descriptor.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.ClassPool;
import javassist.CtClass;
import javassist.CtPrimitiveType;
import javassist.NotFoundException;
import java.util.Map;

/**
 * A support class for dealing with descriptors.
 *
 * <p>See chapter 4.3 in "The Java Virtual Machine Specification (2nd ed.)"
 */
public class Descriptor {
    /**
     * Converts a class name into the internal representation used in
     * the JVM.
     *
     * <p>Note that <code>toJvmName(toJvmName(s))</code> is equivalent
     * to <code>toJvmName(s)</code>.
     */
    public static String toJvmName(String classname) {
        return classname.replace('.', '/');
    }

    /**
     * Converts a class name from the internal representation used in
     * the JVM to the normal one used in Java.
     */
    public static String toJavaName(String classname) {
        return classname.replace('/', '.');
    }

    /**
     * Returns the internal representation of the class name in the
     * JVM.
     */
    public static String toJvmName(CtClass clazz) {
        if (clazz.isArray())
            return of(clazz);
        else
            return toJvmName(clazz.getName());
    }

    /**
     * Converts to a Java class name from a descriptor.
     *
     * @param descriptor        type descriptor.
     */
    public static String toClassName(String descriptor) {
        int arrayDim = 0;
        int i = 0;
        char c = descriptor.charAt(0);
        while (c == '[') {
            ++arrayDim;
            c = descriptor.charAt(++i);
        }

        String name;
        if (c == 'L') {
            int i2 = descriptor.indexOf(';', i++);
            name = descriptor.substring(i, i2).replace('/', '.');
            i = i2;
        }
        else if (c == 'V')
            name =  "void";
        else if (c == 'I')
            name = "int";
        else if (c == 'B')
            name = "byte";
        else if (c == 'J')
            name = "long";
        else if (c == 'D')
            name = "double";
        else if (c == 'F')
            name = "float";
        else if (c == 'C')
            name = "char";
        else if (c == 'S')
            name = "short";
        else if (c == 'Z')
            name = "boolean";
        else
            throw new RuntimeException("bad descriptor: " + descriptor);

        if (i + 1 != descriptor.length())
            throw new RuntimeException("multiple descriptors?: " + descriptor);

        if (arrayDim == 0)
            return name;
        else {
            StringBuffer sbuf = new StringBuffer(name);
            do {
                sbuf.append("[]");
            } while (--arrayDim > 0);

            return sbuf.toString();
        }
    }

    /**
     * Converts to a descriptor from a Java class name
     */
    public static String of(String classname) {
        if (classname.equals("void"))
            return "V";
        else if (classname.equals("int"))
            return "I";
        else if (classname.equals("byte"))
            return "B";
        else if (classname.equals("long"))
            return "J";
        else if (classname.equals("double"))
            return "D";
        else if (classname.equals("float"))
            return "F";
        else if (classname.equals("char"))
            return "C";
        else if (classname.equals("short"))
            return "S";
        else if (classname.equals("boolean"))
            return "Z";
        else
            return "L" + toJvmName(classname) + ";";
    }

    /**
     * Substitutes a class name
     * in the given descriptor string.
     *
     * @param desc    descriptor string
     * @param oldname replaced JVM class name
     * @param newname substituted JVM class name
     *
     * @see Descriptor#toJvmName(String)
     */
    public static String rename(String desc, String oldname, String newname) {
        if (desc.indexOf(oldname) < 0)
            return desc;

        StringBuffer newdesc = new StringBuffer();
        int head = 0;
        int i = 0;
        for (;;) {
            int j = desc.indexOf('L', i);
            if (j < 0)
                break;
            else if (desc.startsWith(oldname, j + 1)
                     && desc.charAt(j + oldname.length() + 1) == ';') {
                newdesc.append(desc.substring(head, j));
                newdesc.append('L');
                newdesc.append(newname);
                newdesc.append(';');
                head = i = j + oldname.length() + 2;
            }
            else {
                i = desc.indexOf(';', j) + 1;
                if (i < 1)
                    break; // ';' was not found.
            }
        }

        if (head == 0)
            return desc;
        else {
            int len = desc.length();
            if (head < len)
                newdesc.append(desc.substring(head, len));

            return newdesc.toString();
        }
    }

    /**
     * Substitutes class names in the given descriptor string
     * according to the given <code>map</code>.
     *
     * @param map a map between replaced and substituted
     *            JVM class names.
     * @see Descriptor#toJvmName(String)
     */
    public static String rename(String desc, Map map) {
        if (map == null)
            return desc;

