1 package org.jscsi.target.scsi.cdb;
2
3
4 import java.nio.ByteBuffer;
5
6 import org.jscsi.target.util.ReadWrite;
7
8
9 /**
10 * This class represents Command Descriptor Blocks for the <code>READ (6)
11 * </code> SCSI command.
12 * <p>
13 * The READ (6) command requests that the device server read the specified logical block(s) and transfer them to the
14 * data-in buffer. Each logical block read includes user data and, if the medium is formatted with protection
15 * information enabled, protection information. Each logical block transferred includes user data but does not include
16 * protection information.
17 * <p>
18 * Although the READ (6) command is limited to addressing up to 2,097,151 logical blocks, this command has been
19 * maintained as mandatory since some system initialization routines require that the READ (6) command be used. System
20 * initialization routines should migrate from the READ (6) command to the READ (10) command, which is capable of
21 * addressing 4,294,947,295 logical blocks, or the READ (16) command, which is capable of addressing
22 * 18,446,744,073,709,551,615 logical blocks.
23 *
24 * @author Andreas Ergenzinger
25 */
26 public class Read6Cdb extends ReadCdb {
27
28 public Read6Cdb (ByteBuffer buffer) {
29 super(buffer);
30 }
31
32 @Override
33 protected long deserializeLogicalBlockAddress (ByteBuffer buffer) {
34 // the first three bits of byte 1 are reserved i.e. must be 0
35 // check that
36 final byte b = buffer.get(1);
37 if (((b >> 5) & 7) != 0) addIllegalFieldPointer(1);
38
39 // read the field's value
40 return ((b & 31) << 16) | ReadWrite.readTwoByteInt(buffer, 2);
41 }
42
43 @Override
44 protected int deserializeTransferLength (ByteBuffer buffer) {
45 /*
46 * A TRANSFER LENGTH field set to zero specifies that 256 logical blocks shall be read. Any other value
47 * specifies the number of logical blocks that shall be read.
48 */
49 final int value = ReadWrite.readOneByteInt(buffer, 4);
50 if (value == 0) return 256;
51 return value;
52 }
53
54 @Override
55 protected int getLogicalBlockAddressFieldIndex () {
56 return 1;
57 }
58
59 @Override
60 protected int getTransferLengthFieldIndex () {
61 return 4;
62 }
63
64 }