xpcom/ds/ArenaAllocatorExtensions.h
author Andreas Farre <farre@mozilla.com>
Sun, 05 May 2019 19:26:51 +0000
changeset 472634 f59b3336d254c80bf2b315a74fea0cb0fa8e0d47
parent 448947 6f3709b3878117466168c40affa7bca0b60cf75b
permissions -rw-r--r--
Bug 1547911 - Don't assert that there are no children when restoring BC. r=nika This is essentially equal to restoring cached children and removing current children from a BrowsingContext, which is the correct behaviour. It would've been better if the current children were removed in a more transparent manner, but it is more important to remove an assert that too eagerly triggers. Differential Revision: https://phabricator.services.mozilla.com/D29945

/* -*- 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/. */

#ifndef mozilla_ArenaAllocatorExtensions_h
#define mozilla_ArenaAllocatorExtensions_h

#include "mozilla/ArenaAllocator.h"
#include "mozilla/CheckedInt.h"
#include "nsAString.h"

/**
 * Extensions to the ArenaAllocator class.
 */
namespace mozilla {

namespace detail {

template <typename T, size_t ArenaSize, size_t Alignment>
T* DuplicateString(const T* aSrc, const CheckedInt<size_t>& aLen,
                   ArenaAllocator<ArenaSize, Alignment>& aArena);

}  // namespace detail

/**
 * Makes an arena allocated null-terminated copy of the source string. The
 * source string must be null-terminated.
 *
 * @param aSrc String to copy.
 * @param aArena The arena to allocate the string copy out of.
 * @return An arena allocated null-terminated string.
 */
template <typename T, size_t ArenaSize, size_t Alignment>
T* ArenaStrdup(const T* aStr, ArenaAllocator<ArenaSize, Alignment>& aArena) {
  return detail::DuplicateString(aStr, nsCharTraits<T>::length(aStr), aArena);
}

/**
 * Makes an arena allocated null-terminated copy of the source string.
 *
 * @param aSrc String to copy.
 * @param aArena The arena to allocate the string copy out of.
 * @return An arena allocated null-terminated string.
 */
template <typename T, size_t ArenaSize, size_t Alignment>
T* ArenaStrdup(const detail::nsTStringRepr<T>& aStr,
               ArenaAllocator<ArenaSize, Alignment>& aArena) {
  return detail::DuplicateString(aStr.BeginReading(), aStr.Length(), aArena);
}

/**
 * Copies the source string and adds a null terminator. Source string does not
 * have to be null terminated.
 */
template <typename T, size_t ArenaSize, size_t Alignment>
T* detail::DuplicateString(const T* aSrc, const CheckedInt<size_t>& aLen,
                           ArenaAllocator<ArenaSize, Alignment>& aArena) {
  const auto byteLen = (aLen + 1) * sizeof(T);
  if (!byteLen.isValid()) {
    return nullptr;
  }

  T* p = static_cast<T*>(aArena.Allocate(byteLen.value(), mozilla::fallible));
  if (p) {
    memcpy(p, aSrc, byteLen.value() - sizeof(T));
    p[aLen.value()] = T(0);
  }

  return p;
}

}  // namespace mozilla

#endif  // mozilla_ArenaAllocatorExtensions_h