packbits.hpp

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#pragma once
 
#include <type_traits>
 
#include "NumCpp/Core/Internal/Error.hpp"
#include "NumCpp/NdArray.hpp"
 
namespace nc
{
    //============================================================================
    // Method Description:
    template<typename dtype, std::enable_if_t<std::is_integral_v<dtype> || std::is_same_v<dtype, bool>, int> = 0>
    NdArray<uint8> packbitsLittleEndian(const NdArray<dtype>& a, Axis axis = Axis::NONE)
    {
        switch (axis)
        {
            case Axis::NONE:
            {
                const auto numFullValues = a.size() / 8;
                const auto leftOvers     = a.size() % 8;
                const auto resultSize    = leftOvers == 0 ? numFullValues : numFullValues + 1;
 
                NdArray<uint8> result(1, resultSize);
                result.fill(0);
 
                for (typename NdArray<dtype>::size_type i = 0; i < numFullValues; ++i)
                {
                    const auto startIdx = i * 8;
                    for (auto bit = 0; bit < 8; ++bit)
                    {
                        auto value = static_cast<uint8>(a[startIdx + bit]);
                        value      = value == 0 ? 0 : 1;
                        result[i] |= (value << bit);
                    }
                }
 
                if (leftOvers != 0)
                {
                    const auto startIdx = numFullValues * 8;
                    for (std::remove_const_t<decltype(leftOvers)> bit = 0; bit < leftOvers; ++bit)
                    {
                        auto value = static_cast<uint8>(a[startIdx + bit]);
                        value      = value == 0 ? 0 : 1;
                        result.back() |= (value << bit);
                    }
                }
 
                return result;
            }
            case Axis::COL:
            {
                const auto aShape        = a.shape();
                const auto numFullValues = aShape.cols / 8;
                const auto leftOvers     = aShape.cols % 8;
                const auto resultSize    = leftOvers == 0 ? numFullValues : numFullValues + 1;
 
                NdArray<uint8> result(aShape.rows, resultSize);
                const auto     resultCSlice = result.cSlice();
                const auto     aCSlice      = a.cSlice();
 
                for (typename NdArray<dtype>::size_type row = 0; row < aShape.rows; ++row)
                {
                    result.put(row, resultCSlice, packbitsLittleEndian(a(row, aCSlice)));
                }
 
                return result;
            }
            case Axis::ROW:
            {
                return packbitsLittleEndian(a.transpose(), Axis::COL).transpose();
            }
            default:
            {
                THROW_INVALID_ARGUMENT_ERROR("Unimplemented axis type.");
                return {}; // get rid of compiler warning
            }
        }
    }
 
    //============================================================================
    // Method Description:
    template<typename dtype, std::enable_if_t<std::is_integral_v<dtype> || std::is_same_v<dtype, bool>, int> = 0>
    NdArray<uint8> packbitsBigEndian(const NdArray<dtype>& a, Axis axis = Axis::NONE)
    {
        switch (axis)
        {
            case Axis::NONE:
            {
                const auto numFullValues = a.size() / 8;
                const auto leftOvers     = a.size() % 8;
                const auto resultSize    = leftOvers == 0 ? numFullValues : numFullValues + 1;
 
                NdArray<uint8> result(1, resultSize);
                result.fill(0);
 
                for (typename NdArray<dtype>::size_type i = 0; i < numFullValues; ++i)
                {
                    const auto startIdx = i * 8;
                    for (auto bit = 0; bit < 8; ++bit)
                    {
                        auto value = static_cast<uint8>(a[startIdx + bit]);
                        value      = value == 0 ? 0 : 1;
                        result[i] |= (value << (7 - bit));
                    }
                }
 
                if (leftOvers != 0)
                {
                    const auto startIdx = numFullValues * 8;
                    for (std::remove_const_t<decltype(leftOvers)> bit = 0; bit < leftOvers; ++bit)
                    {
                        auto value = static_cast<uint8>(a[startIdx + bit]);
                        value      = value == 0 ? 0 : 1;
                        result.back() |= (value << (7 - bit));
                    }
                }
 
                return result;
            }
            case Axis::COL:
            {
                const auto aShape        = a.shape();
                const auto numFullValues = aShape.cols / 8;
                const auto leftOvers     = aShape.cols % 8;
                const auto resultSize    = leftOvers == 0 ? numFullValues : numFullValues + 1;
 
                NdArray<uint8> result(aShape.rows, resultSize);
                const auto     resultCSlice = result.cSlice();
                const auto     aCSlice      = a.cSlice();
 
                for (typename NdArray<dtype>::size_type row = 0; row < aShape.rows; ++row)
                {
                    result.put(row, resultCSlice, packbitsBigEndian(a(row, aCSlice)));
                }
 
                return result;
            }
            case Axis::ROW:
            {
                return packbitsBigEndian(a.transpose(), Axis::COL).transpose();
            }
            default:
            {
                THROW_INVALID_ARGUMENT_ERROR("Unimplemented axis type.");
                return {}; // get rid of compiler warning
            }
        }
    }
 
} // namespace nc