1 ------------------------------------------------------------------------------
   2 ------------------------------------------------------------------------------
   3 -- This file is part of 'Cryostat', an Ada library for persistent storage.  --
   4 --                                                                          --
   5 -- (C) 2020 Stanislav Datskovskiy ( www.loper-os.org )                      --
   6 -- http://wot.deedbot.org/17215D118B7239507FAFED98B98228A001ABFFC7.html     --
   7 --                                                                          --
   8 -- You do not have, nor can you ever acquire the right to use, copy or      --
   9 -- distribute this software ; Should you use this software for any purpose, --
  10 -- or copy and distribute it to anyone or in any manner, you are breaking   --
  11 -- the laws of whatever soi-disant jurisdiction, and you promise to         --
  12 -- continue doing so for the indefinite future. In any case, please         --
  13 -- always : read and understand any software ; verify any PGP signatures    --
  14 -- that you use - for any purpose.                                          --
  15 ------------------------------------------------------------------------------
  16 ------------------------------------------------------------------------------
  17 
  18 with System;
  19 with Unix;   use Unix;
  20 with PMaps;  use PMaps;
  21 
  22 
  23 generic
  24    
  25    -- The type of the item that will live in the Cryostat :
  26    type Form is limited private;
  27    
  28    -- The path of the backing file :
  29    Path     : in String;
  30    
  31    -- Whether the contents of the Cryostat will be writable :
  32    Writable : in Boolean;
  33    
  34    -- Whether the backing file is to be created if it does not already exist :
  35    Create   : in Boolean;
  36 
  37 package Cryostat is
  38    
  39    pragma Preelaborate;
  40    
  41    -- The concrete datum of type Form that will live in the Cryostat :
  42    Item : Form;
  43    
  44    -- Test if the Cryostat is usable
  45    function IsReady return Boolean;
  46    
  47    -- If the Cryostat is writable, sync it to disk immediately
  48    procedure Sync;
  49    
  50    -- Zero the entire mapped space of the Cryostat
  51    procedure Zap;
  52    
  53    -- Close the Cryostat and mark it unusable.
  54    -- Normally, this is unnecessary (Finalize will do it)
  55    procedure Stop;
  56    
  57 private
  58    
  59    -- The actual number of bytes occupied by an instance of the Form type :
  60    Footprint : constant Word := Form'Size / System.Storage_Unit;
  61    
  62    -- Instantiate a memory map using the given params :
  63    Map : PMap(Handle => OpenMapFile(Path     => Path,
  64                                     Writable => Writable,
  65                                     Create   => Create),
  66               Length   => Footprint,
  67               Offset   => 0, -- Offsetted maps not supported yet!
  68               Create   => Create,
  69               Writable => Writable);
  70    
  71    -- Force Item to reside at the obtained address :
  72    for Item'Address use GetAddress(Map);
  73    
  74 end Cryostat;