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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;