MonoGame.Extended/Source/MonoGame.Extended.Entities/Aspect.cs

// Original code dervied from:
// https://github.com/thelinuxlich/artemis_CSharp/blob/master/Artemis_XNA_INDEPENDENT/Aspect.cs

// --------------------------------------------------------------------------------------------------------------------
// <copyright file="Aspect.cs" company="GAMADU.COM">
//     Copyright © 2013 GAMADU.COM. AllOf rights reserved.
//
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//        2. Redistributions in binary form must reproduce the above copyright notice, this list
//           of conditions and the following disclaimer in the documentation and/or other materials
//           provided with the distribution.
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//     FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GAMADU.COM OR
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// </copyright>
// <summary>
//   Specify a Filter class to filter what Entities (with what Components) a EntitySystem will ProcessInternal.
// </summary>
// --------------------------------------------------------------------------------------------------------------------

using System.Linq.Expressions;

namespace MonoGame.Extended.Entities
{
    internal class Aspect
    {
        // match entities with components using boolean logic: 
        // (A and B and C and ..) AND (D or E or F or ...) AND NOT(G or H or I or ..)

        // match components that have: 
        //  all of the set {A, B, C, ..} and 
        //  have any of the set {D, E, F, ..} but
        //  do not have any of the set {G, H, I, ..}
        // all(A, B, C, ..).any(D, E, F, ..).no(G, H, I, ..)

        // e.g does match
        // components:  010001110
        // andMask:     000001110
        // orMask:      111000000
        // norMask:     000000001

        // e.g does match
        // components:  100011110
        // andMask:     000001110
        // orMask:      111000000
        // norMask:     000000001

        // e.g does not match
        // components:  100001111
        // andMask:     000011110
        // orMask:      111000000
        // norMask:     000000001

        // e.g does not match
        // components:  000001111
        // andMask:     000011110
        // orMask:      111000000
        // norMask:     000100000

        internal BitVector AndMask;
        internal BitVector OrMask;
        internal BitVector NorMask;
        internal static BitVector Result;

        public Aspect(BitVector andMask, BitVector orMask, BitVector norMask)
        {
            if (Result == null)
                Result = new BitVector(andMask.Length);
            AndMask = new BitVector(andMask);
            OrMask = orMask.EqualsZero() ? new BitVector(andMask.Length, true) : new BitVector(orMask);
            NorMask = new BitVector(norMask);
        }

        internal bool Matches(BitVector componentBits)
        {
            AndMask.And(componentBits, ref Result);
            if (!Result.Equals(AndMask))
                return false;
            NorMask.And(componentBits, ref Result);
            if (!Result.EqualsZero())
                return false;
            OrMask.And(componentBits, ref Result);
            return !Result.EqualsZero();
        }
    }
}