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

--                                                                          --

--                         GNAT COMPILER COMPONENTS                         --

--                                                                          --

--                             A L I . U T I L                              --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--          Copyright (C) 1992-2011, 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.  See the GNU General Public License --

-- for  more details.  You should have  received  a copy of the GNU General --

-- Public License  distributed with GNAT; see file COPYING3.  If not, go to --

-- http://www.gnu.org/licenses for a complete copy of the license.          --

--                                                                          --

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

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

--                                                                          --

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

--  This child unit provides utility data structures and procedures used

--  for manipulation of ALI data by the gnatbind and gnatmake.

package ALI.Util is

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

   -- Source File Table --

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

   --  A table entry is built for every source file that is in the source

   --  dependency table of any ALI file that is part of the current program.

   No_Source_Id : constant Source_Id := Source_Id'First;

   --  Special value indicating no Source table entry

   First_Source_Entry : constant Source_Id := No_Source_Id + 1;

   --  Id of first actual entry in table

   type Source_Record is record

      Sfile : File_Name_Type;

      --  Name of source file

      Stamp : Time_Stamp_Type;

      --  Time stamp value. If Check_Source_Files is set and the source

      --  file is located, then Stamp is set from the source file. Otherwise

      --  Stamp is set from the latest stamp value found in any of the

      --  ALI files for the current program.

      Source_Found : Boolean;

      --  This flag is set to True if the corresponding source file was

      --  located and the Stamp value was set from the actual source file.

      --  It is always false if Check_Source_Files is not set.

      All_Timestamps_Match : Boolean;

      --  This flag is set only if all files referencing this source file

      --  have a matching time stamp, and also, if Source_Found is True,

      --  then the stamp of the source file also matches. If this flag is

      --  True, then checksums for this file are never referenced. We only

      --  use checksums if there are time stamp mismatches.

      All_Checksums_Match : Boolean;

      --  This flag is set only if all files referencing this source file

      --  have checksums, and if all these checksums match. If this flag

      --  is set to True, then the binder will ignore a timestamp mismatch.

      --  An absent checksum causes this flag to be set False, and a mismatch

      --  of checksums also causes it to be set False. The checksum of the

      --  actual source file (if Source_Found is True) is included only if

      --  All_Timestamps_Match is False (since checksums are only interesting

      --  if we have time stamp mismatches, and we want to avoid computing the

      --  checksum of the source file if it is not needed.)

      Checksum : Word;

      --  If no dependency line has a checksum for this source file (i.e. the

      --  corresponding entries in the source dependency records all have the

      --  Checksum_Present flag set False), then this field is undefined. If

      --  at least one dependency entry has a checksum present, then this

      --  field contains one of the possible checksum values that has been

      --  seen. This is used to set All_Checksums_Match properly.

   end record;

   package Source is new Table.Table (

     Table_Component_Type => Source_Record,

     Table_Index_Type     => Source_Id,

     Table_Low_Bound      => First_Source_Entry,

     Table_Initial        => 1000,

     Table_Increment      => 200,

     Table_Name           => "Source");

   procedure Initialize_ALI_Source;

   --  Initialize Source table

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

   -- Subprograms for Manipulating ALI Information --

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

   procedure Read_Withed_ALIs

     (Id            : ALI_Id;

      Ignore_Errors : Boolean := False);

   --  Process an ALI file which has been read and scanned by looping through

   --  all withed units in the ALI file, checking if they have been processed.

   --  Each unit that has not yet been processed will be read, scanned, and

   --  processed recursively. If Ignore_Errors is True, then failure to read an

   --  ALI file is not reported as an error, and scanning continues with other

   --  ALI files.

   procedure Set_Source_Table (A : ALI_Id);

   --  Build source table entry corresponding to the ALI file whose id is A

   procedure Set_Source_Table;

   --  Build the entire source table

   function Time_Stamp_Mismatch

     (A         : ALI_Id;

      Read_Only : Boolean := False) return File_Name_Type;

   --  Looks in the Source_Table and checks time stamp mismatches between

   --  the sources there and the sources in the Sdep section of ali file whose

   --  id is A. If no time stamp mismatches are found No_File is returned.

   --  Otherwise return the first file for which there is a mismatch.

   --  Note that in check source files mode (Check_Source_Files = True), the

   --  time stamp in the Source_Table should be the actual time stamp of the

   --  source files. In minimal recompilation mode (Minimal_Recompilation set

   --  to True, no mismatch is found if the file's timestamp has not changed.

   --  If Read_Only is True, missing sources are not considered.

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

   -- Subprograms for manipulating checksums --

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

   Checksum_Error : constant Word := 16#FFFF_FFFF#;

   --  This value is used to indicate an error in computing the checksum.

   --  When comparing checksums for smart recompilation, the CRC_Error

   --  value is never considered to match. This could possibly result

   --  in a false negative, but that is never harmful, it just means

   --  that in unusual cases an unnecessary recompilation occurs.

   function Get_File_Checksum (Fname : File_Name_Type) return Word;

   --  Compute checksum for the given file. As far as possible, this circuit

   --  computes exactly the same value computed by the compiler, but it does

   --  not matter if it gets it wrong in marginal cases, since the only result

   --  is to miss some smart recompilation cases, correct functioning is not

   --  affected by a miscomputation. Returns Checksum_Error if the file is

   --  missing or has an error.

   function Checksums_Match (Checksum1, Checksum2 : Word) return Boolean;

   pragma Inline (Checksums_Match);

   --  Returns True if Checksum1 and Checksum2 have the same value and are

   --  not equal to Checksum_Error, returns False in all other cases. This

   --  routine must always be used to compare for checksum equality, to

   --  ensure that the case of Checksum_Error is handled properly.

end ALI.Util;