bytecode.java

Javassist是一个开源的分析、编辑和创建Java字节码的类库。是由东京技术学院的数学和计算机科学系的 Shigeru Chiba 所创建的。它已加入了开放源代码JBoss 应用服务器项目,通过使

/*
 * Javassist, a Java-bytecode translator toolkit.
 * Copyright (C) 1999-2006 Shigeru Chiba. All Rights Reserved.
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License.  Alternatively, the contents of this file may be used under
 * the terms of the GNU Lesser General Public License Version 2.1 or later.
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 */

package javassist.bytecode;

import javassist.CtClass;
import javassist.CtPrimitiveType;

class ByteVector implements Cloneable {
    private byte[] buffer;
    private int size;

    public ByteVector() {
        buffer = new byte[64];
        size = 0;
    }

    public Object clone() throws CloneNotSupportedException {
        ByteVector bv = (ByteVector)super.clone();
        bv.buffer = (byte[])buffer.clone();
        return bv;
    }

    public final int getSize() { return size; }

    public final byte[] copy() {
        byte[] b = new byte[size];
        arraycopy(buffer, b, size);
        return b;
    }

    public int read(int offset) {
        if (offset < 0 || size <= offset)
            throw new ArrayIndexOutOfBoundsException(offset);

        return buffer[offset];
    }

    public void write(int offset, int value) {
        if (offset < 0 || size <= offset)
            throw new ArrayIndexOutOfBoundsException(offset);

        buffer[offset] = (byte)value;
    }

    public void add(int code) {
        addGap(1);
        buffer[size - 1] = (byte)code;
    }

    public void addGap(int length) {
        if (size + length > buffer.length) {
            int newSize = size << 1;
            if (newSize < size + length)
                newSize = size + length;

            byte[] newBuf = new byte[newSize];
            arraycopy(buffer, newBuf, size);
            buffer = newBuf;
        }

        size += length;
    }

    private static void arraycopy(byte[] src, byte[] dest, int size) {
        for (int i = 0; i < size; i++)
            dest[i] = src[i];
    }
}

/**
 * A utility class for producing a bytecode sequence.
 *
 * <p>A <code>Bytecode</code> object is an unbounded array
 * containing bytecode.  For example,
 *
 * <ul><pre>ConstPool cp = ...;    // constant pool table
 * Bytecode b = new Bytecode(cp, 1, 0);
 * b.addIconst(3);
 * b.addReturn(CtClass.intType);
 * CodeAttribute ca = b.toCodeAttribute();</ul></pre>
 *
 * <p>This program produces a Code attribute including a bytecode
 * sequence:
 *
 * <ul><pre>iconst_3
 * ireturn</pre></ul>
 *
 * @see ConstPool
 * @see CodeAttribute
 */
public class Bytecode extends ByteVector implements Cloneable, Opcode {
    /**
     * Represents the <code>CtClass</code> file using the
     * constant pool table given to this <code>Bytecode</code> object.
     */
    public static final CtClass THIS = ConstPool.THIS;

    ConstPool constPool;
    int maxStack, maxLocals;
    ExceptionTable tryblocks;
    private int stackDepth;

    /**
     * Constructs a <code>Bytecode</code> object with an empty bytecode
     * sequence.
     *
     * <p>The parameters <code>stacksize</code> and <code>localvars</code>
     * specify initial values
     * of <code>max_stack</code> and <code>max_locals</code>.
     * They can be changed later.
     *
     * @param cp                constant pool table.
     * @param stacksize         <code>max_stack</code>.
     * @param localvars         <code>max_locals</code>.
     */
    public Bytecode(ConstPool cp, int stacksize, int localvars) {
        constPool = cp;
        maxStack = stacksize;
        maxLocals = localvars;
        tryblocks = new ExceptionTable(cp);
        stackDepth = 0;
    }

    /**
     * Constructs a <code>Bytecode</code> object with an empty bytecode
     * sequence.  The initial values of <code>max_stack</code> and
     * <code>max_locals</code> are zero.
     * 
     * @param cp            constant pool table.
     * @see Bytecode#setMaxStack(int)
     * @see Bytecode#setMaxLocals(int)
     */
    public Bytecode(ConstPool cp) {
        this(cp, 0, 0);
    }

