classfilewriter.java

java中比较著名的js引擎当属mozilla开源的rhino

/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0
 *
 * 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. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * 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.
 *
 * The Original Code is Rhino code, released
 * May 6, 1999.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1997-1999
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Roger Lawrence
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License Version 2 or later (the "GPL"), in which
 * case the provisions of the GPL are applicable instead of those above. If
 * you wish to allow use of your version of this file only under the terms of
 * the GPL and not to allow others to use your version of this file under the
 * MPL, indicate your decision by deleting the provisions above and replacing
 * them with the notice and other provisions required by the GPL. If you do
 * not delete the provisions above, a recipient may use your version of this
 * file under either the MPL or the GPL.
 *
 * ***** END LICENSE BLOCK ***** */

package org.mozilla.classfile;

import org.mozilla.javascript.ObjToIntMap;
import org.mozilla.javascript.ObjArray;
import org.mozilla.javascript.UintMap;

import java.io.*;

/**
 * ClassFileWriter
 *
 * A ClassFileWriter is used to write a Java class file. Methods are
 * provided to create fields and methods, and within methods to write
 * Java bytecodes.
 *
 * @author Roger Lawrence
 */
public class ClassFileWriter {

    /**
     * Construct a ClassFileWriter for a class.
     *
     * @param className the name of the class to write, including
     *        full package qualification.
     * @param superClassName the name of the superclass of the class
     *        to write, including full package qualification.
     * @param sourceFileName the name of the source file to use for
     *        producing debug information, or null if debug information
     *        is not desired
     */
    public ClassFileWriter(String className, String superClassName,
                           String sourceFileName)
    {
        generatedClassName = className;
        itsConstantPool = new ConstantPool(this);
        itsThisClassIndex = itsConstantPool.addClass(className);
        itsSuperClassIndex = itsConstantPool.addClass(superClassName);
        if (sourceFileName != null)
            itsSourceFileNameIndex = itsConstantPool.addUtf8(sourceFileName);
        itsFlags = ACC_PUBLIC;
    }

    public final String getClassName()
    {
        return generatedClassName;
    }

    /**
     * Add an interface implemented by this class.
     *
     * This method may be called multiple times for classes that
     * implement multiple interfaces.
     *
     * @param interfaceName a name of an interface implemented
     *        by the class being written, including full package
     *        qualification.
     */
    public void addInterface(String interfaceName) {
        short interfaceIndex = itsConstantPool.addClass(interfaceName);
        itsInterfaces.add(new Short(interfaceIndex));
    }

    public static final short
        ACC_PUBLIC = 0x0001,
        ACC_PRIVATE = 0x0002,
        ACC_PROTECTED = 0x0004,
        ACC_STATIC = 0x0008,
        ACC_FINAL = 0x0010,
        ACC_SYNCHRONIZED = 0x0020,
        ACC_VOLATILE = 0x0040,
        ACC_TRANSIENT = 0x0080,
        ACC_NATIVE = 0x0100,
        ACC_ABSTRACT = 0x0400;

    /**
     * Set the class's flags.
     *
     * Flags must be a set of the following flags, bitwise or'd
     * together:
     *      ACC_PUBLIC
     *      ACC_PRIVATE
     *      ACC_PROTECTED
     *      ACC_FINAL
     *      ACC_ABSTRACT
     * TODO: check that this is the appropriate set
     * @param flags the set of class flags to set
     */
    public void setFlags(short flags) {
        itsFlags = flags;
    }

    static String getSlashedForm(String name)
    {
        return name.replace('.', '/');
    }

    /**
     * Convert Java class name in dot notation into
     * "Lname-with-dots-replaced-by-slashes;" form suitable for use as
     * JVM type signatures.
     */
    public static String classNameToSignature(String name)
    {
        int nameLength = name.length();
        int colonPos = 1 + nameLength;
        char[] buf = new char[colonPos + 1];
        buf[0] = 'L';
        buf[colonPos] = ';';
        name.getChars(0, nameLength, buf, 1);
        for (int i = 1; i != colonPos; ++i) {
            if (buf[i] == '.') {
                buf[i] = '/';
            }
        }
        return new String(buf, 0, colonPos + 1);
    }

