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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<title>Seed Modules: Seed Reference Manual</title>
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<a href="#seed-Modules.description" class="shortcut">Description</a></span>
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<div class="refentry">
<a name="seed-Modules"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2><span class="refentrytitle"><a name="seed-Modules.top_of_page"></a>Seed Modules</span></h2>
<p>Seed Modules — Native C modules for Seed</p>
</td>
<td class="gallery_image" valign="top" align="right"></td>
</tr></table></div>
<div class="refsect1">
<a name="seed-Modules.functions"></a><h2>Functions</h2>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="functions_return">
<col class="functions_name">
</colgroup>
<tbody>
<tr>
<td class="define_keyword">#define</td>
<td class="function_name">
<a class="link" href="seed-Modules.html#CHECK-ARG-COUNT:CAPS" title="CHECK_ARG_COUNT()">CHECK_ARG_COUNT</a><span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="define_keyword">#define</td>
<td class="function_name">
<a class="link" href="seed-Modules.html#DEFINE-ENUM-MEMBER:CAPS" title="DEFINE_ENUM_MEMBER()">DEFINE_ENUM_MEMBER</a><span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="define_keyword">#define</td>
<td class="function_name">
<a class="link" href="seed-Modules.html#DEFINE-ENUM-MEMBER-EXT:CAPS" title="DEFINE_ENUM_MEMBER_EXT()">DEFINE_ENUM_MEMBER_EXT</a><span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="seed-JS-Objects.html#SeedObject" title="SeedObject"><span class="returnvalue">SeedObject</span></a>
</td>
<td class="function_name">
<span class="c_punctuation">(</span><a class="link" href="seed-Modules.html#SeedModuleInitCallback" title="SeedModuleInitCallback ()">*SeedModuleInitCallback</a><span class="c_punctuation">)</span> <span class="c_punctuation">()</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="seed-Modules.includes"></a><h2>Includes</h2>
<pre class="synopsis">#include <seed/seed.h>
</pre>
</div>
<div class="refsect1">
<a name="seed-Modules.description"></a><h2>Description</h2>
<p>
Seed includes a simple system for creating C modules which can be loaded and manipulated from JavaScript. This is used for implementing performance-critical code closer to the silicon, as well as binding non-introspectable libraries in an attractive way.
</p>
<p>Numerous binding modules are included in the Seed repository; when writing a new native module, it would be wise to look over these before beginning, as they have many tidbits of useful knowledge for writing modules.</p>
<div class="example">
<a name="id-1.4.12.5.4"></a><p class="title"><b>Example 11. Very simple example C module</b></p>
<div class="example-contents"><pre class="programlisting">
#include <glib.h>
#include <seed-module.h>
SeedObject seed_module_init(SeedEngine * eng)
{
/* Say hello! */
g_print("Hello, Seed Module World!\n");
/* Return an empty object as the module's namespace */
return seed_make_object (eng->context, NULL, NULL);
}
</pre></div>
</div>
<br class="example-break"><p>Above is a C module which does absolutely nothing useful. When a module is loaded, <code class="function">seed_module_init()</code> is called, which should have the signature of <a class="link" href="seed-Modules.html#SeedModuleInitCallback" title="SeedModuleInitCallback ()"><code class="function">SeedModuleInitCallback()</code></a>. You're passed the global <a class="link" href="seed-Initialization.html#SeedEngine" title="struct SeedEngine"><span class="type">SeedEngine</span></a>, and the value you return is the namespace for your module. Say, for example, you place a static function on that object:</p>
<div class="example">
<a name="id-1.4.12.5.6"></a><p class="title"><b>Example 12. C module with a function</b></p>
<div class="example-contents"><pre class="programlisting">
#include <glib.h>
#include <seed-module.h>
/* Our function, with the signature of SeedFunctionCallback(); say hello! */
SeedValue say_hello_to(SeedContext ctx,
SeedObject function,
SeedObject this_object,
gsize argument_count,
const SeedValue arguments[],
SeedException *exception)
{
guchar * name;
/* Check that only one argument was passed into the function.
