http://asm.objectweb.org/asm-tree/: A very small and fast Java bytecode manipulation framework (ObjectWeb)
  • Eric Bruneton
  • Eugene Kuleshov
  • Remi Forax 
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.

/***
 * 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.tree.analysis;

import java.util.ArrayList;
import java.util.List;

import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.IincInsnNode;
import org.objectweb.asm.tree.InvokeDynamicInsnNode;
import org.objectweb.asm.tree.MethodInsnNode;
import org.objectweb.asm.tree.MultiANewArrayInsnNode;
import org.objectweb.asm.tree.VarInsnNode;


A symbolic execution stack frame. A stack frame contains a set of local
variable slots, and an operand stack. Warning: long and double values are
represented by two slots in local variables, and by one slot in
the operand stack.

Author:Eric Bruneton
Type parameters:
  • <V> – 
           type of the Value used for the analysis.
/**
 * A symbolic execution stack frame. A stack frame contains a set of local
 * variable slots, and an operand stack. Warning: long and double values are
 * represented by <i>two</i> slots in local variables, and by <i>one</i> slot in
 * the operand stack.
 * 
 * @param <V>
 *            type of the Value used for the analysis.
 * 
 * @author Eric Bruneton
 */
public class Frame<V extends Value> {

    
The expected return type of the analyzed method, or null if the
method returns void.

/**
     * The expected return type of the analyzed method, or <tt>null</tt> if the
     * method returns void.
     */
    private V returnValue;

    
The local variables and operand stack of this frame.

/**
     * The local variables and operand stack of this frame.
     */
    private V[] values;

    
The number of local variables of this frame.

/**
     * The number of local variables of this frame.
     */
    private int locals;

    
The number of elements in the operand stack.

/**
     * The number of elements in the operand stack.
     */
    private int top;

    
Constructs a new frame with the given size.

Params:
  • nLocals – 
           the maximum number of local variables of the frame.
  • nStack – 
           the maximum stack size of the frame.
/**
     * Constructs a new frame with the given size.
     * 
     * @param nLocals
     *            the maximum number of local variables of the frame.
     * @param nStack
     *            the maximum stack size of the frame.
     */
    public Frame(final int nLocals, final int nStack) {
        this.values = (V[]) new Value[nLocals + nStack];
        this.locals = nLocals;
    }

    
Constructs a new frame that is identical to the given frame.

Params:
  • src – 
           a frame.
/**
     * Constructs a new frame that is identical to the given frame.
     * 
     * @param src
     *            a frame.
     */
    public Frame(final Frame<? extends V> src) {
        this(src.locals, src.values.length - src.locals);
        init(src);
    }

    
Copies the state of the given frame into this frame.

Params:
  • src – 
           a frame.
Returns:this frame.
/**
     * Copies the state of the given frame into this frame.
     * 
     * @param src
     *            a frame.
     * @return this frame.
     */
    public Frame<V> init(final Frame<? extends V> src) {
        returnValue = src.returnValue;
        System.arraycopy(src.values, 0, values, 0, values.length);
        top = src.top;
        return this;
    }

    
Sets the expected return type of the analyzed method.

Params:
  • v – 
           the expected return type of the analyzed method, or
           null if the method returns void.
/**
     * Sets the expected return type of the analyzed method.
     * 
     * @param v
     *            the expected return type of the analyzed method, or
     *            <tt>null</tt> if the method returns void.
     */
    public void setReturn(final V v) {
        returnValue = v;
    }

    
Returns the maximum number of local variables of this frame.

Returns:the maximum number of local variables of this frame.
/**
     * Returns the maximum number of local variables of this frame.
     * 
     * @return the maximum number of local variables of this frame.
     */
    public int getLocals() {
        return locals;
    }

    
Returns the value of the given local variable.

