rewrite world/player state tracking (#453)

2 files changed, 61 insertions, 0 deletions

diff --git a/src/SMAPI/Framework/StateTracking/Comparers/EquatableComparer.cs b/src/SMAPI/Framework/StateTracking/Comparers/EquatableComparer.cs
new file mode 100644
index 00000000..a96ffdb6
--- /dev/null
+++ b/src/SMAPI/Framework/StateTracking/Comparers/EquatableComparer.cs
@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+
+namespace StardewModdingAPI.Framework.StateTracking.Comparers
+{
+    /// <summary>Compares instances using <see cref="IEqualityComparer{T}.Equals(T,T)"/>.</summary>
+    /// <typeparam name="T">The value type.</typeparam>
+    internal class EquatableComparer<T> : IEqualityComparer<T> where T : IEquatable<T>
+    {
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Determines whether the specified objects are equal.</summary>
+        /// <returns>true if the specified objects are equal; otherwise, false.</returns>
+        /// <param name="x">The first object to compare.</param>
+        /// <param name="y">The second object to compare.</param>
+        public bool Equals(T x, T y)
+        {
+            if (x == null)
+                return y == null;
+            return x.Equals(y);
+        }
+
+        /// <summary>Get a hash code for the specified object.</summary>
+        /// <param name="obj">The value.</param>
+        public int GetHashCode(T obj)
+        {
+            return RuntimeHelpers.GetHashCode(obj);
+        }
+    }
+}
diff --git a/src/SMAPI/Framework/StateTracking/Comparers/ObjectReferenceComparer.cs b/src/SMAPI/Framework/StateTracking/Comparers/ObjectReferenceComparer.cs
new file mode 100644
index 00000000..ef9adafb
--- /dev/null
+++ b/src/SMAPI/Framework/StateTracking/Comparers/ObjectReferenceComparer.cs
@@ -0,0 +1,29 @@
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+
+namespace StardewModdingAPI.Framework.StateTracking.Comparers
+{
+    /// <summary>A comparer which considers two references equal if they point to the same instance.</summary>
+    /// <typeparam name="T">The value type.</typeparam>
+    internal class ObjectReferenceComparer<T> : IEqualityComparer<T>
+    {
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Determines whether the specified objects are equal.</summary>
+        /// <returns>true if the specified objects are equal; otherwise, false.</returns>
+        /// <param name="x">The first object to compare.</param>
+        /// <param name="y">The second object to compare.</param>
+        public bool Equals(T x, T y)
+        {
+            return object.ReferenceEquals(x, y);
+        }
+
+        /// <summary>Get a hash code for the specified object.</summary>
+        /// <param name="obj">The value.</param>
+        public int GetHashCode(T obj)
+        {
+            return RuntimeHelpers.GetHashCode(obj);
+        }
+    }
+}