    /**
     * Creates and returns a copy of this object.
     * The constant pool object is shared between this object
     * and the cloned object.
     */
    public Object clone() {
        try {
            Bytecode bc = (Bytecode)super.clone();
            bc.tryblocks = (ExceptionTable)tryblocks.clone();
            return bc;
        }
        catch (CloneNotSupportedException cnse) {
            throw new RuntimeException(cnse);
        }
    }

    /**
     * Gets a constant pool table.
     */
    public ConstPool getConstPool() { return constPool; }

    /**
     * Returns <code>exception_table</code>.
     */
    public ExceptionTable getExceptionTable() { return tryblocks; }

    /**
     * Converts to a <code>CodeAttribute</code>.
     */
    public CodeAttribute toCodeAttribute() {
        return new CodeAttribute(constPool, maxStack, maxLocals,
                                 get(), tryblocks);
    }

    /**
     * Returns the length of the bytecode sequence.
     */
    public int length() {
        return getSize();
    }

    /**
     * Returns the produced bytecode sequence.
     */
    public byte[] get() {
        return copy();
    }

    /**
     * Gets <code>max_stack</code>.
     */
    public int getMaxStack() { return maxStack; }

    /**
     * Sets <code>max_stack</code>.
     *
     * <p>This value may be automatically updated when an instruction
     * is appended.  A <code>Bytecode</code> object maintains the current
     * stack depth whenever an instruction is added
     * by <code>addOpcode()</code>.  For example, if DUP is appended,
     * the current stack depth is increased by one.  If the new stack
     * depth is more than <code>max_stack</code>, then it is assigned
     * to <code>max_stack</code>.  However, if branch instructions are
     * appended, the current stack depth may not be correctly maintained.
     *
     * @see #addOpcode(int)
     */
    public void setMaxStack(int size) {
        maxStack = size;
    }

    /**
     * Gets <code>max_locals</code>.
     */
    public int getMaxLocals() { return maxLocals; }

    /**
     * Sets <code>max_locals</code>.
     */
    public void setMaxLocals(int size) {
        maxLocals = size;
    }

    /**
     * Sets <code>max_locals</code>.
     *
     * <p>This computes the number of local variables
     * used to pass method parameters and sets <code>max_locals</code>
     * to that number plus <code>locals</code>.
     *
     * @param isStatic          true if <code>params</code> must be
     *                          interpreted as parameters to a static method.
     * @param params            parameter types.
     * @param locals            the number of local variables excluding
     *                          ones used to pass parameters.
     */
    public void setMaxLocals(boolean isStatic, CtClass[] params,
                             int locals) {
        if (!isStatic)
            ++locals;

        if (params != null) {
            CtClass doubleType = CtClass.doubleType;
            CtClass longType = CtClass.longType;
            int n = params.length;
            for (int i = 0; i < n; ++i) {
                CtClass type = params[i];
                if (type == doubleType || type == longType)
                    locals += 2;
                else
                    ++locals;
            }
        }

        maxLocals = locals;
    }

    /**
     * Increments <code>max_locals</code>.
     */
    public void incMaxLocals(int diff) {
        maxLocals += diff;
    }

    /**
     * Adds a new entry of <code>exception_table</code>.
     */
    public void addExceptionHandler(int start, int end,
                                    int handler, CtClass type) {
        addExceptionHandler(start, end, handler,
                            constPool.addClassInfo(type));
    }

    /**
     * Adds a new entry of <code>exception_table</code>.
     *
     * @param type      the fully-qualified name of a throwable class.
     */
    public void addExceptionHandler(int start, int end,
                                    int handler, String type) {
        addExceptionHandler(start, end, handler,
                            constPool.addClassInfo(type));
    }

    /**
     * Adds a new entry of <code>exception_table</code>.
     */
    public void addExceptionHandler(int start, int end,
                                    int handler, int type) {
        tryblocks.add(start, end, handler, type);
    }

