weex_core/Source/include/wtf/IndexedContainerIterator.h

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
#pragma once

#include <type_traits>

namespace WTF {

template<class Container>
class IndexedContainerIterator {
public:
    IndexedContainerIterator()
        : m_container(nullptr)
        , m_index(0)
    {
    }

    IndexedContainerIterator(const Container& container, unsigned index)
        : m_container(&container)
        , m_index(findNext(index))
    {
    }

    auto operator*() -> typename std::result_of<decltype(&Container::at)(const Container, unsigned)>::type
    {
        return m_container->at(m_index);
    }

    IndexedContainerIterator& operator++()
    {
        m_index = findNext(m_index + 1);
        return *this;
    }

    bool operator==(const IndexedContainerIterator& other) const
    {
        ASSERT(m_container == other.m_container);
        return m_index == other.m_index;
    }

    bool operator!=(const IndexedContainerIterator& other) const
    {
        return !(*this == other);
    }

private:
    unsigned findNext(unsigned index)
    {
        while (index < m_container->size() && !m_container->at(index))
            index++;
        return index;
    }

    const Container* m_container;
    unsigned m_index;
};

} // namespace WTF