void b2CollidePolygonAndCircle()

in Box2D/Collision/b2CollideCircle.cpp [51:154]
87 lines of code
11 McCabe index (conditional complexity)

void b2CollidePolygonAndCircle(
	b2Manifold* manifold,
	const b2PolygonShape* polygonA, const b2Transform& xfA,
	const b2CircleShape* circleB, const b2Transform& xfB)
{
	manifold->pointCount = 0;

	// Compute circle position in the frame of the polygon.
	b2Vec2 c = b2Mul(xfB, circleB->m_p);
	b2Vec2 cLocal = b2MulT(xfA, c);

	// Find the min separating edge.
	int32 normalIndex = 0;
	float32 separation = -b2_maxFloat;
	float32 radius = polygonA->m_radius + circleB->m_radius;
	int32 vertexCount = polygonA->m_count;
	const b2Vec2* vertices = polygonA->m_vertices;
	const b2Vec2* normals = polygonA->m_normals;

	for (int32 i = 0; i < vertexCount; ++i)
	{
		float32 s = b2Dot(normals[i], cLocal - vertices[i]);

		if (s > radius)
		{
			// Early out.
			return;
		}

		if (s > separation)
		{
			separation = s;
			normalIndex = i;
		}
	}

	// Vertices that subtend the incident face.
	int32 vertIndex1 = normalIndex;
	int32 vertIndex2 = vertIndex1 + 1 < vertexCount ? vertIndex1 + 1 : 0;
	b2Vec2 v1 = vertices[vertIndex1];
	b2Vec2 v2 = vertices[vertIndex2];

	// If the center is inside the polygon ...
	if (separation < b2_epsilon)
	{
		manifold->pointCount = 1;
		manifold->type = b2Manifold::e_faceA;
		manifold->localNormal = normals[normalIndex];
		manifold->localPoint = 0.5f * (v1 + v2);
		manifold->points[0].localPoint = circleB->m_p;
		manifold->points[0].id.key = 0;
		return;
	}

	// Compute barycentric coordinates
	float32 u1 = b2Dot(cLocal - v1, v2 - v1);
	float32 u2 = b2Dot(cLocal - v2, v1 - v2);
	if (u1 <= 0.0f)
	{
		if (b2DistanceSquared(cLocal, v1) > radius * radius)
		{
			return;
		}

		manifold->pointCount = 1;
		manifold->type = b2Manifold::e_faceA;
		manifold->localNormal = cLocal - v1;
		manifold->localNormal.Normalize();
		manifold->localPoint = v1;
		manifold->points[0].localPoint = circleB->m_p;
		manifold->points[0].id.key = 0;
	}
	else if (u2 <= 0.0f)
	{
		if (b2DistanceSquared(cLocal, v2) > radius * radius)
		{
			return;
		}

		manifold->pointCount = 1;
		manifold->type = b2Manifold::e_faceA;
		manifold->localNormal = cLocal - v2;
		manifold->localNormal.Normalize();
		manifold->localPoint = v2;
		manifold->points[0].localPoint = circleB->m_p;
		manifold->points[0].id.key = 0;
	}
	else
	{
		b2Vec2 faceCenter = 0.5f * (v1 + v2);
		float32 separation = b2Dot(cLocal - faceCenter, normals[vertIndex1]);
		if (separation > radius)
		{
			return;
		}

		manifold->pointCount = 1;
		manifold->type = b2Manifold::e_faceA;
		manifold->localNormal = normals[vertIndex1];
		manifold->localPoint = faceCenter;
		manifold->points[0].localPoint = circleB->m_p;
		manifold->points[0].id.key = 0;
	}
}