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 --                            $Revision: 1.1.16.1 $
  10 --                                                                          --
  11 --          Copyright (C) 1992-1997 Free Software Foundation, Inc.          --
  12 --                                                                          --
  13 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  14 -- terms of the  GNU General Public License as published  by the Free Soft- --
  15 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  16 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  17 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  18 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  19 -- for  more details.  You should have  received  a copy of the GNU General --
  20 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  21 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  22 -- MA 02111-1307, USA.                                                      --
  23 --                                                                          --
  24 -- As a special exception,  if other files  instantiate  generics from this --
  25 -- unit, or you link  this unit with other files  to produce an executable, --
  26 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  27 -- covered  by the  GNU  General  Public  License.  This exception does not --
  28 -- however invalidate  any other reasons why  the executable file  might be --
  29 -- covered by the  GNU Public License.                                      --
  30 --                                                                          --
  31 -- GNAT was originally developed  by the GNAT team at  New York University. --
  32 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  33 --                                                                          --
  34 ------------------------------------------------------------------------------
  35
  36 with System.Unsigned_Types; use System.Unsigned_Types;
  37 with System.Val_Util;       use System.Val_Util;
  38
  39 package body System.Val_Uns is
  40
  41    -------------------
  42    -- Scan_Unsigned --
  43    -------------------
  44
  45    function Scan_Unsigned
  46      (Str  : String;
  47       Ptr  : access Integer;
  48       Max  : Integer)
  49       return Unsigned
  50    is
  51       P : Integer;
  52       --  Local copy of the pointer
  53
  54       Uval : Unsigned;
  55       --  Accumulated unsigned integer result
  56
  57       Expon : Integer;
  58       --  Exponent value
  59
  60       Minus : Boolean := False;
  61       --  Set to True if minus sign is present, otherwise to False. Note that
  62       --  a minus sign is permissible for the singular case of -0, and in any
  63       --  case the pointer is left pointing past a negative integer literal.
  64
  65       Overflow : Boolean := False;
  66       --  Set True if overflow is detected at any point
  67
  68       Start : Positive;
  69       --  Save location of first non-blank character
  70
  71       Base_Char : Character;
  72       --  Base character (# or :) in based case
  73
  74       Base : Unsigned := 10;
  75       --  Base value (reset in based case)
  76
  77       Digit : Unsigned;
  78       --  Digit value
  79
  80    begin
  81       Scan_Sign (Str, Ptr, Max, Minus, Start);
  82
  83       if Str (Ptr.all) not in '0' .. '9' then
  84          Ptr.all := Start;
  85          raise Constraint_Error;
  86       end if;
  87
  88       P := Ptr.all;
  89       Uval := Character'Pos (Str (P)) - Character'Pos ('0');
  90       P := P + 1;
  91
  92       --  Scan out digits of what is either the number or the base.
  93       --  In either case, we are definitely scanning out in base 10.
  94
  95       declare
  96          Umax : constant := (Unsigned'Last - 9) / 10;
  97          --  Max value which cannot overflow on accumulating next digit
  98
  99          Umax10 : constant := Unsigned'Last / 10;
 100          --  Numbers bigger than Umax10 overflow if multiplied by 10
 101
 102       begin
 103          --  Loop through decimal digits
 104          loop
 105             exit when P > Max;
 106
 107             Digit := Character'Pos (Str (P)) - Character'Pos ('0');
 108
 109             --  Non-digit encountered
 110
 111             if Digit > 9 then
 112                if Str (P) = '_' then
 113                   Scan_Underscore (Str, P, Ptr, Max, False);
 114                else
 115                   exit;
 116                end if;
 117
 118             --  Accumulate result, checking for overflow
 119
 120             else
 121                if Uval <= Umax then
 122                   Uval := 10 * Uval + Digit;
 123
 124                elsif Uval > Umax10 then
 125                   Overflow := True;
 126
 127                else
 128                   Uval := 10 * Uval + Digit;
 129
 130                   if Uval < Umax10 then
 131                      Overflow := True;
 132                   end if;
 133                end if;
 134
 135                P := P + 1;
 136             end if;
 137          end loop;
 138       end;
 139
 140       Ptr.all := P;
 141
 142       --  Deal with based case
 143
 144       if P < Max and then (Str (P) = ':' or else Str (P) = '#') then
 145          Base_Char := Str (P);
 146          P := P + 1;
 147          Base := Uval;
 148          Uval := 0;
 149
 150          --  Check base value. Overflow is set True if we find a bad base, or
 151          --  a digit that is out of range of the base. That way, we scan out
 152          --  the numeral that is still syntactically correct, though illegal.
