MixinUtils.java

/*
 *  This file is part of Cubic Chunks Mod, licensed under the MIT License (MIT).
 *
 *  Copyright (c) 2015 contributors
 *
 *  Permission is hereby granted, free of charge, to any person obtaining a copy
 *  of this software and associated documentation files (the "Software"), to deal
 *  in the Software without restriction, including without limitation the rights
 *  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 *  copies of the Software, and to permit persons to whom the Software is
 *  furnished to do so, subject to the following conditions:
 *
 *  The above copyright notice and this permission notice shall be included in
 *  all copies or substantial portions of the Software.
 *
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 *  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 *  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 *  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 *  THE SOFTWARE.
 */
package cubicchunks.asm;

import net.minecraft.util.math.BlockPos;
import net.minecraft.world.World;

import cubicchunks.world.ICubicWorld;

public class MixinUtils {
	/**
	 * This method should be used as a replacement of {@link BlockPos#getY()} when modifying vanilla height check.
	 * <p>
	 * Most of the time modifying it using {@link org.spongepowered.asm.mixin.injection.ModifyConstant} is not possible
	 * because 0 can't be replaced when used in comparison (JVM has separate instruction for it).
	 * <p>
	 * So instead of trying to fix these height checks, it's eaier to modify value returned by BlockPos#getY() to fit
	 * within the vanilla height range when the check should be successful, and be outside of that range otherwise.
	 * <p>
	 * This hack has some limitations - it can't be used in methods where BlockPos#getY() is used for anything other
	 * than a height check since the retuned value would be completely wrong. Fortunately most vanilla methods with
	 * hardcoded height checks don't use BlockPos#getY() for anything else.
	 */
	public static int getReplacementY(ICubicWorld world, BlockPos pos) {
		return getReplacementY(world, pos.getY());
	}

	/**
	 * Convenience method with World as argument that calls {@link MixinUtils#getReplacementY(ICubicWorld, BlockPos)}
	 */
	public static int getReplacementY(World world, BlockPos pos) {
		return getReplacementY((ICubicWorld) world, pos);
	}

	public static int getReplacementY(World world, int y) {
		return getReplacementY((ICubicWorld) world, y);
	}

	public static int getReplacementY(ICubicWorld world, int y) {
		if (y < world.getMinHeight() || y >= world.getMaxHeight()) {
			return y;
		}
		return 64;
	}
}