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[Go] Add imtype, goin, goout, godirectorin, and godirectorout

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typemaps, to support writing Go code to convert between types.
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Ian Lance Taylor 2014-09-05 17:54:19 -07:00
commit 1addbb46a8
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Doc/Manual/Go.html
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@ -30,6 +30,7 @@
<li><a href="#Go_primitive_type_mappings">Default Go primitive type mappings</a>
<li><a href="#Go_output_arguments">Output arguments</a>
<li><a href="#Go_adding_additional_code">Adding additional go code</a>
<li><a href="#Go_typemaps">Go typemaps</a>
</ul>
</ul>
</div>
@ -692,5 +693,123 @@ func bar() {
</pre>
</div>
<H3><a name="Go_typemaps"></a>23.3.11 Go typemaps</H3>
<p>
You can use the <tt>%typemap</tt> directive to modify SWIG's default
wrapping behavior for specific C/C++ types. You need to be familiar
with the material in the general
"<a href="Typemaps.html#Typemaps">Typemaps</a>" chapter. That chapter
explains how to define a typemap. This section describes some
specific typemaps used for Go.
</p>
<p>
In general type conversion code may be written either in C/C++ or in
Go. The choice to make normally depends on where memory should be
allocated. To allocate memory controlled by the Go garbage collector,
write Go code. To allocate memory in the C/C++ heap, write C code.
</p>
<table BORDER summary="Go Typemaps">
<tr>
<td><b>Typemap</b></td>
<td><b>Description</b></td>
</tr>
<tr>
<td>gotype</td>
<td>
The Go type to use for a C++ type. This type will appear in the
generated Go wrapper function. If this is not defined SWIG will use a
default as <a href="#Go_primitive_type_mappings">described above</a>.
</td>
</tr>
<tr>
<td>imtype</td>
<td>
An intermediate Go type used by the "goin", "goout", "godirectorin",
and "godirectorout" typemaps. If this typemap is not defined for a
C/C++ type, the gotype typemape will be used. This is useful when
gotype is best converted to C/C++ using Go code.
</td>
</tr>
<tr>
<td>goin</td>
<td>
Go code to convert from gotype to imtype when calling a C/C++
function. SWIG will then internally convert imtype to a C/C++ type
and pass it down. If this is not defined no conversion is done.
</td>
</tr>
<tr>
<td>in</td>
<td>
C/C++ code to convert the internally generated C/C++ type, based on
imtype, into the C/C++ type that a function call expects. If this is
not defined the value will simply be cast to the desired type.
</td>
</tr>
<tr>
<td>out</td>
<td>
C/C++ code to convert the C/C++ type that a function call returns into
the internally generated C/C++ type, based on imtype, that will be
returned to Go. If this is not defined the value will simply be cast
to the desired type.
</td>
</tr>
<tr>
<td>goout</td>
<td>
Go code to convert a value returned from a C/C++ function from imtype
to gotype. If this is not defined no conversion is done.
</td>
</tr>
<tr>
<td>directorin</td>
<td>
C/C++ code to convert the C/C++ type used to call a director method
into the internally generated C/C++ type, based on imtype, that will
be passed to Go. If this is not defined the value will simply be cast
to the desired type.
</td>
</tr>
<tr>
<td>godirectorin</td>
<td>
Go code to convert a value used to call a director method from imtype
to gotype. If this is not defined no conversion is done.
</td>
</tr>
<tr>
<td>godirectorout</td>
<td>
Go code to convert a value returned from a director method from gotype
to imtype. If this is not defined no conversion is done.
</td>
</tr>
<tr>
<td>directorout</td>
<td>
C/C++ code to convert a value returned from a director method from the
internally generated C/C++ type, based on imtype, into the type that
the method should return If this is not defined the value will simply
be cast to the desired type.
</td>
</tr>
</table>
</body>
</html>