text: /*
  * 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.
  */
  
  #include <Box2D/Dynamics/b2Body.h>
  #include <Box2D/Dynamics/b2Fixture.h>
  #include <Box2D/Dynamics/b2World.h>
  #include <Box2D/Dynamics/Contacts/b2Contact.h>
  #include <Box2D/Dynamics/Joints/b2Joint.h>
  
  b2Body::b2Body(const b2BodyDef* bd, b2World* world)
  {
  	b2Assert(bd->position.IsValid());
  	b2Assert(bd->linearVelocity.IsValid());
  	b2Assert(b2IsValid(bd->angle));
  	b2Assert(b2IsValid(bd->angularVelocity));
  	b2Assert(b2IsValid(bd->angularDamping) && bd->angularDamping >= 0.0f);
  	b2Assert(b2IsValid(bd->linearDamping) && bd->linearDamping >= 0.0f);
  
  	m_flags = 0;
  
  	if (bd->bullet)
  	{
  		m_flags |= e_bulletFlag;
  	}
  	if (bd->fixedRotation)
  	{
  		m_flags |= e_fixedRotationFlag;
  	}
  	if (bd->allowSleep)
  	{
  		m_flags |= e_autoSleepFlag;
  	}
  	if (bd->awake)
  	{
  		m_flags |= e_awakeFlag;
  	}
  	if (bd->active)
  	{
  		m_flags |= e_activeFlag;
  	}
  
  	m_world = world;
  
  	m_xf.p = bd->position;
  	m_xf.q.Set(bd->angle);
  
  	m_sweep.localCenter.SetZero();
  	m_sweep.c0 = m_xf.p;
  	m_sweep.c = m_xf.p;
  	m_sweep.a0 = bd->angle;
  	m_sweep.a = bd->angle;
  	m_sweep.alpha0 = 0.0f;
  
  	m_jointList = NULL;
  	m_contactList = NULL;
  	m_prev = NULL;
  	m_next = NULL;
  
  	m_linearVelocity = bd->linearVelocity;
  	m_angularVelocity = bd->angularVelocity;
  
  	m_linearDamping = bd->linearDamping;
  	m_angularDamping = bd->angularDamping;
  	m_gravityScale = bd->gravityScale;
  
  	m_force.SetZero();
  	m_torque = 0.0f;
  
  	m_sleepTime = 0.0f;
  
  	m_type = bd->type;
  
  	if (m_type == b2_dynamicBody)
  	{
  		m_mass = 1.0f;
  		m_invMass = 1.0f;
  	}
  	else
  	{
  		m_mass = 0.0f;
  		m_invMass = 0.0f;
  	}
  
  	m_I = 0.0f;
  	m_invI = 0.0f;
  
  	m_userData = bd->userData;
  
  	m_fixtureList = NULL;
  	m_fixtureCount = 0;
  }
  
  b2Body::~b2Body()
  {
  	// shapes and joints are destroyed in b2World::Destroy
  }
  
  void b2Body::SetType(b2BodyType type)
  {
  	b2Assert(m_world->IsLocked() == false);
  	if (m_world->IsLocked() == true)
  	{
  		return;
  	}
  
  	if (m_type == type)
  	{
  		return;
  	}
  
  	m_type = type;
  
  	ResetMassData();
  
  	if (m_type == b2_staticBody)
  	{
  		m_linearVelocity.SetZero();
  		m_angularVelocity = 0.0f;
  		m_sweep.a0 = m_sweep.a;
  		m_sweep.c0 = m_sweep.c;
  		SynchronizeFixtures();
  	}
  
  	SetAwake(true);
  
  	m_force.SetZero();
  	m_torque = 0.0f;
  
  	// Delete the attached contacts.
  	b2ContactEdge* ce = m_contactList;
  	while (ce)
  	{
  		b2ContactEdge* ce0 = ce;
  		ce = ce->next;
  		m_world->m_contactManager.Destroy(ce0->contact);
  	}
  	m_contactList = NULL;
  
