dynamic_bitset_view.hpp

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// Copyright 2024 Man Group Operations Limited
//
// Licensed 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 "sparrow/buffer/buffer_view.hpp"
#include "sparrow/buffer/dynamic_bitset/dynamic_bitset_base.hpp"
 
namespace sparrow
{
    template <std::integral T, null_count_policy NCP = tracking_null_count<>>
    class dynamic_bitset_view : public dynamic_bitset_base<buffer_view<T>, NCP>
    {
    public:
 
        using base_type = dynamic_bitset_base<buffer_view<T>, NCP>;  
        using storage_type = typename base_type::storage_type;  
        using block_type = typename base_type::block_type;      
        using size_type = typename base_type::size_type;        

        constexpr dynamic_bitset_view(block_type* p, size_type n);

        constexpr dynamic_bitset_view(block_type* p, size_type n, size_type offset);

        constexpr dynamic_bitset_view(block_type* p, size_type n, size_type offset, size_type null_count);
 
        constexpr ~dynamic_bitset_view() = default;
 
        constexpr dynamic_bitset_view(const dynamic_bitset_view&) = default;
        constexpr dynamic_bitset_view(dynamic_bitset_view&&) noexcept = default;
 
        constexpr dynamic_bitset_view& operator=(const dynamic_bitset_view&) = default;
        constexpr dynamic_bitset_view& operator=(dynamic_bitset_view&&) noexcept = default;

        [[nodiscard]] constexpr dynamic_bitset_view slice_view(size_type start, size_type length) const;

        [[nodiscard]] constexpr dynamic_bitset_view slice_view(size_type start) const;
    };
 
    template <std::integral T, null_count_policy NCP>
    constexpr dynamic_bitset_view<T, NCP>::dynamic_bitset_view(block_type* p, size_type n)
        : base_type(storage_type(p, p != nullptr ? this->compute_block_count(n) : 0), n)
    {
    }
 
    template <std::integral T, null_count_policy NCP>
    constexpr dynamic_bitset_view<T, NCP>::dynamic_bitset_view(block_type* p, size_type n, size_type offset)
        : base_type(storage_type(p, p != nullptr ? this->compute_block_count(n + offset) : 0), n, offset)
    {
    }
 
    template <std::integral T, null_count_policy NCP>
    constexpr dynamic_bitset_view<T, NCP>::dynamic_bitset_view(
        block_type* p,
        size_type n,
        size_type offset,
        size_type null_count
    )
        : base_type(storage_type(p, p != nullptr ? this->compute_block_count(n + offset) : 0), n, offset, null_count)
    {
    }
 
    template <std::integral T, null_count_policy NCP>
    constexpr auto dynamic_bitset_view<T, NCP>::slice_view(size_type start, size_type length) const
        -> dynamic_bitset_view
    {
        if (start + length > this->size())
        {
            throw std::out_of_range("slice_view: start + length exceeds bitset size");
        }
 
        const size_type new_offset = this->offset() + start;
 
        // Calculate the null count for the slice if tracking is enabled
        if constexpr (NCP::track_null_count)
        {
            size_type slice_null_count = 0;
            for (size_type i = 0; i < length; ++i)
            {
                if (!this->test(start + i))
                {
                    ++slice_null_count;
                }
            }
            return dynamic_bitset_view(const_cast<block_type*>(this->data()), length, new_offset, slice_null_count);
        }
        else
        {
            return dynamic_bitset_view(const_cast<block_type*>(this->data()), length, new_offset);
        }
    }
 
    template <std::integral T, null_count_policy NCP>
    constexpr auto dynamic_bitset_view<T, NCP>::slice_view(size_type start) const -> dynamic_bitset_view
    {
        if (start > this->size())
        {
            throw std::out_of_range("slice_view: start exceeds bitset size");
        }
 
        return slice_view(start, this->size() - start);
    }
}