package org.jscsi.target.scsi.modeSense;

 import org.jscsi.target.scsi.ISerializable;

 /**

  * Instances {@link ModeParameterHeader} are part of {@link ModeParameterList} objects and specify the layout and length

  * of the following non-header fields.

  * 

  * @author Andreas Ergenzinger

  */

 public abstract class ModeParameterHeader implements ISerializable {

     /**

      * When using the MODE SENSE command, the MODE DATA LENGTH field indicates the length in bytes of the following data

      * that is available to be transferred. The mode data length does not include the number of bytes in the MODE DATA

      * LENGTH field.

      * <p>

      * When using the MODE SELECT command, this field is reserved.

      * <p>

      * Logical units that support more than 256 bytes of block descriptors and mode pages may need to implement ten-byte

      * mode commands. The mode data length field in the six-byte CDB header limits the returned data to 256 bytes.

      */

     protected final int modeDataLength;

     /**

      * The contents of the MEDIUM TYPE field are unique for each device type. For direct-access block devices, the value

      * must be 0x00.

      */

     protected final byte mediumType = (byte) 0x00;

     /**

      * The DEVICE-SPECIFIC PARAMETER field is unique for each device type. For direct-access block devices the byte

      * looks like this:

      * <p>

      * <code>

      * +---+---+---+---+---+---+---+---+---+<br/>

      * |bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |<br/>

      * +---+---+---+---+---+---+---+---+---+<br/>

      * |___|WP_|RESERV-|DPO|___RESERVED____|<br/>

      * |___|___|__ED___|FUA|_______________|<br/>

      * +---+---+---+---+---+---+---+---+---+

      * </code>

      * <p>

      * When used with the MODE SELECT command, the write protect (WP) bit is not defined. When used with the MODE SENSE

      * command, a WP bit set to one indicates that the medium is write-protected. A WP bit set to zero indicates that

      * the medium is not write-protected. When the software write protect (SWP) bit in the Control mode page (see SPC-4)

      * is set to one, the WP bit shall be set to one.

      * <p>

      * When the SWP bit in the Control mode page is set to zero, the WP bit shall be set to one if the medium is

      * write-protected (e.g., due to mechanisms outside the scope of this standard) or zero if the medium is not

      * write-protected.

      * <p>

      * When used with the MODE SELECT command, the DPOFUA bit is reserved. When used with the MODE SENSE command, a

      * DPOFUA bit set to zero indicates that the device server does not support the DPO and FUA bits. When used with the

      * MODE SENSE command, a DPOFUA bit set to one indicates that the device server supports the DPO and FUA bits.

      * <p>

      * So, the simulated logical unit of the jSCSI Target must always use a value of 0x00.

      */

     protected final byte deviceSpecificParameter = (byte) 0x00;

     /**

      * The BLOCK DESCRIPTOR LENGTH field contains the length in bytes of all the block descriptors. It is equal to the

      * number of block descriptors times eight if the LONGLBA bit is set to zero or times sixteen if the LONGLBA bit is

      * set to one, and does not include mode pages or vendor specific parameters (e.g., page code set to zero), if any,

      * that may follow the last block descriptor. A block descriptor length of zero indicates that no block descriptors

      * are included in the mode parameter list. This condition shall not be considered an error.

      */

     protected final int blockDescriptorLength;

     /**

      * The abstract constructor.

      * 

      * @param modeDataLength the length in bytes of all MODE DATA list elements

      * @param blockDescriptorLength the length in bytes of all BLOCK DESCRIPTOR list elements

      */

     public ModeParameterHeader (final int modeDataLength, final int blockDescriptorLength) {

         this.modeDataLength = modeDataLength;

         this.blockDescriptorLength = blockDescriptorLength;

     }

 }