ASM: a very small and fast Java bytecode manipulation framework
Copyright (c) 2000-2011 INRIA, France Telecom
All rights reserved.
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modification, are permitted provided that the following conditions
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   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.
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   contributors may be used to endorse or promote products derived from
   this software without specific prior written permission.
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2011 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.objectweb.asm.commons;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.objectweb.asm.Handle;
import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;

A MethodVisitor to insert before, after and around advices in methods and constructors. 

The behavior for constructors is like this:

as long as the INVOKESPECIAL for the object initialization has not been
reached, every bytecode instruction is dispatched in the ctor code visitor
when this one is reached, it is only added in the ctor code visitor and a
JP invoke is added
after that, only the other code visitor receives the instructions

Author:
Eugene Kuleshov, Eric Bruneton/**
 * A {@link org.objectweb.asm.MethodVisitor} to insert before, after and around
 * advices in methods and constructors.
 * <p>
 * The behavior for constructors is like this:
 * <ol>
 * 
 * <li>as long as the INVOKESPECIAL for the object initialization has not been
 * reached, every bytecode instruction is dispatched in the ctor code visitor</li>
 * 
 * <li>when this one is reached, it is only added in the ctor code visitor and a
 * JP invoke is added</li>
 * 
 * <li>after that, only the other code visitor receives the instructions</li>
 * 
 * </ol>
 * 
 * @author Eugene Kuleshov
 * @author Eric Bruneton
 */
public abstract class AdviceAdapter extends GeneratorAdapter implements Opcodes {

    private static final Object THIS = new Object();

    private static final Object OTHER = new Object();

    protected int methodAccess;

    protected String methodDesc;

    private boolean constructor;

    private boolean superInitialized;

    private List<Object> stackFrame;

    private Map<Label, List<Object>> branches;

    
Creates a new AdviceAdapter. 
Params:
api –  the ASM API version implemented by this visitor. Must be one of Opcodes.ASM4.
mv – 
           the method visitor to which this adapter delegates calls.
access –  the method's access flags (see Opcodes).
name – 
           the method's name.
desc –  the method's descriptor (see Type)./**
     * Creates a new {@link AdviceAdapter}.
     * 
     * @param api
     *            the ASM API version implemented by this visitor. Must be one
     *            of {@link Opcodes#ASM4}.
     * @param mv
     *            the method visitor to which this adapter delegates calls.
     * @param access
     *            the method's access flags (see {@link Opcodes}).
     * @param name
     *            the method's name.
     * @param desc
     *            the method's descriptor (see {@link Type Type}).
     */
    protected AdviceAdapter(final int api, final MethodVisitor mv,
            final int access, final String name, final String desc) {
        super(api, mv, access, name, desc);
        methodAccess = access;
        methodDesc = desc;
        constructor = "<init>".equals(name);
    }

    @Override
    public void visitCode() {
        mv.visitCode();
        if (constructor) {
            stackFrame = new ArrayList<Object>();
            branches = new HashMap<Label, List<Object>>();
        } else {
            superInitialized = true;
            onMethodEnter();
        }
    }

    @Override
    public void visitLabel(final Label label) {
        mv.visitLabel(label);
        if (constructor && branches != null) {
            List<Object> frame = branches.get(label);
            if (frame != null) {
                stackFrame = frame;
                branches.remove(label);
            }
        }
    }

