1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/xpcom/base/StaticPtr.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,254 @@
1.4 +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* vim: set sw=2 ts=8 et ft=cpp : */
1.6 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +
1.10 +#ifndef mozilla_StaticPtr_h
1.11 +#define mozilla_StaticPtr_h
1.12 +
1.13 +#include "mozilla/Assertions.h"
1.14 +#include "mozilla/NullPtr.h"
1.15 +
1.16 +namespace mozilla {
1.17 +
1.18 +/**
1.19 + * StaticAutoPtr and StaticRefPtr are like nsAutoPtr and nsRefPtr, except they
1.20 + * are suitable for use as global variables.
1.21 + *
1.22 + * In particular, a global instance of Static{Auto,Ref}Ptr doesn't cause the
1.23 + * compiler to emit a static initializer (in release builds, anyway).
1.24 + *
1.25 + * In order to accomplish this, Static{Auto,Ref}Ptr must have a trivial
1.26 + * constructor and destructor. As a consequence, it cannot initialize its raw
1.27 + * pointer to 0 on construction, and it cannot delete/release its raw pointer
1.28 + * upon destruction.
1.29 + *
1.30 + * Since the compiler guarantees that all global variables are initialized to
1.31 + * 0, these trivial constructors are safe, so long as you use
1.32 + * Static{Auto,Ref}Ptr as a global variable. If you use Static{Auto,Ref}Ptr as
1.33 + * a stack variable or as a class instance variable, you will get what you
1.34 + * deserve.
1.35 + *
1.36 + * Static{Auto,Ref}Ptr have a limited interface as compared to ns{Auto,Ref}Ptr;
1.37 + * this is intentional, since their range of acceptable uses is smaller.
1.38 + */
1.39 +
1.40 +template<class T>
1.41 +class StaticAutoPtr
1.42 +{
1.43 + public:
1.44 + // In debug builds, check that mRawPtr is initialized for us as we expect
1.45 + // by the compiler. In non-debug builds, don't declare a constructor
1.46 + // so that the compiler can see that the constructor is trivial.
1.47 +#ifdef DEBUG
1.48 + StaticAutoPtr()
1.49 + {
1.50 + MOZ_ASSERT(!mRawPtr);
1.51 + }
1.52 +#endif
1.53 +
1.54 + StaticAutoPtr<T>& operator=(T* rhs)
1.55 + {
1.56 + Assign(rhs);
1.57 + return *this;
1.58 + }
1.59 +
1.60 + T* get() const
1.61 + {
1.62 + return mRawPtr;
1.63 + }
1.64 +
1.65 + operator T*() const
1.66 + {
1.67 + return get();
1.68 + }
1.69 +
1.70 + T* operator->() const
1.71 + {
1.72 + MOZ_ASSERT(mRawPtr);
1.73 + return get();
1.74 + }
1.75 +
1.76 + T& operator*() const
1.77 + {
1.78 + return *get();
1.79 + }
1.80 +
1.81 + private:
1.82 + // Disallow copy constructor, but only in debug mode. We only define
1.83 + // a default constructor in debug mode (see above); if we declared
1.84 + // this constructor always, the compiler wouldn't generate a trivial
1.85 + // default constructor for us in non-debug mode.
1.86 +#ifdef DEBUG
1.87 + StaticAutoPtr(StaticAutoPtr<T> &other);
1.88 +#endif
1.89 +
1.90 + void Assign(T* newPtr)
1.91 + {
1.92 + MOZ_ASSERT(!newPtr || mRawPtr != newPtr);
1.93 + T* oldPtr = mRawPtr;
1.94 + mRawPtr = newPtr;
1.95 + delete oldPtr;
1.96 + }
1.97 +
1.98 + T* mRawPtr;
1.99 +};
1.100 +
1.101 +template<class T>
1.102 +class StaticRefPtr
1.103 +{
1.104 +public:
1.105 + // In debug builds, check that mRawPtr is initialized for us as we expect
1.106 + // by the compiler. In non-debug builds, don't declare a constructor
1.107 + // so that the compiler can see that the constructor is trivial.
