elementvalue.java

Java Bytecode Editor 是一个 JAVA 的字节码反汇编和修改器。它可以很方便的修改已经编译成 Class 文件的 JAVA 文件。

/*
    This library 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.
*/
package org.gjt.jclasslib.structures.elementvalues;

import org.gjt.jclasslib.structures.*;

import java.io.*;

/**
 * Describes an  <tt>ElementValue</tt> attribute structure.
 *
 * @author <a href="mailto:[e-mail]">Vitor Carreira</a>
 * @version $Revision: 1.1 $ $Date: 2005/11/01 13:18:24 $
 */
public abstract class ElementValue extends AbstractStructure {

    public final static char BYTE_TAG = 'B';
    public final static char CHAR_TAG = 'C';
    public final static char DOUBLE_TAG = 'D';
    public final static char FLOAT_TAG = 'F';
    public final static char INT_TAG = 'I';
    public final static char LONG_TAG = 'J';
    public final static char SHORT_TAG = 'S';
    public final static char BOOL_TAG = 'Z';
    public final static char STRING_TAG = 's';
    public final static char ENUM_TAG = 'e';
    public final static char CLASS_TAG = 'c';
    public final static char ARRAY_TAG = '[';
    public final static char ANNOTATION_TAG = '@';

    public final static String BYTE_TAG_VERBOSE = "byte";
    public final static String CHAR_TAG_VERBOSE = "String";
    public final static String DOUBLE_TAG_VERBOSE = "double";
    public final static String FLOAT_TAG_VERBOSE = "float";
    public final static String INT_TAG_VERBOSE = "int";
    public final static String LONG_TAG_VERBOSE = "long";
    public final static String SHORT_TAG_VERBOSE = "short";
    public final static String BOOL_TAG_VERBOSE = "boolean";
    public final static String STRING_TAG_VERBOSE = "String";
    public final static String ENUM_TAG_VERBOSE = "Enum";
    public final static String CLASS_TAG_VERBOSE = "Class";
    public final static String ARRAY_TAG_VERBOSE = "Array";
    public final static String ANNOTATION_TAG_VERBOSE = "Annotation";

    protected static final int INITIAL_LENGTH = 1;
    private int tag;

    public ElementValue(int tag) {
        this.tag = tag;
    }


    /**
     * Factory for creating <tt>ElementValue</tt> structures.
     *
     * @param in        the <tt>DataInput</tt> from which to read the
     *                  <tt>ElementValue</tt> structure
     * @param classFile the parent class file of the structure to be created
     * @return the new <tt>ElementValue</tt> structure
     * @throws org.gjt.jclasslib.structures.InvalidByteCodeException
     *                             if the byte code is invalid
     * @throws java.io.IOException if an exception occurs with the <tt>DataInput</tt>
     */
    public static ElementValue create(DataInput in, ClassFile classFile)
            throws InvalidByteCodeException, IOException {

        int tagType = in.readUnsignedByte();

        ElementValue entry = null;
        switch (tagType) {
            case BOOL_TAG:
            case BYTE_TAG:
            case CHAR_TAG:
            case DOUBLE_TAG:
            case FLOAT_TAG:
            case SHORT_TAG:
            case INT_TAG:
            case LONG_TAG:
            case STRING_TAG:
                entry = new ConstElementValue(tagType);
                break;
            case ENUM_TAG:
                entry = new EnumElementValue();
                break;
            case CLASS_TAG:
                entry = new ClassElementValue();
                break;
            case ANNOTATION_TAG:
                entry = new AnnotationElementValue();
                break;
            case ARRAY_TAG:
                entry = new ArrayElementValue();
                break;
            default:
                throw new InvalidByteCodeException("Unknown tag " + (char)tagType);
        }
        entry.setClassFile(classFile);
        entry.read(in);

        return entry;
    }


    public void write(DataOutput out) throws InvalidByteCodeException, IOException {
        super.write(out);

        out.writeByte(tag);

        if (debug) debug("wrote ");
    }


    protected abstract int getSpecificLength();

    final public int getLength() {
        return INITIAL_LENGTH + getSpecificLength();
    }

    public abstract String getEntryName();

    protected String printAccessFlagsVerbose(int accessFlags) {
        if (accessFlags != 0)
            throw new RuntimeException("Access flags should be zero: " + Integer.toHexString(accessFlags));
        return "";
    }

    public int getTag() {
        return tag;
    }

    public static String getTagDescription(int tag) {
        switch (tag) {
            case BOOL_TAG:
                return BOOL_TAG_VERBOSE;
            case BYTE_TAG:
                return BYTE_TAG_VERBOSE;
            case CHAR_TAG:
                return CHAR_TAG_VERBOSE;
            case DOUBLE_TAG:
                return DOUBLE_TAG_VERBOSE;
            case FLOAT_TAG:
                return FLOAT_TAG_VERBOSE;
            case SHORT_TAG:
                return SHORT_TAG_VERBOSE;
            case INT_TAG:
                return INT_TAG_VERBOSE;
            case LONG_TAG:
                return LONG_TAG_VERBOSE;
            case STRING_TAG:
                return STRING_TAG_VERBOSE;
            case ENUM_TAG:
                return ENUM_TAG_VERBOSE;
            case CLASS_TAG:
                return CLASS_TAG_VERBOSE;
            case ANNOTATION_TAG:
                return ANNOTATION_TAG_VERBOSE;
            case ARRAY_TAG:
                return ARRAY_TAG_VERBOSE;
            default:
                return "Unknown";
        }
    }


}