[英]SWIG struct pointer as output parameter
我有一个结构:
struct some_struct_s {
int arg1;
int arg2;
};
我有一个C函数:
int func(some_struct_s *output);
两者都%included
在我的SWIG文件中。
我希望将some_struct_s *output
视为输出参数。 Python示例:
int_val, some_struct_output = func()
手册中介绍了POD类型(第10.1.3节)的“输出参数”,但非POD类型则没有。
如何告诉SWIG我希望some_struct_s *output
为输出参数?
从文档中 :
11.5.7“ argout”类型图
“ argout”类型映射用于从参数返回值。 这最常用于为需要返回多个值的C / C ++函数编写包装器。 几乎总是将“ argout”类型映射与“ in”类型映射---可能会忽略输入值。
这是您的代码的完整示例(为简洁起见,没有错误检查):
%module test
// Declare an input typemap that suppresses requiring any input and
// declare a temporary stack variable to hold the return data.
%typemap(in,numinputs=0) some_struct_s* (some_struct_s tmp) %{
$1 = &tmp;
%}
// Declare an output argument typemap. In this case, we'll use
// a tuple to hold the structure data (no error checking).
%typemap(argout) some_struct_s* (PyObject* o) %{
o = PyTuple_New(2);
PyTuple_SET_ITEM(o,0,PyLong_FromLong($1->arg1));
PyTuple_SET_ITEM(o,1,PyLong_FromLong($1->arg2));
$result = SWIG_Python_AppendOutput($result,o);
%}
// Instead of a header file, we'll just declare this code inline.
// This includes the code in the wrapper, as well as telling SWIG
// to create wrappers in the target language.
%inline %{
struct some_struct_s {
int arg1;
int arg2;
};
int func(some_struct_s *output)
{
output->arg1 = 1;
output->arg2 = 2;
return 0;
}
%}
下面的演示。 请注意, int
返回值零以及输出参数作为元组都作为列表返回。
>>> import test
>>> test.func()
[0, (1, 2)]
如果您不想使用类型映射,还可以注入代码来创建对象,然后将其返回以对用户隐藏:
%module test
%rename(_func) func; // Give the wrapper a different name
%inline %{
struct some_struct_s {
int arg1;
int arg2;
};
int func(struct some_struct_s *output)
{
output->arg1 = 1;
output->arg2 = 2;
return 0;
}
%}
// Declare your interface
%pythoncode %{
def func():
s = some_struct_s()
r = _func(s)
return r,s
%}
演示:
>>> import test
>>> r,s=test.func()
>>> r
0
>>> s
<test.some_struct_s; proxy of <Swig Object of type 'some_struct_s *' at 0x000001511D70A880> >
>>> s.arg1
1
>>> s.arg2
2
如果仔细选择SWIG宏,则可以使类型映射语言不可知:
%module test
%typemap(in,numinputs=0) struct some_struct_s *output %{
$1 = malloc(sizeof(struct some_struct_s));
%}
%typemap(argout) struct some_struct_s* output {
%append_output(SWIG_NewPointerObj($1,$1_descriptor,1));
}
%inline %{
struct some_struct_s {
int arg1;
int arg2;
};
int func(struct some_struct_s *output)
{
output->arg1 = 1;
output->arg2 = 2;
return 0;
}
%}
演示:
>>> import test
>>> r,s=test.func()
>>> r
0
>>> s
<test.some_struct_s; proxy of <Swig Object of type 'some_struct_s *' at 0x000001DD0425A700> >
>>> s.arg1
1
>>> s.arg2
2
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