    @Override
    public void visitInsn(final int opcode) {
        if (constructor) {
            int s;
            switch (opcode) {
            case RETURN: // empty stack
                onMethodExit(opcode);
                break;
            case IRETURN: // 1 before n/a after
            case FRETURN: // 1 before n/a after
            case ARETURN: // 1 before n/a after
            case ATHROW: // 1 before n/a after
                popValue();
                onMethodExit(opcode);
                break;
            case LRETURN: // 2 before n/a after
            case DRETURN: // 2 before n/a after
                popValue();
                popValue();
                onMethodExit(opcode);
                break;
            case NOP:
            case LALOAD: // remove 2 add 2
            case DALOAD: // remove 2 add 2
            case LNEG:
            case DNEG:
            case FNEG:
            case INEG:
            case L2D:
            case D2L:
            case F2I:
            case I2B:
            case I2C:
            case I2S:
            case I2F:
            case ARRAYLENGTH:
                break;
            case ACONST_NULL:
            case ICONST_M1:
            case ICONST_0:
            case ICONST_1:
            case ICONST_2:
            case ICONST_3:
            case ICONST_4:
            case ICONST_5:
            case FCONST_0:
            case FCONST_1:
            case FCONST_2:
            case F2L: // 1 before 2 after
            case F2D:
            case I2L:
            case I2D:
                pushValue(OTHER);
                break;
            case LCONST_0:
            case LCONST_1:
            case DCONST_0:
            case DCONST_1:
                pushValue(OTHER);
                pushValue(OTHER);
                break;
            case IALOAD: // remove 2 add 1
            case FALOAD: // remove 2 add 1
            case AALOAD: // remove 2 add 1
            case BALOAD: // remove 2 add 1
            case CALOAD: // remove 2 add 1
            case SALOAD: // remove 2 add 1
            case POP:
            case IADD:
            case FADD:
            case ISUB:
            case LSHL: // 3 before 2 after
            case LSHR: // 3 before 2 after
            case LUSHR: // 3 before 2 after
            case L2I: // 2 before 1 after
            case L2F: // 2 before 1 after
            case D2I: // 2 before 1 after
            case D2F: // 2 before 1 after
            case FSUB:
            case FMUL:
            case FDIV:
            case FREM:
            case FCMPL: // 2 before 1 after
            case FCMPG: // 2 before 1 after
            case IMUL:
            case IDIV:
            case IREM:
            case ISHL:
            case ISHR:
            case IUSHR:
            case IAND:
            case IOR:
            case IXOR:
            case MONITORENTER:
            case MONITOREXIT:
                popValue();
                break;
            case POP2:
            case LSUB:
            case LMUL:
            case LDIV:
            case LREM:
            case LADD:
            case LAND:
            case LOR:
            case LXOR:
            case DADD:
            case DMUL:
            case DSUB:
            case DDIV:
            case DREM:
                popValue();
                popValue();
                break;
            case IASTORE:
            case FASTORE:
            case AASTORE:
            case BASTORE:
            case CASTORE:
            case SASTORE:
            case LCMP: // 4 before 1 after
            case DCMPL:
            case DCMPG:
                popValue();
                popValue();
                popValue();
                break;
            case LASTORE:
            case DASTORE:
                popValue();
                popValue();
                popValue();
                popValue();
                break;
            case DUP:
                pushValue(peekValue());
                break;
            case DUP_X1:
                s = stackFrame.size();
                stackFrame.add(s - 2, stackFrame.get(s - 1));
                break;
            case DUP_X2:
                s = stackFrame.size();
                stackFrame.add(s - 3, stackFrame.get(s - 1));
                break;
            case DUP2:
                s = stackFrame.size();
                stackFrame.add(s - 2, stackFrame.get(s - 1));
                stackFrame.add(s - 2, stackFrame.get(s - 1));
                break;
            case DUP2_X1:
                s = stackFrame.size();
                stackFrame.add(s - 3, stackFrame.get(s - 1));
                stackFrame.add(s - 3, stackFrame.get(s - 1));
                break;
            case DUP2_X2:
                s = stackFrame.size();
                stackFrame.add(s - 4, stackFrame.get(s - 1));
                stackFrame.add(s - 4, stackFrame.get(s - 1));
                break;
            case SWAP:
                s = stackFrame.size();
                stackFrame.add(s - 2, stackFrame.get(s - 1));
                stackFrame.remove(s);
                break;
            }
        } else {
            switch (opcode) {
            case RETURN:
            case IRETURN:
            case FRETURN:
            case ARETURN:
            case LRETURN:
            case DRETURN:
            case ATHROW:
                onMethodExit(opcode);
                break;
            }
        }
        mv.visitInsn(opcode);
    }

    @Override
    public void visitVarInsn(final int opcode, final int var) {
        super.visitVarInsn(opcode, var);
        if (constructor) {
            switch (opcode) {
            case ILOAD:
            case FLOAD:
                pushValue(OTHER);
                break;
            case LLOAD:
            case DLOAD:
                pushValue(OTHER);
                pushValue(OTHER);
                break;
            case ALOAD:
                pushValue(var == 0 ? THIS : OTHER);
                break;
            case ASTORE:
            case ISTORE:
            case FSTORE:
                popValue();
                break;
            case LSTORE:
            case DSTORE:
                popValue();
                popValue();
                break;
            }
        }
    }

