typedef int  (*PK_UCOPRD_f_t)(const int  guise,    const int  format,
                              const PK_UCHAR_t name[],
                              const PK_LOGICAL_t skiphd,
                                    int *strid);



  Open various guises of part file for reading

Receives:
  int                       guise          --- class of file:
                                           ---  FFCSNP,FFCXMT
                                           ---  FFCXMP,FFCXMD
                                           ---  snapshot,C-transmit,
                                           ---  partition,delta
  int                       format         --- format code:
                                           ---  FFBNRY,FFTEXT (binary or text)
  PK_UCHAR_t                name[]         --- key which identifies file
                                           ---  (null-terminated Unicode)
  PK_LOGICAL_t              skiphd         --- action required on opening file
                                           --- PK_LOGICAL_true:
                                           ---  skip header (the usual case) or
                                           --- PK_LOGICAL_false:
                                           ---  leave header (used by Frustrum
                                           ---                acceptance tests)

Returns:
  int                      *strid          --- id for stream on which
                                           --- file is open
Return codes:               FR_no_errors
                            FR_bad_name
                            FR_not_found
                            FR_bad_header
                            FR_open_fail


Description:
  This function opens various guises of existing part files for
  reading, i.e. C transmit, partition and deltas, and snapshot
  files, using a Unicode key.

  If the skiphd flag is set to PK_LOGICAL_true, the header data is
  skipped when the file is opened. This is the mode which is used by
  Parasolid.

  If the skiphd flag is set to PK_LOGICAL_false, the header data is not
  skipped when the file is opened; the preamble, the parts data and the
  trailer are read by subsequent calls to FFREAD. This mode is only used
  by the TESTFR to validate what has been written by a particular
  implementation.

  The routine returns a frustrum stream identifier or strid.
  This is used in subsequent calls to FFREAD and FFCLOS.