javassist/src/main/javassist/bytecode/MethodInfo.java

/*
 * Javassist, a Java-bytecode translator toolkit.
 * Copyright (C) 1999-2004 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.List;
import java.util.LinkedList;

/**
 * <code>method_info</code> structure.
 *
 * @see javassist.CtMethod#getMethodInfo()
 * @see javassist.CtConstructor#getMethodInfo()
 */
public final class MethodInfo {
    ConstPool constPool;
    int accessFlags;
    int name;
    int descriptor;
    LinkedList attribute;       // may be null

    /**
     * The name of constructors: <code>&lt;init&gt</code>.
     */
    public static final String nameInit = "<init>";

    /**
     * The name of class initializer (static initializer):
     * <code>&lt;clinit&gt</code>.
     */
    public static final String nameClinit = "<clinit>";

    private MethodInfo(ConstPool cp) {
        constPool = cp;
        attribute = null;
    }

    /**
     * Constructs a <code>method_info</code> structure.
     * The initial value of <code>access_flags</code> is zero.
     *
     * @param cp                a constant pool table
     * @param methodname        method name
     * @param desc              method descriptor
     *
     * @see Descriptor
     */
    public MethodInfo(ConstPool cp, String methodname, String desc) {
        this(cp);
        accessFlags = 0;
        name = cp.addUtf8Info(methodname);
        descriptor = constPool.addUtf8Info(desc);
    }

    MethodInfo(ConstPool cp, DataInputStream in) throws IOException {
        this(cp);
        read(in);
    }

    /**
     * Constructs a copy of <code>method_info</code> structure.
     * Class names appearing in the source <code>method_info</code>
     * are renamed according to <code>classnameMap</code>.
     *
     * <p>Note: only <code>Code</code> and <code>Exceptions</code>
     * attributes are copied from the source.  The other attributes
     * are ignored.
     *
     * @param cp                a constant pool table
     * @param methodname        a method name
     * @param src               a source <code>method_info</code>
     * @param classnameMap      specifies pairs of replaced and substituted
     *                          name.
     * @see Descriptor
     */
    public MethodInfo(ConstPool cp, String methodname, MethodInfo src,
                      Map classnameMap) throws BadBytecode {
        this(cp);
        read(src, methodname, classnameMap);
    }

    void prune(ConstPool cp) {
        attribute = null;
        name = cp.addUtf8Info(getName());
        descriptor = cp.addUtf8Info(getDescriptor());
        constPool = cp;
    }

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

    /**
     * Sets a method name.
     */
    public void setName(String newName) {
        name = constPool.addUtf8Info(newName);
    }

    /**
     * Returns true if this is not a constructor or a class initializer
     * (static initializer).
     */
    public boolean isMethod() {
        String n = getName();
        return !n.equals(nameInit) && !n.equals(nameClinit);
    }

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

    /**
     * Returns true if this is a constructor.
     */
    public boolean isConstructor() {
        return getName().equals(nameInit);
    }

    /**
     * Returns true if this is a class initializer (static initializer).
     */
    public boolean isStaticInitializer() {
        return getName().equals(nameClinit);
    }

    /**
     * Returns access flags.
     *
     * @see AccessFlag
     */
    public int getAccessFlags() {
        return accessFlags;
    }

    /**
     * Sets access flags.
     *
     * @see AccessFlag
     */
    public void setAccessFlags(int acc) {
        accessFlags = acc;
    }

    /**
     * Returns a method descriptor.
     *
     * @see Descriptor
     */
    public String getDescriptor() {
        return constPool.getUtf8Info(descriptor);
    }

    /**
     * Sets a method descriptor.
     *
     * @see Descriptor
     */
    public void setDescriptor(String desc) {
        if (!desc.equals(getDescriptor()))
            descriptor = constPool.addUtf8Info(desc);
    }

    /**
     * Returns all the attributes.
     * A new element can be added to the returned list
     * and an existing element can be removed from the list.
     *
     * @return a list of <code>AttributeInfo</code> objects.
     * @see AttributeInfo
     */
    public List getAttributes() {
        if (attribute == null)
            attribute = new LinkedList();

        return attribute;
    }

    /**
     * Returns the attribute with the specified name.
     * If it is not found, this method returns null.
     *
     * @param name      attribute name
     * @return          an <code>AttributeInfo</code> object or null.
     */
    public AttributeInfo getAttribute(String name) {
        return AttributeInfo.lookup(attribute, name);
    }

    /**
     * Appends an attribute.  If there is already an attribute with
     * the same name, the new one substitutes for it.
     */
    public void addAttribute(AttributeInfo info) {
        if (attribute == null)
            attribute = new LinkedList();

        AttributeInfo.remove(attribute, info.getName());
        attribute.add(info);
    }

