[SL.Core] Extend HashHelper.Combine to accept 2, 3, or 4 args

src/SixLabors.Core/Helpers/HashHelpers.cs

@@ -13,7 +13,7 @@ namespace SixLabors
         /// </summary>
         /// <param name="h1">Hash code one</param>
         /// <param name="h2">Hash code two</param>
-        /// <returns>Returns a hash code for the two specified has codes.</returns>
+        /// <returns>Returns a hash code for the provided hash codes.</returns>
         public static int Combine(int h1, int h2)
         {
             unchecked
@@ -24,5 +24,39 @@ namespace SixLabors
                 return ((int)rol5 + h1) ^ h2;
             }
         }
+
+        /// <summary>
+        /// Combines the three specified hash codes.
+        /// </summary>
+        /// <param name="h1">The first </param>
+        /// <param name="h2">Hash code two</param>
+        /// <param name="h3">Hash code three</param>
+        /// <returns>Returns a hash code for the provided hash codes.</returns>
+        public static int Combine(int h1, int h2, int h3)
+        {
+            int hash = Combine(h1, h2);
+
+            hash = Combine(hash, h3);
+
+            return hash;
+        }
+
+        /// <summary>
+        /// Combines the four specified hash codes.
+        /// </summary>
+        /// <param name="h1">The first </param>
+        /// <param name="h2">Hash code two</param>
+        /// <param name="h3">Hash code three</param>
+        /// <param name="h4">Hash code four</param>
+        /// <returns>Returns a hash code for the provided hash codes.</returns>
+        public static int Combine(int h1, int h2, int h3, int h4)
+        {
+            int hash = Combine(h1, h2);
+
+            hash = Combine(hash, h3);
+            hash = Combine(hash, h4);
+
+            return hash;
+        }
     }
 }

src/SixLabors.Core/Primitives/Rectangle.cs

@@ -460,11 +460,12 @@ namespace SixLabors.Primitives
 
         private int GetHashCode(Rectangle rectangle)
         {
-            int hashCode = rectangle.X.GetHashCode();
-            hashCode = HashHelpers.Combine(hashCode, rectangle.Y.GetHashCode());
-            hashCode = HashHelpers.Combine(hashCode, rectangle.Width.GetHashCode());
-            hashCode = HashHelpers.Combine(hashCode, rectangle.Height.GetHashCode());
-            return hashCode;
+            return HashHelpers.Combine(
+                rectangle.X.GetHashCode(),
+                rectangle.Y.GetHashCode(),
+                rectangle.Width.GetHashCode(),
+                rectangle.Height.GetHashCode()
+            );
         }
     }
 }

src/SixLabors.Core/Primitives/RectangleF.cs

@@ -393,11 +393,12 @@ namespace SixLabors.Primitives
 
         private int GetHashCode(RectangleF rectangle)
         {
-            int hashCode = rectangle.X.GetHashCode();
-            hashCode = HashHelpers.Combine(hashCode, rectangle.Y.GetHashCode());
-            hashCode = HashHelpers.Combine(hashCode, rectangle.Width.GetHashCode());
-            hashCode = HashHelpers.Combine(hashCode, rectangle.Height.GetHashCode());
-            return hashCode;
+            return HashHelpers.Combine(
+                rectangle.X.GetHashCode(),
+                rectangle.Y.GetHashCode(),
+                rectangle.Width.GetHashCode(),
+                rectangle.Height.GetHashCode()
+            );
         }
     }
 }