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1 // Copyright 2016 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #ifndef PDFIUM_THIRD_PARTY_BASE_PTR_UTIL_H_
6 #define PDFIUM_THIRD_PARTY_BASE_PTR_UTIL_H_
7 
8 #include <memory>
9 #include <utility>
10 
11 namespace pdfium {
12 
13 // Helper to transfer ownership of a raw pointer to a std::unique_ptr<T>.
14 // Note that std::unique_ptr<T> has very different semantics from
15 // std::unique_ptr<T[]>: do not use this helper for array allocations.
16 template <typename T>
WrapUnique(T * ptr)17 std::unique_ptr<T> WrapUnique(T* ptr) {
18   return std::unique_ptr<T>(ptr);
19 }
20 
21 namespace internal {
22 
23 template <typename T>
24 struct MakeUniqueResult {
25   using Scalar = std::unique_ptr<T>;
26 };
27 
28 template <typename T>
29 struct MakeUniqueResult<T[]> {
30   using Array = std::unique_ptr<T[]>;
31 };
32 
33 template <typename T, size_t N>
34 struct MakeUniqueResult<T[N]> {
35   using Invalid = void;
36 };
37 
38 }  // namespace internal
39 
40 // Helper to construct an object wrapped in a std::unique_ptr. This is an
41 // implementation of C++14's std::MakeUnique that can be used in Chrome.
42 //
43 // MakeUnique<T>(args) should be preferred over WrapUnique(new T(args)): bare
44 // calls to `new` should be treated with scrutiny.
45 //
46 // Usage:
47 //   // ptr is a std::unique_ptr<std::string>
48 //   auto ptr = MakeUnique<std::string>("hello world!");
49 //
50 //   // arr is a std::unique_ptr<int[]>
51 //   auto arr = MakeUnique<int[]>(5);
52 
53 // Overload for non-array types. Arguments are forwarded to T's constructor.
54 template <typename T, typename... Args>
55 typename internal::MakeUniqueResult<T>::Scalar MakeUnique(Args&&... args) {
56   return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
57 }
58 
59 // Overload for array types of unknown bound, e.g. T[]. The array is allocated
60 // with `new T[n]()` and value-initialized: note that this is distinct from
61 // `new T[n]`, which default-initializes.
62 template <typename T>
63 typename internal::MakeUniqueResult<T>::Array MakeUnique(size_t size) {
64   return std::unique_ptr<T>(new typename std::remove_extent<T>::type[size]());
65 }
66 
67 // Overload to reject array types of known bound, e.g. T[n].
68 template <typename T, typename... Args>
69 typename internal::MakeUniqueResult<T>::Invalid MakeUnique(Args&&... args) =
70     delete;
71 
72 }  // namespace pdfium
73 
74 #endif  // PDFIUM_THIRD_PARTY_BASE_PTR_UTIL_H_
75