  	// Touch the proxies so that new contacts will be created (when appropriate)
  	b2BroadPhase* broadPhase = &m_world->m_contactManager.m_broadPhase;
  	for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
  	{
  		int32 proxyCount = f->m_proxyCount;
  		for (int32 i = 0; i < proxyCount; ++i)
  		{
  			broadPhase->TouchProxy(f->m_proxies[i].proxyId);
  		}
  	}
  }
  
  b2Fixture* b2Body::CreateFixture(const b2FixtureDef* def)
  {
  	b2Assert(m_world->IsLocked() == false);
  	if (m_world->IsLocked() == true)
  	{
  		return NULL;
  	}
  
  	b2BlockAllocator* allocator = &m_world->m_blockAllocator;
  
  	void* memory = allocator->Allocate(sizeof(b2Fixture));
  	b2Fixture* fixture = new (memory) b2Fixture;
  	fixture->Create(allocator, this, def);
  
  	if (m_flags & e_activeFlag)
  	{
  		b2BroadPhase* broadPhase = &m_world->m_contactManager.m_broadPhase;
  		fixture->CreateProxies(broadPhase, m_xf);
  	}
  
  	fixture->m_next = m_fixtureList;
  	m_fixtureList = fixture;
  	++m_fixtureCount;
  
  	fixture->m_body = this;
  
  	// Adjust mass properties if needed.
  	if (fixture->m_density > 0.0f)
  	{
  		ResetMassData();
  	}
  
  	// Let the world know we have a new fixture. This will cause new contacts
  	// to be created at the beginning of the next time step.
  	m_world->m_flags |= b2World::e_newFixture;
  
  	return fixture;
  }
  
  b2Fixture* b2Body::CreateFixture(const b2Shape* shape, float32 density)
  {
  	b2FixtureDef def;
  	def.shape = shape;
  	def.density = density;
  
  	return CreateFixture(&def);
  }
  
  void b2Body::DestroyFixture(b2Fixture* fixture)
  {
  	b2Assert(m_world->IsLocked() == false);
  	if (m_world->IsLocked() == true)
  	{
  		return;
  	}
  
  	b2Assert(fixture->m_body == this);
  
  	// Remove the fixture from this body's singly linked list.
  	b2Assert(m_fixtureCount > 0);
  	b2Fixture** node = &m_fixtureList;
  	bool found = false;
  	while (*node != NULL)
  	{
  		if (*node == fixture)
  		{
  			*node = fixture->m_next;
  			found = true;
  			break;
  		}
  
  		node = &(*node)->m_next;
  	}
  
  	// You tried to remove a shape that is not attached to this body.
  	b2Assert(found);
  
  	// Destroy any contacts associated with the fixture.
  	b2ContactEdge* edge = m_contactList;
  	while (edge)
  	{
  		b2Contact* c = edge->contact;
  		edge = edge->next;
  
  		b2Fixture* fixtureA = c->GetFixtureA();
  		b2Fixture* fixtureB = c->GetFixtureB();
  
  		if (fixture == fixtureA || fixture == fixtureB)
  		{
  			// This destroys the contact and removes it from
  			// this body's contact list.
  			m_world->m_contactManager.Destroy(c);
  		}
  	}
  
  	b2BlockAllocator* allocator = &m_world->m_blockAllocator;
  
  	if (m_flags & e_activeFlag)
  	{
  		b2BroadPhase* broadPhase = &m_world->m_contactManager.m_broadPhase;
  		fixture->DestroyProxies(broadPhase);
  	}
  
  	fixture->Destroy(allocator);
  	fixture->m_body = NULL;
  	fixture->m_next = NULL;
  	fixture->~b2Fixture();
  	allocator->Free(fixture, sizeof(b2Fixture));
  
  	--m_fixtureCount;
  
  	// Reset the mass data.
  	ResetMassData();
  }
  
  void b2Body::ResetMassData()
  {
  	// Compute mass data from shapes. Each shape has its own density.
  	m_mass = 0.0f;
  	m_invMass = 0.0f;
  	m_I = 0.0f;
  	m_invI = 0.0f;
  	m_sweep.localCenter.SetZero();
  
  	// Static and kinematic bodies have zero mass.
  	if (m_type == b2_staticBody || m_type == b2_kinematicBody)
  	{
  		m_sweep.c0 = m_xf.p;
  		m_sweep.c = m_xf.p;
  		m_sweep.a0 = m_sweep.a;
  		return;
  	}
  
  	b2Assert(m_type == b2_dynamicBody);
  
