matching nbt tags w/ recipe items

a.java

	private static boolean isTagSubset(@Nullable NBTTagCompound recipeTag, @Nullable NBTTagCompound suppliedTag) {
		//check that the user supplied item has, at least, the same nbt tags as the recipe item
		//it is OK if the supplied item has *more* tags - however all the tags that *are* specified
		//in the recipe item must match
		
		//check easy cases
		//if there's no specified recipe nbt tag, anything goes
		if(recipeTag == null || recipeTag.isEmpty()) return true;
		//if the recipe has nbt but the supplied item doesn't, there's no way it can match
		if(suppliedTag == null || suppliedTag.isEmpty()) return false;
		//if the recipe simply has more nbt tags than the supplied item, there's no way it can match
		if(recipeTag.getKeySet().size() > suppliedTag.getKeySet().size()) return false;
		
		//it's not an easy case, so we actually have to check the contents of each tag
		
		for(String key : suppliedTag.getKeySet()) {
			//it's ok if the recipe is missing a key from the supplied item
			if(!recipeTag.hasKey(key)) continue;
			
			NBTBase suppliedEntry = suppliedTag.getTag(key);
			NBTBase recipeEntry = recipeTag.getTag(key);
			
			//if a value is present on both tags but they do not match, fail
			if(suppliedEntry instanceof NBTTagCompound && recipeEntry instanceof NBTTagCompound) {
				//recurse into tag compounds (see issue #42)
				if(!isTagSubset((NBTTagCompound) suppliedEntry, (NBTTagCompound) recipeEntry)) return false;
			} else {
				if(!suppliedEntry.equals(recipeEntry)) return false;
			}
		}
		
		return true;
	}