Params:
  • i – 
           a local variable index.
Throws:
Returns:the value of the given local variable.
/**
     * Returns the value of the given local variable.
     * 
     * @param i
     *            a local variable index.
     * @return the value of the given local variable.
     * @throws IndexOutOfBoundsException
     *             if the variable does not exist.
     */
    public V getLocal(final int i) throws IndexOutOfBoundsException {
        if (i >= locals) {
            throw new IndexOutOfBoundsException(
                    "Trying to access an inexistant local variable");
        }
        return values[i];
    }

    
Sets the value of the given local variable.

Params:
  • i – 
           a local variable index.
  • value – 
           the new value of this local variable.
Throws:
/**
     * Sets the value of the given local variable.
     * 
     * @param i
     *            a local variable index.
     * @param value
     *            the new value of this local variable.
     * @throws IndexOutOfBoundsException
     *             if the variable does not exist.
     */
    public void setLocal(final int i, final V value)
            throws IndexOutOfBoundsException {
        if (i >= locals) {
            throw new IndexOutOfBoundsException(
                    "Trying to access an inexistant local variable " + i);
        }
        values[i] = value;
    }

    
Returns the number of values in the operand stack of this frame. Long and
double values are treated as single values.

Returns:the number of values in the operand stack of this frame.
/**
     * Returns the number of values in the operand stack of this frame. Long and
     * double values are treated as single values.
     * 
     * @return the number of values in the operand stack of this frame.
     */
    public int getStackSize() {
        return top;
    }

    
Returns the value of the given operand stack slot.

Params:
  • i – 
           the index of an operand stack slot.
Throws:
Returns:the value of the given operand stack slot.
/**
     * Returns the value of the given operand stack slot.
     * 
     * @param i
     *            the index of an operand stack slot.
     * @return the value of the given operand stack slot.
     * @throws IndexOutOfBoundsException
     *             if the operand stack slot does not exist.
     */
    public V getStack(final int i) throws IndexOutOfBoundsException {
        return values[i + locals];
    }

    
Clears the operand stack of this frame.

/**
     * Clears the operand stack of this frame.
     */
    public void clearStack() {
        top = 0;
    }

    
Pops a value from the operand stack of this frame.

Throws:
Returns:the value that has been popped from the stack.
/**
     * Pops a value from the operand stack of this frame.
     * 
     * @return the value that has been popped from the stack.
     * @throws IndexOutOfBoundsException
     *             if the operand stack is empty.
     */
    public V pop() throws IndexOutOfBoundsException {
        if (top == 0) {
            throw new IndexOutOfBoundsException(
                    "Cannot pop operand off an empty stack.");
        }
        return values[--top + locals];
    }

    
Pushes a value into the operand stack of this frame.

Params:
  • value – 
           the value that must be pushed into the stack.
Throws:
/**
     * Pushes a value into the operand stack of this frame.
     * 
     * @param value
     *            the value that must be pushed into the stack.
     * @throws IndexOutOfBoundsException
     *             if the operand stack is full.
     */
    public void push(final V value) throws IndexOutOfBoundsException {
        if (top + locals >= values.length) {
            throw new IndexOutOfBoundsException(
                    "Insufficient maximum stack size.");
        }
        values[top++ + locals] = value;
    }

    public void execute(final AbstractInsnNode insn,
            final Interpreter<V> interpreter) throws AnalyzerException {
        V value1, value2, value3, value4;
        List<V> values;
        int var;