  	// Accumulate mass over all fixtures.
  	b2Vec2 localCenter = b2Vec2_zero;
  	for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
  	{
  		if (f->m_density == 0.0f)
  		{
  			continue;
  		}
  
  		b2MassData massData;
  		f->GetMassData(&massData);
  		m_mass += massData.mass;
  		localCenter += massData.mass * massData.center;
  		m_I += massData.I;
  	}
  
  	// Compute center of mass.
  	if (m_mass > 0.0f)
  	{
  		m_invMass = 1.0f / m_mass;
  		localCenter *= m_invMass;
  	}
  	else
  	{
  		// Force all dynamic bodies to have a positive mass.
  		m_mass = 1.0f;
  		m_invMass = 1.0f;
  	}
  
  	if (m_I > 0.0f && (m_flags & e_fixedRotationFlag) == 0)
  	{
  		// Center the inertia about the center of mass.
  		m_I -= m_mass * b2Dot(localCenter, localCenter);
  		b2Assert(m_I > 0.0f);
  		m_invI = 1.0f / m_I;
  
  	}
  	else
  	{
  		m_I = 0.0f;
  		m_invI = 0.0f;
  	}
  
  	// Move center of mass.
  	b2Vec2 oldCenter = m_sweep.c;
  	m_sweep.localCenter = localCenter;
  	m_sweep.c0 = m_sweep.c = b2Mul(m_xf, m_sweep.localCenter);
  
  	// Update center of mass velocity.
  	m_linearVelocity += b2Cross(m_angularVelocity, m_sweep.c - oldCenter);
  }
  
  void b2Body::SetMassData(const b2MassData* massData)
  {
  	b2Assert(m_world->IsLocked() == false);
  	if (m_world->IsLocked() == true)
  	{
  		return;
  	}
  
  	if (m_type != b2_dynamicBody)
  	{
  		return;
  	}
  
  	m_invMass = 0.0f;
  	m_I = 0.0f;
  	m_invI = 0.0f;
  
  	m_mass = massData->mass;
  	if (m_mass <= 0.0f)
  	{
  		m_mass = 1.0f;
  	}
  
  	m_invMass = 1.0f / m_mass;
  
  	if (massData->I > 0.0f && (m_flags & b2Body::e_fixedRotationFlag) == 0)
  	{
  		m_I = massData->I - m_mass * b2Dot(massData->center, massData->center);
  		b2Assert(m_I > 0.0f);
  		m_invI = 1.0f / m_I;
  	}
  
  	// Move center of mass.
  	b2Vec2 oldCenter = m_sweep.c;
  	m_sweep.localCenter =  massData->center;
  	m_sweep.c0 = m_sweep.c = b2Mul(m_xf, m_sweep.localCenter);
  
  	// Update center of mass velocity.
  	m_linearVelocity += b2Cross(m_angularVelocity, m_sweep.c - oldCenter);
  }
  
  bool b2Body::ShouldCollide(const b2Body* other) const
  {
  	// At least one body should be dynamic.
  	#ifndef ALLOW_KINEMATIC_COLLISION
  	if (m_type != b2_dynamicBody && other->m_type != b2_dynamicBody)
  	{
  		return false;
  	}
  	#endif
  
  	// Does a joint prevent collision?
  	for (b2JointEdge* jn = m_jointList; jn; jn = jn->next)
  	{
  		if (jn->other == other)
  		{
  			if (jn->joint->m_collideConnected == false)
  			{
  				return false;
  			}
  		}
  	}
  
  	return true;
  }
  
  void b2Body::SetTransform(const b2Vec2& position, float32 angle)
  {
  	b2Assert(m_world->IsLocked() == false);
  	if (m_world->IsLocked() == true)
  	{
  		return;
  	}
  
  	m_xf.q.Set(angle);
  	m_xf.p = position;
  
  	m_sweep.c = b2Mul(m_xf, m_sweep.localCenter);
  	m_sweep.a = angle;
  
