package org.jscsi.target.scsi.modeSense;

 import java.nio.ByteBuffer;

 import org.jscsi.target.scsi.ISerializable;

 import org.jscsi.target.util.BitManip;

 /**

  * MODE PAGEs are sent in response to successful <code>MODE SENSE</code> SCSI commands. There are two different,

  * command-specific formats for MODE PAGEs - the PAGE_0 FORMAT and the SUB-PAGE FORMAT, represented by the non-abstract

  * children of this class, {@link Page_0FormatModePage} and {@link SubPageFormatModePage}, respectively.

  * 

  * @author Andreas Ergenzinger

  */

 public abstract class ModePage implements ISerializable {

     /**

      * This value plus {@link #pageLength} equals the length in bytes of a MODE PAGE using the SUB-PAGE FORMAT.

      */

     private static final int SUB_PAGE_FORMAT_PAGE_LENGTH_MODIFIER = 4;

     /**

      * This value plus {@link #pageLength} equals the length in bytes of a MODE PAGE using the PAGE_0 FORMAT.

      */

     private static final int PAGE_0_FORMAT_PAGE_LENGTH_MODIFIER = 2;

     /**

      * When using the MODE SENSE command, a parameters saveable (PS) bit set to one indicates that the mode page may be

      * saved by the logical unit in a nonvolatile, vendor specific location. A PS bit set to zero indicates that the

      * device server is not able to save the supporte parameters. When using the MODE SELECT command, the PS bit is

      * reserved.

      */

     private final boolean parametersSaveable;

     /**

      * A SubPage Format (SPF) bit set to <code>false</code>/zero indicates that the page_0 mode page format is being

      * used. A SPF bit set to <code>true</code>/one indicates that the sub_page mode page format is being used.

      */

     private final boolean subPageFormat;

     /**

      * Specifies what kind of information is contained in the MODE PAGE.

      */

     private final int pageCode;

     /**

      * The number of bytes following the PAGE LENGTH field.

      */

     protected final int pageLength;

     /**

      * This value plus {@link #pageLength} equals the length in bytes of the MODE PAGE.

      */

     private final int pageLengthModifier;

     /**

      * The abstract constructor.

      * 

      * @param parametersSaveable value of the PARAMETERS SAVEABLE bit

      * @param subPageFormat <code>true</code> if and only if the SUB-PAGE FORMAT is to be used

      * @param pageCode specifies the kind of information is contained in the MODE PAGE

      * @param pageLength the value of the PAGE LENGTH field

      */

     public ModePage (final boolean parametersSaveable, final boolean subPageFormat, final int pageCode, final int pageLength) {

         this.parametersSaveable = parametersSaveable;

         this.subPageFormat = subPageFormat;

         if (subPageFormat)

             pageLengthModifier = SUB_PAGE_FORMAT_PAGE_LENGTH_MODIFIER;

         else

             pageLengthModifier = PAGE_0_FORMAT_PAGE_LENGTH_MODIFIER;

         this.pageCode = pageCode;

         this.pageLength = pageLength;

     }

     public final void serialize (final ByteBuffer byteBuffer, final int index) {

         // serialize first byte

         // (for convenience reasons from least significant to most significant

         // field)

         byte b = (byte) pageCode;// PAGE CODE

         b = BitManip.getByteWithBitSet(b, 6, subPageFormat);// SPF

         b = BitManip.getByteWithBitSet(b, 7, parametersSaveable);// PS

         byteBuffer.position(index);

         byteBuffer.put(b);

         // serialize remaining fields

         serializeSubPageCode(byteBuffer, index);

         serializePageLength(byteBuffer, index);

         serializeModeParameters(byteBuffer, index);

     }

     /**

      * This method serializes the SUBPAGE CODE field, if the mode page format says this field exists (only for the

      * sub_page mode page format).

      * 

      * @param buffer where to insert the serialized object representation

      * @param index the position of the first byte of the serialized object in the {@link ByteBuffer}

      */

     protected abstract void serializeSubPageCode (final ByteBuffer buffer, final int index);

     /**

      * Serializes the PAGE LENGTH field.

      * 

      * @param buffer where to insert the serialized object representation

      * @param index the position of the first byte of the serialized object in the {@link ByteBuffer}

      */

     protected abstract void serializePageLength (final ByteBuffer buffer, final int index);

     /**

      * @param buffer where to insert the serialized object representation

      * @param index the position of the first byte of the serialized object in the {@link ByteBuffer}

      */

     protected abstract void serializeModeParameters (final ByteBuffer buffer, final int index);

     public final int size () {

         return pageLength + pageLengthModifier;

     }

 }