gcc/ada/s-valuns.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                       S Y S T E M . V A L _ U N S                        --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-1997 Free Software Foundation, Inc.          --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  20 -- MA 02111-1307, USA.                                                      --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNAT was originally developed  by the GNAT team at  New York University. --
  30 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 with System.Unsigned_Types; use System.Unsigned_Types;
  35 with System.Val_Util;       use System.Val_Util;
  36
  37 package body System.Val_Uns is
  38
  39    -------------------
  40    -- Scan_Unsigned --
  41    -------------------
  42
  43    function Scan_Unsigned
  44      (Str  : String;
  45       Ptr  : access Integer;
  46       Max  : Integer)
  47       return Unsigned
  48    is
  49       P : Integer;
  50       --  Local copy of the pointer
  51
  52       Uval : Unsigned;
  53       --  Accumulated unsigned integer result
  54
  55       Expon : Integer;
  56       --  Exponent value
  57
  58       Minus : Boolean := False;
  59       --  Set to True if minus sign is present, otherwise to False. Note that
  60       --  a minus sign is permissible for the singular case of -0, and in any
  61       --  case the pointer is left pointing past a negative integer literal.
  62
  63       Overflow : Boolean := False;
  64       --  Set True if overflow is detected at any point
  65
  66       Start : Positive;
  67       --  Save location of first non-blank character
  68
  69       Base_Char : Character;
  70       --  Base character (# or :) in based case
  71
  72       Base : Unsigned := 10;
  73       --  Base value (reset in based case)
  74
  75       Digit : Unsigned;
  76       --  Digit value
  77
  78    begin
  79       Scan_Sign (Str, Ptr, Max, Minus, Start);
  80
  81       if Str (Ptr.all) not in '0' .. '9' then
  82          Ptr.all := Start;
  83          raise Constraint_Error;
  84       end if;
  85
  86       P := Ptr.all;
  87       Uval := Character'Pos (Str (P)) - Character'Pos ('0');
  88       P := P + 1;
  89
  90       --  Scan out digits of what is either the number or the base.
  91       --  In either case, we are definitely scanning out in base 10.
  92
  93       declare
  94          Umax : constant := (Unsigned'Last - 9) / 10;
  95          --  Max value which cannot overflow on accumulating next digit
  96
  97          Umax10 : constant := Unsigned'Last / 10;
  98          --  Numbers bigger than Umax10 overflow if multiplied by 10
  99
 100       begin
 101          --  Loop through decimal digits
 102          loop
 103             exit when P > Max;
 104
 105             Digit := Character'Pos (Str (P)) - Character'Pos ('0');
 106
 107             --  Non-digit encountered
 108
 109             if Digit > 9 then
 110                if Str (P) = '_' then
 111                   Scan_Underscore (Str, P, Ptr, Max, False);
 112                else
 113                   exit;
 114                end if;
 115
 116             --  Accumulate result, checking for overflow
 117
 118             else
 119                if Uval <= Umax then
 120                   Uval := 10 * Uval + Digit;
 121
 122                elsif Uval > Umax10 then
 123                   Overflow := True;
 124
 125                else
 126                   Uval := 10 * Uval + Digit;
 127
 128                   if Uval < Umax10 then
 129                      Overflow := True;
 130                   end if;
 131                end if;
 132
 133                P := P + 1;
 134             end if;
 135          end loop;
 136       end;
 137
 138       Ptr.all := P;
 139
 140       --  Deal with based case
 141
 142       if P < Max and then (Str (P) = ':' or else Str (P) = '#') then
 143          Base_Char := Str (P);
 144          P := P + 1;
 145          Base := Uval;
 146          Uval := 0;
 147
 148          --  Check base value. Overflow is set True if we find a bad base, or
 149          --  a digit that is out of range of the base. That way, we scan out
 150          --  the numeral that is still syntactically correct, though illegal.
 151          --  We use a safe base of 16 for this scan, to avoid zero divide.