  	m_sweep.c0 = m_sweep.c;
  	m_sweep.a0 = angle;
  
  	b2BroadPhase* broadPhase = &m_world->m_contactManager.m_broadPhase;
  	for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
  	{
  		f->Synchronize(broadPhase, m_xf, m_xf);
  	}
  }
  
  void b2Body::SynchronizeFixtures()
  {
  	b2Transform xf1;
  	xf1.q.Set(m_sweep.a0);
  	xf1.p = m_sweep.c0 - b2Mul(xf1.q, m_sweep.localCenter);
  
  	b2BroadPhase* broadPhase = &m_world->m_contactManager.m_broadPhase;
  	for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
  	{
  		f->Synchronize(broadPhase, xf1, m_xf);
  	}
  }
  
  void b2Body::SetActive(bool flag)
  {
  	b2Assert(m_world->IsLocked() == false);
  
  	if (flag == IsActive())
  	{
  		return;
  	}
  
  	if (flag)
  	{
  		m_flags |= e_activeFlag;
  
  		// Create all proxies.
  		b2BroadPhase* broadPhase = &m_world->m_contactManager.m_broadPhase;
  		for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
  		{
  			f->CreateProxies(broadPhase, m_xf);
  		}
  
  		// Contacts are created the next time step.
  	}
  	else
  	{
  		m_flags &= ~e_activeFlag;
  
  		// Destroy all proxies.
  		b2BroadPhase* broadPhase = &m_world->m_contactManager.m_broadPhase;
  		for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
  		{
  			f->DestroyProxies(broadPhase);
  		}
  
  		// Destroy the attached contacts.
  		b2ContactEdge* ce = m_contactList;
  		while (ce)
  		{
  			b2ContactEdge* ce0 = ce;
  			ce = ce->next;
  			m_world->m_contactManager.Destroy(ce0->contact);
  		}
  		m_contactList = NULL;
  	}
  }
  
  void b2Body::SetFixedRotation(bool flag)
  {
  	bool status = (m_flags & e_fixedRotationFlag) == e_fixedRotationFlag;
  	if (status == flag)
  	{
  		return;
  	}
  
  	if (flag)
  	{
  		m_flags |= e_fixedRotationFlag;
  	}
  	else
  	{
  		m_flags &= ~e_fixedRotationFlag;
  	}
  
  	m_angularVelocity = 0.0f;
  
  	ResetMassData();
  }
  
  void b2Body::Dump()
  {
  	int32 bodyIndex = m_islandIndex;
  
  	b2Log("{\n");
  	b2Log("  b2BodyDef bd;\n");
  	b2Log("  bd.type = b2BodyType(%d);\n", m_type);
  	b2Log("  bd.position.Set(%.15lef, %.15lef);\n", m_xf.p.x, m_xf.p.y);
  	b2Log("  bd.angle = %.15lef;\n", m_sweep.a);
  	b2Log("  bd.linearVelocity.Set(%.15lef, %.15lef);\n", m_linearVelocity.x, m_linearVelocity.y);
  	b2Log("  bd.angularVelocity = %.15lef;\n", m_angularVelocity);
  	b2Log("  bd.linearDamping = %.15lef;\n", m_linearDamping);
  	b2Log("  bd.angularDamping = %.15lef;\n", m_angularDamping);
  	b2Log("  bd.allowSleep = bool(%d);\n", m_flags & e_autoSleepFlag);
  	b2Log("  bd.awake = bool(%d);\n", m_flags & e_awakeFlag);
  	b2Log("  bd.fixedRotation = bool(%d);\n", m_flags & e_fixedRotationFlag);
  	b2Log("  bd.bullet = bool(%d);\n", m_flags & e_bulletFlag);
  	b2Log("  bd.active = bool(%d);\n", m_flags & e_activeFlag);
  	b2Log("  bd.gravityScale = %.15lef;\n", m_gravityScale);
  	b2Log("  bodies[%d] = m_world->CreateBody(&bd);\n", m_islandIndex);
  	b2Log("\n");
  	for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
  	{
  		b2Log("  {\n");
  		f->Dump(bodyIndex);
  		b2Log("  }\n");
  	}
  	b2Log("}\n");
  }
  