1 files changed, 94 insertions, 0 deletions
diff --git a/src/StardewModdingAPI/Framework/ModLoading/RewriteHelper.cs b/src/StardewModdingAPI/Framework/ModLoading/RewriteHelper.cs
new file mode 100644
index 00000000..56a60a72
--- /dev/null
+++ b/src/StardewModdingAPI/Framework/ModLoading/RewriteHelper.cs
@@ -0,0 +1,94 @@
+using System;
+using System.Linq;
+using System.Reflection;
+using Mono.Cecil;
+using Mono.Cecil.Cil;
+
+namespace StardewModdingAPI.Framework.ModLoading
+{
+    /// <summary>Provides helper methods for field rewriters.</summary>
+    internal static class RewriteHelper
+    {
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Get the field reference from an instruction if it matches.</summary>
+        /// <param name="instruction">The IL instruction.</param>
+        public static FieldReference AsFieldReference(Instruction instruction)
+        {
+            return instruction.OpCode == OpCodes.Ldfld || instruction.OpCode == OpCodes.Ldsfld || instruction.OpCode == OpCodes.Stfld || instruction.OpCode == OpCodes.Stsfld
+                ? (FieldReference)instruction.Operand
+                : null;
+        }
+
+        /// <summary>Get the method reference from an instruction if it matches.</summary>
+        /// <param name="instruction">The IL instruction.</param>
+        public static MethodReference AsMethodReference(Instruction instruction)
+        {
+            return instruction.OpCode == OpCodes.Call || instruction.OpCode == OpCodes.Callvirt
+                ? (MethodReference)instruction.Operand
+                : null;
+        }
+
+        /// <summary>Get whether a type matches a type reference.</summary>
+        /// <param name="type">The defined type.</param>
+        /// <param name="reference">The type reference.</param>
+        public static bool IsSameType(Type type, TypeReference reference)
+        {
+            // same namespace & name
+            if (type.Namespace != reference.Namespace || type.Name != reference.Name)
+                return false;
+
+            // same generic parameters
+            if (type.IsGenericType)
+            {
+                if (!reference.IsGenericInstance)
+                    return false;
+
+                Type[] defGenerics = type.GetGenericArguments();
+                TypeReference[] refGenerics = ((GenericInstanceType)reference).GenericArguments.ToArray();
+                if (defGenerics.Length != refGenerics.Length)
+                    return false;
+                for (int i = 0; i < defGenerics.Length; i++)
+                {
+                    if (!RewriteHelper.IsSameType(defGenerics[i], refGenerics[i]))
+                        return false;
+                }
+            }
+
+            return true;
+        }
+
+        /// <summary>Get whether a method definition matches the signature expected by a method reference.</summary>
+        /// <param name="definition">The method definition.</param>
+        /// <param name="reference">The method reference.</param>
+        public static bool HasMatchingSignature(MethodInfo definition, MethodReference reference)
+        {
+            // same name
+            if (definition.Name != reference.Name)
+                return false;
+
+            // same arguments
+            ParameterInfo[] definitionParameters = definition.GetParameters();
+            ParameterDefinition[] referenceParameters = reference.Parameters.ToArray();
+            if (referenceParameters.Length != definitionParameters.Length)
+                return false;
+            for (int i = 0; i < referenceParameters.Length; i++)
+            {
+                if (!RewriteHelper.IsSameType(definitionParameters[i].ParameterType, referenceParameters[i].ParameterType))
+                    return false;
+            }
+            return true;
+        }
+
+        /// <summary>Get whether a type has a method whose signature matches the one expected by a method reference.</summary>
+        /// <param name="type">The type to check.</param>
+        /// <param name="reference">The method reference.</param>
+        public static bool HasMatchingSignature(Type type, MethodReference reference)
+        {
+            return type
+                .GetMethods(BindingFlags.Instance | BindingFlags.DeclaredOnly | BindingFlags.Public)
+                .Any(method => RewriteHelper.HasMatchingSignature(method, reference));
+        }
+    }
+}