        switch (insn.getOpcode()) {
        case Opcodes.NOP:
            break;
        case Opcodes.ACONST_NULL:
        case Opcodes.ICONST_M1:
        case Opcodes.ICONST_0:
        case Opcodes.ICONST_1:
        case Opcodes.ICONST_2:
        case Opcodes.ICONST_3:
        case Opcodes.ICONST_4:
        case Opcodes.ICONST_5:
        case Opcodes.LCONST_0:
        case Opcodes.LCONST_1:
        case Opcodes.FCONST_0:
        case Opcodes.FCONST_1:
        case Opcodes.FCONST_2:
        case Opcodes.DCONST_0:
        case Opcodes.DCONST_1:
        case Opcodes.BIPUSH:
        case Opcodes.SIPUSH:
        case Opcodes.LDC:
            push(interpreter.newOperation(insn));
            break;
        case Opcodes.ILOAD:
        case Opcodes.LLOAD:
        case Opcodes.FLOAD:
        case Opcodes.DLOAD:
        case Opcodes.ALOAD:
            push(interpreter.copyOperation(insn,
                    getLocal(((VarInsnNode) insn).var)));
            break;
        case Opcodes.IALOAD:
        case Opcodes.LALOAD:
        case Opcodes.FALOAD:
        case Opcodes.DALOAD:
        case Opcodes.AALOAD:
        case Opcodes.BALOAD:
        case Opcodes.CALOAD:
        case Opcodes.SALOAD:
            value2 = pop();
            value1 = pop();
            push(interpreter.binaryOperation(insn, value1, value2));
            break;
        case Opcodes.ISTORE:
        case Opcodes.LSTORE:
        case Opcodes.FSTORE:
        case Opcodes.DSTORE:
        case Opcodes.ASTORE:
            value1 = interpreter.copyOperation(insn, pop());
            var = ((VarInsnNode) insn).var;
            setLocal(var, value1);
            if (value1.getSize() == 2) {
                setLocal(var + 1, interpreter.newValue(null));
            }
            if (var > 0) {
                Value local = getLocal(var - 1);
                if (local != null && local.getSize() == 2) {
                    setLocal(var - 1, interpreter.newValue(null));
                }
            }
            break;
        case Opcodes.IASTORE:
        case Opcodes.LASTORE:
        case Opcodes.FASTORE:
        case Opcodes.DASTORE:
        case Opcodes.AASTORE:
        case Opcodes.BASTORE:
        case Opcodes.CASTORE:
        case Opcodes.SASTORE:
            value3 = pop();
            value2 = pop();
            value1 = pop();
            interpreter.ternaryOperation(insn, value1, value2, value3);
            break;
        case Opcodes.POP:
            if (pop().getSize() == 2) {
                throw new AnalyzerException(insn, "Illegal use of POP");
            }
            break;
        case Opcodes.POP2:
            if (pop().getSize() == 1) {
                if (pop().getSize() != 1) {
                    throw new AnalyzerException(insn, "Illegal use of POP2");
                }
            }
            break;
        case Opcodes.DUP:
            value1 = pop();
            if (value1.getSize() != 1) {
                throw new AnalyzerException(insn, "Illegal use of DUP");
            }
            push(value1);
            push(interpreter.copyOperation(insn, value1));
            break;
        case Opcodes.DUP_X1:
            value1 = pop();
            value2 = pop();
            if (value1.getSize() != 1 || value2.getSize() != 1) {
                throw new AnalyzerException(insn, "Illegal use of DUP_X1");
            }
            push(interpreter.copyOperation(insn, value1));
            push(value2);
            push(value1);
            break;
        case Opcodes.DUP_X2:
            value1 = pop();
            if (value1.getSize() == 1) {
                value2 = pop();
                if (value2.getSize() == 1) {
                    value3 = pop();
                    if (value3.getSize() == 1) {
                        push(interpreter.copyOperation(insn, value1));
                        push(value3);
                        push(value2);
                        push(value1);
                        break;
                    }
                } else {
                    push(interpreter.copyOperation(insn, value1));
                    push(value2);
                    push(value1);
                    break;
                }
            }
            throw new AnalyzerException(insn, "Illegal use of DUP_X2");
        case Opcodes.DUP2:
            value1 = pop();
            if (value1.getSize() == 1) {
                value2 = pop();
                if (value2.getSize() == 1) {
                    push(value2);
                    push(value1);
                    push(interpreter.copyOperation(insn, value2));
                    push(interpreter.copyOperation(insn, value1));
                    break;
                }
            } else {
                push(value1);
                push(interpreter.copyOperation(insn, value1));
                break;
            }
            throw new AnalyzerException(insn, "Illegal use of DUP2");
