Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 308 insertions, 0 deletions

diff --git a/mfbt/RangedPtr.h b/mfbt/RangedPtr.h
new file mode 100644
index 0000000000..9aec59f936
--- /dev/null
+++ b/mfbt/RangedPtr.h
@@ -0,0 +1,308 @@
+/* -*- 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>
+#include <cstddef>
+
+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 {
+  template <typename U>
+  friend 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();
+  }
+
+  RangedPtr(const RangedPtr& aOther)
+      : mPtr(aOther.mPtr)
+#ifdef DEBUG
+        ,
+        mRangeStart(aOther.mRangeStart),
+        mRangeEnd(aOther.mRangeEnd)
+#endif
+  {
+    checkSanity();
+  }
+
+  template <typename U>
+  MOZ_IMPLICIT RangedPtr(const RangedPtr<U>& aOther)
+      : mPtr(aOther.mPtr)
+#ifdef DEBUG
+        ,
+        mRangeStart(aOther.mRangeStart),
+        mRangeEnd(aOther.mRangeEnd)
+#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);
+  }
+
+  template <typename U>
+  RangedPtr<U> ReinterpretCast() const {
+#ifdef DEBUG
+    return {reinterpret_cast<U*>(mPtr), reinterpret_cast<U*>(mRangeStart),
+            reinterpret_cast<U*>(mRangeEnd)};
+#else
+    return {reinterpret_cast<U*>(mPtr), nullptr, nullptr};
+#endif
+  }
+
+  /*
+   * 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);
+  }
+
+  bool operator==(std::nullptr_t) const { return mPtr == nullptr; }
+  bool operator!=(std::nullptr_t) const { return mPtr != nullptr; }
+
+  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;
+};
+
+} /* namespace mozilla */
+
+#endif /* mozilla_RangedPtr_h */