/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ /* vim: set ts=8 sts=2 et sw=2 tw=80: */ /* This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ /* * Implements a smart pointer asserted to remain within a range specified at * construction. */ #ifndef mozilla_RangedPtr_h #define mozilla_RangedPtr_h #include "mozilla/ArrayUtils.h" #include "mozilla/Assertions.h" #include "mozilla/Attributes.h" #include <stdint.h> namespace mozilla { /* * RangedPtr is a smart pointer restricted to an address range specified at * creation. The pointer (and any smart pointers derived from it) must remain * within the range [start, end] (inclusive of end to facilitate use as * sentinels). Dereferencing or indexing into the pointer (or pointers derived * from it) must remain within the range [start, end). All the standard pointer * operators are defined on it; in debug builds these operations assert that the * range specified at construction is respected. * * In theory passing a smart pointer instance as an argument can be slightly * slower than passing a T* (due to ABI requirements for passing structs versus * passing pointers), if the method being called isn't inlined. If you are in * extremely performance-critical code, you may want to be careful using this * smart pointer as an argument type. * * RangedPtr<T> intentionally does not implicitly convert to T*. Use get() to * explicitly convert to T*. Keep in mind that the raw pointer of course won't * implement bounds checking in debug builds. */ template<typename T> class RangedPtr { T* mPtr; #ifdef DEBUG T* const mRangeStart; T* const mRangeEnd; #endif void checkSanity() { MOZ_ASSERT(mRangeStart <= mPtr); MOZ_ASSERT(mPtr <= mRangeEnd); } /* Creates a new pointer for |aPtr|, restricted to this pointer's range. */ RangedPtr<T> create(T* aPtr) const { #ifdef DEBUG return RangedPtr<T>(aPtr, mRangeStart, mRangeEnd); #else return RangedPtr<T>(aPtr, nullptr, size_t(0)); #endif } uintptr_t asUintptr() const { return reinterpret_cast<uintptr_t>(mPtr); } public: RangedPtr(T* aPtr, T* aStart, T* aEnd) : mPtr(aPtr) #ifdef DEBUG , mRangeStart(aStart), mRangeEnd(aEnd) #endif { MOZ_ASSERT(mRangeStart <= mRangeEnd); checkSanity(); } RangedPtr(T* aPtr, T* aStart, size_t aLength) : mPtr(aPtr) #ifdef DEBUG , mRangeStart(aStart), mRangeEnd(aStart + aLength) #endif { MOZ_ASSERT(aLength <= size_t(-1) / sizeof(T)); MOZ_ASSERT(reinterpret_cast<uintptr_t>(mRangeStart) + aLength * sizeof(T) >= reinterpret_cast<uintptr_t>(mRangeStart)); checkSanity(); } /* Equivalent to RangedPtr(aPtr, aPtr, aLength). */ RangedPtr(T* aPtr, size_t aLength) : mPtr(aPtr) #ifdef DEBUG , mRangeStart(aPtr), mRangeEnd(aPtr + aLength) #endif { MOZ_ASSERT(aLength <= size_t(-1) / sizeof(T)); MOZ_ASSERT(reinterpret_cast<uintptr_t>(mRangeStart) + aLength * sizeof(T) >= reinterpret_cast<uintptr_t>(mRangeStart)); checkSanity(); } /* Equivalent to RangedPtr(aArr, aArr, N). */ template<size_t N> explicit RangedPtr(T (&aArr)[N]) : mPtr(aArr) #ifdef DEBUG , mRangeStart(aArr), mRangeEnd(aArr + N) #endif { checkSanity(); } T* get() const { return mPtr; } explicit operator bool() const { return mPtr != nullptr; } void checkIdenticalRange(const RangedPtr<T>& aOther) const { MOZ_ASSERT(mRangeStart == aOther.mRangeStart); MOZ_ASSERT(mRangeEnd == aOther.mRangeEnd); } /* * You can only assign one RangedPtr into another if the two pointers have * the same valid range: * * char arr1[] = "hi"; * char arr2[] = "bye"; * RangedPtr<char> p1(arr1, 2); * p1 = RangedPtr<char>(arr1 + 1, arr1, arr1 + 2); // works * p1 = RangedPtr<char>(arr2, 3); // asserts */ RangedPtr<T>& operator=(const RangedPtr<T>& aOther) { checkIdenticalRange(aOther); mPtr = aOther.mPtr; checkSanity(); return *this; } RangedPtr<T> operator+(size_t aInc) const { MOZ_ASSERT(aInc <= size_t(-1) / sizeof(T)); MOZ_ASSERT(asUintptr() + aInc * sizeof(T) >= asUintptr()); return create(mPtr + aInc); } RangedPtr<T> operator-(size_t aDec) const { MOZ_ASSERT(aDec <= size_t(-1) / sizeof(T)); MOZ_ASSERT(asUintptr() - aDec * sizeof(T) <= asUintptr()); return create(mPtr - aDec); } /* * You can assign a raw pointer into a RangedPtr if the raw pointer is * within the range specified at creation. */ template <typename U> RangedPtr<T>& operator=(U* aPtr) { *this = create(aPtr); return *this; } template <typename U> RangedPtr<T>& operator=(const RangedPtr<U>& aPtr) { MOZ_ASSERT(mRangeStart <= aPtr.mPtr); MOZ_ASSERT(aPtr.mPtr <= mRangeEnd); mPtr = aPtr.mPtr; checkSanity(); return *this; } RangedPtr<T>& operator++() { return (*this += 1); } RangedPtr<T> operator++(int) { RangedPtr<T> rcp = *this; ++*this; return rcp; } RangedPtr<T>& operator--() { return (*this -= 1); } RangedPtr<T> operator--(int) { RangedPtr<T> rcp = *this; --*this; return rcp; } RangedPtr<T>& operator+=(size_t aInc) { *this = *this + aInc; return *this; } RangedPtr<T>& operator-=(size_t aDec) { *this = *this - aDec; return *this; } T& operator[](ptrdiff_t aIndex) const { MOZ_ASSERT(size_t(aIndex > 0 ? aIndex : -aIndex) <= size_t(-1) / sizeof(T)); return *create(mPtr + aIndex); } T& operator*() const { MOZ_ASSERT(mPtr >= mRangeStart); MOZ_ASSERT(mPtr < mRangeEnd); return *mPtr; } T* operator->() const { MOZ_ASSERT(mPtr >= mRangeStart); MOZ_ASSERT(mPtr < mRangeEnd); return mPtr; } template <typename U> bool operator==(const RangedPtr<U>& aOther) const { return mPtr == aOther.mPtr; } template <typename U> bool operator!=(const RangedPtr<U>& aOther) const { return !(*this == aOther); } template<typename U> bool operator==(const U* u) const { return mPtr == u; } template<typename U> bool operator!=(const U* u) const { return !(*this == u); } template <typename U> bool operator<(const RangedPtr<U>& aOther) const { return mPtr < aOther.mPtr; } template <typename U> bool operator<=(const RangedPtr<U>& aOther) const { return mPtr <= aOther.mPtr; } template <typename U> bool operator>(const RangedPtr<U>& aOther) const { return mPtr > aOther.mPtr; } template <typename U> bool operator>=(const RangedPtr<U>& aOther) const { return mPtr >= aOther.mPtr; } size_t operator-(const RangedPtr<T>& aOther) const { MOZ_ASSERT(mPtr >= aOther.mPtr); return PointerRangeSize(aOther.mPtr, mPtr); } private: RangedPtr() = delete; T* operator&() = delete; }; } /* namespace mozilla */ #endif /* mozilla_RangedPtr_h */