b2Joint.h

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/*
* Copyright (c) 2006-2007 Erin Catto http://www.box2d.org
*
* 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 B2_JOINT_H
#define B2_JOINT_H

#include <Box2D/Common/b2Math.h>

class b2Body;
class b2Joint;
struct b2SolverData;
class b2BlockAllocator;

enum b2JointType
{
        e_unknownJoint,
        e_revoluteJoint,
        e_prismaticJoint,
        e_distanceJoint,
        e_pulleyJoint,
        e_mouseJoint,
        e_gearJoint,
        e_wheelJoint,
    e_weldJoint,
        e_frictionJoint,
        e_ropeJoint,
        e_motorJoint
};

enum b2LimitState
{
        e_inactiveLimit,
        e_atLowerLimit,
        e_atUpperLimit,
        e_equalLimits
};

struct b2Jacobian
{
        b2Vec2 linear;
        float32 angularA;
        float32 angularB;
};

struct b2JointEdge
{
        b2Body* other;                  
        b2Joint* joint;                 
        b2JointEdge* prev;              
        b2JointEdge* next;              
};

struct b2JointDef
{
        b2JointDef()
        {
                type = e_unknownJoint;
                userData = NULL;
                bodyA = NULL;
                bodyB = NULL;
                collideConnected = false;
        }

        b2JointType type;

        void* userData;

        b2Body* bodyA;

        b2Body* bodyB;

        bool collideConnected;
};

class b2Joint
{
public:

        b2JointType GetType() const;

        b2Body* GetBodyA();

        b2Body* GetBodyB();

        virtual b2Vec2 GetAnchorA() const = 0;

        virtual b2Vec2 GetAnchorB() const = 0;

        virtual b2Vec2 GetReactionForce(float32 inv_dt) const = 0;

        virtual float32 GetReactionTorque(float32 inv_dt) const = 0;

        b2Joint* GetNext();
        const b2Joint* GetNext() const;

        void* GetUserData() const;

        void SetUserData(void* data);

        bool IsActive() const;

        bool GetCollideConnected() const;

        virtual void Dump() { b2Log("// Dump is not supported for this joint type.\n"); }

        virtual void ShiftOrigin(const b2Vec2& newOrigin) { B2_NOT_USED(newOrigin);  }

protected:
        friend class b2World;
        friend class b2Body;
        friend class b2Island;
        friend class b2GearJoint;

        static b2Joint* Create(const b2JointDef* def, b2BlockAllocator* allocator);
        static void Destroy(b2Joint* joint, b2BlockAllocator* allocator);

        b2Joint(const b2JointDef* def);
        virtual ~b2Joint() {}

        virtual void InitVelocityConstraints(const b2SolverData& data) = 0;
        virtual void SolveVelocityConstraints(const b2SolverData& data) = 0;

        // This returns true if the position errors are within tolerance.
        virtual bool SolvePositionConstraints(const b2SolverData& data) = 0;

        b2JointType m_type;
        b2Joint* m_prev;
        b2Joint* m_next;
        b2JointEdge m_edgeA;
        b2JointEdge m_edgeB;
        b2Body* m_bodyA;
        b2Body* m_bodyB;

        int32 m_index;

        bool m_islandFlag;
        bool m_collideConnected;

        void* m_userData;
};

inline b2JointType b2Joint::GetType() const
{
        return m_type;
}

inline b2Body* b2Joint::GetBodyA()
{
        return m_bodyA;
}

inline b2Body* b2Joint::GetBodyB()
{
        return m_bodyB;
}

inline b2Joint* b2Joint::GetNext()
{
        return m_next;
}

inline const b2Joint* b2Joint::GetNext() const
{
        return m_next;
}

inline void* b2Joint::GetUserData() const
{
        return m_userData;
}

inline void b2Joint::SetUserData(void* data)
{
        m_userData = data;
}

inline bool b2Joint::GetCollideConnected() const
{
        return m_collideConnected;
}

#endif