ContactKey.hpp

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/*
 * Copyright (c) 2017 Louis Langholtz https://github.com/louis-langholtz/PlayRho
 *
 * This software is provided 'as-is', without any express or implied
 * warranty. In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 */
 
#ifndef PLAYRHO_DYNAMICS_CONTACTS_CONTACTKEY_HPP
#define PLAYRHO_DYNAMICS_CONTACTS_CONTACTKEY_HPP
 
 
#include <PlayRho/Common/Settings.hpp>
#include <utility>
#include <algorithm>
#include <functional>
#include <cassert>
 
namespace playrho {
 
class ContactKey
{
public:
    PLAYRHO_CONSTEXPR inline ContactKey() noexcept
    {
        // Intentionally empty
    }
    
    PLAYRHO_CONSTEXPR inline ContactKey(ContactCounter fp1, ContactCounter fp2) noexcept:
        m_ids{std::minmax(fp1, fp2)}
    {
        // Intentionally empty
    }
 
    PLAYRHO_CONSTEXPR inline ContactCounter GetMin() const noexcept
    {
        return std::get<0>(m_ids);
    }
    
    PLAYRHO_CONSTEXPR inline ContactCounter GetMax() const noexcept
    {
        return std::get<1>(m_ids);
    }
 
private:
    std::pair<ContactCounter, ContactCounter> m_ids{
        static_cast<ContactCounter>(-1), static_cast<ContactCounter>(-1)
    };
};
 
PLAYRHO_CONSTEXPR inline bool operator== (const ContactKey lhs, const ContactKey rhs) noexcept
{
    return lhs.GetMin() == rhs.GetMin() && lhs.GetMax() == rhs.GetMax();
}
 
PLAYRHO_CONSTEXPR inline bool operator!= (const ContactKey lhs, const ContactKey rhs) noexcept
{
    return !(lhs == rhs);
}
 
PLAYRHO_CONSTEXPR inline bool operator< (const ContactKey lhs, const ContactKey rhs) noexcept
{
    return (lhs.GetMin() < rhs.GetMin())
        || ((lhs.GetMin() == rhs.GetMin()) && (lhs.GetMax() < rhs.GetMax()));
}
 
PLAYRHO_CONSTEXPR inline bool operator<= (const ContactKey lhs, const ContactKey rhs) noexcept
{
    return (lhs.GetMin() < rhs.GetMin())
    || ((lhs.GetMin() == rhs.GetMin()) && (lhs.GetMax() <= rhs.GetMax()));
}
 
PLAYRHO_CONSTEXPR inline bool operator> (const ContactKey lhs, const ContactKey rhs) noexcept
{
    return (lhs.GetMin() > rhs.GetMin())
        || ((lhs.GetMin() == rhs.GetMin()) && (lhs.GetMax() > rhs.GetMax()));
}
 
PLAYRHO_CONSTEXPR inline bool operator>= (const ContactKey lhs, const ContactKey rhs) noexcept
{
    return (lhs.GetMin() > rhs.GetMin())
    || ((lhs.GetMin() == rhs.GetMin()) && (lhs.GetMax() >= rhs.GetMax()));
}
 
namespace d2 {
 
class Fixture;
class Contact;
 
using KeyedContactPtr = std::pair<ContactKey, Contact*>;
 
ContactKey GetContactKey(const Fixture& fixtureA, ChildCounter childIndexA,
                         const Fixture& fixtureB, ChildCounter childIndexB) noexcept;
 
ContactKey GetContactKey(const Contact& contact) noexcept;
 
inline Contact* GetContactPtr(KeyedContactPtr value)
{
    return std::get<1>(value);
}
 
} // namespace d2
} // namespace playrho
 
namespace std
{
    template <>
    struct hash<playrho::ContactKey>
    {
        using argument_type = playrho::ContactKey;
        
        using result_type = std::size_t;
 
        PLAYRHO_CONSTEXPR inline std::size_t operator()(const playrho::ContactKey& key) const
        {
            // Use simple and fast Knuth multiplicative hash...
            const auto a = std::size_t{key.GetMin()} * 2654435761u;
            const auto b = std::size_t{key.GetMax()} * 2654435761u;
            return a ^ b;
        }
    };
} // namespace std
 
#endif // PLAYRHO_DYNAMICS_CONTACTS_CONTACTKEY_HPP