    @Override
    public void visitFieldInsn(final int opcode, final String owner,
            final String name, final String desc) {
        mv.visitFieldInsn(opcode, owner, name, desc);
        if (constructor) {
            char c = desc.charAt(0);
            boolean longOrDouble = c == 'J' || c == 'D';
            switch (opcode) {
            case GETSTATIC:
                pushValue(OTHER);
                if (longOrDouble) {
                    pushValue(OTHER);
                }
                break;
            case PUTSTATIC:
                popValue();
                if (longOrDouble) {
                    popValue();
                }
                break;
            case PUTFIELD:
                popValue();
                if (longOrDouble) {
                    popValue();
                    popValue();
                }
                break;
            // case GETFIELD:
            default:
                if (longOrDouble) {
                    pushValue(OTHER);
                }
            }
        }
    }

    @Override
    public void visitIntInsn(final int opcode, final int operand) {
        mv.visitIntInsn(opcode, operand);
        if (constructor && opcode != NEWARRAY) {
            pushValue(OTHER);
        }
    }

    @Override
    public void visitLdcInsn(final Object cst) {
        mv.visitLdcInsn(cst);
        if (constructor) {
            pushValue(OTHER);
            if (cst instanceof Double || cst instanceof Long) {
                pushValue(OTHER);
            }
        }
    }

    @Override
    public void visitMultiANewArrayInsn(final String desc, final int dims) {
        mv.visitMultiANewArrayInsn(desc, dims);
        if (constructor) {
            for (int i = 0; i < dims; i++) {
                popValue();
            }
            pushValue(OTHER);
        }
    }

    @Override
    public void visitTypeInsn(final int opcode, final String type) {
        mv.visitTypeInsn(opcode, type);
        // ANEWARRAY, CHECKCAST or INSTANCEOF don't change stack
        if (constructor && opcode == NEW) {
            pushValue(OTHER);
        }
    }

    @Override
    public void visitMethodInsn(final int opcode, final String owner,
            final String name, final String desc) {
        mv.visitMethodInsn(opcode, owner, name, desc);
        if (constructor) {
            Type[] types = Type.getArgumentTypes(desc);
            for (int i = 0; i < types.length; i++) {
                popValue();
                if (types[i].getSize() == 2) {
                    popValue();
                }
            }
            switch (opcode) {
            // case INVOKESTATIC:
            // break;
            case INVOKEINTERFACE:
            case INVOKEVIRTUAL:
                popValue(); // objectref
                break;
            case INVOKESPECIAL:
                Object type = popValue(); // objectref
                if (type == THIS && !superInitialized) {
                    onMethodEnter();
                    superInitialized = true;
                    // once super has been initialized it is no longer
                    // necessary to keep track of stack state
                    constructor = false;
                }
                break;
            }

            Type returnType = Type.getReturnType(desc);
            if (returnType != Type.VOID_TYPE) {
                pushValue(OTHER);
                if (returnType.getSize() == 2) {
                    pushValue(OTHER);
                }
            }
        }
    }

    @Override
    public void visitInvokeDynamicInsn(String name, String desc, Handle bsm,
            Object... bsmArgs) {
        mv.visitInvokeDynamicInsn(name, desc, bsm, bsmArgs);
        if (constructor) {
            Type[] types = Type.getArgumentTypes(desc);
            for (int i = 0; i < types.length; i++) {
                popValue();
                if (types[i].getSize() == 2) {
                    popValue();
                }
            }

            Type returnType = Type.getReturnType(desc);
            if (returnType != Type.VOID_TYPE) {
                pushValue(OTHER);
                if (returnType.getSize() == 2) {
                    pushValue(OTHER);
                }
            }
        }
    }

    @Override
    public void visitJumpInsn(final int opcode, final Label label) {
        mv.visitJumpInsn(opcode, label);
        if (constructor) {
            switch (opcode) {
            case IFEQ:
            case IFNE:
            case IFLT:
            case IFGE:
            case IFGT:
            case IFLE:
            case IFNULL:
            case IFNONNULL:
                popValue();
                break;
            case IF_ICMPEQ:
            case IF_ICMPNE:
            case IF_ICMPLT:
            case IF_ICMPGE:
            case IF_ICMPGT:
            case IF_ICMPLE:
            case IF_ACMPEQ:
            case IF_ACMPNE:
                popValue();
                popValue();
                break;
            case JSR:
                pushValue(OTHER);
                break;
            }
            addBranch(label);
        }
    }

