The Tor Browser: comparison mfbt/RangedPtr.h

--1:000000000000
+:df8dabfa5067
+/* -*- 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* ptr;
+#ifdef DEBUG
+T* const rangeStart;
+T* const rangeEnd;
+#endif
+typedef void (RangedPtr::* ConvertibleToBool)();
+void nonNull() {}
+void checkSanity() {
+MOZ_ASSERT(rangeStart <= ptr);
+MOZ_ASSERT(ptr <= rangeEnd);
+}
+/* Creates a new pointer for |p|, restricted to this pointer's range. */
+RangedPtr<T> create(T *p) const {
+#ifdef DEBUG
+return RangedPtr<T>(p, rangeStart, rangeEnd);
+#else
+return RangedPtr<T>(p, nullptr, size_t(0));
+#endif
+}
+uintptr_t asUintptr() const { return uintptr_t(ptr); }
+public:
+RangedPtr(T* p, T* start, T* end)
+: ptr(p)
+#ifdef DEBUG
+, rangeStart(start), rangeEnd(end)
+#endif
+{
+MOZ_ASSERT(rangeStart <= rangeEnd);
+checkSanity();
+}
+RangedPtr(T* p, T* start, size_t length)
+: ptr(p)
+#ifdef DEBUG
+, rangeStart(start), rangeEnd(start + length)
+#endif
+{
+MOZ_ASSERT(length <= size_t(-1) / sizeof(T));
+MOZ_ASSERT(uintptr_t(rangeStart) + length * sizeof(T) >= uintptr_t(rangeStart));
+checkSanity();
+}
+/* Equivalent to RangedPtr(p, p, length). */
+RangedPtr(T* p, size_t length)
+: ptr(p)
+#ifdef DEBUG
+, rangeStart(p), rangeEnd(p + length)
+#endif
+{
+MOZ_ASSERT(length <= size_t(-1) / sizeof(T));
+MOZ_ASSERT(uintptr_t(rangeStart) + length * sizeof(T) >= uintptr_t(rangeStart));
+checkSanity();
+}
+/* Equivalent to RangedPtr(arr, arr, N). */
+template<size_t N>
+RangedPtr(T (&arr)[N])
+: ptr(arr)
+#ifdef DEBUG
+, rangeStart(arr), rangeEnd(arr + N)
+#endif
+{
+checkSanity();
+}
+T* get() const {
+return ptr;
+}
+operator ConvertibleToBool() const { return ptr ? &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>& other) {
+MOZ_ASSERT(rangeStart == other.rangeStart);
+MOZ_ASSERT(rangeEnd == other.rangeEnd);
+ptr = other.ptr;
+checkSanity();
+return *this;
+}
+RangedPtr<T> operator+(size_t inc) {
+MOZ_ASSERT(inc <= size_t(-1) / sizeof(T));
+MOZ_ASSERT(asUintptr() + inc * sizeof(T) >= asUintptr());
+return create(ptr + inc);
+}
+RangedPtr<T> operator-(size_t dec) {
+MOZ_ASSERT(dec <= size_t(-1) / sizeof(T));
+MOZ_ASSERT(asUintptr() - dec * sizeof(T) <= asUintptr());
+return create(ptr - dec);
+}
+/*
+* 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* p) {
+*this = create(p);
+return *this;
+}
+template <typename U>
+RangedPtr<T>& operator=(const RangedPtr<U>& p) {
+MOZ_ASSERT(rangeStart <= p.ptr);
+MOZ_ASSERT(p.ptr <= rangeEnd);
+ptr = p.ptr;
+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 inc) {
+*this = *this + inc;
+return *this;
+}
+RangedPtr<T>& operator-=(size_t dec) {
+*this = *this - dec;
+return *this;
+}
+T& operator[](int index) const {
+MOZ_ASSERT(size_t(index > 0 ? index : -index) <= size_t(-1) / sizeof(T));
+return *create(ptr + index);
+}
+T& operator*() const {
+MOZ_ASSERT(ptr >= rangeStart);
+MOZ_ASSERT(ptr < rangeEnd);
+return *ptr;
+}
+template <typename U>
+bool operator==(const RangedPtr<U>& other) const {
+return ptr == other.ptr;
+}
+template <typename U>
+bool operator!=(const RangedPtr<U>& other) const {
+return !(*this == other);
+}
+template<typename U>
+bool operator==(const U* u) const {
+return ptr == u;
+}
+template<typename U>
+bool operator!=(const U* u) const {
+return !(*this == u);
+}
+template <typename U>
+bool operator<(const RangedPtr<U>& other) const {
+return ptr < other.ptr;
+}
+template <typename U>
+bool operator<=(const RangedPtr<U>& other) const {
+return ptr <= other.ptr;
+}
+template <typename U>
+bool operator>(const RangedPtr<U>& other) const {
+return ptr > other.ptr;
+}
+template <typename U>
+bool operator>=(const RangedPtr<U>& other) const {
+return ptr >= other.ptr;
+}
+size_t operator-(const RangedPtr<T>& other) const {
+MOZ_ASSERT(ptr >= other.ptr);
+return PointerRangeSize(other.ptr, ptr);
+}
+private:
+RangedPtr() MOZ_DELETE;
+T* operator&() MOZ_DELETE;
+};
+} /* namespace mozilla */
+#endif /* mozilla_RangedPtr_h */

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comparison: mfbt/RangedPtr.h

mfbt/RangedPtr.h