Java CodeAttribute.iterator方法代码示例

import scouter.javassist.bytecode.CodeAttribute; //导入方法依赖的package包/类
/**
 * Returns true if the constructor (or static initializer)
 * is the default one.  This method returns true if the constructor
 * takes some arguments but it does not perform anything except
 * calling <code>super()</code> (the no-argument constructor of
 * the super class).
 */
public boolean isEmpty() {
    CodeAttribute ca = getMethodInfo2().getCodeAttribute();
    if (ca == null)
        return false;       // native or abstract??
                            // they are not allowed, though.

    ConstPool cp = ca.getConstPool();
    CodeIterator it = ca.iterator();
    try {
        int pos, desc;
        int op0 = it.byteAt(it.next());
        return op0 == Opcode.RETURN     // empty static initializer
            || (op0 == Opcode.ALOAD_0
                && it.byteAt(pos = it.next()) == Opcode.INVOKESPECIAL
                && (desc = cp.isConstructor(getSuperclassName(),
                                            it.u16bitAt(pos + 1))) != 0
                && "()V".equals(cp.getUtf8Info(desc))
                && it.byteAt(it.next()) == Opcode.RETURN
                && !it.hasNext());
    }
    catch (BadBytecode e) {}
    return false;
}
 

import scouter.javassist.bytecode.CodeAttribute; //导入方法依赖的package包/类
/**
 * Returns true if this constructor calls a constructor
 * of the super class.  This method returns false if it
 * calls another constructor of this class by <code>this()</code>. 
 */
public boolean callsSuper() throws CannotCompileException {
    CodeAttribute codeAttr = methodInfo.getCodeAttribute();
    if (codeAttr != null) {
        CodeIterator it = codeAttr.iterator();
        try {
            int index = it.skipSuperConstructor();
            return index >= 0;
        }
        catch (BadBytecode e) {
            throw new CannotCompileException(e);
        }
    }

    return false;
}
 

import scouter.javassist.bytecode.CodeAttribute; //导入方法依赖的package包/类
public Subroutine[] scan(MethodInfo method) throws BadBytecode {
    CodeAttribute code = method.getCodeAttribute();
    CodeIterator iter = code.iterator();

    subroutines = new Subroutine[code.getCodeLength()];
    subTable.clear();
    done.clear();

    scan(0, iter, null);

    ExceptionTable exceptions = code.getExceptionTable();
    for (int i = 0; i < exceptions.size(); i++) {
        int handler = exceptions.handlerPc(i);
        // If an exception is thrown in subroutine, the handler
        // is part of the same subroutine.
        scan(handler, iter, subroutines[exceptions.startPc(i)]);
    }

    return subroutines;
}
 

import scouter.javassist.bytecode.CodeAttribute; //导入方法依赖的package包/类
private static void insertAuxInitializer(CodeAttribute codeAttr,
                                         Bytecode initializer,
                                         int stacksize)
    throws BadBytecode
{
    CodeIterator it = codeAttr.iterator();
    int index = it.skipSuperConstructor();
    if (index < 0) {
        index = it.skipThisConstructor();
        if (index >= 0)
            return;         // this() is called.

        // Neither this() or super() is called.
    }

    int pos = it.insertEx(initializer.get());
    it.insert(initializer.getExceptionTable(), pos);
    int maxstack = codeAttr.getMaxStack();
    if (maxstack < stacksize)
        codeAttr.setMaxStack(stacksize);
}
 

import scouter.javassist.bytecode.CodeAttribute; //导入方法依赖的package包/类
/**
 * Returns true if the method body is empty, that is, <code>{}</code>.
 * It also returns true if the method is an abstract method.
 */
public boolean isEmpty() {
    CodeAttribute ca = getMethodInfo2().getCodeAttribute();
    if (ca == null)         // abstract or native
        return (getModifiers() & Modifier.ABSTRACT) != 0;

    CodeIterator it = ca.iterator();
    try {
        return it.hasNext() && it.byteAt(it.next()) == Opcode.RETURN
            && !it.hasNext();
    }
    catch (BadBytecode e) {}
    return false;
}
 

import scouter.javassist.bytecode.CodeAttribute; //导入方法依赖的package包/类
int getStartPosOfBody(CodeAttribute ca) throws CannotCompileException {
    CodeIterator ci = ca.iterator();
    try {
        ci.skipConstructor();
        return ci.next();
    }
    catch (BadBytecode e) {
        throw new CannotCompileException(e);
    }
}
 

import scouter.javassist.bytecode.CodeAttribute; //导入方法依赖的package包/类
private static void removeConsCall(CodeAttribute ca)
    throws CannotCompileException
{
    CodeIterator iterator = ca.iterator();
    try {
        int pos = iterator.skipConstructor();
        if (pos >= 0) {
            int mref = iterator.u16bitAt(pos + 1);
            String desc = ca.getConstPool().getMethodrefType(mref);
            int num = Descriptor.numOfParameters(desc) + 1;
            if (num > 3)
                pos = iterator.insertGapAt(pos, num - 3, false).position;

            iterator.writeByte(Opcode.POP, pos++);  // this
            iterator.writeByte(Opcode.NOP, pos);
            iterator.writeByte(Opcode.NOP, pos + 1);
            Descriptor.Iterator it = new Descriptor.Iterator(desc);
            while (true) {
                it.next();
                if (it.isParameter())
                    iterator.writeByte(it.is2byte() ? Opcode.POP2 : Opcode.POP,
                                       pos++);
                else
                    break;
            }
        }
    }
    catch (BadBytecode e) {
        throw new CannotCompileException(e);
    }
}
 

