AlwaysValidPointer - forwarding constructor and tests

Bug: webrtc:10335
Change-Id: I1305ccf8d4f1b25f89fef7d26b090741d5f57f7e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/256106
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Jonas Oreland <jonaso@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36264}

rtc_base/memory/BUILD.gn

@@ -45,10 +45,12 @@ rtc_library("unittests") {
   testonly = true
   sources = [
     "aligned_malloc_unittest.cc",
+    "always_valid_pointer_unittest.cc",
     "fifo_buffer_unittest.cc",
   ]
   deps = [
     ":aligned_malloc",
+    ":always_valid_pointer",
     ":fifo_buffer",
     "../../test:test_support",
   ]
@@ -56,4 +58,5 @@ rtc_library("unittests") {
 
 rtc_source_set("always_valid_pointer") {
   sources = [ "always_valid_pointer.h" ]
+  deps = [ "..:checks" ]
 }

rtc_base/memory/always_valid_pointer.h

@@ -11,13 +11,16 @@
 #define RTC_BASE_MEMORY_ALWAYS_VALID_POINTER_H_
 
 #include <memory>
+#include <utility>
+
+#include "rtc_base/checks.h"
 
 namespace webrtc {
 
 // This template allows the instantiation of a pointer to Interface in such a
 // way that if it is passed a null pointer, an object of class Default will be
 // created, which will be deallocated when the pointer is deleted.
-template <typename Interface, typename Default>
+template <typename Interface, typename Default = Interface>
 class AlwaysValidPointer {
  public:
   explicit AlwaysValidPointer(Interface* pointer)
@@ -26,6 +29,14 @@ class AlwaysValidPointer {
     RTC_DCHECK(pointer_);
   }
 
+  template <typename... Args>
+  AlwaysValidPointer(Interface* pointer, Args... args)
+      : owned_instance_(
+            pointer ? nullptr : std::make_unique<Default>(std::move(args...))),
+        pointer_(pointer ? pointer : owned_instance_.get()) {
+    RTC_DCHECK(pointer_);
+  }
+
   Interface* get() { return pointer_; }
   Interface* operator->() { return pointer_; }
   Interface& operator*() { return *pointer_; }

rtc_base/memory/always_valid_pointer_unittest.cc

@@ -0,0 +1,49 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "rtc_base/memory/always_valid_pointer.h"
+
+#include <string>
+
+#include "test/gtest.h"
+
+namespace webrtc {
+
+TEST(AlwaysValidPointerTest, DefaultToEmptyValue) {
+  AlwaysValidPointer<std::string> ptr(nullptr);
+  EXPECT_EQ(*ptr, "");
+}
+TEST(AlwaysValidPointerTest, DefaultWithForwardedArgument) {
+  AlwaysValidPointer<std::string> ptr(nullptr, "test");
+  EXPECT_EQ(*ptr, "test");
+}
+TEST(AlwaysValidPointerTest, DefaultToSubclass) {
+  struct A {
+    virtual ~A() {}
+    virtual int f() = 0;
+  };
+  struct B : public A {
+    int b = 0;
+    explicit B(int val) : b(val) {}
+    virtual ~B() {}
+    int f() override { return b; }
+  };
+  AlwaysValidPointer<A, B> ptr(nullptr, 3);
+  EXPECT_EQ(ptr->f(), 3);
+  EXPECT_EQ((*ptr).f(), 3);
+  EXPECT_EQ(ptr.get()->f(), 3);
+}
+TEST(AlwaysValidPointerTest, NonDefaultValue) {
+  std::string str("keso");
+  AlwaysValidPointer<std::string> ptr(&str, "test");
+  EXPECT_EQ(*ptr, "keso");
+}
+
+}  // namespace webrtc