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  CLASS: VolumeInfo     --DVM
  PUBLIC METHODS:
    VolumeInfo()   - Default constructor:
                   sid=0;name="";num,
                   fileDataStart=257;
                   erased,unerased=empty 
 
  USAGE NOTES:
   This is normally for inspection only.
  
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  METHOD:  Archive::getVolumeInfo
       
     Return volume information to the archive user.
 
  ARGS:
     sid_t sid,            IN    surface id of volume
     UINT16 *nvols         OUT   # volumes. > 0 if is or has been root.
     char *vsname          OUT   volume set name (132 bytes)
     char *vname           OUT   volume name (32 bytes)
     UINT16 *vid           OUT   ordinal volume number - 0,1,2,...
     ExtentList *unerased  OUT   unerased space information
     ExtentList *erased    OUT   erased space information
     UINT32 *dataStart     OUT   where file data starts (end of fsd seq + 1)
 
  RETURNS:
     Returns True if volume has a UDF label; otherwise, returns False.
  
  PRE-CONDS:
  
  POST-CONDS:
  
  ERRORS:
  
  NOTES:
   This temporarily changes the mediaType and sectorSize states of
   the Archive object, but then changes them back to what they were.
 
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