    /**
     * Returns the length of bytecode sequence
     * that have been added so far.
     */
    public int currentPc() {
        return getSize();
    }

    /**
     * Reads a signed 8bit value at the offset from the beginning of the
     * bytecode sequence.
     *
     * @throws ArrayIndexOutOfBoundsException   if offset is invalid.
     */
    public int read(int offset) {
        return super.read(offset);
    }

    /**
     * Reads a signed 16bit value at the offset from the beginning of the
     * bytecode sequence.
     */
    public int read16bit(int offset) {
        int v1 = read(offset);
        int v2 = read(offset + 1);
        return (v1 << 8) + (v2 & 0xff);
    }

    /**
     * Reads a signed 32bit value at the offset from the beginning of the
     * bytecode sequence.
     */
    public int read32bit(int offset) {
        int v1 = read16bit(offset);
        int v2 = read16bit(offset + 2);
        return (v1 << 16) + (v2 & 0xffff);
    }

    /**
     * Writes an 8bit value at the offset from the beginning of the
     * bytecode sequence.
     *
     * @throws ArrayIndexOutOfBoundsException   if offset is invalid.
     */
    public void write(int offset, int value) {
        super.write(offset, value);
    }

    /**
     * Writes an 16bit value at the offset from the beginning of the
     * bytecode sequence.
     */
    public void write16bit(int offset, int value) {
        write(offset, value >> 8);
        write(offset + 1, value);
    }

    /**
     * Writes an 32bit value at the offset from the beginning of the
     * bytecode sequence.
     */
    public void write32bit(int offset, int value) {
        write16bit(offset, value >> 16);
        write16bit(offset + 2, value);
    }

    /**
     * Appends an 8bit value to the end of the bytecode sequence.
     */
    public void add(int code) {
        super.add(code);
    }

    /**
     * Appends a 32bit value to the end of the bytecode sequence.
     */
    public void add32bit(int value) {
        add(value >> 24);
        add(value >> 16);
        add(value >> 8);
        add(value);
    }

    /**
     * Appends the length-byte gap to the end of the bytecode sequence.
     *
     * @param length    the gap length in byte.
     */
    public void addGap(int length) {
        super.addGap(length);
    }

    /**
     * Appends an 8bit opcode to the end of the bytecode sequence.
     * The current stack depth is updated.
     * <code>max_stack</code> is updated if the current stack depth
     * is the deepest so far.
     *
     * <p>Note: some instructions such as INVOKEVIRTUAL does not
     * update the current stack depth since the increment depends
     * on the method signature.
     * <code>growStack()</code> must be explicitly called.
     */
    public void addOpcode(int code) {
        add(code);
        growStack(STACK_GROW[code]);
    }

    /**
     * Increases the current stack depth.
     * It also updates <code>max_stack</code> if the current stack depth
     * is the deepest so far.
     *
     * @param diff      the number added to the current stack depth.
     */
    public void growStack(int diff) {
        setStackDepth(stackDepth + diff);
    }

    /**
     * Returns the current stack depth.
     */
    public int getStackDepth() { return stackDepth; }

    /**
     * Sets the current stack depth.
     * It also updates <code>max_stack</code> if the current stack depth
     * is the deepest so far.
     *
     * @param depth     new value.
     */
    public void setStackDepth(int depth) {
        stackDepth = depth;
        if (stackDepth > maxStack)
            maxStack = stackDepth;
    }

    /**
     * Appends a 16bit value to the end of the bytecode sequence.
     * It never changes the current stack depth.
     */
    public void addIndex(int index) {
        add(index >> 8);
        add(index);
    }

    /**
     * Appends ALOAD or (WIDE) ALOAD_&lt;n&gt;
     *
     * @param n         an index into the local variable array.
     */
    public void addAload(int n) {
        if (n < 4)
            addOpcode(42 + n);          // aload_<n>
        else if (n < 0x100) {
            addOpcode(ALOAD);           // aload
            add(n);
        }
        else {
            addOpcode(WIDE);
            addOpcode(ALOAD);
            addIndex(n);
        }
    }

    /**
     * Appends ASTORE or (WIDE) ASTORE_&lt;n&gt;
     *