Java CodeIterator.lookAhead方法代码示例

import javassist.bytecode.CodeIterator; //导入方法依赖的package包/类
private void scan(int pos, CodeIterator iter, Subroutine sub) throws BadBytecode {
    // Skip already processed blocks
    if (done.contains(Integer.valueOf(pos)))
        return;

    done.add(Integer.valueOf(pos));

    int old = iter.lookAhead();
    iter.move(pos);

    boolean next;
    do {
        pos = iter.next();
        next = scanOp(pos, iter, sub) && iter.hasNext();
    } while (next);

    iter.move(old);
}
 

import javassist.bytecode.CodeIterator; //导入方法依赖的package包/类
protected void runEditor(ExprEditor ed, CodeIterator oldIterator)
    throws CannotCompileException
{
    CodeAttribute codeAttr = oldIterator.get();
    int orgLocals = codeAttr.getMaxLocals();
    int orgStack = codeAttr.getMaxStack();
    int newLocals = locals();
    codeAttr.setMaxStack(stack());
    codeAttr.setMaxLocals(newLocals);
    ExprEditor.LoopContext context
        = new ExprEditor.LoopContext(newLocals);
    int size = oldIterator.getCodeLength();
    int endPos = oldIterator.lookAhead();
    oldIterator.move(currentPos);
    if (ed.doit(thisClass, thisMethod, context, oldIterator, endPos))
        edited = true;

    oldIterator.move(endPos + oldIterator.getCodeLength() - size);
    codeAttr.setMaxLocals(orgLocals);
    codeAttr.setMaxStack(orgStack);
    maxLocals = context.maxLocals;
    maxStack += context.maxStack;
}
 

import javassist.bytecode.CodeIterator; //导入方法依赖的package包/类
private void scan(int pos, CodeIterator iter, Subroutine sub) throws BadBytecode {
    // Skip already processed blocks
    if (done.contains(new Integer(pos)))
        return;

    done.add(new Integer(pos));

    int old = iter.lookAhead();
    iter.move(pos);

    boolean next;
    do {
        pos = iter.next();
        next = scanOp(pos, iter, sub) && iter.hasNext();
    } while (next);

    iter.move(old);
}
 

import javassist.bytecode.CodeIterator; //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 javassist.bytecode.CodeIterator; //导入方法依赖的package包/类
private int lookAhead(CodeIterator iter, int pos) throws BadBytecode {
    if (! iter.hasNext())
        throw new BadBytecode("Execution falls off end! [pos = " + pos + "]");

    return iter.lookAhead();
}