added exception for an overflow in getPositionInfo

(CASTOR way was just to fill everything with 0)

Drive/Drive.hh

@@ -166,7 +166,7 @@ namespace Tape {
      */
     virtual void positionToLogicalObject (uint32_t blockId) throw (Exception) {
       SCSI::Structures::locate10CDB_t cdb;
-      uint32_t blkId = ntohl(blockId);
+      uint32_t blkId = SCSI::Structures::fromLtoB32(blockId);
       
       memcpy (cdb.logicalObjectID, &blkId, sizeof(cdb.logicalObjectID));
             
@@ -220,10 +220,13 @@ namespace Tape {
         posInfo.dirtyObjectsCount = SCSI::Structures::toU32(positionData.blocksInBuffer);
         posInfo.dirtyBytesCount   = SCSI::Structures::toU32(positionData.bytesInBuffer);          
       } else {
-        posInfo.currentPosition   = 0;
-        posInfo.oldestDirtyObject = 0;
-        posInfo.dirtyObjectsCount = 0;
-        posInfo.dirtyBytesCount   = 0;    
+        /* An overflow has occurred in at least one of the returned position
+         * data fields. The application should use the LONG FORM to obtain the 
+         * current position or the application should use the EXTENDED FORM to
+         * obtain the current position and number of bytes in the object buffer.
+         * (note) For T10000 we have only SHORT FORM.
+         */
+        throw Tape::Exception(std::string("An overflow has occurred in getPostitionInfo"));
       }
       return posInfo;
     }

SCSI/Structures.hh

@@ -133,6 +133,17 @@ namespace SCSI {
       return (int32_t)(ntohl (*((uint32_t *) t)));
     }
     
+    /**
+     * Helper function to convert from little-endian to big-endian.
+     * @param t a 32 bit number in the little-endian form
+     * @return  a 32 bit number in the big-endian form
+     */
+    inline uint32_t fromLtoB32(uint32_t t)
+    {
+      /* Like network, SCSI is BigEndian */
+      return htonl(t);
+    }
+    
     /**
      * Helper function to deal with endianness.
      * @param t byte array in SCSI order representing a 16 bits number