TypePath.java

/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2013 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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package org.objectweb.asm;

/**
 * The path to a type argument, wildcard bound, array element type, or static
 * inner type within an enclosing type.
 * 
 * @author Eric Bruneton
 */
public class TypePath {

    /**
     * A type path step that steps into the element type of an array type. See
     * {@link #getStep getStep}.
     */
    public final static int ARRAY_ELEMENT = 0;

    /**
     * A type path step that steps into the nested type of a class type. See
     * {@link #getStep getStep}.
     */
    public final static int INNER_TYPE = 1;

    /**
     * A type path step that steps into the bound of a wildcard type. See
     * {@link #getStep getStep}.
     */
    public final static int WILDCARD_BOUND = 2;

    /**
     * A type path step that steps into a type argument of a generic type. See
     * {@link #getStep getStep}.
     */
    public final static int TYPE_ARGUMENT = 3;

    /**
     * The byte array where the path is stored, in Java class file format.
     */
    byte[] b;

    /**
     * The offset of the first byte of the type path in 'b'.
     */
    int offset;

    /**
     * Creates a new type path.
     * 
     * @param b
     *            the byte array containing the type path in Java class file
     *            format.
     * @param offset
     *            the offset of the first byte of the type path in 'b'.
     */
    TypePath(byte[] b, int offset) {
        this.b = b;
        this.offset = offset;
    }

    /**
     * Returns the length of this path.
     * 
     * @return the length of this path.
     */
    public int getLength() {
        return b[offset];
    }

    /**
     * Returns the value of the given step of this path.
     * 
     * @param index
     *            an index between 0 and {@link #getLength()}, exclusive.
     * @return {@link #ARRAY_ELEMENT ARRAY_ELEMENT}, {@link #INNER_TYPE
     *         INNER_TYPE}, {@link #WILDCARD_BOUND WILDCARD_BOUND}, or
     *         {@link #TYPE_ARGUMENT TYPE_ARGUMENT}.
     */
    public int getStep(int index) {
        return b[offset + 2 * index + 1];
    }

    /**
     * Returns the index of the type argument that the given step is stepping
     * into. This method should only be used for steps whose value is
     * {@link #TYPE_ARGUMENT TYPE_ARGUMENT}.
     * 
     * @param index
     *            an index between 0 and {@link #getLength()}, exclusive.
     * @return the index of the type argument that the given step is stepping
     *         into.
     */
    public int getStepArgument(int index) {
        return b[offset + 2 * index + 2];
    }

    /**
     * Converts a type path in string form, in the format used by
     * {@link #toString()}, into a TypePath object.
     * 
     * @param typePath
     *            a type path in string form, in the format used by
     *            {@link #toString()}. May be null or empty.
     * @return the corresponding TypePath object, or null if the path is empty.
     */
    public static TypePath fromString(final String typePath) {
        if (typePath == null || typePath.length() == 0) {
            return null;
        }
        int n = typePath.length();
        ByteVector out = new ByteVector(n);
        out.putByte(0);
        for (int i = 0; i < n;) {
            char c = typePath.charAt(i++);
            if (c == '[') {
                out.put11(ARRAY_ELEMENT, 0);
            } else if (c == '.') {
                out.put11(INNER_TYPE, 0);
            } else if (c == '*') {
                out.put11(WILDCARD_BOUND, 0);
            } else if (c >= '0' && c <= '9') {
                int typeArg = c - '0';
                while (i < n && (c = typePath.charAt(i)) >= '0' && c <= '9') {
                    typeArg = typeArg * 10 + c - '0';
                    i += 1;
                }
                if (i < n && typePath.charAt(i) == ';') {
                    i += 1;
                }
                out.put11(TYPE_ARGUMENT, typeArg);
            }
        }
        out.data[0] = (byte) (out.length / 2);
        return new TypePath(out.data, 0);
    }

    /**
     * Returns a string representation of this type path. {@link #ARRAY_ELEMENT
     * ARRAY_ELEMENT} steps are represented with '[', {@link #INNER_TYPE
     * INNER_TYPE} steps with '.', {@link #WILDCARD_BOUND WILDCARD_BOUND} steps
     * with '*' and {@link #TYPE_ARGUMENT TYPE_ARGUMENT} steps with their type
     * argument index in decimal form followed by ';'.
     */
    @Override
    public String toString() {
        int length = getLength();
        StringBuilder result = new StringBuilder(length * 2);
        for (int i = 0; i < length; ++i) {
            switch (getStep(i)) {
            case ARRAY_ELEMENT:
                result.append('[');
                break;
            case INNER_TYPE:
                result.append('.');
                break;
            case WILDCARD_BOUND:
                result.append('*');
                break;
            case TYPE_ARGUMENT:
                result.append(getStepArgument(i)).append(';');
                break;
            default:
                result.append('_');
            }
        }
        return result.toString();
    }
}