    /**
     * Returns an Exceptions attribute.
     *
     * @return          an Exceptions attribute
     *                  or null if it is not specified.
     */
    public ExceptionsAttribute getExceptionsAttribute() {
        AttributeInfo info
            = AttributeInfo.lookup(attribute, ExceptionsAttribute.tag);
        return (ExceptionsAttribute)info;
    }

    /**
     * Returns a Code attribute.
     *
     * @return          a Code attribute
     *                  or null if it is not specified.
     */
    public CodeAttribute getCodeAttribute() {
        AttributeInfo info
            = AttributeInfo.lookup(attribute, CodeAttribute.tag);
        return (CodeAttribute)info;
    }

    /**
     * Removes an Exception attribute.
     */
    public void removeExceptionsAttribute() {
        AttributeInfo.remove(attribute, ExceptionsAttribute.tag);
    }

    /**
     * Adds an Exception attribute.
     *
     * <p>The added attribute must share the same constant pool table
     * as this <code>method_info</code> structure.
     */
    public void setExceptionsAttribute(ExceptionsAttribute cattr) {
        removeExceptionsAttribute();
        if (attribute == null)
            attribute = new LinkedList();

        attribute.add(cattr);
    }

    /**
     * Removes a Code attribute.
     */
    public void removeCodeAttribute() {
        AttributeInfo.remove(attribute, CodeAttribute.tag);
    }

    /**
     * Adds a Code attribute.
     *
     * <p>The added attribute must share the same constant pool table
     * as this <code>method_info</code> structure.
     */
    public void setCodeAttribute(CodeAttribute cattr) {
        removeCodeAttribute();
        if (attribute == null)
            attribute = new LinkedList();

        attribute.add(cattr);
    }

    /**
     * Returns the line number of the source line corresponding to the
     * specified bytecode contained in this method.
     *
     * @param pos       the position of the bytecode (&gt;= 0).
     *                  an index into the code array.
     * @return -1       if this information is not available.
     */
    public int getLineNumber(int pos) {
        CodeAttribute ca = getCodeAttribute();
        if (ca == null)
            return -1;

        LineNumberAttribute ainfo =
            (LineNumberAttribute)ca.getAttribute(LineNumberAttribute.tag);
        if (ainfo == null)
            return -1;

        return ainfo.toLineNumber(pos);
    }

    /**
     * Changes a super constructor called by this constructor.
     *
     * <p>This method modifies a call to <code>super()</code>,
     * which should be at the
     * head of a constructor body, so that a constructor in a different
     * super class is called.  This method does not change actural
     * parameters.  Hence the new super class must have a constructor
     * with the same signature as the original one.
     *
     * <p>This method should be called when the super class
     * of the class declaring this method is changed.
     *
     * <p>This method does not perform anything unless this
     * <code>MethodInfo</code> represents a constructor.
     *
     * @param superclass        the new super class
     */
    public void setSuperclass(String superclass) throws BadBytecode {
        if (!isConstructor())
            return;

        CodeAttribute ca = getCodeAttribute();
        byte[] code = ca.getCode();
        CodeIterator iterator = ca.iterator();
        int pos = iterator.skipSuperConstructor();
        if (pos >= 0) { // not this()
            ConstPool cp = constPool;
            int mref = ByteArray.readU16bit(code, pos + 1);
            int nt = cp.getMethodrefNameAndType(mref);
            int sc = cp.addClassInfo(superclass);
            int mref2 = cp.addMethodrefInfo(sc, nt);
            ByteArray.write16bit(mref2, code, pos + 1);
        }
    }

    private void read(MethodInfo src, String methodname, Map classnames)
        throws BadBytecode
    {
        ConstPool destCp = constPool;
        accessFlags = src.accessFlags;
        name = destCp.addUtf8Info(methodname);

        ConstPool srcCp = src.constPool;
        String desc = srcCp.getUtf8Info(src.descriptor);
        String desc2 = Descriptor.rename(desc, classnames);
        descriptor = destCp.addUtf8Info(desc2);

        attribute = new LinkedList();
        ExceptionsAttribute eattr = src.getExceptionsAttribute();
        if (eattr != null)
            attribute.add(eattr.copy(destCp, classnames));

        CodeAttribute cattr = src.getCodeAttribute();
        if (cattr != null)
            attribute.add(cattr.copy(destCp, classnames));
    }

    private void read(DataInputStream in) throws IOException {
        accessFlags = in.readUnsignedShort();
        name = in.readUnsignedShort();
        descriptor = in.readUnsignedShort();
        int n = in.readUnsignedShort();
        attribute = new LinkedList();
        for (int i = 0; i < n; ++i)
            attribute.add(AttributeInfo.read(constPool, in));
    }

    void write(DataOutputStream out) throws IOException {
        out.writeShort(accessFlags);
        out.writeShort(name);
        out.writeShort(descriptor);

        if (attribute == null)
            out.writeShort(0);
        else {
            out.writeShort(attribute.size());
            AttributeInfo.writeAll(attribute, out);
        }
    }
}