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

--                                                                          --

--                         GNAT COMPILER COMPONENTS                         --

--                                                                          --

--                      S Y S T E M . V A L _ R E A L                       --

--                                                                          --

--                                 B o d y                                  --

--                                                                          --

--          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.                                     --

--                                                                          --

-- 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.Powten_Table; use System.Powten_Table;

with System.Val_Util;     use System.Val_Util;

with System.Float_Control;

package body System.Val_Real is

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

   -- Scan_Real --

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

   function Scan_Real

     (Str : String;

      Ptr : not null access Integer;

      Max : Integer) return Long_Long_Float

   is

      P : Integer;

      --  Local copy of string pointer

      Base : Long_Long_Float;

      --  Base value

      Uval : Long_Long_Float;

      --  Accumulated float result

      subtype Digs is Character range '0' .. '9';

      --  Used to check for decimal digit

      Scale : Integer := 0;

      --  Power of Base to multiply result by

      Start : Positive;

      --  Position of starting non-blank character

      Minus : Boolean;

      --  Set to True if minus sign is present, otherwise to False

      Bad_Base : Boolean := False;

      --  Set True if Base out of range or if out of range digit

      After_Point : Natural := 0;

      --  Set to 1 after the point

      Num_Saved_Zeroes : Natural := 0;

      --  This counts zeroes after the decimal point. A non-zero value means

      --  that this number of previously scanned digits are zero. If the end

      --  of the number is reached, these zeroes are simply discarded, which

      --  ensures that trailing zeroes after the point never affect the value

      --  (which might otherwise happen as a result of rounding). With this

      --  processing in place, we can ensure that, for example, we get the

      --  same exact result from 1.0E+49 and 1.0000000E+49. This is not

      --  necessarily required in a case like this where the result is not

      --  a machine number, but it is certainly a desirable behavior.

      procedure Bad_Based_Value;

      pragma No_Return (Bad_Based_Value);

      --  Raise exception for bad based value

      procedure Scanf;

      --  Scans integer literal value starting at current character position.

      --  For each digit encountered, Uval is multiplied by 10.0, and the new

      --  digit value is incremented. In addition Scale is decremented for each

      --  digit encountered if we are after the point (After_Point = 1). The

      --  longest possible syntactically valid numeral is scanned out, and on

      --  return P points past the last character. On entry, the current

      --  character is known to be a digit, so a numeral is definitely present.

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

      -- Bad_Based_Value --

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

      procedure Bad_Based_Value is

      begin

         raise Constraint_Error with

           "invalid based literal for 'Value";

      end Bad_Based_Value;

      -----------

      -- Scanf --

      -----------

      procedure Scanf is

         Digit : Natural;

      begin

         loop

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

            P := P + 1;

            --  Save up trailing zeroes after the decimal point

            if Digit = 0 and then After_Point = 1 then

               Num_Saved_Zeroes := Num_Saved_Zeroes + 1;

            --  Here for a non-zero digit

            else

               --  First deal with any previously saved zeroes

               if Num_Saved_Zeroes /= 0 then

                  while Num_Saved_Zeroes > Maxpow loop

                     Uval := Uval * Powten (Maxpow);

                     Num_Saved_Zeroes := Num_Saved_Zeroes - Maxpow;

                     Scale := Scale - Maxpow;

                  end loop;

                  Uval := Uval * Powten (Num_Saved_Zeroes);

                  Scale := Scale - Num_Saved_Zeroes;

                  Num_Saved_Zeroes := 0;

               end if;

               --  Accumulate new digit

               Uval := Uval * 10.0 + Long_Long_Float (Digit);

               Scale := Scale - After_Point;

            end if;

            --  Done if end of input field

            if P > Max then

               return;

            --  Check next character

            elsif Str (P) not in Digs then

               if Str (P) = '_' then

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

               else

                  return;

               end if;

            end if;

         end loop;

      end Scanf;

   --  Start of processing for System.Scan_Real

   begin

      --  We call the floating-point processor reset routine so that we can

      --  be sure the floating-point processor is properly set for conversion

      --  calls. This is notably need on Windows, where calls to the operating

      --  system randomly reset the processor into 64-bit mode.

