Java tutorial
/* * This file is part of Sponge, licensed under the MIT License (MIT). * * Copyright (c) SpongePowered.org <http://www.spongepowered.org> * Copyright (c) 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 org.spongepowered.asm.mixin.injection.invoke; import java.util.Arrays; import java.util.List; import org.objectweb.asm.Type; import org.objectweb.asm.tree.InsnList; import org.objectweb.asm.tree.MethodInsnNode; import org.spongepowered.asm.mixin.injection.InjectionPoint; import org.spongepowered.asm.mixin.injection.InvalidInjectionException; import org.spongepowered.asm.mixin.injection.code.Injector; import org.spongepowered.asm.mixin.injection.struct.InjectionInfo; import org.spongepowered.asm.mixin.injection.struct.Target; /** * A bytecode injector which allows a single argument of a chosen method call to * be altered. */ public class ModifyArgInjector extends InvokeInjector { /** * Index of the target arg or -1 to find the arg automatically (only works * where there is only one arg of specified type on the element) */ private final int index; /** * True if processing in single arg mode, the callback only accepts a single * arg of the same type as the return. Otherwise the handler method is * expected to have matching args to the target invocation */ private final boolean singleArgMode; /** * @param info Injection info * @param index target arg index */ public ModifyArgInjector(InjectionInfo info, int index) { super(info, "@ModifyArg"); this.index = index; this.singleArgMode = this.methodArgs.length == 1; } /* (non-Javadoc) * @see org.spongepowered.asm.mixin.injection.callback.BytecodeInjector * #sanityCheck(org.spongepowered.asm.mixin.injection.callback.Target, * java.util.List) */ @Override protected void sanityCheck(Target target, List<InjectionPoint> injectionPoints) { super.sanityCheck(target, injectionPoints); if (this.singleArgMode) { if (!this.methodArgs[0].equals(this.returnType)) { throw new InvalidInjectionException(this.info, "@ModifyArg return type must match the parameter type." + " ARG=" + this.methodArgs[0] + " RETURN=" + this.returnType); } } } /** * Do the injection */ @Override protected void inject(Target target, MethodInsnNode node) { Type[] args = Type.getArgumentTypes(node.desc); int argIndex = this.findArgIndex(target, args); InsnList insns = new InsnList(); int extraLocals = 0; if (this.singleArgMode) { extraLocals = this.injectSingleArgHandler(target, args, argIndex, insns); } else { extraLocals = this.injectMultiArgHandler(target, args, argIndex, insns); } target.method.instructions.insertBefore(node, insns); target.method.maxLocals = Math.max(target.maxLocals, target.method.maxLocals + extraLocals); target.method.maxStack = Math.max(target.maxStack, target.method.maxStack + 2 - (extraLocals - 1)); } /** * Inject handler opcodes for a single arg handler */ private int injectSingleArgHandler(Target target, Type[] args, int argIndex, InsnList insns) { int[] argMap = this.storeArgs(target, args, insns, argIndex); this.invokeHandlerWithArgs(args, insns, argMap, argIndex, argIndex + 1); this.pushArgs(args, insns, argMap, argIndex + 1, args.length); return (target.method.maxLocals - argMap[argMap.length - 1]) + 1 + args[args.length - 1].getSize(); } /** * Inject handler opcodes for a multi arg handler */ private int injectMultiArgHandler(Target target, Type[] args, int argIndex, InsnList insns) { if (!Arrays.equals(args, this.methodArgs)) { throw new InvalidInjectionException(this.info, "@ModifyArg method targets a method with an invalid signature " + Injector.printArgs(args) + ", expected " + Injector.printArgs(this.methodArgs)); } int[] argMap = this.storeArgs(target, args, insns, 0); this.pushArgs(args, insns, argMap, 0, argIndex); this.invokeHandlerWithArgs(args, insns, argMap, 0, args.length); this.pushArgs(args, insns, argMap, argIndex + 1, args.length); return (target.method.maxLocals - argMap[argMap.length - 1]) + 1 + args[args.length - 1].getSize(); } protected int findArgIndex(Target target, Type[] args) { if (this.index > -1) { if (this.index >= args.length || !args[this.index].equals(this.returnType)) { throw new InvalidInjectionException(this.info, "Specified index " + this.index + " for @ModifyArg is invalid for args " + Injector.printArgs(args) + ", expected " + this.returnType); } return this.index; } int argIndex = -1; for (int arg = 0; arg < args.length; arg++) { if (!args[arg].equals(this.returnType)) { continue; } if (argIndex != -1) { throw new InvalidInjectionException(this.info, "Found duplicate args with index [" + argIndex + ", " + arg + "] matching type " + this.returnType + " for @ModifyArg target " + target + " in " + this.classNode.name + ". Please specify index of desired arg."); } argIndex = arg; } if (argIndex == -1) { throw new InvalidInjectionException(this.info, "Could not find arg matching type " + this.returnType + " for @ModifyArg target " + target + " in " + this.classNode.name); } return argIndex; } }