Support flags in Fiddle::MemoryView.new and .export (#209)

Accept an optional `flags` argument, expose the flag values as
constants, and reject unsupported flags in `Fiddle::Pointer`'s provider.

Author: himura467

ext/fiddle/memory_view.c

@@ -103,21 +103,25 @@ rb_fiddle_memview_s_available_p(VALUE klass, VALUE target)
 }
 
 static VALUE
-rb_fiddle_memview_s_export(VALUE klass, VALUE target)
+rb_fiddle_memview_s_export(int argc, VALUE *argv, VALUE klass)
 {
     ID id_new;
     CONST_ID(id_new, "new");
-    VALUE memview = rb_funcall(klass, id_new, 1, target);
+    VALUE memview = rb_funcallv(klass, id_new, argc, argv);
     return rb_ensure(rb_yield, memview, rb_fiddle_memview_release, memview);
 }
 
 static VALUE
-rb_fiddle_memview_initialize(VALUE obj, VALUE target)
+rb_fiddle_memview_initialize(int argc, VALUE *argv, VALUE obj)
 {
+    VALUE target, flags_v;
+    rb_scan_args(argc, argv, "11", &target, &flags_v);
+    int flags = NIL_P(flags_v) ? 0 : NUM2INT(flags_v);
+
     struct memview_data *data;
     TypedData_Get_Struct(obj, struct memview_data, &fiddle_memview_data_type, data);
 
-    if (!rb_memory_view_get(target, &data->view, 0)) {
+    if (!rb_memory_view_get(target, &data->view, flags)) {
         data->view.obj = Qnil;
         rb_raise(rb_eArgError, "Unable to get a memory view from %+"PRIsVALUE, target);
     }
@@ -314,9 +318,18 @@ 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_const(rb_cMemoryView, "SIMPLE", INT2NUM(RUBY_MEMORY_VIEW_SIMPLE));
+    rb_define_const(rb_cMemoryView, "WRITABLE", INT2NUM(RUBY_MEMORY_VIEW_WRITABLE));
+    rb_define_const(rb_cMemoryView, "FORMAT", INT2NUM(RUBY_MEMORY_VIEW_FORMAT));
+    rb_define_const(rb_cMemoryView, "MULTI_DIMENSIONAL", INT2NUM(RUBY_MEMORY_VIEW_MULTI_DIMENSIONAL));
+    rb_define_const(rb_cMemoryView, "STRIDES", INT2NUM(RUBY_MEMORY_VIEW_STRIDES));
+    rb_define_const(rb_cMemoryView, "ROW_MAJOR", INT2NUM(RUBY_MEMORY_VIEW_ROW_MAJOR));
+    rb_define_const(rb_cMemoryView, "COLUMN_MAJOR", INT2NUM(RUBY_MEMORY_VIEW_COLUMN_MAJOR));
+    rb_define_const(rb_cMemoryView, "ANY_CONTIGUOUS", INT2NUM(RUBY_MEMORY_VIEW_ANY_CONTIGUOUS));
+    rb_define_const(rb_cMemoryView, "INDIRECT", INT2NUM(RUBY_MEMORY_VIEW_INDIRECT));
     rb_define_singleton_method(rb_cMemoryView, "available?", rb_fiddle_memview_s_available_p, 1);
-    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_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);

ext/fiddle/pointer.c

@@ -137,6 +137,8 @@ fiddle_ptr_memory_view_available_p(VALUE obj)
 static bool
 fiddle_ptr_get_memory_view(VALUE obj, rb_memory_view_t *view, int flags)
 {
+    if (flags != RUBY_MEMORY_VIEW_SIMPLE) return false;
+
     struct ptr_data *data = fiddle_ptr_check_memory_view(obj);
     rb_memory_view_init_as_byte_array(view, obj, data->ptr, data->size, true);
 

test/fiddle/test_memory_view.rb

@@ -36,6 +36,31 @@ def test_available?
       assert {!MemoryView.available?(Object.new)}
     end
 
+    def test_new_with_flags
+      ptr = Pointer["hello world"]
+      mview = MemoryView.new(ptr, MemoryView::SIMPLE)
+      begin
+        assert_equal(ptr.size, mview.byte_size)
+      ensure
+        mview.release
+      end
+    end
+
+    def test_new_with_unsupported_flags
+      ptr = Pointer["hello world"]
+      assert_raise(ArgumentError) do
+        MemoryView.new(ptr, MemoryView::WRITABLE)
+      end
+    end
+
+    def test_export_with_flags
+      str = "hello world"
+      mview_str = MemoryView.export(Pointer[str], MemoryView::SIMPLE) do |mview|
+        mview.to_s
+      end
+      assert_equal(str, mview_str)
+    end
+
     def test_memory_view_from_pointer
       str = Marshal.load(Marshal.dump("hello world"))
       ptr = Pointer[str]