BGN2/bgn2/src/Curvepoint.cpp

#include "Curvepoint.hpp"

Curvepoint::Curvepoint()
{
    curvepoint_fp_setneutral(point);
}

Curvepoint::Curvepoint(const curvepoint_fp_t input)
{
    curvepoint_fp_set(point, input);
}

Curvepoint Curvepoint::operator+(const Curvepoint& b) const
{
    
    Curvepoint retval;

    if (*this == b)
        curvepoint_fp_double(retval.point, point);
    else
        curvepoint_fp_add_vartime(retval.point, point, b.point);

    return retval;
}

Curvepoint Curvepoint::operator-(const Curvepoint& b) const
{
    Curvepoint retval;

    if (!(*this == b))
    {
        Curvepoint inverseB;
        curvepoint_fp_neg(inverseB.point, b.point);
        curvepoint_fp_add_vartime(retval.point, point, inverseB.point);
    }

    return retval;
}

Curvepoint Curvepoint::operator*(const Scalar& exp) const
{
    Curvepoint retval;

    exp.mult(retval.point, point);

    return retval;
}

bool Curvepoint::operator==(const Curvepoint& b) const
{
    bool retval;
    curvepoint_fp_t affine_this_point, affine_b_point;

    curvepoint_fp_set(affine_this_point, point);
    curvepoint_fp_set(affine_b_point, b.point);

    if (!(fpe_isone(affine_this_point->m_z) || fpe_iszero(affine_this_point->m_z)))
        curvepoint_fp_makeaffine(affine_this_point);

    if (!(fpe_isone(affine_b_point->m_z) || fpe_iszero(affine_b_point->m_z)))
        curvepoint_fp_makeaffine(affine_b_point);

    retval =           fpe_iseq(affine_this_point->m_x, affine_b_point->m_x);
    retval = retval && fpe_iseq(affine_this_point->m_y, affine_b_point->m_y);
    retval = retval || (fpe_iszero(affine_this_point->m_z) && fpe_iszero(affine_b_point->m_z));

    return retval;
}

bool Curvepoint::operator<(const Curvepoint& b) const
{
    bool lessThan[2];
    bool equal[2];
    curvepoint_fp_t affine_this_point, affine_b_point;

    lessThan[0] = lessThan[1] = false;

    curvepoint_fp_set(affine_this_point, point);
    curvepoint_fp_set(affine_b_point, b.point);

    if (fpe_iszero(affine_this_point->m_z))
    {
        // this case would be equal
        if (fpe_iszero(affine_b_point->m_z))
            return false;

        // point at infinity is less than all other points
        return true;
    }

    if (fpe_iszero(affine_b_point->m_z))
        return false;

    // already checked for the point at infinity, so we don't have to redo that here
    if (!fpe_isone(affine_this_point->m_z))
        curvepoint_fp_makeaffine(affine_this_point);

    if (!fpe_isone(affine_b_point->m_z))
        curvepoint_fp_makeaffine(affine_b_point);

    for (int i = 11; i >= 0; i--)
    {
        if (affine_this_point->m_x->v[i] > affine_b_point->m_x->v[i])
        {
            lessThan[0] = false;
            break;
        }
        if (affine_this_point->m_x->v[i] < affine_b_point->m_x->v[i])
        {
            lessThan[0] = true;
            break;
        }
    }

    for (int i = 11; i >= 0; i--)
    {
        if (affine_this_point->m_y->v[i] > affine_b_point->m_y->v[i])
        {
            lessThan[1] = false;
            break;
        }
        if (affine_this_point->m_y->v[i] < affine_b_point->m_y->v[i])
        {
            lessThan[1] = true;
            break;
        }
    }

    equal[0] = fpe_iseq(affine_this_point->m_x, affine_b_point->m_x);
    equal[1] = fpe_iseq(affine_this_point->m_y, affine_b_point->m_y);

    // sort is lesser x value first, and then lesser y value second if x's are equal
    return equal[0] ? (equal[1] ? false : lessThan[1]) : lessThan[0];
}

bool Curvepoint::operator>(const Curvepoint& b) const
{
    return !(*this < b);
}

bool Curvepoint::operator<=(const Curvepoint& b) const
{
    return (*this == b) || (*this < b);
}

bool Curvepoint::operator>=(const Curvepoint& b) const
{
    return (*this == b) || !(*this < b);
}

bool Curvepoint::operator!=(const Curvepoint& b) const
{
    return !(*this == b);
}

void Curvepoint::make_affine()
{
    if (!(fpe_isone(point->m_z) || fpe_iszero(point->m_z)))
        curvepoint_fp_makeaffine(point);
}

std::ostream& operator<<(std::ostream& os, const Curvepoint& output)
{
    Curvepoint affine_out = output;
    affine_out.make_affine();
    
    os << Fpe(affine_out.point->m_x) << Fpe(affine_out.point->m_y) << Fpe(affine_out.point->m_z);

    return os;
}

std::istream& operator>>(std::istream& is, Curvepoint& input)
{
    Fpe x, y, z;
    is >> x >> y >> z;

    fpe_set(input.point->m_x, x.data);
    fpe_set(input.point->m_y, y.data);
    fpe_set(input.point->m_z, z.data);

    return is;
}

size_t CurvepointHash::operator()(const Curvepoint& x) const
{
    if (fpe_iszero(x.point->m_z))
    {
        return 0;
    }

    size_t retval;
    std::hash<double> hasher;

    Curvepoint affine_x = x;
    affine_x.make_affine();

    for (int j = 0; j < 12; j++)
    {
        retval ^= hasher(affine_x.point->m_x->v[j]);
        retval ^= hasher(affine_x.point->m_y->v[j]);
    }

    return retval;
}