    /**
     * Add a field to the class.
     *
     * @param fieldName the name of the field
     * @param type the type of the field using ...
     * @param flags the attributes of the field, such as ACC_PUBLIC, etc.
     *        bitwise or'd together
     */
    public void addField(String fieldName, String type, short flags) {
        short fieldNameIndex = itsConstantPool.addUtf8(fieldName);
        short typeIndex = itsConstantPool.addUtf8(type);
        itsFields.add(new ClassFileField(fieldNameIndex, typeIndex, flags));
    }

    /**
     * Add a field to the class.
     *
     * @param fieldName the name of the field
     * @param type the type of the field using ...
     * @param flags the attributes of the field, such as ACC_PUBLIC, etc.
     *        bitwise or'd together
     * @param value an initial integral value
     */
    public void addField(String fieldName, String type, short flags,
                         int value)
    {
        short fieldNameIndex = itsConstantPool.addUtf8(fieldName);
        short typeIndex = itsConstantPool.addUtf8(type);
        ClassFileField field = new ClassFileField(fieldNameIndex, typeIndex,
                                                  flags);
        field.setAttributes(itsConstantPool.addUtf8("ConstantValue"),
                            (short)0,
                            (short)0,
                            itsConstantPool.addConstant(value));
        itsFields.add(field);
    }

    /**
     * Add a field to the class.
     *
     * @param fieldName the name of the field
     * @param type the type of the field using ...
     * @param flags the attributes of the field, such as ACC_PUBLIC, etc.
     *        bitwise or'd together
     * @param value an initial long value
     */
    public void addField(String fieldName, String type, short flags,
                         long value)
    {
        short fieldNameIndex = itsConstantPool.addUtf8(fieldName);
        short typeIndex = itsConstantPool.addUtf8(type);
        ClassFileField field = new ClassFileField(fieldNameIndex, typeIndex,
                                                  flags);
        field.setAttributes(itsConstantPool.addUtf8("ConstantValue"),
                            (short)0,
                            (short)2,
                            itsConstantPool.addConstant(value));
        itsFields.add(field);
    }

    /**
     * Add a field to the class.
     *
     * @param fieldName the name of the field
     * @param type the type of the field using ...
     * @param flags the attributes of the field, such as ACC_PUBLIC, etc.
     *        bitwise or'd together
     * @param value an initial double value
     */
    public void addField(String fieldName, String type, short flags,
                         double value)
    {
        short fieldNameIndex = itsConstantPool.addUtf8(fieldName);
        short typeIndex = itsConstantPool.addUtf8(type);
        ClassFileField field = new ClassFileField(fieldNameIndex, typeIndex,
                                                  flags);
        field.setAttributes(itsConstantPool.addUtf8("ConstantValue"),
                            (short)0,
                            (short)2,
                            itsConstantPool.addConstant(value));
        itsFields.add(field);
    }

    /**
     * Add Information about java variable to use when generating the local
     * variable table.
     *
     * @param name variable name.
     * @param type variable type as bytecode descriptor string.
     * @param startPC the starting bytecode PC where this variable is live,
     *                 or -1 if it does not have a Java register.
     * @param register the Java register number of variable
     *                 or -1 if it does not have a Java register.
     */
    public void addVariableDescriptor(String name, String type, int startPC, int register)
    {
        int nameIndex = itsConstantPool.addUtf8(name);
        int descriptorIndex = itsConstantPool.addUtf8(type);
        int [] chunk = { nameIndex, descriptorIndex, startPC, register };
        if (itsVarDescriptors == null) {
            itsVarDescriptors = new ObjArray();
        }
        itsVarDescriptors.add(chunk);
    }

