misc optimization (#6436)

Content.Shared/Damage/DamageSpecifier.cs

@@ -22,7 +22,7 @@ namespace Content.Shared.Damage
     ///     functions to apply resistance sets and supports basic math operations to modify this dictionary.
     /// </remarks>
     [DataDefinition]
-    public class DamageSpecifier
+    public class DamageSpecifier : IEquatable<DamageSpecifier>
     {
         [JsonPropertyName("types")]
         [DataField("types", customTypeSerializer: typeof(PrototypeIdDictionarySerializer<FixedPoint2, DamageTypePrototype>))]
@@ -384,7 +384,21 @@ namespace Content.Shared.Damage
             return newDamage;
         }
 
-        public static DamageSpecifier operator -(DamageSpecifier damageSpecA, DamageSpecifier damageSpecB) => damageSpecA + -damageSpecB;
+        // Here we define the subtraction operator explicitly, rather than implicitly via something like X + (-1 * Y).
+        // This is faster because FixedPoint2 multiplication is somewhat involved.
+        public static DamageSpecifier operator -(DamageSpecifier damageSpecA, DamageSpecifier damageSpecB)
+        {
+            DamageSpecifier newDamage = new(damageSpecA);
+
+            foreach (var entry in damageSpecB.DamageDict)
+            {
+                if (!newDamage.DamageDict.TryAdd(entry.Key, -entry.Value))
+                {
+                    newDamage.DamageDict[entry.Key] -= entry.Value;
+                }
+            }
+            return newDamage;
+        }
 
         public static DamageSpecifier operator +(DamageSpecifier damageSpec) => damageSpec;
 
@@ -393,6 +407,20 @@ namespace Content.Shared.Damage
         public static DamageSpecifier operator *(float factor, DamageSpecifier damageSpec) => damageSpec * factor;
 
         public static DamageSpecifier operator *(FixedPoint2 factor, DamageSpecifier damageSpec) => damageSpec * factor;
+
+        public bool Equals(DamageSpecifier? other)
+        {
+            if (other == null || DamageDict.Count != other.DamageDict.Count)
+                return false;
+
+            foreach (var (key, value) in DamageDict)
+            {
+                if (!other.DamageDict.TryGetValue(key, out var otherValue) || value != otherValue)
+                    return false;
+            }
+
+            return true;
+        }
     }
     #endregion
 }