o">::</span><span class="n">MyDNASubRecord</span><span class="o">::</span><span class="n">write</span><span class="p">(</span><a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">IStreamWriter</span></a><span class="o">&</span> <span class="n">__dna_writer</span><span class="p">)</span> <span class="k">const</span>
<span class="p">{</span>
<span class="cm">/* m_subVal */</span>
<span class="n">__dna_writer</span><span class="p">.</span><span class="n">writeUint32Big</span><span class="p">(</span><span class="n">m_subVal</span><span class="p">);</span>
<span class="p">}</span></code></pre></figure>
</div>
<h2>All together now!</h2>
<p>
Once the read/write implementations are compiled in, the application may invoke
them however's convenient:
</p>
<div class="atIDE">
<div class="atReadLayer">
<h1>main.cpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><span class="cp">#include <iostream></span>
<span class="cp">#include <athena/FileReader.hpp></span>
<span class="cp">#include "DNADemo.hpp"</span>
<span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">int</span> <span class="n">argc</span><span class="p">,</span> <span class="kt">char</span><span class="o">*</span> <span class="n">argv</span><span class="p">[])</span>
<span class="p">{</span>
<a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">FileReader</span></a> <span class="n">reader</span><span class="p">(</span><span class="s">"MyDemoData.bin"</span><span class="p">);</span>
<span class="n">MyDNARecord</span> <span class="n">record</span><span class="p">;</span>
<span class="n">record</span><span class="p">.</span><span class="n">read</span><span class="p">(</span><span class="n">reader</span><span class="p">);</span> <span class="cm">/* DNA implementation called here */</span>
<span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="s">"Val1: "</span> <span class="o"><<</span> <span class="n">record</span><span class="p">.</span><span class="n">m_val1</span> <span class="o"><<</span> <span class="s">" Val2: "</span> <span class="o"><<</span> <span class="n">record</span><span class="p">.</span><span class="n">m_val2</span> <span class="o"><<</span> <span class="s">"</span><span class="se">\n</span><span class="s">"</span><span class="p">;</span>
<span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
<span class="p">}</span></code></pre></figure>
</div>
<div class="atWriteLayer">
<h1>main.cpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><span class="cp">#include <iostream></span>
<span class="cp">#include <athena/FileWriter.hpp></span>
<span class="cp">#include "DNADemo.cpp"</span>
<span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">int</span> <span class="n">argc</span><span class="p">,</span> <span class="kt">char</span><span class="o">*</span> <span class="n">argv</span><span class="p">[])</span>
<span class="p">{</span>
<a href=""><span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">FileWriter</span></a> <span class="n">writer</span><span class="p">(</span><span class="s">"MyDemoData.bin"</span><span class="p">);</span>
<span class="n">MyDNARecord</span> <span class="n">record</span><span class="p">;</span>
<span class="n">record</span><span class="p">.</span><span class="n">m_val1</span> <span class="o">=</span> <span class="mh">0x42</span><span class="p">;</span>
<span class="n">record</span><span class="p">.</span><span class="n">m_val2</span> <span class="o">=</span> <span class="mf">3.14159265359</span><span class="p">;</span>
<span class="n">record</span><span class="p">.</span><span class="n">write</span><span class="p">(</span><span class="n">writer</span><span class="p">);</span> <span class="cm">/* DNA implementation called here */</span>
<span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
<span class="p">}</span></code></pre></figure>
</div>
</div>
</div>
<a id="yaml" class="anchor-target"></a>
<div class="atSection atYAML">
<h1 class="atSectionTitle">YAML</h1>
<p>
Having a uniform system to interchange binary data is nice, but we musn't forget
the human programmers that work with the data and design systems around it.
This is where having a textual representation of the structured data is convenient.
<a href="https://en.wikipedia.org/wiki/YAML">YAML</a> is a simplistic data-serialization
format, capable of organizing string-representations of data members into mappings and
sequences with multiple levels of hierarchy.
</p>
<p>
<a href="">athena::io::DNA</a> has been subclassed as <a href="">athena::io::DNAYaml</a>
to have ATDNA generate YAML serialization/deserialization alongside the binary readers/writers.
