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

    public static CtClass[] getParameterTypes(String desc, ClassPool cp)
        throws NotFoundException
    {
        if (desc.charAt(0) != '(')
            return null;
        else {
            int num = numOfParameters(desc);
            CtClass[] args = new CtClass[num];
            int n = 0;
            int i = 1;
            do {
                i = toCtClass(cp, desc, i, args, n++);
            } while (i > 0);
            return args;
        }
    }

    /**
     * Returns true if the list of the parameter types of desc1 is equal to
     * that of desc2.
     * For example, "(II)V" and "(II)I" are equal.
     */
    public static boolean eqParamTypes(String desc1, String desc2) {
        if (desc1.charAt(0) != '(')
            return false;

        for (int i = 0; true; ++i) {
            char c = desc1.charAt(i);
            if (c != desc2.charAt(i))
                return false;

            if (c == ')')
                return true;
        }
    }

    /**
     * Returns the signature of the given descriptor.  The signature does
     * not include the return type.  For example, the signature of "(I)V"
     * is "(I)".
     */
    public static String getParamDescriptor(String decl) {
        return decl.substring(0, decl.indexOf(')') + 1);
    }

    /**
     * Returns the <code>CtClass</code> object representing the return
     * type specified by the given descriptor.
     *
     * @param desc descriptor
     * @param cp   the class pool used for obtaining
     *             a <code>CtClass</code> object.
     */
    public static CtClass getReturnType(String desc, ClassPool cp)
        throws NotFoundException
    {
        int i = desc.indexOf(')');
        if (i < 0)
            return null;
        else {
            CtClass[] type = new CtClass[1];
            toCtClass(cp, desc, i + 1, type, 0);
            return type[0];
        }
    }

    /**
     * Returns the number of the prameters included in the given
     * descriptor.
     *
     * @param desc descriptor
     */
    public static int numOfParameters(String desc) {
        int n = 0;
        int i = 1;
        for (;;) {
            char c = desc.charAt(i);
            if (c == ')')
                break;

            while (c == '[')
                c = desc.charAt(++i);

            if (c == 'L') {
                i = desc.indexOf(';', i) + 1;
                if (i <= 0)
                    throw new IndexOutOfBoundsException("bad descriptor");
            }
            else
                ++i;

            ++n;
        }

        return n;
    }

    /**
     * Returns a <code>CtClass</code> object representing the type
     * specified by the given descriptor.
     *
     * <p>This method works even if the package-class separator is
     * not <code>/</code> but <code>.</code> (period).  For example,
     * it accepts <code>Ljava.lang.Object;</code>
     * as well as <code>Ljava/lang/Object;</code>.
     *
     * @param desc descriptor
     * @param cp   the class pool used for obtaining
     *             a <code>CtClass</code> object.
     */
    public static CtClass toCtClass(String desc, ClassPool cp)
        throws NotFoundException
    {
        CtClass[] clazz = new CtClass[1];
        int res = toCtClass(cp, desc, 0, clazz, 0);
        if (res >= 0)
            return clazz[0];
        else {
            // maybe, you forgot to surround the class name with
            // L and ;.  It violates the protocol, but I'm tolerant...
            return cp.get(desc.replace('/', '.'));
        }
    }

    private static int toCtClass(ClassPool cp, String desc, int i,
                                 CtClass[] args, int n)
        throws NotFoundException
    {
        int i2;
        String name;

        int arrayDim = 0;
        char c = desc.charAt(i);
        while (c == '[') {
            ++arrayDim;
            c = desc.charAt(++i);
        }

        if (c == 'L') {
            i2 = desc.indexOf(';', ++i);
            name = desc.substring(i, i2++).replace('/', '.');
        }
        else {
            CtClass type = toPrimitiveClass(c);
            if (type == null)
                return -1; // error

            i2 = i + 1;
            if (arrayDim == 0) {
                args[n] = type;
                return i2; // neither an array type or a class type
            }
            else
                name = type.getName();
        }

