/*

 * 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.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun in the LICENSE file that accompanied this code.

 *

 * 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.

 */

/*

 * The Original Code is HAT. The Initial Developer of the

 * Original Code is Bill Foote, with contributions from others

 */

package com.sun.tools.hat.internal.model;

import java.io.IOException;

import com.sun.tools.hat.internal.parser.ReadBuffer;

/*

 * Base class for lazily read Java heap objects.

 */

public abstract class JavaLazyReadObject extends JavaHeapObject {

    // file offset from which this object data starts

    private final long offset;

    protected JavaLazyReadObject(long offset) {

        this.offset = offset;

    }

    public final int getSize() {

        return getValueLength() + getClazz().getMinimumObjectSize();

    }

    protected final long getOffset() {

        return offset;

    }

    // return the length of the data for this object

    protected final int getValueLength() {

        try {

            return readValueLength();

        } catch (IOException exp) {

            System.err.println("lazy read failed at offset " + offset);

            exp.printStackTrace();

            return 0;

        }

    }

    // get this object's content as byte array

    protected final byte[] getValue() {

        try {

            return readValue();

        } catch (IOException exp) {

            System.err.println("lazy read failed at offset " + offset);

            exp.printStackTrace();

            return Snapshot.EMPTY_BYTE_ARRAY;

        }

    }

    // get ID of this object

    public final long getId() {

        try {

            ReadBuffer buf = getClazz().getReadBuffer();

            int idSize = getClazz().getIdentifierSize();

            if (idSize == 4) {

                return ((long)buf.getInt(offset)) & Snapshot.SMALL_ID_MASK;

            } else {

                return buf.getLong(offset);

            }

        } catch (IOException exp) {

            System.err.println("lazy read failed at offset " + offset);

            exp.printStackTrace();

            return -1;

        }

    }

    protected abstract int readValueLength() throws IOException;

    protected abstract byte[] readValue() throws IOException;

    // make Integer or Long for given object ID

    protected static Number makeId(long id) {

        if ((id & ~Snapshot.SMALL_ID_MASK) == 0) {

            return new Integer((int)id);

        } else {

            return new Long(id);

        }

    }

    // get ID as long value from Number

    protected static long getIdValue(Number num) {

        long id = num.longValue();

        if (num instanceof Integer) {

            id &= Snapshot.SMALL_ID_MASK;

        }

        return id;

    }

    // read object ID from given index from given byte array

    protected final long objectIdAt(int index, byte[] data) {

        int idSize = getClazz().getIdentifierSize();

        if (idSize == 4) {

            return ((long)intAt(index, data)) & Snapshot.SMALL_ID_MASK;

        } else {

            return longAt(index, data);

        }

    }

    // utility methods to read primitive types from byte array

    protected static byte byteAt(int index, byte[] value) {

        return value[index];

    }

    protected static boolean booleanAt(int index, byte[] value) {

        return (value[index] & 0xff) == 0? false: true;

    }

    protected static char charAt(int index, byte[] value) {

        int b1 = ((int) value[index++] & 0xff);

        int b2 = ((int) value[index++] & 0xff);

        return (char) ((b1 << 8) + b2);

    }

    protected static short shortAt(int index, byte[] value) {

        int b1 = ((int) value[index++] & 0xff);

        int b2 = ((int) value[index++] & 0xff);

        return (short) ((b1 << 8) + b2);

    }

    protected static int intAt(int index, byte[] value) {

        int b1 = ((int) value[index++] & 0xff);

        int b2 = ((int) value[index++] & 0xff);

        int b3 = ((int) value[index++] & 0xff);

        int b4 = ((int) value[index++] & 0xff);

        return ((b1 << 24) + (b2 << 16) + (b3 << 8) + b4);

    }

    protected static long longAt(int index, byte[] value) {

        long val = 0;

        for (int j = 0; j < 8; j++) {

            val = val << 8;

            int b = ((int)value[index++]) & 0xff;

            val |= b;

        }

        return val;

    }

    protected static float floatAt(int index, byte[] value) {

        int val = intAt(index, value);

        return Float.intBitsToFloat(val);

    }

    protected static double doubleAt(int index, byte[] value) {

        long val = longAt(index, value);

        return Double.longBitsToDouble(val);

    }

}