Add a Retained Pointer smart class.

It's going to be hard to fix some XFA object leaks without
this. Put this in fxcrt/ as we should be able to make the
FX strings take advantage of this.

BUG=pdfium:55

Review URL: https://codereview.chromium.org/1805683002

3 files changed, 83 insertions, 26 deletions

diff --git a/core/fxcrt/include/cfx_retain_ptr.h b/core/fxcrt/include/cfx_retain_ptr.h
new file mode 100644
index 0000000000..25edd585cb
--- /dev/null
+++ b/core/fxcrt/include/cfx_retain_ptr.h
@@ -0,0 +1,57 @@
+// Copyright 2016 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_INCLUDE_CFX_RETAIN_PTR_H_
+#define CORE_FXCRT_INCLUDE_CFX_RETAIN_PTR_H_
+
+#include <memory>
+
+#include "core/fxcrt/include/fx_memory.h"
+
+template <class T>
+class CFX_RetainPtr {
+ public:
+  explicit CFX_RetainPtr(T* pObj) : m_pObj(pObj) {
+    if (m_pObj)
+      m_pObj->Retain();
+  }
+
+  CFX_RetainPtr() : CFX_RetainPtr(nullptr) {}
+  CFX_RetainPtr(const CFX_RetainPtr& that) : CFX_RetainPtr(that.Get()) {}
+  CFX_RetainPtr(CFX_RetainPtr&& that) { Swap(that); }
+
+  template <class U>
+  CFX_RetainPtr(const CFX_RetainPtr<U>& that)
+      : CFX_RetainPtr(that.Get()) {}
+
+  void Reset(T* obj = nullptr) {
+    if (obj)
+      obj->Retain();
+    m_pObj.reset(obj);
+  }
+
+  T* Get() const { return m_pObj.get(); }
+  void Swap(CFX_RetainPtr& that) { m_pObj.swap(that.m_pObj); }
+
+  CFX_RetainPtr& operator=(const CFX_RetainPtr& that) {
+    if (*this != that)
+      Reset(that.Get());
+    return *this;
+  }
+
+  bool operator==(const CFX_RetainPtr& that) const {
+    return Get() == that.Get();
+  }
+
+  bool operator!=(const CFX_RetainPtr& that) const { return !(*this == that); }
+
+  operator bool() const { return !!m_pObj; }
+  T& operator*() const { return *m_pObj.get(); }
+  T* operator->() const { return m_pObj.get(); }
+
+ private:
+  std::unique_ptr<T, ReleaseDeleter<T>> m_pObj;
+};
+
+#endif  // CORE_FXCRT_INCLUDE_CFX_RETAIN_PTR_H_
diff --git a/core/fxcrt/include/fx_basic.h b/core/fxcrt/include/fx_basic.h
index 8a7afda137..feeb6e756d 100644
--- a/core/fxcrt/include/fx_basic.h
+++ b/core/fxcrt/include/fx_basic.h
@@ -15,32 +15,6 @@
 #include "core/fxcrt/include/fx_string.h"
 #include "core/fxcrt/include/fx_system.h"
 
-// The FX_ArraySize(arr) macro returns the # of elements in an array arr.
-// The expression is a compile-time constant, and therefore can be
-// used in defining new arrays, for example.  If you use FX_ArraySize on
-// a pointer by mistake, you will get a compile-time error.
-//
-// One caveat is that FX_ArraySize() doesn't accept any array of an
-// anonymous type or a type defined inside a function.
-#define FX_ArraySize(array) (sizeof(ArraySizeHelper(array)))
-
-// This template function declaration is used in defining FX_ArraySize.
-// Note that the function doesn't need an implementation, as we only
-// use its type.
-template <typename T, size_t N>
-char(&ArraySizeHelper(T(&array)[N]))[N];
-
-// Used with std::unique_ptr to FX_Free raw memory.
-struct FxFreeDeleter {
-  inline void operator()(void* ptr) const { FX_Free(ptr); }
-};
-
-// Used with std::unique_ptr to Release() objects that can't be deleted.
-template <class T>
-struct ReleaseDeleter {
-  inline void operator()(T* ptr) const { ptr->Release(); }
-};
-
 class CFX_BinaryBuf {
  public:
   CFX_BinaryBuf();
diff --git a/core/fxcrt/include/fx_memory.h b/core/fxcrt/include/fx_memory.h
index c3dafc8d5e..2614016550 100644
--- a/core/fxcrt/include/fx_memory.h
+++ b/core/fxcrt/include/fx_memory.h
@@ -74,6 +74,32 @@ inline void* FX_ReallocOrDie(void* ptr,
 
 #define FX_Free(ptr) free(ptr)
 
+// The FX_ArraySize(arr) macro returns the # of elements in an array arr.
+// The expression is a compile-time constant, and therefore can be
+// used in defining new arrays, for example.  If you use FX_ArraySize on
+// a pointer by mistake, you will get a compile-time error.
+//
+// One caveat is that FX_ArraySize() doesn't accept any array of an
+// anonymous type or a type defined inside a function.
+#define FX_ArraySize(array) (sizeof(ArraySizeHelper(array)))
+
+// This template function declaration is used in defining FX_ArraySize.
+// Note that the function doesn't need an implementation, as we only
+// use its type.
+template <typename T, size_t N>
+char(&ArraySizeHelper(T(&array)[N]))[N];
+
+// Used with std::unique_ptr to FX_Free raw memory.
+struct FxFreeDeleter {
+  inline void operator()(void* ptr) const { FX_Free(ptr); }
+};
+
+// Used with std::unique_ptr to Release() objects that can't be deleted.
+template <class T>
+struct ReleaseDeleter {
+  inline void operator()(T* ptr) const { ptr->Release(); }
+};
+
 class CFX_DestructObject {
  public:
   virtual ~CFX_DestructObject() {}