xpcom/ds/ArenaAllocatorExtensions.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_ArenaAllocatorExtensions_h
   8 #define mozilla_ArenaAllocatorExtensions_h
   9
  10 #include "mozilla/ArenaAllocator.h"
  11 #include "mozilla/CheckedInt.h"
  12 #include "nsAString.h"
  13
  14 /**
  15  * Extensions to the ArenaAllocator class.
  16  */
  17 namespace mozilla {
  18
  19 namespace detail {
  20
  21 template <typename T, size_t ArenaSize, size_t Alignment>
  22 T* DuplicateString(const T* aSrc, const CheckedInt<size_t>& aLen,
  23                    ArenaAllocator<ArenaSize, Alignment>& aArena);
  24
  25 }  // namespace detail
  26
  27 /**
  28  * Makes an arena allocated null-terminated copy of the source string. The
  29  * source string must be null-terminated.
  30  *
  31  * @param aSrc String to copy.
  32  * @param aArena The arena to allocate the string copy out of.
  33  * @return An arena allocated null-terminated string.
  34  */
  35 template <typename T, size_t ArenaSize, size_t Alignment>
  36 T* ArenaStrdup(const T* aStr, ArenaAllocator<ArenaSize, Alignment>& aArena) {
  37   return detail::DuplicateString(aStr, nsCharTraits<T>::length(aStr), aArena);
  38 }
  39
  40 /**
  41  * Makes an arena allocated null-terminated copy of the source string.
  42  *
  43  * @param aSrc String to copy.
  44  * @param aArena The arena to allocate the string copy out of.
  45  * @return An arena allocated null-terminated string.
  46  */
  47 template <typename T, size_t ArenaSize, size_t Alignment>
  48 T* ArenaStrdup(const detail::nsTStringRepr<T>& aStr,
  49                ArenaAllocator<ArenaSize, Alignment>& aArena) {
  50   return detail::DuplicateString(aStr.BeginReading(), aStr.Length(), aArena);
  51 }
  52
  53 /**
  54  * Copies the source string and adds a null terminator. Source string does not
  55  * have to be null terminated.
  56  */
  57 template <typename T, size_t ArenaSize, size_t Alignment>
  58 T* detail::DuplicateString(const T* aSrc, const CheckedInt<size_t>& aLen,
  59                            ArenaAllocator<ArenaSize, Alignment>& aArena) {
  60   const auto byteLen = (aLen + 1) * sizeof(T);
  61   if (!byteLen.isValid()) {
  62     return nullptr;
  63   }
  64
  65   T* p = static_cast<T*>(aArena.Allocate(byteLen.value(), mozilla::fallible));
  66   if (p) {
  67     memcpy(p, aSrc, byteLen.value() - sizeof(T));
  68     p[aLen.value()] = T(0);
  69   }
  70
  71   return p;
  72 }
  73
  74 }  // namespace mozilla
  75
  76 #endif  // mozilla_ArenaAllocatorExtensions_h