--  GHDL Run Time (GRT) - 'value subprograms.
--  Copyright (C) 2002, 2003, 2004, 2005 Tristan Gingold
--
--  GHDL is free software; you can redistribute it and/or modify it under
--  the terms of the GNU General Public License as published by the Free
--  Software Foundation; either version 2, or (at your option) any later
--  version.
--
--  GHDL is distributed in the hope that it will be useful, but WITHOUT 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
--  along with GCC; see the file COPYING.  If not, write to the Free
--  Software Foundation, 59 Temple Place - Suite 330, Boston, MA
--  02111-1307, USA.
with Grt.Errors; use Grt.Errors;

package body Grt.Values is

   NBSP : constant Character := Character'Val (160);
   HT : constant Character := Character'Val (9);

   function Ghdl_Value_I32 (Str : Std_String_Ptr) return Ghdl_I32
   is
      S : constant Std_String_Basep := Str.Base;
      Len : constant Ghdl_Index_Type := Str.Bounds.Dim_1.Length;
      Pos : Ghdl_Index_Type := 0;
      C : Character;
      Sep : Character;
      Val, D, Base : Ghdl_I32;
      Exp : Integer;
   begin
      --  LRM 14.1
      --  Leading [and trailing] whitespace is allowed and ignored.
      --
      --  GHDL: allow several leading whitespace.
      while Pos < Len loop
         case S (Pos) is
            when ' '
              | NBSP
              | HT =>
               Pos := Pos + 1;
            when others =>
               exit;
         end case;
      end loop;

      if Pos = Len then
         Error_E ("'value: empty string");
      end if;
      C := S (Pos);

      --  Be user friendly.
      if C = '-' or C = '+' then
         Error_E ("'value: leading sign +/- not allowed");
      end if;

      Val := 0;
      loop
         if C in '0' .. '9' then
            Val := Val * 10 + Character'Pos (C) - Character'Pos ('0');
            Pos := Pos + 1;
            exit when Pos >= Len;
            C := S (Pos);
         else
            Error_E ("'value: decimal digit expected");
         end if;
         case C is
            when '_' =>
               Pos := Pos + 1;
               if Pos >= Len then
                  Error_E ("'value: trailing underscore");
               end if;
               C := S (Pos);
            when '#'
              | ':'
              | 'E'
              | 'e' =>
               exit;
            when ' '
              | NBSP
              | HT =>
               Pos := Pos + 1;
               exit;
            when others =>
               null;
         end case;
      end loop;

      if Pos >= Len then
         return Val;
      end if;

      if C = '#' or C = ':' then
         Base := Val;
         Val := 0;
         Sep := C;
         Pos := Pos + 1;
         if Base < 2 or Base > 16 then
            Error_E ("'value: bad base");
         end if;
         if Pos >= Len then
            Error_E ("'value: missing based integer");
         end if;
         C := S (Pos);
         loop
            case C is
               when '0' .. '9' =>
                  D := Character'Pos (C) - Character'Pos ('0');
               when 'a' .. 'f' =>
                  D := Character'Pos (C) - Character'Pos ('a') + 10;
               when 'A' .. 'F' =>
                  D := Character'Pos (C) - Character'Pos ('A') + 10;
               when others =>
                  Error_E ("'value: digit expected");
            end case;
            if D > Base then
               Error_E ("'value: digit greather than base");
            end if;
            Val := Val * Base + D;
            Pos := Pos + 1;
            if Pos >= Len then
               Error_E ("'value: missing end sign number");
            end if;
            C := S (Pos);
            if C = '#' or C = ':' then
               if C /= Sep then
                  Error_E ("'value: sign number mismatch");
               end if;
               Pos := Pos + 1;
               exit;
            elsif C = '_' then
               Pos := Pos + 1;
               if Pos >= Len then
                  Error_E ("'value: no character after underscore");
               end if;
               C := S (Pos);
            end if;
         end loop;
      else
         Base := 10;
      end if;

      -- Handle exponent.
      if C = 'e' or C = 'E' then
         Pos := Pos + 1;
         if Pos >= Len then
            Error_E ("'value: no character after exponent");
         end if;
         C := S (Pos);
         if C = '+' then
            Pos := Pos + 1;
            if Pos >= Len then
               Error_E ("'value: no character after sign");
            end if;
            C := S (Pos);
         elsif C = '-' then
            Error_E ("'value: negativ exponent not allowed");
         end if;
         Exp := 0;
         loop
            if C in '0' .. '9' then
               Exp := Exp * 10 + Character'Pos (C) - Character'Pos ('0');
               Pos := Pos + 1;
               exit when Pos >= Len;
               C := S (Pos);
            else
               Error_E ("'value: decimal digit expected");
            end if;
            case C is
               when '_' =>
                  Pos := Pos + 1;
                  if Pos >= Len then
                     Error_E ("'value: trailing underscore");
                  end if;
                  C := S (Pos);
               when ' '
                 | NBSP
                 | HT =>
                  Pos := Pos + 1;
                  exit;
               when others =>
                  null;
            end case;
         end loop;
         while Exp > 0 loop
            if Exp mod 2 = 1 then
               Val := Val * Base;
            end if;
            Exp := Exp / 2;
            Base := Base * Base;
         end loop;
      end if;

      --  LRM 14.1
      --  [Leading] and trailing whitespace is allowed and ignored.
      --
      --  GHDL: allow several leading whitespace.
      while Pos < Len loop
         case S (Pos) is
            when ' '
              | NBSP
              | HT =>
               Pos := Pos + 1;
            when others =>
               Error_E ("'value: trailing characters after blank");
         end case;
      end loop;

      return Val;
   end Ghdl_Value_I32;

end Grt.Values;