fernflower/src/de/fernflower/main/rels/LambdaProcessor.java

package de.fernflower.main.rels;

import java.io.IOException;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import de.fernflower.code.CodeConstants;
import de.fernflower.code.Instruction;
import de.fernflower.code.InstructionSequence;
import de.fernflower.main.ClassesProcessor;
import de.fernflower.main.ClassesProcessor.ClassNode;
import de.fernflower.main.DecompilerContext;
import de.fernflower.struct.StructClass;
import de.fernflower.struct.StructMethod;
import de.fernflower.struct.attr.StructBootstrapMethodsAttribute;
import de.fernflower.struct.attr.StructGeneralAttribute;
import de.fernflower.struct.consts.LinkConstant;
import de.fernflower.struct.consts.PooledConstant;
import de.fernflower.struct.consts.PrimitiveConstant;
import de.fernflower.struct.gen.MethodDescriptor;
import de.fernflower.util.InterpreterUtil;

public class LambdaProcessor {

	private static final String JAVAC_LAMBDA_CLASS = "java/lang/invoke/LambdaMetafactory"; 
	private static final String JAVAC_LAMBDA_METHOD = "metafactory";
	private static final String JAVAC_LAMBDA_METHOD_DESCRIPTOR = "(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;";
	
	public void processClass(ClassNode node) throws IOException {

		for(ClassNode child : node.nested) {
			processClass(child);
		}
		
		if(node.nested.isEmpty()) {
			hasLambda(node);
		}
	}

	public boolean hasLambda(ClassNode node) throws IOException {

		ClassesProcessor clprocessor = DecompilerContext.getClassprocessor();
		StructClass cl = node.classStruct;
		
		if(cl.getBytecodeVersion() < CodeConstants.BYTECODE_JAVA_8) { // lamda beginning with Java 8
			return false;
		}
		
		StructBootstrapMethodsAttribute bootstrap = (StructBootstrapMethodsAttribute)cl.getAttributes().getWithKey(StructGeneralAttribute.ATTRIBUTE_BOOTSTRAP_METHODS);
		if(bootstrap != null && bootstrap.getMethodsNumber() > 0) {
			
			Set<Integer> lambda_methods = new HashSet<Integer>();
			
			// find lambda bootstrap constants
			for(int i = 0; i < bootstrap.getMethodsNumber(); ++i) {
				LinkConstant method_ref = bootstrap.getMethodReference(i); // method handle
				
				if(JAVAC_LAMBDA_CLASS.equals(method_ref.classname) && 
						JAVAC_LAMBDA_METHOD.equals(method_ref.elementname) &&
						JAVAC_LAMBDA_METHOD_DESCRIPTOR.equals(method_ref.descriptor)) {  // check for javac lambda structure. FIXME: extend for Eclipse etc. at some point
					lambda_methods.add(i);
				}
			}
			
			if(lambda_methods.isEmpty()) {
				return false;
			}
			
			Map<String, String> mapMethodsLambda = new HashMap<String, String>(); 
			
			// iterate over code and find invocations of bootstrap methods. Replace them with anonymous classes.
			for(StructMethod mt: cl.getMethods()) {
				mt.expandData();
				
				InstructionSequence seq = mt.getInstructionSequence();
				if(seq != null && seq.length() > 0) {
					int len = seq.length();
					
					for(int i = 0; i < len; ++i) {
						Instruction instr = seq.getInstr(i);
						
						if(instr.opcode == CodeConstants.opc_invokedynamic) {
							LinkConstant invoke_dynamic = cl.getPool().getLinkConstant(instr.getOperand(0));
							
							if(lambda_methods.contains(invoke_dynamic.index1)) { // lambda invocation found
								
								List<PooledConstant> bootstrap_arguments = bootstrap.getMethodArguments(invoke_dynamic.index1);
								MethodDescriptor md = MethodDescriptor.parseDescriptor(invoke_dynamic.descriptor);

								String lambda_class_name = md.ret.value;
								String lambda_method_name = invoke_dynamic.elementname; 
								String lambda_method_descriptor = ((PrimitiveConstant)bootstrap_arguments.get(2)).getString(); // method type
								
								LinkConstant content_method_handle = (LinkConstant)bootstrap_arguments.get(1);

								ClassNode node_lambda = clprocessor.new ClassNode(content_method_handle.elementname, content_method_handle.descriptor, lambda_class_name, 
																																	lambda_method_name, lambda_method_descriptor, cl);
								node_lambda.simpleName = cl.qualifiedName + "##Lambda_" + invoke_dynamic.index1 + "_" + invoke_dynamic.index2;
								node_lambda.enclosingMethod = InterpreterUtil.makeUniqueKey(mt.getName(), mt.getDescriptor());

								node.nested.add(node_lambda);
								node_lambda.parent = node;
								
								clprocessor.getMapRootClasses().put(node_lambda.simpleName, node_lambda);
								mapMethodsLambda.put(node_lambda.lambda_information.content_method_key, node_lambda.simpleName);
							}
						}
					}
				}
			}
			
			// build class hierarchy on lambda 
			for(ClassNode nd : node.nested) {
				if(nd.type == ClassNode.CLASS_LAMBDA) {
					String parent_class_name = mapMethodsLambda.get(nd.enclosingMethod);
					if(parent_class_name != null) {
						ClassNode parent_class = clprocessor.getMapRootClasses().get(parent_class_name);
						
						parent_class.nested.add(nd);
						nd.parent = parent_class;
					}
				}
			}
			
			// FIXME: mixed hierarchy? 
			
		}
		
		return false;
	}
	
}