mixin skeleton for use in mods depending on fpl.

src/main/java/com/falsepattern/lib/mixin/MinecraftURLClassPath.java

@@ -0,0 +1,74 @@
+package com.falsepattern.lib.mixin;
+
+import cpw.mods.fml.common.Loader;
+import cpw.mods.fml.common.ModClassLoader;
+import lombok.val;
+import net.minecraft.launchwrapper.LaunchClassLoader;
+import sun.misc.URLClassPath;
+
+import java.io.File;
+import java.lang.reflect.Field;
+
+/**
+ * Backport from spongemixins 1.3 for compat with the curseforge 1.2.0 version.
+ *
+ * Also added Grimoire protection.
+ */
+public final class MinecraftURLClassPath {
+    /**
+     *  Utility to manipulate the minecraft URL ClassPath
+     */
+
+    private static final URLClassPath ucp;
+    private static final boolean GRIMOIRE;
+
+    static {
+        boolean grimoire;
+        try {
+            Class.forName("io.github.crucible.grimoire.Grimoire", false, MinecraftURLClassPath.class.getClassLoader());
+            grimoire = true;
+        } catch (ClassNotFoundException ignored) {
+            grimoire = false;
+        }
+        GRIMOIRE = grimoire;
+        if (!GRIMOIRE) {
+            try {
+                val modClassLoaderField = Loader.class.getDeclaredField("modClassLoader");
+                modClassLoaderField.setAccessible(true);
+
+                val loaderinstanceField = Loader.class.getDeclaredField("instance");
+                loaderinstanceField.setAccessible(true);
+
+                val mainClassLoaderField = ModClassLoader.class.getDeclaredField("mainClassLoader");
+                mainClassLoaderField.setAccessible(true);
+
+                val ucpField = LaunchClassLoader.class.getSuperclass().getDeclaredField("ucp");
+                ucpField.setAccessible(true);
+
+                Object loader = loaderinstanceField.get(null);
+                val modClassLoader = (ModClassLoader) modClassLoaderField.get(loader);
+                val mainClassLoader = (LaunchClassLoader) mainClassLoaderField.get(modClassLoader);
+                ucp = (URLClassPath) ucpField.get(mainClassLoader);
+            } catch (NoSuchFieldException | IllegalAccessException e) {
+                throw new RuntimeException(e.getMessage());
+            }
+        } else {
+            ucp = null;
+            System.err.println("Grimoire detected, disabling jar loading utility");
+        }
+    }
+
+    /**
+     * Adds a Jar to the Minecraft URL ClassPath
+     *  - Needed when using mixins on classes outside of Minecraft or other coremods
+     */
+    public static void addJar(File pathToJar) throws Exception {
+        if (!GRIMOIRE)
+            ucp.addURL(pathToJar.toURI().toURL());
+    }
+
+    private MinecraftURLClassPath() {
+    }
+
+
+}