    @Override
    public void visitLookupSwitchInsn(final Label dflt, final int[] keys,
            final Label[] labels) {
        mv.visitLookupSwitchInsn(dflt, keys, labels);
        if (constructor) {
            popValue();
            addBranches(dflt, labels);
        }
    }

    @Override
    public void visitTableSwitchInsn(final int min, final int max,
            final Label dflt, final Label... labels) {
        mv.visitTableSwitchInsn(min, max, dflt, labels);
        if (constructor) {
            popValue();
            addBranches(dflt, labels);
        }
    }

    @Override
    public void visitTryCatchBlock(Label start, Label end, Label handler,
            String type) {
        super.visitTryCatchBlock(start, end, handler, type);
        if (constructor && !branches.containsKey(handler)) {
            List<Object> stackFrame = new ArrayList<Object>();
            stackFrame.add(OTHER);
            branches.put(handler, stackFrame);
        }
    }

    private void addBranches(final Label dflt, final Label[] labels) {
        addBranch(dflt);
        for (int i = 0; i < labels.length; i++) {
            addBranch(labels[i]);
        }
    }

    private void addBranch(final Label label) {
        if (branches.containsKey(label)) {
            return;
        }
        branches.put(label, new ArrayList<Object>(stackFrame));
    }

    private Object popValue() {
        return stackFrame.remove(stackFrame.size() - 1);
    }

    private Object peekValue() {
        return stackFrame.get(stackFrame.size() - 1);
    }

    private void pushValue(final Object o) {
        stackFrame.add(o);
    }

    
Called at the beginning of the method or after super class class call in
the constructor. 



Custom code can use or change all the local variables, but should not
change state of the stack.
/**
     * Called at the beginning of the method or after super class class call in
     * the constructor. <br>
     * <br>
     * 
     * <i>Custom code can use or change all the local variables, but should not
     * change state of the stack.</i>
     */
    protected void onMethodEnter() {
    }

    
Called before explicit exit from the method using either return or throw.
Top element on the stack contains the return value or exception instance.
For example:
  public void onMethodExit(int opcode) {
    if(opcode==RETURN) {
        visitInsn(ACONST_NULL);
    } else if(opcode==ARETURN || opcode==ATHROW) {
        dup();
    } else {
        if(opcode==LRETURN || opcode==DRETURN) {
            dup2();
        } else {
            dup();
        }
        box(Type.getReturnType(this.methodDesc));
    }
    visitIntInsn(SIPUSH, opcode);
    visitMethodInsn(INVOKESTATIC, owner, "onExit", "(Ljava/lang/Object;I)V");
  }
  // an actual call back method
  public static void onExit(Object param, int opcode) {
    ...





Custom code can use or change all the local variables, but should not
change state of the stack.
Params:
opcode – 
           one of the RETURN, IRETURN, FRETURN, ARETURN, LRETURN, DRETURN
           or ATHROW/**
     * Called before explicit exit from the method using either return or throw.
     * Top element on the stack contains the return value or exception instance.
     * For example:
     * 
     * <pre>
     *   public void onMethodExit(int opcode) {
     *     if(opcode==RETURN) {
     *         visitInsn(ACONST_NULL);
     *     } else if(opcode==ARETURN || opcode==ATHROW) {
     *         dup();
     *     } else {
     *         if(opcode==LRETURN || opcode==DRETURN) {
     *             dup2();
     *         } else {
     *             dup();
     *         }
     *         box(Type.getReturnType(this.methodDesc));
     *     }
     *     visitIntInsn(SIPUSH, opcode);
     *     visitMethodInsn(INVOKESTATIC, owner, "onExit", "(Ljava/lang/Object;I)V");
     *   }
     * 
     *   // an actual call back method
     *   public static void onExit(Object param, int opcode) {
     *     ...
     * </pre>
     * 
     * <br>
     * <br>
     * 
     * <i>Custom code can use or change all the local variables, but should not
     * change state of the stack.</i>
     * 
     * @param opcode
     *            one of the RETURN, IRETURN, FRETURN, ARETURN, LRETURN, DRETURN
     *            or ATHROW
     * 
     */
    protected void onMethodExit(int opcode) {
    }

    // TODO onException, onMethodCall
}