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

--                                                                          --

--                         GNAT COMPILER COMPONENTS                         --

--                                                                          --

--                       S Y S T E M . V A L _ U N S                        --

--                                                                          --

--                                 B o d y                                  --

--                                                                          --

--          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.      --

--                                                                          --

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

with System.Unsigned_Types; use System.Unsigned_Types;

with System.Val_Util;       use System.Val_Util;

package body System.Val_Uns is

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

   -- Scan_Raw_Unsigned --

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

   function Scan_Raw_Unsigned

     (Str : String;

      Ptr : not null access Integer;

      Max : Integer) return Unsigned

   is

      P : Integer;

      --  Local copy of the pointer

      Uval : Unsigned;

      --  Accumulated unsigned integer result

      Expon : Integer;

      --  Exponent value

      Overflow : Boolean := False;

      --  Set True if overflow is detected at any point

      Base_Char : Character;

      --  Base character (# or :) in based case

      Base : Unsigned := 10;

      --  Base value (reset in based case)

      Digit : Unsigned;

      --  Digit value

   begin

      P := Ptr.all;

      Uval := Character'Pos (Str (P)) - Character'Pos ('0');

      P := P + 1;

      --  Scan out digits of what is either the number or the base.

      --  In either case, we are definitely scanning out in base 10.

      declare

         Umax : constant := (Unsigned'Last - 9) / 10;

         --  Max value which cannot overflow on accumulating next digit

         Umax10 : constant := Unsigned'Last / 10;

         --  Numbers bigger than Umax10 overflow if multiplied by 10

      begin

         --  Loop through decimal digits

         loop

            exit when P > Max;

            Digit := Character'Pos (Str (P)) - Character'Pos ('0');

            --  Non-digit encountered

            if Digit > 9 then

               if Str (P) = '_' then

                  Scan_Underscore (Str, P, Ptr, Max, False);

               else

                  exit;

               end if;

            --  Accumulate result, checking for overflow

            else

               if Uval <= Umax then

                  Uval := 10 * Uval + Digit;

               elsif Uval > Umax10 then

                  Overflow := True;

               else

                  Uval := 10 * Uval + Digit;

                  if Uval < Umax10 then

                     Overflow := True;

                  end if;

               end if;

               P := P + 1;

            end if;

         end loop;

      end;

      Ptr.all := P;

      --  Deal with based case

      if P < Max and then (Str (P) = ':' or else Str (P) = '#') then

         Base_Char := Str (P);

         P := P + 1;

         Base := Uval;

         Uval := 0;

         --  Check base value. Overflow is set True if we find a bad base, or

         --  a digit that is out of range of the base. That way, we scan out

         --  the numeral that is still syntactically correct, though illegal.

         --  We use a safe base of 16 for this scan, to avoid zero divide.

         if Base not in 2 .. 16 then

            Overflow := True;

            Base :=  16;

         end if;

         --  Scan out based integer

         declare

            Umax : constant Unsigned := (Unsigned'Last - Base + 1) / Base;

            --  Max value which cannot overflow on accumulating next digit

            UmaxB : constant Unsigned := Unsigned'Last / Base;

            --  Numbers bigger than UmaxB overflow if multiplied by base

         begin

            --  Loop to scan out based integer value

            loop

               --  We require a digit at this stage

               if Str (P) in '0' .. '9' then

                  Digit := Character'Pos (Str (P)) - Character'Pos ('0');

               elsif Str (P) in 'A' .. 'F' then

                  Digit :=

                    Character'Pos (Str (P)) - (Character'Pos ('A') - 10);

               elsif Str (P) in 'a' .. 'f' then

                  Digit :=

                    Character'Pos (Str (P)) - (Character'Pos ('a') - 10);

               --  If we don't have a digit, then this is not a based number

               --  after all, so we use the value we scanned out as the base

               --  (now in Base), and the pointer to the base character was

               --  already stored in Ptr.all.

               else

                  Uval := Base;

                  exit;

               end if;

               --  If digit is too large, just signal overflow and continue.

               --  The idea here is to keep scanning as long as the input is

               --  syntactically valid, even if we have detected overflow

               if Digit >= Base then

                  Overflow := True;

               --  Here we accumulate the value, checking overflow

               elsif Uval <= Umax then

                  Uval := Base * Uval + Digit;

               elsif Uval > UmaxB then

                  Overflow := True;

               else

                  Uval := Base * Uval + Digit;

                  if Uval < UmaxB then

                     Overflow := True;

                  end if;

               end if;

               --  If at end of string with no base char, not a based number

               --  but we signal Constraint_Error and set the pointer past

               --  the end of the field, since this is what the ACVC tests

               --  seem to require, see CE3704N, line 204.

               P := P + 1;

               if P > Max then

                  Ptr.all := P;

                  raise Constraint_Error;

               end if;

               --  If terminating base character, we are done with loop

               if Str (P) = Base_Char then

                  Ptr.all := P + 1;

                  exit;

               --  Deal with underscore

               elsif Str (P) = '_' then

                  Scan_Underscore (Str, P, Ptr, Max, True);

               end if;

            end loop;

         end;

      end if;

      --  Come here with scanned unsigned value in Uval. The only remaining

      --  required step is to deal with exponent if one is present.

      Expon := Scan_Exponent (Str, Ptr, Max);

      if Expon /= 0 and then Uval /= 0 then

         --  For non-zero value, scale by exponent value. No need to do this

         --  efficiently, since use of exponent in integer literals is rare,

         --  and in any case the exponent cannot be very large.

         declare

            UmaxB : constant Unsigned := Unsigned'Last / Base;

            --  Numbers bigger than UmaxB overflow if multiplied by base

         begin

            for J in 1 .. Expon loop

               if Uval > UmaxB then

                  Overflow := True;

                  exit;

               end if;

               Uval := Uval * Base;

            end loop;

         end;

      end if;

      --  Return result, dealing with sign and overflow

      if Overflow then

         raise Constraint_Error;

      else

         return Uval;

      end if;

   end Scan_Raw_Unsigned;

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

   -- Scan_Unsigned --

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

   function Scan_Unsigned

     (Str : String;

      Ptr : not null access Integer;

      Max : Integer) return Unsigned

   is

      Start : Positive;

      --  Save location of first non-blank character

   begin

      Scan_Plus_Sign (Str, Ptr, Max, Start);

      if Str (Ptr.all) not in '0' .. '9' then

         Ptr.all := Start;

         raise Constraint_Error;

      end if;

      return Scan_Raw_Unsigned (Str, Ptr, Max);

   end Scan_Unsigned;

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

   -- Value_Unsigned --

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

   function Value_Unsigned (Str : String) return Unsigned is

      V : Unsigned;

      P : aliased Integer := Str'First;

   begin

      V := Scan_Unsigned (Str, P'Access, Str'Last);

      Scan_Trailing_Blanks (Str, P);

      return V;

   end Value_Unsigned;

end System.Val_Uns;