gecko-dev/layout/style/nsRuleData.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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/. */

#include "nsRuleData.h"

#include "mozilla/Poison.h"
#include <stdint.h>

inline size_t
nsRuleData::GetPoisonOffset()
{
  // Fill in mValueOffsets such that mValueStorage + mValueOffsets[i]
  // will yield the frame poison value for all uninitialized value
  // offsets.
  static_assert(sizeof(uintptr_t) == sizeof(size_t),
                "expect uintptr_t and size_t to be the same size");
  static_assert(uintptr_t(-1) > uintptr_t(0),
                "expect uintptr_t to be unsigned");
  static_assert(size_t(-1) > size_t(0),
                "expect size_t to be unsigned");
  uintptr_t framePoisonValue = mozPoisonValue();
  return size_t(framePoisonValue - uintptr_t(mValueStorage)) /
         sizeof(nsCSSValue);
}

nsRuleData::nsRuleData(uint32_t aSIDs, nsCSSValue* aValueStorage,
                       nsPresContext* aContext, nsStyleContext* aStyleContext)
  : mSIDs(aSIDs),
    mPresContext(aContext),
    mStyleContext(aStyleContext),
    mValueStorage(aValueStorage)
{
#ifndef MOZ_VALGRIND
  size_t framePoisonOffset = GetPoisonOffset();
  for (size_t i = 0; i < nsStyleStructID_Length; ++i) {
    mValueOffsets[i] = framePoisonOffset;
  }
#endif
}

#ifdef DEBUG
nsRuleData::~nsRuleData()
{
#ifndef MOZ_VALGRIND
  // assert nothing in mSIDs has poison value
  size_t framePoisonOffset = GetPoisonOffset();
  for (size_t i = 0; i < nsStyleStructID_Length; ++i) {
    MOZ_ASSERT(!(mSIDs & (1 << i)) || mValueOffsets[i] != framePoisonOffset,
               "value in SIDs was left with poison offset");
  }
#endif
}
#endif