InternalTypeEnumeration.java

/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification
 *             of Java bytecode.
 *
 * Copyright (c) 2002-2017 Eric Lafortune @ GuardSquare
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.classfile.util;

import proguard.classfile.ClassConstants;


/**
 * An <code>InternalTypeEnumeration</code> provides an enumeration of all
 * types listed in a given internal descriptor or signature of a class, a
 * method, or a field.
 *
 * The leading formal type parameters, if any, can be retrieved separately.
 *
 * The return type of a method descriptor can also be retrieved separately.
 *
 * @author Eric Lafortune
 */
public class InternalTypeEnumeration
{
    private String descriptor;
    private int    formalTypeParametersIndex;
    private int    openIndex;
    private int    closeIndex;
    private int    index;


    /**
     * Creates a new InternalTypeEnumeration for the given method descriptor.
     */
    public InternalTypeEnumeration(String descriptor)
    {
        this.descriptor = descriptor;

        // Find any formal type parameters.
        if (descriptor.charAt(0) == ClassConstants.TYPE_GENERIC_START)
        {
            formalTypeParametersIndex = 1;

            int nestingLevel = 1;
            do
            {
                char c = descriptor.charAt(formalTypeParametersIndex++);
                switch (c)
                {
                    case ClassConstants.TYPE_GENERIC_START:
                    {
                        nestingLevel++;
                        break;
                    }
                    case ClassConstants.TYPE_GENERIC_END:
                    {
                        nestingLevel--;
                        break;
                    }
                }
            }
            while (nestingLevel > 0);
        }

        this.openIndex  = descriptor.indexOf(ClassConstants.METHOD_ARGUMENTS_OPEN,
                                             formalTypeParametersIndex);

        this.closeIndex = openIndex >= 0 ?
            descriptor.indexOf(ClassConstants.METHOD_ARGUMENTS_CLOSE, openIndex) :
            descriptor.length();

        this.index = openIndex >= 0 ?
            openIndex + 1 :
            formalTypeParametersIndex;
    }


    /**
     * Returns whether the descriptor has leading formal type parameters.
     */
    public boolean hasFormalTypeParameters()
    {
        return formalTypeParametersIndex > 0;
    }


    /**
     * Returns the leading formal type parameters from the descriptor.
     */
    public String formalTypeParameters()
    {
        return descriptor.substring(0, formalTypeParametersIndex);
    }


    /**
     * Returns whether the descriptor is a method signature.
     */
    public boolean isMethodSignature()
    {
        return openIndex >= 0;
    }


    /**
     * Returns whether the enumeration can provide more types from the method
     * descriptor.
     */
    public boolean hasMoreTypes()
    {
        return index < closeIndex;
    }


    /**
     * Returns the next type from the method descriptor.
     */
    public String nextType()
    {
        int startIndex = index;

        skipArray();

        char c = descriptor.charAt(index++);
        switch (c)
        {
            case ClassConstants.TYPE_CLASS_START:
            case ClassConstants.TYPE_GENERIC_VARIABLE_START:
            {
                skipClass();
                break;
            }
            case ClassConstants.TYPE_GENERIC_START:
            {
                skipGeneric();
                break;
            }
        }

        return descriptor.substring(startIndex, index);
    }


    /**
     * Returns the return type from the descriptor, assuming it's a method
     * descriptor.
     */
    public String returnType()
    {
        return descriptor.substring(closeIndex + 1);
    }


    // Small utility methods.

    private void skipArray()
    {
        while (descriptor.charAt(index) == ClassConstants.TYPE_ARRAY)
        {
            index++;
        }
    }


    private void skipClass()
    {
        while (true)
        {
            char c = descriptor.charAt(index++);
            switch (c)
            {
                case ClassConstants.TYPE_GENERIC_START:
                    skipGeneric();
                    break;

                case ClassConstants.TYPE_CLASS_END:
                    return;
            }
        }
    }


    private void skipGeneric()
    {
        int nestingLevel = 1;

        do
        {
            char c = descriptor.charAt(index++);
            switch (c)
            {
                case ClassConstants.TYPE_GENERIC_START:
                    nestingLevel++;
                    break;

                case ClassConstants.TYPE_GENERIC_END:
                    nestingLevel--;
                    break;
            }
        }
        while (nestingLevel > 0);
    }


    /**
     * A main method for testing the type enumeration.
     */
    public static void main(String[] args)
    {
        try
        {
            for (int index = 0; index < args.length; index++)
            {
                String descriptor = args[index];

                System.out.println("Descriptor ["+descriptor+"]");
                InternalTypeEnumeration enumeration = new InternalTypeEnumeration(descriptor);

                if (enumeration.hasFormalTypeParameters())
                {
                    System.out.println("  Formal type parameters ["+enumeration.formalTypeParameters()+"]");
                }

                while (enumeration.hasMoreTypes())
                {
                    System.out.println("  Type ["+enumeration.nextType()+"]");
                }

                if (enumeration.isMethodSignature())
                {
                    System.out.println("  Return type ["+enumeration.returnType()+"]");
                }
            }
        }
        catch (Exception ex)
        {
            ex.printStackTrace();
        }
    }
}