attributeinfo.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 java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.Map;
import java.util.LinkedList;
import java.util.ListIterator;

// Note: if you define a new subclass of AttributeInfo, then
//       update AttributeInfo.read(), .copy(), and (maybe) write().

/**
 * <code>attribute_info</code> structure.
 */
public class AttributeInfo {
    protected ConstPool constPool;
    int name;
    byte[] info;

    protected AttributeInfo(ConstPool cp, int attrname, byte[] attrinfo) {
        constPool = cp;
        name = attrname;
        info = attrinfo;
    }

    protected AttributeInfo(ConstPool cp, String attrname) {
        this(cp, attrname, (byte[])null);
    }

    /**
     * Constructs an <code>attribute_info</code> structure.
     *
     * @param cp                constant pool table
     * @param attrname          attribute name
     * @param attrinfo          <code>info</code> field
     *                          of <code>attribute_info</code> structure.
     */
    public AttributeInfo(ConstPool cp, String attrname, byte[] attrinfo) {
        this(cp, cp.addUtf8Info(attrname), attrinfo);
    }

    protected AttributeInfo(ConstPool cp, int n, DataInputStream in)
        throws IOException
    {
        constPool = cp;
        name = n;
        int len = in.readInt();
        info = new byte[len];
        if (len > 0)
            in.readFully(info);
    }

    static AttributeInfo read(ConstPool cp, DataInputStream in)
        throws IOException
    {
        int name = in.readUnsignedShort();
        String nameStr = cp.getUtf8Info(name);
        if (nameStr.charAt(0) < 'L') {
            if (nameStr.equals(AnnotationDefaultAttribute.tag))
                return new AnnotationDefaultAttribute(cp, name, in);
            else if (nameStr.equals(CodeAttribute.tag))
                return new CodeAttribute(cp, name, in);
            else if (nameStr.equals(ConstantAttribute.tag))
                return new ConstantAttribute(cp, name, in);
            else if (nameStr.equals(DeprecatedAttribute.tag))
                return new DeprecatedAttribute(cp, name, in);
            else if (nameStr.equals(EnclosingMethodAttribute.tag))
                return new EnclosingMethodAttribute(cp, name, in);
            else if (nameStr.equals(ExceptionsAttribute.tag))
                return new ExceptionsAttribute(cp, name, in);
            else if (nameStr.equals(InnerClassesAttribute.tag))
                return new InnerClassesAttribute(cp, name, in);
        }
        else {
            /* Note that the names of Annotations attributes begin with 'R'. 
             */
            if (nameStr.equals(LineNumberAttribute.tag))
                return new LineNumberAttribute(cp, name, in);
            else if (nameStr.equals(LocalVariableAttribute.tag)
                     || nameStr.equals(LocalVariableAttribute.typeTag))
                return new LocalVariableAttribute(cp, name, in);
            else if (nameStr.equals(AnnotationsAttribute.visibleTag)
                     || nameStr.equals(AnnotationsAttribute.invisibleTag)) {
                // RuntimeVisibleAnnotations or RuntimeInvisibleAnnotations
                return new AnnotationsAttribute(cp, name, in);
            }
            else if (nameStr.equals(ParameterAnnotationsAttribute.visibleTag)
                || nameStr.equals(ParameterAnnotationsAttribute.invisibleTag))
                return new ParameterAnnotationsAttribute(cp, name, in);
            else if (nameStr.equals(SignatureAttribute.tag))
                return new SignatureAttribute(cp, name, in);
            else if (nameStr.equals(SourceFileAttribute.tag))
                return new SourceFileAttribute(cp, name, in);
            else if (nameStr.equals(SyntheticAttribute.tag))
                return new SyntheticAttribute(cp, name, in);
            else if (nameStr.equals(StackMapTable.tag))
                return new StackMapTable(cp, name, in);
        }

        return new AttributeInfo(cp, name, in);
    }

    /**
     * Returns an attribute name.
     */
    public String getName() {
        return constPool.getUtf8Info(name);
    }

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

    /**
     * Returns the length of this <code>attribute_info</code>
     * structure.
     * The returned value is <code>attribute_length + 6</code>.
     */
    public int length() {
        return info.length + 6;
    }

    /**
     * Returns the <code>info</code> field
     * of this <code>attribute_info</code> structure.
     *
     * <p>This method is not available if the object is an instance
     * of <code>CodeAttribute</code>.
     */
    public byte[] get() { return info; }

    /**
     * Sets the <code>info</code> field
     * of this <code>attribute_info</code> structure.
     *
     * <p>This method is not available if the object is an instance
     * of <code>CodeAttribute</code>.
     */
    public void set(byte[] newinfo) { info = newinfo; }

    /**
     * Makes a copy.  Class names are replaced according to the
     * given <code>Map</code> object.
     *
     * @param newCp     the constant pool table used by the new copy.
     * @param classnames        pairs of replaced and substituted
     *                          class names.
     */
    public AttributeInfo copy(ConstPool newCp, Map classnames) {
        int s = info.length;
        byte[] srcInfo = info;
        byte[] newInfo = new byte[s];
        for (int i = 0; i < s; ++i)
            newInfo[i] = srcInfo[i];

        return new AttributeInfo(newCp, getName(), newInfo);
    }

    void write(DataOutputStream out) throws IOException {
        out.writeShort(name);
        out.writeInt(info.length);
        if (info.length > 0)
            out.write(info);
    }

    static int getLength(LinkedList list) {
        int size = 0;
        int n = list.size();
        for (int i = 0; i < n; ++i) {
            AttributeInfo attr = (AttributeInfo)list.get(i);
            size += attr.length();
        }

        return size;
    }

    static AttributeInfo lookup(LinkedList list, String name) {
        if (list == null)
            return null;

        ListIterator iterator = list.listIterator();
        while (iterator.hasNext()) {
            AttributeInfo ai = (AttributeInfo)iterator.next();
            if (ai.getName().equals(name))
                return ai;
        }

        return null;            // no such attribute
    }

    static synchronized void remove(LinkedList list, String name) {
        if (list == null)
            return;

        ListIterator iterator = list.listIterator();
        while (iterator.hasNext()) {
            AttributeInfo ai = (AttributeInfo)iterator.next();
            if (ai.getName().equals(name))
                iterator.remove();
        }
    }

    static void writeAll(LinkedList list, DataOutputStream out)
        throws IOException
    {
        if (list == null)
            return;

        int n = list.size();
        for (int i = 0; i < n; ++i) {
            AttributeInfo attr = (AttributeInfo)list.get(i);
            attr.write(out);
        }
    }

    static LinkedList copyAll(LinkedList list, ConstPool cp) {
        if (list == null)
            return null;

        LinkedList newList = new LinkedList();
        int n = list.size();
        for (int i = 0; i < n; ++i) {
            AttributeInfo attr = (AttributeInfo)list.get(i);
            newList.add(attr.copy(cp, null));
        }

        return newList;
    }
}