        case Opcodes.DUP2_X1:
            value1 = pop();
            if (value1.getSize() == 1) {
                value2 = pop();
                if (value2.getSize() == 1) {
                    value3 = pop();
                    if (value3.getSize() == 1) {
                        push(interpreter.copyOperation(insn, value2));
                        push(interpreter.copyOperation(insn, value1));
                        push(value3);
                        push(value2);
                        push(value1);
                        break;
                    }
                }
            } else {
                value2 = pop();
                if (value2.getSize() == 1) {
                    push(interpreter.copyOperation(insn, value1));
                    push(value2);
                    push(value1);
                    break;
                }
            }
            throw new AnalyzerException(insn, "Illegal use of DUP2_X1");
        case Opcodes.DUP2_X2:
            value1 = pop();
            if (value1.getSize() == 1) {
                value2 = pop();
                if (value2.getSize() == 1) {
                    value3 = pop();
                    if (value3.getSize() == 1) {
                        value4 = pop();
                        if (value4.getSize() == 1) {
                            push(interpreter.copyOperation(insn, value2));
                            push(interpreter.copyOperation(insn, value1));
                            push(value4);
                            push(value3);
                            push(value2);
                            push(value1);
                            break;
                        }
                    } else {
                        push(interpreter.copyOperation(insn, value2));
                        push(interpreter.copyOperation(insn, value1));
                        push(value3);
                        push(value2);
                        push(value1);
                        break;
                    }
                }
            } else {
                value2 = pop();
                if (value2.getSize() == 1) {
                    value3 = pop();
                    if (value3.getSize() == 1) {
                        push(interpreter.copyOperation(insn, value1));
                        push(value3);
                        push(value2);
                        push(value1);
                        break;
                    }
                } else {
                    push(interpreter.copyOperation(insn, value1));
                    push(value2);
                    push(value1);
                    break;
                }
            }
            throw new AnalyzerException(insn, "Illegal use of DUP2_X2");
        case Opcodes.SWAP:
            value2 = pop();
            value1 = pop();
            if (value1.getSize() != 1 || value2.getSize() != 1) {
                throw new AnalyzerException(insn, "Illegal use of SWAP");
            }
            push(interpreter.copyOperation(insn, value2));
            push(interpreter.copyOperation(insn, value1));
            break;
        case Opcodes.IADD:
        case Opcodes.LADD:
        case Opcodes.FADD:
        case Opcodes.DADD:
        case Opcodes.ISUB:
        case Opcodes.LSUB:
        case Opcodes.FSUB:
        case Opcodes.DSUB:
        case Opcodes.IMUL:
        case Opcodes.LMUL:
        case Opcodes.FMUL:
        case Opcodes.DMUL:
        case Opcodes.IDIV:
        case Opcodes.LDIV:
        case Opcodes.FDIV:
        case Opcodes.DDIV:
        case Opcodes.IREM:
        case Opcodes.LREM:
        case Opcodes.FREM:
        case Opcodes.DREM:
            value2 = pop();
            value1 = pop();
            push(interpreter.binaryOperation(insn, value1, value2));
            break;
        case Opcodes.INEG:
        case Opcodes.LNEG:
        case Opcodes.FNEG:
        case Opcodes.DNEG:
            push(interpreter.unaryOperation(insn, pop()));
            break;
        case Opcodes.ISHL:
        case Opcodes.LSHL:
        case Opcodes.ISHR:
        case Opcodes.LSHR:
        case Opcodes.IUSHR:
        case Opcodes.LUSHR:
        case Opcodes.IAND:
        case Opcodes.LAND:
        case Opcodes.IOR:
        case Opcodes.LOR:
        case Opcodes.IXOR:
        case Opcodes.LXOR:
            value2 = pop();
            value1 = pop();
            push(interpreter.binaryOperation(insn, value1, value2));
            break;
        case Opcodes.IINC:
            var = ((IincInsnNode) insn).var;
            setLocal(var, interpreter.unaryOperation(insn, getLocal(var)));
            break;
        case Opcodes.I2L:
        case Opcodes.I2F:
        case Opcodes.I2D:
        case Opcodes.L2I:
        case Opcodes.L2F:
        case Opcodes.L2D:
        case Opcodes.F2I:
        case Opcodes.F2L:
        case Opcodes.F2D:
