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------------------------------------------------------------------------------

--                                                                          --

--                         GNAT RUN-TIME COMPONENTS                         --

--                                                                          --

--                     S Y S T E M . D I R E C T _ I O                      --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--          Copyright (C) 1992-2009, Free Software Foundation, Inc.         --

--                                                                          --

-- GNAT is free software;  you can  redistribute it  and/or modify it under --

-- terms of the  GNU General Public License as published  by the Free Soft- --

-- ware  Foundation;  either version 3,  or (at your option) any later ver- --

-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --

-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --

-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --

--                                                                          --

-- As a special exception under Section 7 of GPL version 3, you are granted --

-- additional permissions described in the GCC Runtime Library Exception,   --

-- version 3.1, as published by the Free Software Foundation.               --

--                                                                          --

-- You should have received a copy of the GNU General Public License and    --

-- a copy of the GCC Runtime Library Exception along with this program;     --

-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --

-- <http://www.gnu.org/licenses/>.                                          --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- Extensive contributions were provided by Ada Core Technologies Inc.      --

--                                                                          --

------------------------------------------------------------------------------

--  This package contains the declaration of the control block used for

--  Direct_IO. This must be declared at the outer library level. It also

--  contains code that is shared between instances of Direct_IO.

with Interfaces.C_Streams;

with Ada.Streams;

with System.File_Control_Block;

with System.Storage_Elements;

package System.Direct_IO is

   package FCB renames System.File_Control_Block;

   type Operation is (Op_Read, Op_Write, Op_Other);

   --  Type used to record last operation (to optimize sequential operations)

   subtype Count is Interfaces.C_Streams.long;

   --  The Count type in each instantiation is derived from this type

   subtype Positive_Count is Count range 1 .. Count'Last;

   type Direct_AFCB is new FCB.AFCB with record

      Index : Count := 1;

      --  Current Index value

      Bytes : Interfaces.C_Streams.size_t;

      --  Length of item in bytes (set from inside generic template)

      Last_Op : Operation := Op_Other;

      --  Last operation performed on file, used to avoid unnecessary

      --  repositioning between successive read or write operations.

   end record;

   function AFCB_Allocate (Control_Block : Direct_AFCB) return FCB.AFCB_Ptr;

   procedure AFCB_Close (File : not null access Direct_AFCB);

   procedure AFCB_Free  (File : not null access Direct_AFCB);

   procedure Read

     (File : in out Direct_AFCB;

      Item : out Ada.Streams.Stream_Element_Array;

      Last : out Ada.Streams.Stream_Element_Offset);

   --  Required overriding of Read, not actually used for Direct_IO

   procedure Write

     (File : in out Direct_AFCB;

      Item : Ada.Streams.Stream_Element_Array);

   --  Required overriding of Write, not actually used for Direct_IO

   type File_Type is access all Direct_AFCB;

   --  File_Type in individual instantiations is derived from this type

   procedure Create

     (File : in out File_Type;

      Mode : FCB.File_Mode := FCB.Inout_File;

      Name : String := "";

      Form : String := "");

   function End_Of_File (File : File_Type) return Boolean;

   function Index (File : File_Type) return Positive_Count;

   procedure Open

     (File : in out File_Type;

      Mode : FCB.File_Mode;

      Name : String;

      Form : String := "");

   procedure Read

     (File : File_Type;

      Item : System.Address;

      Size : Interfaces.C_Streams.size_t;

      From : Positive_Count);

   procedure Read

     (File : File_Type;

      Item : System.Address;

      Size : Interfaces.C_Streams.size_t);

   procedure Reset (File : in out File_Type; Mode : FCB.File_Mode);

   procedure Reset (File : in out File_Type);

   procedure Set_Index (File : File_Type; To : Positive_Count);

   function Size (File : File_Type) return Count;

   procedure Write

     (File   : File_Type;

      Item   : System.Address;

      Size   : Interfaces.C_Streams.size_t;

      Zeroes : System.Storage_Elements.Storage_Array);

   --  Note: Zeroes is the buffer of zeroes used to fill out partial records

   --  The following procedures have a File_Type formal of mode IN OUT because

   --  they may close the original file. The Close operation may raise an

   --  exception, but in that case we want any assignment to the formal to

   --  be effective anyway, so it must be passed by reference (or the caller

   --  will be left with a dangling pointer).

   pragma Export_Procedure

     (Internal        => Reset,

      External        => "",

      Parameter_Types => (File_Type),

      Mechanism       => Reference);

   pragma Export_Procedure

     (Internal        => Reset,

      External        => "",

      Parameter_Types => (File_Type, FCB.File_Mode),

      Mechanism       => (File => Reference));

end System.Direct_IO;