    /**
     * Add a method and begin adding code.
     *
     * This method must be called before other methods for adding code,
     * exception tables, etc. can be invoked.
     *
     * @param methodName the name of the method
     * @param type a string representing the type
     * @param flags the attributes of the field, such as ACC_PUBLIC, etc.
     *        bitwise or'd together
     */
    public void startMethod(String methodName, String type, short flags) {
        short methodNameIndex = itsConstantPool.addUtf8(methodName);
        short typeIndex = itsConstantPool.addUtf8(type);
        itsCurrentMethod = new ClassFileMethod(methodNameIndex, typeIndex,
                                               flags);
        itsMethods.add(itsCurrentMethod);
    }

    /**
     * Complete generation of the method.
     *
     * After this method is called, no more code can be added to the
     * method begun with <code>startMethod</code>.
     *
     * @param maxLocals the maximum number of local variable slots
     *        (a.k.a. Java registers) used by the method
     * @param vars the array of the variables for the method,
     *        or null if none
     */
    public void stopMethod(short maxLocals) {
        if (itsCurrentMethod == null)
            throw new IllegalStateException("No method to stop");

        fixLabelGotos();

        itsMaxLocals = maxLocals;

        int lineNumberTableLength = 0;
        if (itsLineNumberTable != null) {
            // 6 bytes for the attribute header
            // 2 bytes for the line number count
            // 4 bytes for each entry
            lineNumberTableLength = 6 + 2 + (itsLineNumberTableTop * 4);
        }

        int variableTableLength = 0;
        if (itsVarDescriptors != null) {
            // 6 bytes for the attribute header
            // 2 bytes for the variable count
            // 10 bytes for each entry
            variableTableLength = 6 + 2 + (itsVarDescriptors.size() * 10);
        }

        int attrLength = 2 +                    // attribute_name_index
                         4 +                    // attribute_length
                         2 +                    // max_stack
                         2 +                    // max_locals
                         4 +                    // code_length
                         itsCodeBufferTop +
                         2 +                    // exception_table_length
                         (itsExceptionTableTop * 8) +
                         2 +                    // attributes_count
                         lineNumberTableLength +
                         variableTableLength;

        byte[] codeAttribute = new byte[attrLength];
        int index = 0;
        int codeAttrIndex = itsConstantPool.addUtf8("Code");
        index = putInt16(codeAttrIndex, codeAttribute, index);
        attrLength -= 6;                 // discount the attribute header
        index = putInt32(attrLength, codeAttribute, index);
        index = putInt16(itsMaxStack, codeAttribute, index);
        index = putInt16(itsMaxLocals, codeAttribute, index);
        index = putInt32(itsCodeBufferTop, codeAttribute, index);
        System.arraycopy(itsCodeBuffer, 0, codeAttribute, index,
                         itsCodeBufferTop);
        index += itsCodeBufferTop;


        if (itsExceptionTableTop > 0) {
            index = putInt16(itsExceptionTableTop, codeAttribute, index);
            for (int i = 0; i < itsExceptionTableTop; i++) {
                ExceptionTableEntry ete = itsExceptionTable[i];
                short startPC = (short)getLabelPC(ete.itsStartLabel);
                short endPC = (short)getLabelPC(ete.itsEndLabel);
                short handlerPC = (short)getLabelPC(ete.itsHandlerLabel);
                short catchType = ete.itsCatchType;
                if (startPC == -1)
                    throw new IllegalStateException("start label not defined");
                if (endPC == -1)
                    throw new IllegalStateException("end label not defined");
                if (handlerPC == -1)
                    throw new IllegalStateException(
                        "handler label not defined");

                index = putInt16(startPC, codeAttribute, index);
                index = putInt16(endPC, codeAttribute, index);
                index = putInt16(handlerPC, codeAttribute, index);
                index = putInt16(catchType, codeAttribute, index);
            }
        }
        else {
            // write 0 as exception table length
            index = putInt16(0, codeAttribute, index);
        }

        int attributeCount = 0;
        if (itsLineNumberTable != null)
            attributeCount++;
        if (itsVarDescriptors != null)
            attributeCount++;
        index = putInt16(attributeCount, codeAttribute, index);