Java tutorial
/* * Copyright (C) 2009-2014 The Project Lombok Authors. * * 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 lombok.patcher.scripts; import java.util.List; import java.util.Set; import lombok.patcher.Hook; import lombok.patcher.MethodLogistics; import lombok.patcher.StackRequest; import lombok.patcher.TargetMatcher; import lombok.patcher.TransplantMapper; import org.objectweb.asm.ClassWriter; import org.objectweb.asm.Label; import org.objectweb.asm.MethodVisitor; import org.objectweb.asm.Opcodes; /** * Receive (optional) 'this' reference as well as any parameters, then choose to return early with provided value, or let * the method continue. */ public class ExitFromMethodEarlyScript extends MethodLevelPatchScript { private final Hook decisionWrapper, valueWrapper; private final Set<StackRequest> requests; private final boolean transplant, insert; private final boolean insertCallOnly; ExitFromMethodEarlyScript(List<TargetMatcher> matchers, Hook decisionWrapper, Hook valueWrapper, boolean transplant, boolean insert, Set<StackRequest> requests) { super(matchers); this.decisionWrapper = decisionWrapper; this.valueWrapper = valueWrapper; this.requests = requests; this.transplant = transplant; this.insert = insert; this.insertCallOnly = decisionWrapper != null && decisionWrapper.getMethodDescriptor().endsWith(")V"); if (!this.insertCallOnly && decisionWrapper != null && !decisionWrapper.getMethodDescriptor().endsWith(")Z")) { throw new IllegalArgumentException( "The decisionWrapper method must either return 'boolean' or return 'void'."); } assert !(insert && transplant); } @Override protected MethodPatcher createPatcher(ClassWriter writer, final String classSpec, TransplantMapper transplantMapper) { MethodPatcher patcher = new MethodPatcher(writer, transplantMapper, new MethodPatcherFactory() { public MethodVisitor createMethodVisitor(String name, String desc, MethodVisitor parent, MethodLogistics logistics) { if (valueWrapper == null && !insertCallOnly && logistics.getReturnOpcode() != Opcodes.RETURN) { throw new IllegalStateException("method " + name + desc + " must return something, but " + "you did not provide a value hook method."); } return new ExitEarly(parent, logistics, classSpec); } }); if (transplant) { patcher.addTransplant(decisionWrapper); if (valueWrapper != null) patcher.addTransplant(valueWrapper); } return patcher; } private class ExitEarly extends MethodVisitor { private final MethodLogistics logistics; private final String ownClassSpec; public ExitEarly(MethodVisitor mv, MethodLogistics logistics, String ownClassSpec) { super(Opcodes.ASM4, mv); this.logistics = logistics; this.ownClassSpec = ownClassSpec; } @Override public void visitCode() { if (decisionWrapper == null) { //Always return early. if (logistics.getReturnOpcode() == Opcodes.RETURN) { mv.visitInsn(Opcodes.RETURN); return; } insertValueWrapperCall(); return; } if (requests.contains(StackRequest.THIS)) logistics.generateLoadOpcodeForThis(mv); for (StackRequest param : StackRequest.PARAMS_IN_ORDER) { if (!requests.contains(param)) continue; logistics.generateLoadOpcodeForParam(param.getParamPos(), mv); } if (insert) insertMethod(decisionWrapper, mv); else super.visitMethodInsn(Opcodes.INVOKESTATIC, transplant ? ownClassSpec : decisionWrapper.getClassSpec(), decisionWrapper.getMethodName(), decisionWrapper.getMethodDescriptor(), false); if (insertCallOnly) { super.visitCode(); return; } /* Inject: * if ([result of decision hook]) { * //if method body is not VOID: * reload-on-stack-what-needs-reloading * invokeReturnValueHook * //end if * xRETURN; * } */ Label label0 = new Label(); mv.visitJumpInsn(Opcodes.IFEQ, label0); if (logistics.getReturnOpcode() == Opcodes.RETURN) { mv.visitInsn(Opcodes.RETURN); } else { if (requests.contains(StackRequest.THIS)) logistics.generateLoadOpcodeForThis(mv); for (StackRequest param : StackRequest.PARAMS_IN_ORDER) { if (!requests.contains(param)) continue; logistics.generateLoadOpcodeForParam(param.getParamPos(), mv); } if (insert) insertMethod(valueWrapper, mv); else super.visitMethodInsn(Opcodes.INVOKESTATIC, transplant ? ownClassSpec : valueWrapper.getClassSpec(), valueWrapper.getMethodName(), valueWrapper.getMethodDescriptor(), false); logistics.generateReturnOpcode(mv); } mv.visitLabel(label0); mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null); super.visitCode(); } private void insertValueWrapperCall() { if (requests.contains(StackRequest.THIS)) logistics.generateLoadOpcodeForThis(mv); for (StackRequest param : StackRequest.PARAMS_IN_ORDER) { if (!requests.contains(param)) continue; logistics.generateLoadOpcodeForParam(param.getParamPos(), mv); } if (insert) insertMethod(valueWrapper, mv); else super.visitMethodInsn(Opcodes.INVOKESTATIC, transplant ? ownClassSpec : valueWrapper.getClassSpec(), valueWrapper.getMethodName(), valueWrapper.getMethodDescriptor(), false); logistics.generateReturnOpcode(mv); } } }