        case Opcodes.D2I:
        case Opcodes.D2L:
        case Opcodes.D2F:
        case Opcodes.I2B:
        case Opcodes.I2C:
        case Opcodes.I2S:
            push(interpreter.unaryOperation(insn, pop()));
            break;
        case Opcodes.LCMP:
        case Opcodes.FCMPL:
        case Opcodes.FCMPG:
        case Opcodes.DCMPL:
        case Opcodes.DCMPG:
            value2 = pop();
            value1 = pop();
            push(interpreter.binaryOperation(insn, value1, value2));
            break;
        case Opcodes.IFEQ:
        case Opcodes.IFNE:
        case Opcodes.IFLT:
        case Opcodes.IFGE:
        case Opcodes.IFGT:
        case Opcodes.IFLE:
            interpreter.unaryOperation(insn, pop());
            break;
        case Opcodes.IF_ICMPEQ:
        case Opcodes.IF_ICMPNE:
        case Opcodes.IF_ICMPLT:
        case Opcodes.IF_ICMPGE:
        case Opcodes.IF_ICMPGT:
        case Opcodes.IF_ICMPLE:
        case Opcodes.IF_ACMPEQ:
        case Opcodes.IF_ACMPNE:
            value2 = pop();
            value1 = pop();
            interpreter.binaryOperation(insn, value1, value2);
            break;
        case Opcodes.GOTO:
            break;
        case Opcodes.JSR:
            push(interpreter.newOperation(insn));
            break;
        case Opcodes.RET:
            break;
        case Opcodes.TABLESWITCH:
        case Opcodes.LOOKUPSWITCH:
            interpreter.unaryOperation(insn, pop());
            break;
        case Opcodes.IRETURN:
        case Opcodes.LRETURN:
        case Opcodes.FRETURN:
        case Opcodes.DRETURN:
        case Opcodes.ARETURN:
            value1 = pop();
            interpreter.unaryOperation(insn, value1);
            interpreter.returnOperation(insn, value1, returnValue);
            break;
        case Opcodes.RETURN:
            if (returnValue != null) {
                throw new AnalyzerException(insn, "Incompatible return type");
            }
            break;
        case Opcodes.GETSTATIC:
            push(interpreter.newOperation(insn));
            break;
        case Opcodes.PUTSTATIC:
            interpreter.unaryOperation(insn, pop());
            break;
        case Opcodes.GETFIELD:
            push(interpreter.unaryOperation(insn, pop()));
            break;
        case Opcodes.PUTFIELD:
            value2 = pop();
            value1 = pop();
            interpreter.binaryOperation(insn, value1, value2);
            break;
        case Opcodes.INVOKEVIRTUAL:
        case Opcodes.INVOKESPECIAL:
        case Opcodes.INVOKESTATIC:
        case Opcodes.INVOKEINTERFACE: {
            values = new ArrayList<V>();
            String desc = ((MethodInsnNode) insn).desc;
            for (int i = Type.getArgumentTypes(desc).length; i > 0; --i) {
                values.add(0, pop());
            }
            if (insn.getOpcode() != Opcodes.INVOKESTATIC) {
                values.add(0, pop());
            }
            if (Type.getReturnType(desc) == Type.VOID_TYPE) {
                interpreter.naryOperation(insn, values);
            } else {
                push(interpreter.naryOperation(insn, values));
            }
            break;
        }
        case Opcodes.INVOKEDYNAMIC: {
            values = new ArrayList<V>();
            String desc = ((InvokeDynamicInsnNode) insn).desc;
            for (int i = Type.getArgumentTypes(desc).length; i > 0; --i) {
                values.add(0, pop());
            }
            if (Type.getReturnType(desc) == Type.VOID_TYPE) {
                interpreter.naryOperation(insn, values);
            } else {
                push(interpreter.naryOperation(insn, values));
            }
            break;
        }
        case Opcodes.NEW:
            push(interpreter.newOperation(insn));
            break;
        case Opcodes.NEWARRAY:
        case Opcodes.ANEWARRAY:
        case Opcodes.ARRAYLENGTH:
            push(interpreter.unaryOperation(insn, pop()));
            break;
        case Opcodes.ATHROW:
            interpreter.unaryOperation(insn, pop());
            break;
        case Opcodes.CHECKCAST:
        case Opcodes.INSTANCEOF:
            push(interpreter.unaryOperation(insn, pop()));
            break;
        case Opcodes.MONITORENTER:
        case Opcodes.MONITOREXIT:
            interpreter.unaryOperation(insn, pop());
            break;
        case Opcodes.MULTIANEWARRAY:
            values = new ArrayList<V>();
            for (int i = ((MultiANewArrayInsnNode) insn).dims; i > 0; --i) {
                values.add(0, pop());
            }
            push(interpreter.naryOperation(insn, values));
            break;
        case Opcodes.IFNULL:
        case Opcodes.IFNONNULL:
            interpreter.unaryOperation(insn, pop());
            break;
        default:
            throw new RuntimeException("Illegal opcode " + insn.getOpcode());
        }
    }

