mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-12-05 03:54:35 +00:00
2a0942be41
--HG-- extra : rebase_source : 668cd394806203ddfa34bd4f226335ff26c846b5
285 lines
6.8 KiB
C++
285 lines
6.8 KiB
C++
/* -*- 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 "mozilla/NullPtr.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
|
|
|
|
typedef void (RangedPtr::* ConvertibleToBool)();
|
|
void nonNull() {}
|
|
|
|
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>
|
|
RangedPtr(T (&aArr)[N])
|
|
: mPtr(aArr)
|
|
#ifdef DEBUG
|
|
, mRangeStart(aArr), mRangeEnd(aArr + N)
|
|
#endif
|
|
{
|
|
checkSanity();
|
|
}
|
|
|
|
T* get() const { return mPtr; }
|
|
|
|
operator ConvertibleToBool() const { return mPtr ? &RangedPtr::nonNull : 0; }
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
MOZ_ASSERT(mRangeStart == aOther.mRangeStart);
|
|
MOZ_ASSERT(mRangeEnd == aOther.mRangeEnd);
|
|
mPtr = aOther.mPtr;
|
|
checkSanity();
|
|
return *this;
|
|
}
|
|
|
|
RangedPtr<T> operator+(size_t aInc)
|
|
{
|
|
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)
|
|
{
|
|
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[](int 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;
|
|
}
|
|
|
|
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() MOZ_DELETE;
|
|
T* operator&() MOZ_DELETE;
|
|
};
|
|
|
|
} /* namespace mozilla */
|
|
|
|
#endif /* mozilla_RangedPtr_h */
|