gcc/m2/gm2-libs-iso/SeqFile.def

   1 (* Library module defined by the International Standard
   2    Information technology - programming languages
   3    BS ISO/IEC 10514-1:1996E Part 1: Modula-2, Base Language.
   4
   5    Copyright ISO/IEC (International Organization for Standardization
   6    and International Electrotechnical Commission) 1996-2021.
   7
   8    It may be freely copied for the purpose of implementation (see page
   9    707 of the Information technology - Programming languages Part 1:
  10    Modula-2, Base Language.  BS ISO/IEC 10514-1:1996).  *)
  11
  12 DEFINITION MODULE SeqFile;
  13
  14   (* Rewindable sequential files *)
  15
  16 IMPORT IOChan, ChanConsts;
  17
  18 TYPE
  19   ChanId = IOChan.ChanId;
  20   FlagSet = ChanConsts.FlagSet;
  21   OpenResults = ChanConsts.OpenResults;
  22
  23   (* Accepted singleton values of FlagSet *)
  24
  25 CONST
  26   (* input operations are requested/available *)
  27   read = FlagSet{ChanConsts.readFlag};
  28
  29   (* output operations are requested/available *)
  30   write = FlagSet{ChanConsts.writeFlag};
  31
  32   (* a file may/must/did exist before the channel is opened *)
  33   old = FlagSet{ChanConsts.oldFlag};
  34
  35   (* text operations are requested/available *)
  36   text = FlagSet{ChanConsts.textFlag};
  37
  38   (* raw operations are requested/available *)
  39   raw = FlagSet{ChanConsts.rawFlag};
  40
  41 PROCEDURE OpenWrite (VAR cid: ChanId; name: ARRAY OF CHAR;
  42                      flags: FlagSet; VAR res: OpenResults);
  43   (*
  44      Attempts to obtain and open a channel connected to a stored
  45      rewindable file of the given name.
  46      The write flag is implied; without the raw flag, text is
  47      implied.  If successful, assigns to cid the identity of
  48      the opened channel, assigns the value opened to res, and
  49      selects output mode, with the write position at the start
  50      of the file (i.e. the file is of zero length).
  51      If a channel cannot be opened as required, the value of
  52      res indicates the reason, and cid identifies the invalid
  53      channel.
  54   *)
  55
  56 PROCEDURE OpenAppend (VAR cid: ChanId; name: ARRAY OF CHAR;
  57                       flags: FlagSet; VAR res: OpenResults);
  58   (*
  59      Attempts to obtain and open a channel connected to a stored
  60      rewindable file of the given name.  The write and old flags
  61      are implied; without the raw flag, text is implied.  If
  62      successful, assigns to cid the identity of the opened channel,
  63      assigns the value opened to res, and selects output mode,
  64      with the write position corresponding to the length of the
  65      file.  If a channel cannot be opened as required, the value
  66      of res indicates the reason, and cid identifies the invalid
  67      channel.
  68   *)
  69
  70 PROCEDURE OpenRead (VAR cid: ChanId; name: ARRAY OF CHAR;
  71                     flags: FlagSet; VAR res: OpenResults);
  72   (* Attempts to obtain and open a channel connected to a stored
  73      rewindable file of the given name.
  74      The read and old flags are implied; without the raw flag,
  75      text is implied.  If successful, assigns to cid the
  76      identity of the opened channel, assigns the value opened to
  77      res, and selects input mode, with the read position
  78      corresponding to the start of the file.
  79      If a channel cannot be opened as required, the value of
  80      res indicates the reason, and cid identifies the invalid
  81      channel.
  82   *)
  83
  84 PROCEDURE IsSeqFile (cid: ChanId): BOOLEAN;
  85   (* Tests if the channel identified by cid is open to a
  86      rewindable sequential file. *)
  87
  88 PROCEDURE Reread (cid: ChanId);
  89   (* If the channel identified by cid is not open to a rewindable
  90      sequential file, the exception wrongDevice is raised;
  91      otherwise attempts to set the read position to the
  92      start of the file, and to select input mode.
  93      If the operation cannot be performed (perhaps because of
  94      insufficient permissions) neither input mode nor output
  95      mode is selected.
  96   *)
  97
  98 PROCEDURE Rewrite (cid: ChanId);
  99   (* If the channel identified by cid is not open to a
 100      rewindable sequential file, the exception wrongDevice is
 101      raised; otherwise, attempts to truncate the file to zero
 102      length, and to select output mode.  If the operation
 103      cannot be performed (perhaps because of insufficient
 104      permissions) neither input mode nor output mode is selected.
 105   *)
 106
 107 PROCEDURE Close (VAR cid: ChanId);
 108   (* If the channel identified by cid is not open to a rewindable
 109      sequential file, the exception wrongDevice is raised;
 110      otherwise closes the channel, and assigns the value
 111      identifying the invalid channel to cid.
 112   *)
 113
 114 END SeqFile.
 115