1 files changed, 131 insertions, 0 deletions
diff --git a/libraries/launcher/org/prismlauncher/utils/ReflectionUtils.java b/libraries/launcher/org/prismlauncher/utils/ReflectionUtils.java
new file mode 100644
index 00000000..484e0d8a
--- /dev/null
+++ b/libraries/launcher/org/prismlauncher/utils/ReflectionUtils.java
@@ -0,0 +1,131 @@
+package org.prismlauncher.utils;
+
+
+import java.applet.Applet;
+import java.io.File;
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.MethodType;
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+
+public final class ReflectionUtils {
+    private static final Logger LOGGER = Logger.getLogger("ReflectionUtils");
+
+    private ReflectionUtils() {
+    }
+
+    /**
+     * Instantiate an applet class by name
+     *
+     * @param appletClassName The name of the applet class to resolve
+     *
+     * @return The instantiated applet class
+     *
+     * @throws ClassNotFoundException if the provided class name cannot be found
+     * @throws NoSuchMethodException  if the no-args constructor cannot be found
+     * @throws IllegalAccessException if the constructor cannot be accessed via method handles
+     * @throws Throwable              any exceptions from the class's constructor
+     */
+    public static Applet createAppletClass(String appletClassName) throws Throwable {
+        Class<?> appletClass = ClassLoader.getSystemClassLoader().loadClass(appletClassName);
+
+        MethodHandle appletConstructor = MethodHandles.lookup().findConstructor(appletClass, MethodType.methodType(void.class));
+        return (Applet) appletConstructor.invoke();
+    }
+
+    /**
+     * Finds a field that looks like a Minecraft base folder in a supplied class
+     *
+     * @param minecraftMainClass the class to scan
+     *
+     * @return The found field.
+     */
+    public static Field getMinecraftGameDirField(Class<?> minecraftMainClass) {
+        LOGGER.fine("Resolving minecraft game directory field");
+        // Field we're looking for is always
+        // private static File obfuscatedName = null;
+        for (Field field : minecraftMainClass.getDeclaredFields()) {
+            // Has to be File
+            if (field.getType() != File.class) {
+                continue;
+            }
+
+            int fieldModifiers = field.getModifiers();
+
+
+            // Must be static
+            if (!Modifier.isStatic(fieldModifiers)) {
+                LOGGER.log(Level.FINE, "Rejecting field {0} because it is not static", field.getName());
+                continue;
+            }
+
+            // Must be private
+            if (!Modifier.isPrivate(fieldModifiers)) {
+                LOGGER.log(Level.FINE, "Rejecting field {0} because it is not private", field.getName());
+                continue;
+            }
+
+            // Must not be final
+            if (Modifier.isFinal(fieldModifiers)) {
+                LOGGER.log(Level.FINE, "Rejecting field {0} because it is final", field.getName());
+                continue;
+            }
+
+            LOGGER.log(Level.FINE, "Identified field {0} to match conditions for minecraft game directory field", field.getName());
+
+            return field;
+        }
+
+        return null;
+    }
+
+    /**
+     * Resolve main entrypoint and returns method handle for it.
+     * <p>
+     * Resolves a method that matches the following signature
+     * <code>
+     * public static void main(String[] args) {
+     * <p>
+     * }
+     * </code>
+     *
+     * @param entrypointClass The entrypoint class to resolve the method from
+     *
+     * @return The method handle for the resolved entrypoint
+     *
+     * @throws NoSuchMethodException  If no method matching the correct signature can be found
+     * @throws IllegalAccessException If method handles cannot access the entrypoint
+     */
+    public static MethodHandle findMainEntrypoint(Class<?> entrypointClass) throws NoSuchMethodException, IllegalAccessException {
+        return MethodHandles.lookup().findStatic(entrypointClass, "main", MethodType.methodType(void.class, String[].class));
+    }
+
+    /**
+     * Resolve main entrypoint and returns method handle for it.
+     * <p>
+     * Resolves a method that matches the following signature
+     * <code>
+     * public static void main(String[] args) {
+     * <p>
+     * }
+     * </code>
+     *
+     * @param entrypointClassName The name of the entrypoint class to resolve the method from
+     *
+     * @return The method handle for the resolved entrypoint
+     *
+     * @throws ClassNotFoundException If a class cannot be found with the provided name
+     * @throws NoSuchMethodException  If no method matching the correct signature can be found
+     * @throws IllegalAccessException If method handles cannot access the entrypoint
+     */
+    public static MethodHandle findMainEntrypoint(String entrypointClassName) throws
+                                                                              ClassNotFoundException,
+                                                                              NoSuchMethodException,
+                                                                              IllegalAccessException {
+        return findMainEntrypoint(ClassLoader.getSystemClassLoader().loadClass(entrypointClassName));
+    }
+}