      System.Float_Control.Reset;

      Scan_Sign (Str, Ptr, Max, Minus, Start);

      P := Ptr.all;

      Ptr.all := Start;

      --  If digit, scan numeral before point

      if Str (P) in Digs then

         Uval := 0.0;

         Scanf;

      --  Initial point, allowed only if followed by digit (RM 3.5(47))

      elsif Str (P) = '.'

        and then P < Max

        and then Str (P + 1) in Digs

      then

         Uval := 0.0;

      --  Any other initial character is an error

      else

         raise Constraint_Error with

           "invalid character in 'Value string";

      end if;

      --  Deal with based case

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

         declare

            Base_Char : constant Character := Str (P);

            Digit     : Natural;

            Fdigit    : Long_Long_Float;

         begin

            --  Set bad base if out of range, and use safe base of 16.0,

            --  to guard against division by zero in the loop below.

            if Uval < 2.0 or else Uval > 16.0 then

               Bad_Base := True;

               Uval := 16.0;

            end if;

            Base := Uval;

            Uval := 0.0;

            P := P + 1;

            --  Special check to allow initial point (RM 3.5(49))

            if Str (P) = '.' then

               After_Point := 1;

               P := P + 1;

            end if;

            --  Loop to scan digits of based number. On entry to the loop we

            --  must have a valid digit. If we don't, then we have an illegal

            --  floating-point value, and we raise Constraint_Error, note that

            --  Ptr at this stage was reset to the proper (Start) value.

            loop

               if P > Max then

                  Bad_Based_Value;

               elsif Str (P) in Digs 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);

               else

                  Bad_Based_Value;

               end if;

               --  Save up trailing zeroes after the decimal point

               if Digit = 0 and then After_Point = 1 then

                  Num_Saved_Zeroes := Num_Saved_Zeroes + 1;

               --  Here for a non-zero digit

               else

                  --  First deal with any previously saved zeroes

                  if Num_Saved_Zeroes /= 0 then

                     Uval := Uval * Base ** Num_Saved_Zeroes;

                     Scale := Scale - Num_Saved_Zeroes;

                     Num_Saved_Zeroes := 0;

                  end if;

                  --  Now accumulate the new digit

                  Fdigit := Long_Long_Float (Digit);

                  if Fdigit >= Base then

                     Bad_Base := True;

                  else

                     Scale := Scale - After_Point;

                     Uval := Uval * Base + Fdigit;

                  end if;

               end if;

               P := P + 1;

               if P > Max then

                  Bad_Based_Value;

               elsif Str (P) = '_' then

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

               else

                  --  Skip past period after digit. Note that the processing

                  --  here will permit either a digit after the period, or the

                  --  terminating base character, as allowed in (RM 3.5(48))

                  if Str (P) = '.' and then After_Point = 0 then

                     P := P + 1;

                     After_Point := 1;

                     if P > Max then

                        Bad_Based_Value;

                     end if;

                  end if;

                  exit when Str (P) = Base_Char;

               end if;

            end loop;

            --  Based number successfully scanned out (point was found)

            Ptr.all := P + 1;

         end;

      --  Non-based case, check for being at decimal point now. Note that

      --  in Ada 95, we do not insist on a decimal point being present

      else

         Base := 10.0;

         After_Point := 1;

         if P <= Max and then Str (P) = '.' then

            P := P + 1;

            --  Scan digits after point if any are present (RM 3.5(46))

            if P <= Max and then Str (P) in Digs then

               Scanf;

            end if;

         end if;

         Ptr.all := P;

      end if;

      --  At this point, we have Uval containing the digits of the value as

      --  an integer, and Scale indicates the negative of the number of digits

      --  after the point. Base contains the base value (an integral value in

      --  the range 2.0 .. 16.0). Test for exponent, must be at least one

      --  character after the E for the exponent to be valid.

      Scale := Scale + Scan_Exponent (Str, Ptr, Max, Real => True);

      --  At this point the exponent has been scanned if one is present and

      --  Scale is adjusted to include the exponent value. Uval contains the

      --  the integral value which is to be multiplied by Base ** Scale.

      --  If base is not 10, use exponentiation for scaling

      if Base /= 10.0 then

         Uval := Uval * Base ** Scale;

      --  For base 10, use power of ten table, repeatedly if necessary

      elsif Scale > 0 then

         while Scale > Maxpow loop

            Uval := Uval * Powten (Maxpow);

            Scale := Scale - Maxpow;

         end loop;

         if Scale > 0 then

            Uval := Uval * Powten (Scale);

         end if;

      elsif Scale < 0 then

         while (-Scale) > Maxpow loop

            Uval := Uval / Powten (Maxpow);

            Scale := Scale + Maxpow;

         end loop;

         if Scale < 0 then

            Uval := Uval / Powten (-Scale);

         end if;

      end if;

      --  Here is where we check for a bad based number

      if Bad_Base then

         Bad_Based_Value;

      --  If OK, then deal with initial minus sign, note that this processing

      --  is done even if Uval is zero, so that -0.0 is correctly interpreted.

      else

         if Minus then

            return -Uval;

         else

            return Uval;

         end if;

      end if;

   end Scan_Real;

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

   -- Value_Real --

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

   function Value_Real (Str : String) return Long_Long_Float is

      V : Long_Long_Float;

      P : aliased Integer := Str'First;

   begin

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

      Scan_Trailing_Blanks (Str, P);

      return V;

   end Value_Real;

end System.Val_Real;