CHECK_ARG_COUNT() is from seed-module.h, which you might find useful. */
CHECK_ARG_COUNT("hello.say_hello_to", 1);
/* Convert the first argument, a <a class="link" href="seed-Native-Type-Conversion.html#SeedValue" title="SeedValue">SeedValue</a>, to a C string */
name = seed_value_to_string(ctx, arguments[0], exception);
g_print("Hello, %s!\n", name);
g_free(name);
return seed_make_null(ctx);
}
/* Define an array of seed_static_function */
seed_static_function gettext_funcs[] = {
{"say_hello_to", say_hello_to, 0}
};
SeedObject seed_module_init(SeedEngine * eng)
{
SeedGlobalContext ctx = eng->context;
/* Create a new class definition with our array of static functions */
seed_class_definition ns_class_def = seed_empty_class;
ns_class_def.static_functions = example_funcs;
/* Create a class from the class definition we just created */
SeedClass ns_class = seed_create_class(&ns_class_def);
/* Instantiate the class; this instance will be the namespace we return */
ns_ref = seed_make_object (ctx, ns_class, NULL);
seed_value_protect (ctx, ns_ref);
return ns_ref;
}
</pre></div>
</div>
<br class="example-break"><p>After building and installing this module (look in the Seed build system for examples of how to get this to work, as well as a copy of seed-module.h, which will be very useful), it will be loadable with the normal Seed import system. Assuming it's installed as libseed_hello.so:</p>
<div class="example">
<a name="id-1.4.12.5.8"></a><p class="title"><b>Example 13. Utilize our second example C module from JavaScript</b></p>
<div class="example-contents"><pre class="programlisting">
hello = imports.hello;
hello.say_hello_to("Tim");
</pre></div>
</div>
<br class="example-break">
</div>
<div class="refsect1">
<a name="seed-Modules.functions_details"></a><h2>Functions</h2>
<div class="refsect2">
<a name="CHECK-ARG-COUNT:CAPS"></a><h3>CHECK_ARG_COUNT()</h3>
<pre class="programlisting">#define CHECK_ARG_COUNT(name, argnum)</pre>
<p>Check that the required number of arguments were passed into a
<a class="link" href="seed-Native-Functions.html#SeedFunctionCallback" title="SeedFunctionCallback ()"><span class="type">SeedFunctionCallback</span></a>. If this is not true, raise an exception and
return <code class="literal">NULL</code>. This requires the callback to use "argument_count",
"ctx", and "exception" as the names of the various function arguments.</p>
<p><em class="parameter"><code>name</code></em>
should be of form "namespace.function_name"</p>
<p>At the moment, there is no way to specify more than one acceptable
argument count.</p>
<div class="refsect3">
<a name="CHECK-ARG-COUNT.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>name</p></td>
<td class="parameter_description"><p>The name of the function being called from, pretty-printed</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>argnum</p></td>
<td class="parameter_description"><p>The number of arguments which should be passed into the function</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="DEFINE-ENUM-MEMBER:CAPS"></a><h3>DEFINE_ENUM_MEMBER()</h3>
<pre class="programlisting">#define DEFINE_ENUM_MEMBER(holder, member)</pre>
<p>Defines a property on <em class="parameter"><code>holder</code></em>
which is named the same as <em class="parameter"><code>member</code></em>
, and
is assigned the value that <em class="parameter"><code>member</code></em>
has in C.</p>
<p>This macro works for defining properties from constants and
#defines as well.</p>
<div class="refsect3">
<a name="DEFINE-ENUM-MEMBER.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>holder</p></td>
<td class="parameter_description"><p>The object on which to define the enum member</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>member</p></td>
<td class="parameter_description"><p>The enum member, as it is named in C</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="DEFINE-ENUM-MEMBER-EXT:CAPS"></a><h3>DEFINE_ENUM_MEMBER_EXT()</h3>
<pre class="programlisting">#define DEFINE_ENUM_MEMBER_EXT(holder, name, val)</pre>
<p>Defines a property on <em class="parameter"><code>holder</code></em>
which is named <em class="parameter"><code>name</code></em>
, and is assigned the
value that <em class="parameter"><code>member</code></em>
has in C. This allows for an override of the enum
member's name, most often to remove a common prefix. For example, to declare
a property named VERSION_MAJOR on the namespace from mfpr's version
constant MPFR_VERSION_MAJOR:</p>
<pre class="programlisting">
DEFINE_ENUM_MEMBER_EXT(ns, "VERSION_MAJOR", MPFR_VERSION_MAJOR);
</pre>
<div class="refsect3">
<a name="DEFINE-ENUM-MEMBER-EXT.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>holder</p></td>
<td class="parameter_description"><p>The object on which to define the enum member</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>name</p></td>
<td class="parameter_description"><p>The enum member, as it should be named in JavaScript</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>val</p></td>
<td class="parameter_description"><p>The enum member, as it is named in C</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="SeedModuleInitCallback"></a><h3>SeedModuleInitCallback ()</h3>
<pre class="programlisting"><a class="link" href="seed-JS-Objects.html#SeedObject" title="SeedObject"><span class="returnvalue">SeedObject</span></a>
<span class="c_punctuation">(</span>*SeedModuleInitCallback<span class="c_punctuation">)</span> (<em class="parameter"><code><a class="link" href="seed-Initialization.html#SeedEngine" title="struct SeedEngine"><span class="type">SeedEngine</span></a> *eng</code></em>);</pre>
<p>
</p>
</div>
</div>
<div class="refsect1">
<a name="seed-Modules.other_details"></a><h2>Types and Values</h2>
</div>
</div>
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