1.108 +#ifdef DEBUG
1.109 + StaticRefPtr()
1.110 + {
1.111 + MOZ_ASSERT(!mRawPtr);
1.112 + }
1.113 +#endif
1.114 +
1.115 + StaticRefPtr<T>& operator=(T* rhs)
1.116 + {
1.117 + AssignWithAddref(rhs);
1.118 + return *this;
1.119 + }
1.120 +
1.121 + StaticRefPtr<T>& operator=(const StaticRefPtr<T>& rhs)
1.122 + {
1.123 + return (this = rhs.mRawPtr);
1.124 + }
1.125 +
1.126 + T* get() const
1.127 + {
1.128 + return mRawPtr;
1.129 + }
1.130 +
1.131 + operator T*() const
1.132 + {
1.133 + return get();
1.134 + }
1.135 +
1.136 + T* operator->() const
1.137 + {
1.138 + MOZ_ASSERT(mRawPtr);
1.139 + return get();
1.140 + }
1.141 +
1.142 + T& operator*() const
1.143 + {
1.144 + return *get();
1.145 + }
1.146 +
1.147 +private:
1.148 + void AssignWithAddref(T* newPtr)
1.149 + {
1.150 + if (newPtr) {
1.151 + newPtr->AddRef();
1.152 + }
1.153 + AssignAssumingAddRef(newPtr);
1.154 + }
1.155 +
1.156 + void AssignAssumingAddRef(T* newPtr)
1.157 + {
1.158 + T* oldPtr = mRawPtr;
1.159 + mRawPtr = newPtr;
1.160 + if (oldPtr) {
1.161 + oldPtr->Release();
1.162 + }
1.163 + }
1.164 +
1.165 + T* mRawPtr;
1.166 +};
1.167 +
1.168 +namespace StaticPtr_internal {
1.169 +class Zero;
1.170 +} // namespace StaticPtr_internal
1.171 +
1.172 +#define REFLEXIVE_EQUALITY_OPERATORS(type1, type2, eq_fn, ...) \
1.173 + template<__VA_ARGS__> \
1.174 + inline bool \
1.175 + operator==(type1 lhs, type2 rhs) \
1.176 + { \
1.177 + return eq_fn; \
1.178 + } \
1.179 + \
1.180 + template<__VA_ARGS__> \
1.181 + inline bool \
1.182 + operator==(type2 lhs, type1 rhs) \
1.183 + { \
1.184 + return rhs == lhs; \
1.185 + } \
1.186 + \
1.187 + template<__VA_ARGS__> \
1.188 + inline bool \
1.189 + operator!=(type1 lhs, type2 rhs) \
1.190 + { \
1.191 + return !(lhs == rhs); \
1.192 + } \
1.193 + \
1.194 + template<__VA_ARGS__> \
1.195 + inline bool \
1.196 + operator!=(type2 lhs, type1 rhs) \
1.197 + { \
1.198 + return !(lhs == rhs); \
1.199 + }
1.200 +
1.201 +// StaticAutoPtr (in)equality operators
1.202 +
1.203 +template<class T, class U>
1.204 +inline bool
1.205 +operator==(const StaticAutoPtr<T>& lhs, const StaticAutoPtr<U>& rhs)
1.206 +{
1.207 + return lhs.get() == rhs.get();
1.208 +}
1.209 +
1.210 +template<class T, class U>
1.211 +inline bool
1.212 +operator!=(const StaticAutoPtr<T>& lhs, const StaticAutoPtr<U>& rhs)
1.213 +{
1.214 + return !(lhs == rhs);
1.215 +}
1.216 +
1.217 +REFLEXIVE_EQUALITY_OPERATORS(const StaticAutoPtr<T>&, const U*,
1.218 + lhs.get() == rhs, class T, class U)
1.219 +
1.220 +REFLEXIVE_EQUALITY_OPERATORS(const StaticAutoPtr<T>&, U*,
1.221 + lhs.get() == rhs, class T, class U)
1.222 +
1.223 +// Let us compare StaticAutoPtr to 0.
1.224 +REFLEXIVE_EQUALITY_OPERATORS(const StaticAutoPtr<T>&, StaticPtr_internal::Zero*,
1.225 + lhs.get() == nullptr, class T)
1.226 +
1.227 +// StaticRefPtr (in)equality operators
1.228 +
1.229 +template<class T, class U>
1.230 +inline bool
1.231 +operator==(const StaticRefPtr<T>& lhs, const StaticRefPtr<U>& rhs)
1.232 +{
1.233 + return lhs.get() == rhs.get();
1.234 +}
1.235 +
1.236 +template<class T, class U>
1.237 +inline bool
1.238 +operator!=(const StaticRefPtr<T>& lhs, const StaticRefPtr<U>& rhs)
1.239 +{
1.240 + return !(lhs == rhs);
1.241 +}
1.242 +
1.243 +REFLEXIVE_EQUALITY_OPERATORS(const StaticRefPtr<T>&, const U*,
1.244 + lhs.get() == rhs, class T, class U)
1.245 +
1.246 +REFLEXIVE_EQUALITY_OPERATORS(const StaticRefPtr<T>&, U*,
1.247 + lhs.get() == rhs, class T, class U)
1.248 +
1.249 +// Let us compare StaticRefPtr to 0.
1.250 +REFLEXIVE_EQUALITY_OPERATORS(const StaticRefPtr<T>&, StaticPtr_internal::Zero*,
1.251 + lhs.get() == nullptr, class T)
1.252 +
1.253 +#undef REFLEXIVE_EQUALITY_OPERATORS
1.254 +
1.255 +} // namespace mozilla
1.256 +
1.257 +#endif
