void b2RopeJoint::InitVelocityConstraints()

in Box2D/Dynamics/Joints/b2RopeJoint.cpp [46:124]
65 lines of code
5 McCabe index (conditional complexity)

void b2RopeJoint::InitVelocityConstraints(const b2SolverData& data)
{
	m_indexA = m_bodyA->m_islandIndex;
	m_indexB = m_bodyB->m_islandIndex;
	m_localCenterA = m_bodyA->m_sweep.localCenter;
	m_localCenterB = m_bodyB->m_sweep.localCenter;
	m_invMassA = m_bodyA->m_invMass;
	m_invMassB = m_bodyB->m_invMass;
	m_invIA = m_bodyA->m_invI;
	m_invIB = m_bodyB->m_invI;

	b2Vec2 cA = data.positions[m_indexA].c;
	float32 aA = data.positions[m_indexA].a;
	b2Vec2 vA = data.velocities[m_indexA].v;
	float32 wA = data.velocities[m_indexA].w;

	b2Vec2 cB = data.positions[m_indexB].c;
	float32 aB = data.positions[m_indexB].a;
	b2Vec2 vB = data.velocities[m_indexB].v;
	float32 wB = data.velocities[m_indexB].w;

	b2Rot qA(aA), qB(aB);

	m_rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
	m_rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
	m_u = cB + m_rB - cA - m_rA;

	m_length = m_u.Length();

	float32 C = m_length - m_maxLength;
	if (C > 0.0f)
	{
		m_state = e_atUpperLimit;
	}
	else
	{
		m_state = e_inactiveLimit;
	}

	if (m_length > b2_linearSlop)
	{
		m_u *= 1.0f / m_length;
	}
	else
	{
		m_u.SetZero();
		m_mass = 0.0f;
		m_impulse = 0.0f;
		return;
	}

	// Compute effective mass.
	float32 crA = b2Cross(m_rA, m_u);
	float32 crB = b2Cross(m_rB, m_u);
	float32 invMass = m_invMassA + m_invIA * crA * crA + m_invMassB + m_invIB * crB * crB;

	m_mass = invMass != 0.0f ? 1.0f / invMass : 0.0f;

	if (data.step.warmStarting)
	{
		// Scale the impulse to support a variable time step.
		m_impulse *= data.step.dtRatio;

		b2Vec2 P = m_impulse * m_u;
		vA -= m_invMassA * P;
		wA -= m_invIA * b2Cross(m_rA, P);
		vB += m_invMassB * P;
		wB += m_invIB * b2Cross(m_rB, P);
	}
	else
	{
		m_impulse = 0.0f;
	}

	data.velocities[m_indexA].v = vA;
	data.velocities[m_indexA].w = wA;
	data.velocities[m_indexB].v = vB;
	data.velocities[m_indexB].w = wB;
}