Add move support for scoped_refptr.
scoped_ptr has
- move constructor.
- move assignment operator.
- .Pass().
This CL adds the same support for scoped_refptr.
The main benefit is reducing unnecessary reference counter updates.
// Example 1
class Foo {
// Without .Pass(), a copy constructor would be called, which
// increments and decrements the reference counter unnecessarily.
// With .Pass(), a move constructor is called which doesn't update
// the reference counter
Foo(scoped_refptr<T> t) : t_(t.Pass()) {}
const scoped_refptr<T> t_;
};
// Example 2
scoped_refptr<Foo> func() {
return scoped_refptr<Foo>(new Foo());
}
main() {
scoped_refptr<Foo> foo;
// The following would be done by a copy assignment operator before,
// but now a move assignment operator will be used instead.
foo = func();
}
// Example 3
class Foo : public base::RefCountedThreadSafe<Foo> {
...
}
void func(scoped_refptr<Foo> foo) {
...
}
main() {
scoped_refptr<Foo> foo(...);
// Because it's moved, the reference counter won't be updated.
massage_loop->PostTask(FROM_HERE,
base::Bind(&func, base::Passed(foo)));
}
Review URL: https://codereview.chromium.org/1076953002
Cr-Commit-Position: refs/heads/master@{#324910}
3 files changed
