merge assembly rewriters into main SMAPI project (#347)

1 files changed, 53 insertions, 0 deletions

diff --git a/src/StardewModdingAPI/Framework/ModLoading/Rewriters/FieldReplaceRewriter.cs b/src/StardewModdingAPI/Framework/ModLoading/Rewriters/FieldReplaceRewriter.cs
new file mode 100644
index 00000000..7b838f13
--- /dev/null
+++ b/src/StardewModdingAPI/Framework/ModLoading/Rewriters/FieldReplaceRewriter.cs
@@ -0,0 +1,53 @@
+using System;
+using System.Reflection;
+using Mono.Cecil;
+using Mono.Cecil.Cil;
+using StardewModdingAPI.Framework.ModLoading.Finders;
+
+namespace StardewModdingAPI.Framework.ModLoading.Rewriters
+{
+    /// <summary>Rewrites references to one field with another.</summary>
+    internal class FieldReplaceRewriter : FieldFinder
+    {
+        /*********
+        ** Properties
+        *********/
+        /// <summary>The new field to reference.</summary>
+        private readonly FieldInfo ToField;
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="type">The type whose field to which references should be rewritten.</param>
+        /// <param name="fromFieldName">The field name to rewrite.</param>
+        /// <param name="toFieldName">The new field name to reference.</param>
+        /// <param name="nounPhrase">A brief noun phrase indicating what the instruction finder matches (or <c>null</c> to generate one).</param>
+        public FieldReplaceRewriter(Type type, string fromFieldName, string toFieldName, string nounPhrase = null)
+            : base(type.FullName, fromFieldName, nounPhrase)
+        {
+            this.ToField = type.GetField(toFieldName);
+            if (this.ToField == null)
+                throw new InvalidOperationException($"The {type.FullName} class doesn't have a {toFieldName} field.");
+        }
+
+        /// <summary>Rewrite a CIL instruction for compatibility.</summary>
+        /// <param name="module">The module being rewritten.</param>
+        /// <param name="cil">The CIL rewriter.</param>
+        /// <param name="instruction">The instruction to rewrite.</param>
+        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        public override bool Rewrite(ModuleDefinition module, ILProcessor cil, Instruction instruction, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            if (!this.IsMatch(instruction))
+                return false;
+
+            FieldReference newRef = module.Import(this.ToField);
+            cil.Replace(instruction, cil.Create(instruction.OpCode, newRef));
+            return true;
+        }
+    }
+}