import scouter.javassist.bytecode.CodeAttribute; //导入方法依赖的package包/类
/**
 * Performs data-flow analysis on a method and returns an array, indexed by
 * instruction position, containing the starting frame state of all reachable
 * instructions. Non-reachable code, and illegal code offsets are represented
 * as a null in the frame state array. This can be used to detect dead code.
 *
 * If the method does not contain code (it is either native or abstract), null
 * is returned.
 *
 * @param clazz the declaring class of the method
 * @param method the method to analyze
 * @return an array, indexed by instruction position, of the starting frame state,
 *         or null if this method doesn't have code
 * @throws BadBytecode if the bytecode does not comply with the JVM specification
 */
public Frame[] analyze(CtClass clazz, MethodInfo method) throws BadBytecode {
    this.clazz = clazz;
    CodeAttribute codeAttribute = method.getCodeAttribute();
    // Native or Abstract
    if (codeAttribute == null)
        return null;

    int maxLocals = codeAttribute.getMaxLocals();
    int maxStack = codeAttribute.getMaxStack();
    int codeLength = codeAttribute.getCodeLength();

    CodeIterator iter = codeAttribute.iterator();
    IntQueue queue = new IntQueue();

    exceptions = buildExceptionInfo(method);
    subroutines = scanner.scan(method);

    Executor executor = new Executor(clazz.getClassPool(), method.getConstPool());
    frames = new Frame[codeLength];
    frames[iter.lookAhead()] = firstFrame(method, maxLocals, maxStack);
    queue.add(iter.next());
    while (!queue.isEmpty()) {
        analyzeNextEntry(method, iter, queue, executor);
    }

    return frames;
}
 

import scouter.javassist.bytecode.CodeAttribute; //导入方法依赖的package包/类
public BasicBlock[] make(MethodInfo minfo) throws BadBytecode {
    CodeAttribute ca = minfo.getCodeAttribute();
    if (ca == null)
        return null;

    CodeIterator ci = ca.iterator();
    return make(ci, 0, ci.getCodeLength(), ca.getExceptionTable());
}
 

import scouter.javassist.bytecode.CodeAttribute; //导入方法依赖的package包/类
/**
 * Performs code conversion.
 */
protected void doit(CtClass clazz, MethodInfo minfo, ConstPool cp)
    throws CannotCompileException
{
   Transformer t;
    CodeAttribute codeAttr = minfo.getCodeAttribute();
    if (codeAttr == null || transformers == null)
        return;
    for (t = transformers; t != null; t = t.getNext())
        t.initialize(cp, clazz, minfo);

    CodeIterator iterator = codeAttr.iterator();
    while (iterator.hasNext()) {
        try {
            int pos = iterator.next();
            for (t = transformers; t != null; t = t.getNext())
                pos = t.transform(clazz, pos, iterator, cp);
        }
        catch (BadBytecode e) {
            throw new CannotCompileException(e);
        }
    }

    int locals = 0;
    int stack = 0;
    for (t = transformers; t != null; t = t.getNext()) {
        int s = t.extraLocals();
        if (s > locals)
            locals = s;

        s = t.extraStack();
        if (s > stack)
            stack = s;
    }

    for (t = transformers; t != null; t = t.getNext())
        t.clean();

    if (locals > 0)
        codeAttr.setMaxLocals(codeAttr.getMaxLocals() + locals);

    if (stack > 0)
        codeAttr.setMaxStack(codeAttr.getMaxStack() + stack);

    try {
    	minfo.rebuildStackMapIf6(clazz.getClassPool(),
                                 clazz.getClassFile2());
    }
    catch (BadBytecode b) {
        throw new CannotCompileException(b.getMessage(), b);
    }
}
 

import scouter.javassist.bytecode.CodeAttribute; //导入方法依赖的package包/类
/**
 * Undocumented method.  Do not use; internal-use only.
 */
public boolean doit(CtClass clazz, MethodInfo minfo)
    throws CannotCompileException
{
    CodeAttribute codeAttr = minfo.getCodeAttribute();
    if (codeAttr == null)
        return false;

    CodeIterator iterator = codeAttr.iterator();
    boolean edited = false;
    LoopContext context = new LoopContext(codeAttr.getMaxLocals());

    while (iterator.hasNext())
        if (loopBody(iterator, clazz, minfo, context))
            edited = true;

    ExceptionTable et = codeAttr.getExceptionTable();
    int n = et.size();
    for (int i = 0; i < n; ++i) {
        Handler h = new Handler(et, i, iterator, clazz, minfo);
        edit(h);
        if (h.edited()) {
            edited = true;
            context.updateMax(h.locals(), h.stack());
        }
    }

    // codeAttr might be modified by other partiess
    // so I check the current value of max-locals.
    if (codeAttr.getMaxLocals() < context.maxLocals)
        codeAttr.setMaxLocals(context.maxLocals);

    codeAttr.setMaxStack(codeAttr.getMaxStack() + context.maxStack);
    try {
        if (edited)
            minfo.rebuildStackMapIf6(clazz.getClassPool(),
                                     clazz.getClassFile2());
    }
    catch (BadBytecode b) {
        throw new CannotCompileException(b.getMessage(), b);
    }

    return edited;
}