/*

 * Copyright 2005 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package ilib;

class ClassReaderWriter implements RuntimeConstants {

    int codeAttributeIndex;

    int lineNumberAttributeIndex;

    int localVarAttributeIndex;

    private final byte[] orig;

    private final byte[] gen;

    private final int sectionLength;

    private static final int GROWTH_FACTOR = 2;

    private static final int SECTIONS = 2;

    private static final String codeAttributeName = "Code";

    private static final String lineNumberAttributeName = "LineNumberTable";

    private static final String localVarAttributeName = "LocalVariableTable";

    private int[] genSectionPos = new int[SECTIONS];

    private int inputPos = 0;

    private int genPos = 0;

    private int markPos = 0;

    private int currentSection = 0;

    private String[] constantPool;

    ClassReaderWriter(byte[] orig) {

        this.orig = orig;

        sectionLength = orig.length * GROWTH_FACTOR;

        gen = new byte[sectionLength * SECTIONS];

        for (int section = 0; section < SECTIONS; ++section) {

            genSectionPos[section] = section * sectionLength;

        }

    }

    int setSection(int section) {

        int prevSection = currentSection;

        genSectionPos[prevSection] = genPos;

        genPos = genSectionPos[section];

        currentSection = section;

        return prevSection;

    }

    byte[] result() {

        int section;

        int totalLength = 0;

        setSection(0); // save current section

        for (section = 0; section < SECTIONS; ++section) {

            int sectionStart = section * sectionLength;

            int sectionGenLength = genSectionPos[section] - sectionStart;

            totalLength += sectionGenLength;

        }

        byte[] newcf = new byte[totalLength];

        int written = 0;

        for (section = 0; section < SECTIONS; ++section) {

            int sectionStart = section * sectionLength;

            int sectionGenLength = genSectionPos[section] - sectionStart;

            System.arraycopy(gen, sectionStart, newcf, written, sectionGenLength);

            written += sectionGenLength;

        }

        return newcf;

    }

    int readU1() {

        return ((int)orig[inputPos++]) & 0xFF;

    }

    int readU2() {

        int res = readU1();

        return (res << 8) + readU1();

    }

    short readS2() {

        int res = readU1();

        return (short)((res << 8) + readU1());

    }

    int readU4() {

        int res = readU2();

        return (res << 16) + readU2();

    }

    void writeU1(int val) {

        gen[genPos++] = (byte)val;

    }

    void writeU2(int val) {

        writeU1(val >> 8);

        writeU1(val & 0xFF);

    }

    void writeU4(int val) {

        writeU2(val >> 16);

        writeU2(val & 0xFFFF);

    }

    int copyU1() {

        int value = readU1();

        writeU1(value);

        return value;

    }

    int copyU2() {

        int value = readU2();

        writeU2(value);

        return value;

    }

    int copyU4() {

        int value = readU4();

        writeU4(value);

        return value;

    }

    void copy(int count) {

        for (int i = 0; i < count; ++i) {

            gen[genPos++] = orig[inputPos++];

        }

    }

    void skip(int count) {

        inputPos += count;

    }

    byte[] readBytes(int count) {

        byte[] bytes = new byte[count];

        for (int i = 0; i < count; ++i) {

            bytes[i] = orig[inputPos++];

        }

        return bytes;

    }

    void writeBytes(byte[] bytes) {

        for (int i = 0; i < bytes.length; ++i) {

            gen[genPos++] = bytes[i];

        }

    }

    byte[] inputBytes() {

        return orig;

    }

    int inputPosition() {

        return inputPos;

    }

    void setInputPosition(int pos) {

        inputPos = pos;

    }

    void markLocalPositionStart() {

        markPos = inputPos;

    }

    int localPosition() {

        return inputPos - markPos;

    }

    void rewind() {

        setInputPosition(markPos);

    }

    int generatedPosition() {

        return genPos;

    }

    void randomAccessWriteU2(int pos, int val) {

        int savePos = genPos;

        genPos = pos;

        writeU2(val);

        genPos = savePos;

    }

    void randomAccessWriteU4(int pos, int val) {

        int savePos = genPos;

        genPos = pos;

        writeU4(val);

        genPos = savePos;

    }

    String constantPoolString(int index) {

        return constantPool[index];

    }

    void copyConstantPool(int constantPoolCount){

        // copy const pool

        constantPool = new String[constantPoolCount];

        // index zero not in class file

        for (int i = 1; i < constantPoolCount; ++i) {

            int tag = readU1();

            writeU1(tag);

            switch (tag) {

                case CONSTANT_CLASS:

                case CONSTANT_STRING:

                    copy(2);

                    break;

                case CONSTANT_FIELD:

                case CONSTANT_METHOD:

                case CONSTANT_INTERFACEMETHOD:

                case CONSTANT_INTEGER:

                case CONSTANT_FLOAT:

                case CONSTANT_NAMEANDTYPE:

                    copy(4);

                    break;

                case CONSTANT_LONG:

                case CONSTANT_DOUBLE:

                    copy(8);

                    ++i;  // these take two CP entries - duh!

                    break;

                case CONSTANT_UTF8:

                    int len = copyU2();

                    byte[] utf8 = readBytes(len);

                    String str = null; // null to shut the compiler up

                    try {

                        str = new String(utf8, "UTF-8");

                    } catch (Exception exc) {

                        throw new Error("CP exception: " + exc);

                    }

                    constantPool[i] = str;

                    if (str.equals(codeAttributeName)) {

                        codeAttributeIndex = i;

                    } else if (str.equals(lineNumberAttributeName)) {

                        lineNumberAttributeIndex = i;

                    } else if (str.equals(localVarAttributeName)) {

                        localVarAttributeIndex = i;

                    }

                    writeBytes(utf8);

                    break;

                default:

                    throw new Error(i + " unexpected CP tag: " + tag);

            }

        }

    }

}