2 files changed, 150 insertions, 0 deletions
diff --git a/core/fxcrt/cfx_unowned_ptr.h b/core/fxcrt/cfx_unowned_ptr.h
new file mode 100644
index 0000000000..11f4e8e38b
--- /dev/null
+++ b/core/fxcrt/cfx_unowned_ptr.h
@@ -0,0 +1,64 @@
+// Copyright 2017 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CORE_FXCRT_CFX_UNOWNED_PTR_H_
+#define CORE_FXCRT_CFX_UNOWNED_PTR_H_
+
+#include <functional>
+#include <memory>
+#include <type_traits>
+#include <utility>
+
+#include "core/fxcrt/fx_memory.h"
+
+template <class T>
+class CFX_UnownedPtr {
+ public:
+  CFX_UnownedPtr() {}
+  CFX_UnownedPtr(const CFX_UnownedPtr& that) : CFX_UnownedPtr(that.Get()) {}
+
+  template <typename U>
+  explicit CFX_UnownedPtr(U* pObj) : m_pObj(pObj) {}
+
+  // Deliberately implicit to allow returning nullptrs.
+  // NOLINTNEXTLINE(runtime/explicit)
+  CFX_UnownedPtr(std::nullptr_t ptr) {}
+
+#if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
+  ~CFX_UnownedPtr() {
+    if (m_pObj)
+      reinterpret_cast<volatile uint8_t*>(m_pObj)[0];
+  }
+#endif
+
+  CFX_UnownedPtr& operator=(T* that) {
+    m_pObj = that;
+    return *this;
+  }
+  CFX_UnownedPtr& operator=(const CFX_UnownedPtr& that) {
+    if (*this != that)
+      m_pObj = that.Get();
+    return *this;
+  }
+
+  bool operator==(const CFX_UnownedPtr& that) const {
+    return Get() == that.Get();
+  }
+  bool operator==(const T* that) const { return Get() == that; }
+  bool operator!=(const CFX_UnownedPtr& that) const { return !(*this == that); }
+  bool operator!=(const T* that) const { return !(*this == that); }
+  bool operator<(const CFX_UnownedPtr& that) const {
+    return std::less<T*>()(Get(), that.Get());
+  }
+
+  T* Get() const { return m_pObj; }
+  explicit operator bool() const { return !!m_pObj; }
+  T& operator*() const { return *m_pObj; }
+  T* operator->() const { return m_pObj; }
+
+ private:
+  T* m_pObj = nullptr;
+};
+
+#endif  // CORE_FXCRT_CFX_UNOWNED_PTR_H_
diff --git a/core/fxcrt/cfx_unowned_ptr_unittest.cpp b/core/fxcrt/cfx_unowned_ptr_unittest.cpp
new file mode 100644
index 0000000000..7d29faedf5
--- /dev/null
+++ b/core/fxcrt/cfx_unowned_ptr_unittest.cpp
@@ -0,0 +1,86 @@
+// Copyright 2017 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/fxcrt/cfx_unowned_ptr.h"
+
+#include <utility>
+#include <vector>
+
+#include "testing/fx_string_testhelpers.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace {
+
+class Clink {
+ public:
+  CFX_UnownedPtr<Clink> next_ = nullptr;
+};
+
+void DeleteDangling() {
+  Clink* ptr1 = new Clink();
+  Clink* ptr2 = new Clink();
+  ptr2->next_ = ptr1;
+  delete ptr1;
+  delete ptr2;
+}
+
+}  // namespace
+
+TEST(fxcrt, UnownedPtrOk) {
+  Clink* ptr1 = new Clink();
+  Clink* ptr2 = new Clink();
+  ptr2->next_ = ptr1;
+  delete ptr2;
+  delete ptr1;
+}
+
+TEST(fxcrt, UnownedPtrNotOk) {
+#if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
+  EXPECT_DEATH(DeleteDangling(), "");
+#else
+  DeleteDangling();
+#endif
+}
+
+TEST(fxcrt, OperatorEQ) {
+  int foo;
+  CFX_UnownedPtr<int> ptr1;
+  EXPECT_TRUE(ptr1 == ptr1);
+
+  CFX_UnownedPtr<int> ptr2;
+  EXPECT_TRUE(ptr1 == ptr2);
+
+  CFX_UnownedPtr<int> ptr3(&foo);
+  EXPECT_TRUE(ptr3 == &foo);
+  EXPECT_FALSE(ptr1 == ptr3);
+
+  ptr1 = &foo;
+  EXPECT_TRUE(ptr1 == ptr3);
+}
+
+TEST(fxcrt, OperatorNE) {
+  int foo;
+  CFX_UnownedPtr<int> ptr1;
+  EXPECT_FALSE(ptr1 != ptr1);
+
+  CFX_UnownedPtr<int> ptr2;
+  EXPECT_FALSE(ptr1 != ptr2);
+
+  CFX_UnownedPtr<int> ptr3(&foo);
+  EXPECT_FALSE(ptr3 != &foo);
+  EXPECT_TRUE(ptr1 != ptr3);
+
+  ptr1 = &foo;
+  EXPECT_FALSE(ptr1 != ptr3);
+}
+
+TEST(fxcrt, OperatorLT) {
+  int foos[2];
+  CFX_UnownedPtr<int> ptr1(&foos[0]);
+  CFX_UnownedPtr<int> ptr2(&foos[1]);
+
+  EXPECT_FALSE(ptr1 < ptr1);
+  EXPECT_TRUE(ptr1 < ptr2);
+  EXPECT_FALSE(ptr2 < ptr1);
+}