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authorDan Sinclair <dsinclair@chromium.org>2017-09-21 16:53:58 -0400
committerChromium commit bot <commit-bot@chromium.org>2017-09-21 21:25:26 +0000
commitaee0db0e6a12bdaacebeb8fb791f4e0d45e18a0d (patch)
tree1e14d60adcffeb0791a0a6c8792d3e9c0109384e /core/fxcrt/unowned_ptr.h
parent8e9e3d8975eeea3429c3b3ea703f04ac34e20e28 (diff)
downloadpdfium-aee0db0e6a12bdaacebeb8fb791f4e0d45e18a0d.tar.xz
Move CFX_UnownedPtr to UnownedPtr
This CL moves CFX_UnownedPtr to UnownedPtr and places in the fxcrt namespace. Bug: pdfium:898 Change-Id: I6d1fa463f365e5cb3aafa8c8a7a5f7eff62ed8e0 Reviewed-on: https://pdfium-review.googlesource.com/14620 Reviewed-by: Tom Sepez <tsepez@chromium.org> Commit-Queue: dsinclair <dsinclair@chromium.org>
Diffstat (limited to 'core/fxcrt/unowned_ptr.h')
-rw-r--r--core/fxcrt/unowned_ptr.h121
1 files changed, 121 insertions, 0 deletions
diff --git a/core/fxcrt/unowned_ptr.h b/core/fxcrt/unowned_ptr.h
new file mode 100644
index 0000000000..012af3ddf7
--- /dev/null
+++ b/core/fxcrt/unowned_ptr.h
@@ -0,0 +1,121 @@
+// 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_UNOWNED_PTR_H_
+#define CORE_FXCRT_UNOWNED_PTR_H_
+
+#include <functional>
+#include <memory>
+#include <type_traits>
+#include <utility>
+
+// UnownedPtr is a smart pointer class that behaves very much like a
+// standard C-style pointer. The advantages of using it over raw
+// pointers are:
+//
+// 1. It documents the nature of the pointer with no need to add a comment
+// explaining that is it // Not owned. Additionally, an attempt to delete
+// an unowned ptr will fail to compile rather than silently succeeding,
+// since it is a class and not a raw pointer.
+//
+// 2. When built for a memory tool like ASAN, the class provides a destructor
+// which checks that the object being pointed to is still alive.
+//
+// Hence, when using UnownedPtr, no dangling pointers are ever permitted,
+// even if they are not de-referenced after becoming dangling. The style of
+// programming required is that the lifetime an object containing an
+// UnownedPtr must be strictly less than the object to which it points.
+//
+// The same checks are also performed at assignment time to prove that the
+// old value was not a dangling pointer, either.
+//
+// The array indexing operation [] is not supported on an unowned ptr,
+// because an unowned ptr expresses a one to one relationship with some
+// other heap object.
+
+namespace fxcrt {
+
+template <class T>
+class UnownedPtr {
+ public:
+ UnownedPtr() {}
+ UnownedPtr(const UnownedPtr& that) : UnownedPtr(that.Get()) {}
+
+ template <typename U>
+ explicit UnownedPtr(U* pObj) : m_pObj(pObj) {}
+
+ // Deliberately implicit to allow returning nullptrs.
+ // NOLINTNEXTLINE(runtime/explicit)
+ UnownedPtr(std::nullptr_t ptr) {}
+
+ ~UnownedPtr() { ProbeForLowSeverityLifetimeIssue(); }
+
+ UnownedPtr& operator=(T* that) {
+ ProbeForLowSeverityLifetimeIssue();
+ m_pObj = that;
+ return *this;
+ }
+
+ UnownedPtr& operator=(const UnownedPtr& that) {
+ ProbeForLowSeverityLifetimeIssue();
+ if (*this != that)
+ m_pObj = that.Get();
+ return *this;
+ }
+
+ bool operator==(const UnownedPtr& that) const { return Get() == that.Get(); }
+ bool operator!=(const UnownedPtr& that) const { return !(*this == that); }
+ bool operator<(const UnownedPtr& that) const {
+ return std::less<T*>()(Get(), that.Get());
+ }
+
+ template <typename U>
+ bool operator==(const U* that) const {
+ return Get() == that;
+ }
+
+ template <typename U>
+ bool operator!=(const U* that) const {
+ return !(*this == that);
+ }
+
+ T* Get() const { return m_pObj; }
+
+ T* Release() {
+ ProbeForLowSeverityLifetimeIssue();
+ T* pTemp = nullptr;
+ std::swap(pTemp, m_pObj);
+ return pTemp;
+ }
+
+ explicit operator bool() const { return !!m_pObj; }
+ T& operator*() const { return *m_pObj; }
+ T* operator->() const { return m_pObj; }
+
+ private:
+ inline void ProbeForLowSeverityLifetimeIssue() {
+#if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
+ if (m_pObj)
+ reinterpret_cast<const volatile uint8_t*>(m_pObj)[0];
+#endif
+ }
+
+ T* m_pObj = nullptr;
+};
+
+template <typename T, typename U>
+inline bool operator==(const U* lhs, const UnownedPtr<T>& rhs) {
+ return rhs == lhs;
+}
+
+template <typename T, typename U>
+inline bool operator!=(const U* lhs, const UnownedPtr<T>& rhs) {
+ return rhs != lhs;
+}
+
+} // namespace fxcrt
+
+using fxcrt::UnownedPtr;
+
+#endif // CORE_FXCRT_UNOWNED_PTR_H_