Hot to get rid of memory allocations/deallocations in swig wrappers?
- by Dmitriy Matveev
I want to use swig for generation of read-only wrappers for a complex object. The object which I want to wrap will always be existent while I will read it. And also I will only use my wrappers at the time that object is existent, thus I don't need any memory management from SWIG.
For following swig interface:
%module test
%immutable;
%inline
%{
struct Foo
{
int a;
};
struct Bar
{
int b;
Foo f;
};
%}
I will have a wrappers which will have a lot of garbage in generated interfaces and do useless work which will reduce performance in my case.
Generated java wrapper for Bar class will be like this:
public class Bar {
private long swigCPtr;
protected boolean swigCMemOwn;
protected Bar(long cPtr, boolean cMemoryOwn) {
swigCMemOwn = cMemoryOwn;
swigCPtr = cPtr;
}
protected static long getCPtr(Bar obj) {
return (obj == null) ? 0 : obj.swigCPtr;
}
protected void finalize() {
delete();
}
public synchronized void delete() {
if (swigCPtr != 0) {
if (swigCMemOwn) {
swigCMemOwn = false;
testJNI.delete_Bar(swigCPtr);
}
swigCPtr = 0;
}
}
public int getB() {
return testJNI.Bar_b_get(swigCPtr, this);
}
public Foo getF() {
return new Foo(testJNI.Bar_f_get(swigCPtr, this), true);
}
public Bar() {
this(testJNI.new_Bar(), true);
}
}
I don't need 'swigCMemOwn' field in my wrapper since it always will be false. All code related to this field will also be useless.
There are also unnecessary logic in native code:
SWIGEXPORT jlong JNICALL Java_some_testJNI_Bar_1f_1get(JNIEnv *jenv, jclass jcls, jlong jarg1, jobject jarg1_) {
jlong jresult = 0 ;
struct Bar *arg1 = (struct Bar *) 0 ;
Foo result;
(void)jenv;
(void)jcls;
(void)jarg1_;
arg1 = *(struct Bar **)&jarg1;
result = ((arg1)->f);
{
Foo * resultptr = (Foo *) malloc(sizeof(Foo));
memmove(resultptr, &result, sizeof(Foo));
*(Foo **)&jresult = resultptr;
}
return jresult;
}
I don't need these calls to malloc and memmove.
I want to force swig to resolve both of these problems, but don't know how. Is it possible?