 153          --  We use a safe base of 16 for this scan, to avoid zero divide.
 154
 155          if Base not in 2 .. 16 then
 156             Overflow := True;
 157             Base :=  16;
 158          end if;
 159
 160          --  Scan out based integer
 161
 162          declare
 163             Umax : constant Unsigned := (Unsigned'Last - Base + 1) / Base;
 164             --  Max value which cannot overflow on accumulating next digit
 165
 166             UmaxB : constant Unsigned := Unsigned'Last / Base;
 167             --  Numbers bigger than UmaxB overflow if multiplied by base
 168
 169          begin
 170             --  Loop to scan out based integer value
 171
 172             loop
 173                --  We require a digit at this stage
 174
 175                if Str (P) in '0' .. '9' then
 176                   Digit := Character'Pos (Str (P)) - Character'Pos ('0');
 177
 178                elsif Str (P) in 'A' .. 'F' then
 179                   Digit :=
 180                     Character'Pos (Str (P)) - (Character'Pos ('A') - 10);
 181
 182                elsif Str (P) in 'a' .. 'f' then
 183                   Digit :=
 184                     Character'Pos (Str (P)) - (Character'Pos ('a') - 10);
 185
 186                --  If we don't have a digit, then this is not a based number
 187                --  after all, so we use the value we scanned out as the base
 188                --  (now in Base), and the pointer to the base character was
 189                --  already stored in Ptr.all.
 190
 191                else
 192                   Uval := Base;
 193                   exit;
 194                end if;
 195
 196                --  If digit is too large, just signal overflow and continue.
 197                --  The idea here is to keep scanning as long as the input is
 198                --  syntactically valid, even if we have detected overflow
 199
 200                if Digit >= Base then
 201                   Overflow := True;
 202
 203                --  Here we accumulate the value, checking overflow
 204
 205                elsif Uval <= Umax then
 206                   Uval := Base * Uval + Digit;
 207
 208                elsif Uval > UmaxB then
 209                   Overflow := True;
 210
 211                else
 212                   Uval := Base * Uval + Digit;
 213
 214                   if Uval < UmaxB then
 215                      Overflow := True;
 216                   end if;
 217                end if;
 218
 219                --  If at end of string with no base char, not a based number
 220                --  but we signal Constraint_Error and set the pointer past
 221                --  the end of the field, since this is what the ACVC tests
 222                --  seem to require, see CE3704N, line 204.
 223
 224                P := P + 1;
 225
 226                if P > Max then
 227                   Ptr.all := P;
 228                   raise Constraint_Error;
 229                end if;
 230
 231                --  If terminating base character, we are done with loop
 232
 233                if Str (P) = Base_Char then
 234                   Ptr.all := P + 1;
 235                   exit;
 236
 237                --  Deal with underscore
 238
 239                elsif Str (P) = '_' then
 240                   Scan_Underscore (Str, P, Ptr, Max, True);
 241                end if;
 242
 243             end loop;
 244          end;
 245       end if;
 246
 247       --  Come here with scanned unsigned value in Uval. The only remaining
 248       --  required step is to deal with exponent if one is present.
 249
 250       Expon := Scan_Exponent (Str, Ptr, Max);
 251
 252       if Expon /= 0 and then Uval /= 0 then
 253
 254          --  For non-zero value, scale by exponent value. No need to do this
 255          --  efficiently, since use of exponent in integer literals is rare,
 256          --  and in any case the exponent cannot be very large.
 257
 258          declare
 259             UmaxB : constant Unsigned := Unsigned'Last / Base;
 260             --  Numbers bigger than UmaxB overflow if multiplied by base
 261
 262          begin
 263             for J in 1 .. Expon loop
 264                if Uval > UmaxB then
 265                   Overflow := True;
 266                   exit;
 267                end if;
 268
 269                Uval := Uval * Base;
 270             end loop;
 271          end;
 272       end if;
 273
 274       --  Return result, dealing with sign and overflow
 275
 276       if Overflow or else (Minus and then Uval /= 0) then
 277          raise Constraint_Error;
 278       else
 279          return Uval;
 280       end if;
 281    end Scan_Unsigned;
 282
 283    --------------------
 284    -- Value_Unsigned --
 285    --------------------
 286
 287    function Value_Unsigned (Str : String) return Unsigned is
 288       V : Unsigned;
 289       P : aliased Integer := Str'First;
 290
 291    begin
 292       V := Scan_Unsigned (Str, P'Access, Str'Last);
 293       Scan_Trailing_Blanks (Str, P);
 294       return V;
 295
 296    end Value_Unsigned;
 297
 298 end System.Val_Uns;