third_party/WebKit/Source/core/editing/iterators/BitStack.cpp

/*
 * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All
 * rights reserved.
 * Copyright (C) 2005 Alexey Proskuryakov.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "core/editing/iterators/BitStack.h"

namespace blink {
static const unsigned bitsInWord = sizeof(unsigned) * 8;
static const unsigned bitInWordMask = bitsInWord - 1;

BitStack::BitStack() : m_size(0) {}

BitStack::~BitStack() {}

void BitStack::push(bool bit) {
  unsigned index = m_size / bitsInWord;
  unsigned shift = m_size & bitInWordMask;
  if (!shift && index == m_words.size()) {
    m_words.grow(index + 1);
    m_words[index] = 0;
  }
  unsigned& word = m_words[index];
  unsigned mask = 1U << shift;
  if (bit)
    word |= mask;
  else
    word &= ~mask;
  ++m_size;
}

void BitStack::pop() {
  if (m_size)
    --m_size;
}

bool BitStack::top() const {
  if (!m_size)
    return false;
  unsigned shift = (m_size - 1) & bitInWordMask;
  unsigned index = (m_size - 1) / bitsInWord;
  return m_words[index] & (1U << shift);
}

unsigned BitStack::size() const {
  return m_size;
}

}  // namespace blink