File : s-valint.adb

------------------------------------------------------------------------------
--                                                                          --
--                         GNAT COMPILER COMPONENTS                         --
--                                                                          --
--                       S Y S T E M . V A L _ I N T                        --
--                                                                          --
--                                 B o d y                                  --
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--                            $Revision: 1.9 $                              --
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--   Copyright (C) 1992,1993,1994,1995,1996 Free Software Foundation, Inc.  --
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------------------------------------------------------------------------------

with System.Unsigned_Types; use System.Unsigned_Types;
with System.Val_Uns;        use System.Val_Uns;
with System.Val_Util;       use System.Val_Util;

package body System.Val_Int is

   ------------------
   -- Scan_Integer --
   ------------------

   function Scan_Integer
     (Str  : String;
      Ptr  : access Integer;
      Max  : Integer)
      return Integer
   is
      Uval : Unsigned;
      --  Unsigned result

      Minus : Boolean := False;
      --  Set to True if minus sign is present, otherwise to False

      Start : Positive;
      --  Saves location of first non-blank (not used in this case)

   begin
      Scan_Sign (Str, Ptr, Max, Minus, Start);
      Uval := Scan_Unsigned (Str, Ptr, Max);

      --  Deal with overflow cases, and also with maximum negative number

      if Uval > Unsigned (Integer'Last) then
         if Minus and then Uval = Unsigned (-(Integer'First)) then
            return Integer'First;
         else
            raise Constraint_Error;
         end if;

      --  Negative values

      elsif Minus then
         return -(Integer (Uval));

      --  Positive values

      else
         return Integer (Uval);
      end if;

   end Scan_Integer;

   -------------------
   -- Value_Integer --
   -------------------

   function Value_Integer (Str : String) return Integer is
      V : Integer;
      P : aliased Integer := Str'First;

   begin
      V := Scan_Integer (Str, P'Access, Str'Last);
      Scan_Trailing_Blanks (Str, P);
      return V;
   end Value_Integer;

end System.Val_Int;