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

            name = sbuf.toString();
        }

        args[n] = cp.get(name);
        return i2;
    }

    private static CtClass toPrimitiveClass(char c) {
        CtClass type = null;
        switch (c) {
        case 'Z' :
            type = CtClass.booleanType;
            break;
        case 'C' :
            type = CtClass.charType;
            break;
        case 'B' :
            type = CtClass.byteType;
            break;
        case 'S' :
            type = CtClass.shortType;
            break;
        case 'I' :
            type = CtClass.intType;
            break;
        case 'J' :
            type = CtClass.longType;
            break;
        case 'F' :
            type = CtClass.floatType;
            break;
        case 'D' :
            type = CtClass.doubleType;
            break;
        case 'V' :
            type = CtClass.voidType;
            break;
        }

        return type;
    }

    /**
     * Computes the dimension of the array represented by the given
     * descriptor.  For example, if the descriptor is <code>"[[I"</code>,
     * then this method returns 2.
     *
     * @param desc the descriptor.
     * @return 0        if the descriptor does not represent an array type.
     */
    public static int arrayDimension(String desc) {
        int dim = 0;
        while (desc.charAt(dim) == '[')
            ++dim;

        return dim;
    }

    /**
     * Returns the descriptor of the type of the array component.
     * For example, if the given descriptor is
     * <code>"[[Ljava/lang/String;"</code> and the given dimension is 2,
     * then this method returns <code>"Ljava/lang/String;"</code>.
     *
     * @param desc the descriptor.
     * @param dim  the array dimension.
     */
    public static String toArrayComponent(String desc, int dim) {
        return desc.substring(dim);
    }

    /**
     * Computes the data size specified by the given descriptor.
     * For example, if the descriptor is "D", this method returns 2.
     *
     * <p>If the descriptor represents a method type, this method returns
     * (the size of the returned value) - (the sum of the data sizes
     * of all the parameters).  For example, if the descriptor is
     * <code>"(I)D"</code>, then this method returns 1 (= 2 - 1).
     *
     * @param desc descriptor
     */
    public static int dataSize(String desc) {
        return dataSize(desc, true);
    }

    /**
     * Computes the data size of parameters.
     * If one of the parameters is double type, the size of that parameter
     * is 2 words.  For example, if the given descriptor is
     *  <code>"(IJ)D"</code>, then this method returns 3.  The size of the
     * return type is not computed.
     * 
     * @param desc      a method descriptor.
     */
    public static int paramSize(String desc) {
        return -dataSize(desc, false);
    }

    private static int dataSize(String desc, boolean withRet) {
        int n = 0;
        char c = desc.charAt(0);
        if (c == '(') {
            int i = 1;
            for (;;) {
                c = desc.charAt(i);
                if (c == ')') {
                    c = desc.charAt(i + 1);
                    break;
                }

                boolean array = false;
                while (c == '[') {
                    array = true;
                    c = desc.charAt(++i);
                }

                if (c == 'L') {
                    i = desc.indexOf(';', i) + 1;
                    if (i <= 0)
                        throw new IndexOutOfBoundsException("bad descriptor");
                }
                else
                    ++i;

                if (!array && (c == 'J' || c == 'D'))
                    n -= 2;
                else
                    --n;
            }
        }

        if (withRet)
            if (c == 'J' || c == 'D')
                n += 2;
            else if (c != 'V')
                ++n;

        return n;
    }

    /**
     * An Iterator over a descriptor.
     */
    public static class Iterator {
        private String desc;
        private int index, curPos;
        private boolean param;

        /**
         * Constructs an iterator.
         *
         * @param s         descriptor.
         */
        public Iterator(String s) {
            desc = s;
            index = curPos = 0;
            param = false;
        }

        /**
         * Returns true if the iteration has more elements.
         */
        public boolean hasNext() {
            return index < desc.length();
        }

        /**
         * Returns true if the current element is a parameter type.
         */
        public boolean isParameter() { return param; }

        /**
         * Returns the first character of the current element.
         */
        public char currentChar() { return desc.charAt(curPos); }

        /**
         * Returns true if the current element is double or long type.
         */
        public boolean is2byte() {
            char c = currentChar();
            return c == 'D' || c == 'J';
        }

        /**
         * Returns the position of the next type character.
         * That type character becomes a new current element.
         */
        public int next() {
            int nextPos = index;
            char c = desc.charAt(nextPos);
            if (c == '(') {
                ++index;
                c = desc.charAt(++nextPos);
                param = true;
            }

            if (c == ')') {
                ++index;
                c = desc.charAt(++nextPos);
                param = false;
            }

            while (c == '[')
                c = desc.charAt(++nextPos);

            if (c == 'L') {
                nextPos = desc.indexOf(';', nextPos) + 1;
                if (nextPos <= 0)
                    throw new IndexOutOfBoundsException("bad descriptor");
            }
            else
                ++nextPos;

            curPos = index;
            index = nextPos;
            return curPos;
        }
    }
}