It's used just like the DNA system from the developer's perspective.
</p>
<div class="atIDE">
<h1>YAMLDemo.hpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><span class="cp">#include <athena/DNAYaml.hpp></span>
<span class="k">using</span> <span class="n">BigYAML</span> <span class="o">=</span> <span class="n">athena</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">DNAYaml</span><span class="o"><</span><span class="n">athena</span><span class="o">::</span><span class="n">BigEndian</span><span class="o">></span><span class="p">;</span>
<span class="k">struct</span> <span class="nl">MyYAMLRecord</span> <span class="p">:</span> <span class="n">BigYAML</span>
<span class="p">{</span>
<span class="cm">/* This macro declares required member functions implementing the </span>
<span class="cm"> * YAML record (generated by ATDNA and linked as a separate .cpp file) */</span>
<span class="n">DECL_YAML</span>
<span class="cm">/* Value<T> template passes T though to the compiler and </span>
<span class="cm"> * exposes the field to ATDNA. Primitive fields without Value<T></span>
<span class="cm"> * are ignored by ATDNA. */</span>
<span class="n">Value</span><span class="o"><</span><span class="n">atUint32</span><span class="o">></span> <span class="n">m_val1</span><span class="p">;</span>
<span class="n">Value</span><span class="o"><</span><span class="kt">float</span><span class="o">></span> <span class="n">m_val2</span><span class="p">;</span>
<span class="n">Value</span><span class="o"><</span><span class="n">atVec3f</span><span class="o">></span> <span class="n">m_val3</span><span class="p">;</span>
<span class="cm">/* Nested record declartions are also processed by ATDNA, </span>
<span class="cm"> * assisting multi-level nested reads/writes */</span>
<span class="k">struct</span> <span class="nl">MyYAMLSubRecord</span> <span class="p">:</span> <span class="n">BigYAML</span>
<span class="p">{</span>
<span class="n">DECL_YAML</span>
<span class="n">Value</span><span class="o"><</span><span class="n">atUint32</span><span class="o">></span> <span class="n">m_subVal</span><span class="p">;</span>
<span class="p">};</span>
<span class="cm">/* Vector<T,DNA_COUNT(N)> template wraps a std::vector containing </span>
<span class="cm"> * N elements of type T. N is captured as a full C++ expression by the </span>
<span class="cm"> * DNA_COUNT macro and pasted within the YAML record implementation. */</span>
<span class="n">Value</span><span class="o"><</span><span class="n">atUint32</span><span class="o">></span> <span class="n">m_subCount</span><span class="p">;</span>
<span class="n">Vector</span><span class="o"><</span><span class="n">MyYAMLSubRecord</span><span class="p">,</span> <span class="n">DNA_COUNT</span><span class="p">(</span><span class="n">m_subCount</span><span class="p">)</span><span class="o">></span> <span class="n">m_subObjs</span><span class="p">;</span>
<span class="p">};</span></code></pre></figure>
</div>
<p>
Now applications can use YAML as a data source/destination in addition to the
original binary format the DNA is based on. Such YAML may look like this:
</p>
<div class="atIDE">
<h1>YAMLDemo.yaml</h1>
<figure class="highlight"><pre><code class="language-yaml" data-lang="yaml"><span class="l-Scalar-Plain">m_val1</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">0x42</span>
<span class="l-Scalar-Plain">m_val2</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">3.14159265359</span>
<span class="l-Scalar-Plain">m_val3</span><span class="p-Indicator">:</span> <span class="p-Indicator">[</span><span class="nv">1.000000</span><span class="p-Indicator">,</span> <span class="nv">2.000000</span><span class="p-Indicator">,</span> <span class="nv">3.000000</span><span class="p-Indicator">]</span>
<span class="l-Scalar-Plain">m_subCount</span><span class="p-Indicator">:</span> <span class="l-Scalar-Plain">0x3</span>
<span class="l-Scalar-Plain">m_subObjs</span><span class="p-Indicator">:</span>
<span class="p-Indicator">-</span> <span class="p-Indicator">{</span><span class="nv">m_subVal</span><span class="p-Indicator">:</span> <span class="nv">0x1</span><span class="p-Indicator">}</span>
<span class="p-Indicator">-</span> <span class="p-Indicator">{</span><span class="nv">m_subVal</span><span class="p-Indicator">:</span> <span class="nv">0x2</span><span class="p-Indicator">}</span>
<span class="p-Indicator">-</span> <span class="p-Indicator">{</span><span class="nv">m_subVal</span><span class="p-Indicator">:</span> <span class="nv">0x3</span><span class="p-Indicator">}</span></code></pre></figure>
</div>
<h2>All together now!</h2>
<p>
The YAML implementations are compiled side-by-side with the DNA implementations.