        StringBuffer newdesc = new StringBuffer();
        int head = 0;
        int i = 0;
        for (;;) {
            int j = desc.indexOf('L', i);
            if (j < 0)
                break;

            int k = desc.indexOf(';', j);
            if (k < 0)
                break;

            i = k + 1;
            String name = desc.substring(j + 1, k);
            String name2 = (String)map.get(name);
            if (name2 != null) {
                newdesc.append(desc.substring(head, j));
                newdesc.append('L');
                newdesc.append(name2);
                newdesc.append(';');
                head = i;
            }
        }

        if (head == 0)
            return desc;
        else {
            int len = desc.length();
            if (head < len)
                newdesc.append(desc.substring(head, len));

            return newdesc.toString();
        }
    }

    /**
     * Returns the descriptor representing the given type.
     */
    public static String of(CtClass type) {
        StringBuffer sbuf = new StringBuffer();
        toDescriptor(sbuf, type);
        return sbuf.toString();
    }

    private static void toDescriptor(StringBuffer desc, CtClass type) {
        if (type.isArray()) {
            desc.append('[');
            try {
                toDescriptor(desc, type.getComponentType());
            }
            catch (NotFoundException e) {
                desc.append('L');
                String name = type.getName();
                desc.append(toJvmName(name.substring(0, name.length() - 2)));
                desc.append(';');
            }
        }
        else if (type.isPrimitive()) {
            CtPrimitiveType pt = (CtPrimitiveType)type;
            desc.append(pt.getDescriptor());
        }
        else { // class type
            desc.append('L');
            desc.append(type.getName().replace('.', '/'));
            desc.append(';');
        }
    }

    /**
     * Returns the descriptor representing a constructor receiving
     * the given parameter types.
     *
     * @param paramTypes parameter types
     */
    public static String ofConstructor(CtClass[] paramTypes) {
        return ofMethod(CtClass.voidType, paramTypes);
    }

    /**
     * Returns the descriptor representing a method that receives
     * the given parameter types and returns the given type.
     *
     * @param returnType return type
     * @param paramTypes parameter types
     */
    public static String ofMethod(CtClass returnType, CtClass[] paramTypes) {
        StringBuffer desc = new StringBuffer();
        desc.append('(');
        if (paramTypes != null) {
            int n = paramTypes.length;
            for (int i = 0; i < n; ++i)
                toDescriptor(desc, paramTypes[i]);
        }

        desc.append(')');
        if (returnType != null)
            toDescriptor(desc, returnType);

        return desc.toString();
    }

    /**
     * Returns the descriptor representing a list of parameter types.
     * For example, if the given parameter types are two <code>int</code>,
     * then this method returns <code>"(II)"</code>.
     *
     * @param paramTypes parameter types
     */
    public static String ofParameters(CtClass[] paramTypes) {
        return ofMethod(null, paramTypes);
    }

    /**
     * Appends a parameter type to the parameter list represented
     * by the given descriptor.
     *
     * <p><code>classname</code> must not be an array type.
     *
     * @param classname parameter type (not primitive type)
     * @param desc      descriptor
     */
    public static String appendParameter(String classname, String desc) {
        int i = desc.indexOf(')');
        if (i < 0)
            return desc;
        else {
            StringBuffer newdesc = new StringBuffer();
            newdesc.append(desc.substring(0, i));
            newdesc.append('L');
            newdesc.append(classname.replace('.', '/'));
            newdesc.append(';');
            newdesc.append(desc.substring(i));
            return newdesc.toString();
        }
    }

    /**
     * Inserts a parameter type at the beginning of the parameter
     * list represented
     * by the given descriptor.
     *
     * <p><code>classname</code> must not be an array type.
     *
     * @param classname parameter type (not primitive type)
     * @param desc      descriptor
     */
    public static String insertParameter(String classname, String desc) {
        if (desc.charAt(0) != '(')
            return desc;
        else
            return "(L" + classname.replace('.', '/') + ';'
                   + desc.substring(1);
    }

    /**
     * Changes the return type included in the given descriptor.
     *
     * <p><code>classname</code> must not be an array type.
     *
     * @param classname return type
     * @param desc      descriptor
     */
    public static String changeReturnType(String classname, String desc) {
        int i = desc.indexOf(')');
        if (i < 0)
            return desc;
        else {
            StringBuffer newdesc = new StringBuffer();
            newdesc.append(desc.substring(0, i + 1));
            newdesc.append('L');
            newdesc.append(classname.replace('.', '/'));
            newdesc.append(';');
            return newdesc.toString();
        }
    }

    /**
     * Returns the <code>CtClass</code> objects representing the parameter
     * types specified by the given descriptor.
     *
     * @param desc descriptor
     * @param cp   the class pool used for obtaining
     *             a <code>CtClass</code> object.
     */