 152
 153          if Base not in 2 .. 16 then
 154             Overflow := True;
 155             Base :=  16;
 156          end if;
 157
 158          --  Scan out based integer
 159
 160          declare
 161             Umax : constant Unsigned := (Unsigned'Last - Base + 1) / Base;
 162             --  Max value which cannot overflow on accumulating next digit
 163
 164             UmaxB : constant Unsigned := Unsigned'Last / Base;
 165             --  Numbers bigger than UmaxB overflow if multiplied by base
 166
 167          begin
 168             --  Loop to scan out based integer value
 169
 170             loop
 171                --  We require a digit at this stage
 172
 173                if Str (P) in '0' .. '9' then
 174                   Digit := Character'Pos (Str (P)) - Character'Pos ('0');
 175
 176                elsif Str (P) in 'A' .. 'F' then
 177                   Digit :=
 178                     Character'Pos (Str (P)) - (Character'Pos ('A') - 10);
 179
 180                elsif Str (P) in 'a' .. 'f' then
 181                   Digit :=
 182                     Character'Pos (Str (P)) - (Character'Pos ('a') - 10);
 183
 184                --  If we don't have a digit, then this is not a based number
 185                --  after all, so we use the value we scanned out as the base
 186                --  (now in Base), and the pointer to the base character was
 187                --  already stored in Ptr.all.
 188
 189                else
 190                   Uval := Base;
 191                   exit;
 192                end if;
 193
 194                --  If digit is too large, just signal overflow and continue.
 195                --  The idea here is to keep scanning as long as the input is
 196                --  syntactically valid, even if we have detected overflow
 197
 198                if Digit >= Base then
 199                   Overflow := True;
 200
 201                --  Here we accumulate the value, checking overflow
 202
 203                elsif Uval <= Umax then
 204                   Uval := Base * Uval + Digit;
 205
 206                elsif Uval > UmaxB then
 207                   Overflow := True;
 208
 209                else
 210                   Uval := Base * Uval + Digit;
 211
 212                   if Uval < UmaxB then
 213                      Overflow := True;
 214                   end if;
 215                end if;
 216
 217                --  If at end of string with no base char, not a based number
 218                --  but we signal Constraint_Error and set the pointer past
 219                --  the end of the field, since this is what the ACVC tests
 220                --  seem to require, see CE3704N, line 204.
 221
 222                P := P + 1;
 223
 224                if P > Max then
 225                   Ptr.all := P;
 226                   raise Constraint_Error;
 227                end if;
 228
 229                --  If terminating base character, we are done with loop
 230
 231                if Str (P) = Base_Char then
 232                   Ptr.all := P + 1;
 233                   exit;
 234
 235                --  Deal with underscore
 236
 237                elsif Str (P) = '_' then
 238                   Scan_Underscore (Str, P, Ptr, Max, True);
 239                end if;
 240
 241             end loop;
 242          end;
 243       end if;
 244
 245       --  Come here with scanned unsigned value in Uval. The only remaining
 246       --  required step is to deal with exponent if one is present.
 247
 248       Expon := Scan_Exponent (Str, Ptr, Max);
 249
 250       if Expon /= 0 and then Uval /= 0 then
 251
 252          --  For non-zero value, scale by exponent value. No need to do this
 253          --  efficiently, since use of exponent in integer literals is rare,
 254          --  and in any case the exponent cannot be very large.
 255
 256          declare
 257             UmaxB : constant Unsigned := Unsigned'Last / Base;
 258             --  Numbers bigger than UmaxB overflow if multiplied by base
 259
 260          begin
 261             for J in 1 .. Expon loop
 262                if Uval > UmaxB then
 263                   Overflow := True;
 264                   exit;
 265                end if;
 266
 267                Uval := Uval * Base;
 268             end loop;
 269          end;
 270       end if;
 271
 272       --  Return result, dealing with sign and overflow
 273
 274       if Overflow or else (Minus and then Uval /= 0) then
 275          raise Constraint_Error;
 276       else
 277          return Uval;
 278       end if;
 279    end Scan_Unsigned;
 280
 281    --------------------
 282    -- Value_Unsigned --
 283    --------------------
 284
 285    function Value_Unsigned (Str : String) return Unsigned is
 286       V : Unsigned;
 287       P : aliased Integer := Str'First;
 288
 289    begin
 290       V := Scan_Unsigned (Str, P'Access, Str'Last);
 291       Scan_Trailing_Blanks (Str, P);
 292       return V;
 293
 294    end Value_Unsigned;
 295
 296 end System.Val_Uns;