The application may invoke them in a similar manner:
</p>
<div class="atIDE">
<div class="atReadLayer">
<h1>main.cpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><span class="cp">#include <stdio.h></span>
<span class="cp">#include <iostream></span>
<span class="cp">#include "YAMLDemo.hpp"</span>
<span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">int</span> <span class="n">argc</span><span class="p">,</span> <span class="kt">char</span><span class="o">*</span> <span class="n">argv</span><span class="p">[])</span>
<span class="p">{</span>
<span class="cm">/* Stdio FILEs are one option. Raw string buffers are also available */</span>
<span class="kt">FILE</span><span class="o">*</span> <span class="n">fp</span> <span class="o">=</span> <span class="n">fopen</span><span class="p">(</span><span class="s">"MyDemoYAML.yaml"</span><span class="p">,</span> <span class="s">"r"</span><span class="p">);</span>
<span class="n">MyYAMLRecord</span> <span class="n">record</span><span class="p">;</span>
<span class="n">record</span><span class="p">.</span><span class="n">fromYAMLFile</span><span class="p">(</span><span class="n">fp</span><span class="p">);</span> <span class="cm">/* YAML implementation called here */</span>
<span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="s">"Val1: "</span> <span class="o"><<</span> <span class="n">record</span><span class="p">.</span><span class="n">m_val1</span> <span class="o"><<</span> <span class="s">" Val2: "</span> <span class="o"><<</span> <span class="n">record</span><span class="p">.</span><span class="n">m_val2</span> <span class="o"><<</span> <span class="s">"</span><span class="se">\n</span><span class="s">"</span><span class="p">;</span>
<span class="n">fclose</span><span class="p">(</span><span class="n">fp</span><span class="p">);</span>
<span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
<span class="p">}</span></code></pre></figure>
</div>
<div class="atWriteLayer">
<h1>main.cpp</h1>
<figure class="highlight"><pre><code class="language-c--" data-lang="c++"><span class="cp">#include <stdio.h></span>
<span class="cp">#include <iostream></span>
<span class="cp">#include "YAMLDemo.hpp"</span>
<span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">int</span> <span class="n">argc</span><span class="p">,</span> <span class="kt">char</span><span class="o">*</span> <span class="n">argv</span><span class="p">[])</span>
<span class="p">{</span>
<span class="cm">/* Stdio FILEs are one option. Raw string buffers are also available */</span>
<span class="kt">FILE</span><span class="o">*</span> <span class="n">fp</span> <span class="o">=</span> <span class="n">fopen</span><span class="p">(</span><span class="s">"MyDemoYAML.yaml"</span><span class="p">,</span> <span class="s">"w"</span><span class="p">);</span>
<span class="n">MyYAMLRecord</span> <span class="n">record</span><span class="p">;</span>
<span class="n">record</span><span class="p">.</span><span class="n">m_val1</span> <span class="o">=</span> <span class="mh">0x42</span><span class="p">;</span>
<span class="n">record</span><span class="p">.</span><span class="n">m_val2</span> <span class="o">=</span> <span class="mf">3.14159265359</span><span class="p">;</span>
<span class="n">record</span><span class="p">.</span><span class="n">toYAMLFile</span><span class="p">(</span><span class="n">fp</span><span class="p">);</span> <span class="cm">/* YAML implementation called here */</span>
<span class="n">fclose</span><span class="p">(</span><span class="n">fp</span><span class="p">);</span>
<span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
<span class="p">}</span></code></pre></figure>
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