Add MemoryView.export and MemoryView#release (#80)

fix#79
Users can release memory views explicitly before process exit.
Reported by xtkoba. Thanks!!!

Author: kou

ext/fiddle/memory_view.c

@@ -36,12 +36,25 @@ fiddle_memview_mark(void *ptr)
 }
 
 staticvoid
-fiddle_memview_free(void*ptr)
+fiddle_memview_release(structmemview_data*data)
 {
-structmemview_data*data=ptr;
+if (NIL_P(data->view.obj)) return;
+
 rb_memory_view_release(&data->view);
-if (data->members)
+data->view.obj=Qnil;
+data->view.byte_size=0;
+if (data->members) {
 xfree(data->members);
+data->members=NULL;
+data->n_members=0;
+ }
+}
+
+staticvoid
+fiddle_memview_free(void*ptr)
+{
+structmemview_data*data=ptr;
+fiddle_memview_release(data);
 xfree(ptr);
 }
 
@@ -63,11 +76,32 @@ rb_fiddle_memview_s_allocate(VALUE klass)
 structmemview_data*data;
 VALUEobj=TypedData_Make_Struct(klass, structmemview_data, &fiddle_memview_data_type, data);
 data->view.obj=Qnil;
+data->view.byte_size=0;
 data->members=NULL;
 data->n_members=0;
 returnobj;
 }
 
+staticVALUE
+rb_fiddle_memview_release(VALUEobj)
+{
+structmemview_data*data;
+TypedData_Get_Struct(obj, structmemview_data, &fiddle_memview_data_type, data);
+
+if (NIL_P(data->view.obj)) returnQnil;
+fiddle_memview_release(data);
+returnQnil;
+}
+
+staticVALUE
+rb_fiddle_memview_s_export(VALUEklass, VALUEtarget)
+{
+IDid_new;
+CONST_ID(id_new, "new");
+VALUEmemview=rb_funcall(klass, id_new, 1, target);
+returnrb_ensure(rb_yield, memview, rb_fiddle_memview_release, memview);
+}
+
 staticVALUE
 rb_fiddle_memview_initialize(VALUEobj, VALUEtarget)
 {
@@ -269,7 +303,9 @@ Init_fiddle_memory_view(void)
 {
 rb_cMemoryView=rb_define_class_under(mFiddle, "MemoryView", rb_cObject);
 rb_define_alloc_func(rb_cMemoryView, rb_fiddle_memview_s_allocate);
+rb_define_singleton_method(rb_cMemoryView, "export", rb_fiddle_memview_s_export, 1);
 rb_define_method(rb_cMemoryView, "initialize", rb_fiddle_memview_initialize, 1);
+rb_define_method(rb_cMemoryView, "release", rb_fiddle_memview_release, 0);
 rb_define_method(rb_cMemoryView, "obj", rb_fiddle_memview_get_obj, 0);
 rb_define_method(rb_cMemoryView, "byte_size", rb_fiddle_memview_get_byte_size, 0);
 rb_define_method(rb_cMemoryView, "readonly?", rb_fiddle_memview_get_readonly, 0);

test/fiddle/test_memory_view.rb

@@ -112,6 +112,22 @@ def test_memory_view_multi_dimensional_with_multiple_members
 assert_equal([-7, -8],mview[1,3])
 end
 
+deftest_export
+str="hello world"
+mview_str=MemoryView.export(Pointer[str])do |mview|
+mview.to_s
+end
+assert_equal(str,mview_str)
+end
+
+deftest_release
+ptr=Pointer["hello world"]
+mview=MemoryView.new(ptr)
+assert_same(ptr,mview.obj)
+mview.release
+assert_nil(mview.obj)
+end
+
 deftest_to_s
 # U+3042 HIRAGANA LETTER A
 data="\u{3042}"