Add in some reverse lookup methods for game registry data

fml/common/cpw/mods/fml/common/registry/GameData.java

@@ -52,6 +52,7 @@ import cpw.mods.fml.common.FMLLog;
 import cpw.mods.fml.common.Loader;
 import cpw.mods.fml.common.LoaderState;
 import cpw.mods.fml.common.ModContainer;
+import cpw.mods.fml.common.registry.GameRegistry.UniqueIdentifier;
 
 public class GameData {
     private static Map<Integer, ItemData> idMap = Maps.newHashMap();
@@ -362,4 +363,28 @@ public class GameData {
             }
         }
     }
+
+    static UniqueIdentifier getUniqueName(Block block)
+    {
+        if (block == null) return null;
+        ItemData itemData = idMap.get(block.field_71990_ca);
+        if (itemData == null || !itemData.isOveridden() || customItemStacks.contains(itemData.getModId(), itemData.getItemType()))
+        {
+            return null;
+        }
+
+        return new UniqueIdentifier(itemData.getModId(), itemData.getItemType());
+    }
+
+    static UniqueIdentifier getUniqueName(Item item)
+    {
+        if (item == null) return null;
+        ItemData itemData = idMap.get(item.field_77779_bT);
+        if (itemData == null || !itemData.isOveridden() || customItemStacks.contains(itemData.getModId(), itemData.getItemType()))
+        {
+            return null;
+        }
+
+        return new UniqueIdentifier(itemData.getModId(), itemData.getItemType());
+    }
 }

fml/common/cpw/mods/fml/common/registry/GameRegistry.java

@@ -430,4 +430,46 @@ public class GameRegistry
 	    }
 	    return null;
 	}
+
+	public static class UniqueIdentifier
+	{
+	    public final String modId;
+	    public final String name;
+        UniqueIdentifier(String modId, String name)
+        {
+            this.modId = modId;
+            this.name = name;
+        }
+	}
+
+	/**
+	 * Look up the mod identifier data for a block.
+	 * Returns null if there is no mod specified mod identifier data, or it is part of a
+	 * custom itemstack definition {@link #registerCustomItemStack}
+	 *
+	 * Note: uniqueness and persistence is only guaranteed by mods using the game registry
+	 * correctly.
+	 *
+	 * @param block to lookup
+     * @return a {@link UniqueIdentifier} for the block or null
+	 */
+	public static UniqueIdentifier findUniqueIdentifierFor(net.minecraft.block.Block block)
+	{
+	    return GameData.getUniqueName(block);
+	}
+    /**
+     * Look up the mod identifier data for an item.
+     * Returns null if there is no mod specified mod identifier data, or it is part of a
+     * custom itemstack definition {@link #registerCustomItemStack}
+     *
+     * Note: uniqueness and persistence is only guaranteed by mods using the game registry
+     * correctly.
+     *
+     * @param item to lookup
+     * @return a {@link UniqueIdentifier} for the item or null
+     */
+    public static UniqueIdentifier findUniqueIdentifierFor(net.minecraft.item.Item item)
+    {
+        return GameData.getUniqueName(item);
+    }
 }