    
Merges this frame with the given frame.

Params:
  • frame – 
           a frame.
  • interpreter – 
           the interpreter used to merge values.
Throws:
Returns:true if this frame has been changed as a result of the
        merge operation, or false otherwise.
/**
     * Merges this frame with the given frame.
     * 
     * @param frame
     *            a frame.
     * @param interpreter
     *            the interpreter used to merge values.
     * @return <tt>true</tt> if this frame has been changed as a result of the
     *         merge operation, or <tt>false</tt> otherwise.
     * @throws AnalyzerException
     *             if the frames have incompatible sizes.
     */
    public boolean merge(final Frame<? extends V> frame,
            final Interpreter<V> interpreter) throws AnalyzerException {
        if (top != frame.top) {
            throw new AnalyzerException(null, "Incompatible stack heights");
        }
        boolean changes = false;
        for (int i = 0; i < locals + top; ++i) {
            V v = interpreter.merge(values[i], frame.values[i]);
            if (!v.equals(values[i])) {
                values[i] = v;
                changes = true;
            }
        }
        return changes;
    }

    
Merges this frame with the given frame (case of a RET instruction).

Params:
  • frame – 
           a frame
  • access – 
           the local variables that have been accessed by the subroutine
           to which the RET instruction corresponds.
Returns:true if this frame has been changed as a result of the
        merge operation, or false otherwise.
/**
     * Merges this frame with the given frame (case of a RET instruction).
     * 
     * @param frame
     *            a frame
     * @param access
     *            the local variables that have been accessed by the subroutine
     *            to which the RET instruction corresponds.
     * @return <tt>true</tt> if this frame has been changed as a result of the
     *         merge operation, or <tt>false</tt> otherwise.
     */
    public boolean merge(final Frame<? extends V> frame, final boolean[] access) {
        boolean changes = false;
        for (int i = 0; i < locals; ++i) {
            if (!access[i] && !values[i].equals(frame.values[i])) {
                values[i] = frame.values[i];
                changes = true;
            }
        }
        return changes;
    }

    
Returns a string representation of this frame.

Returns:a string representation of this frame.
/**
     * Returns a string representation of this frame.
     * 
     * @return a string representation of this frame.
     */
    @Override
    public String toString() {
        StringBuffer b = new StringBuffer();
        for (int i = 0; i < getLocals(); ++i) {
            b.append(getLocal(i));
        }
        b.append(' ');
        for (int i = 0; i < getStackSize(); ++i) {
            b.append(getStack(i).toString());
        }
        return b.toString();
    }
}