gcc/ada/s-valrea.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                      S Y S T E M . V A L _ R E A L                       --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2005 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,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, 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.Powten_Table; use System.Powten_Table;
  35 with System.Val_Util;     use System.Val_Util;
  36
  37 package body System.Val_Real is
  38
  39    ---------------
  40    -- Scan_Real --
  41    ---------------
  42
  43    function Scan_Real
  44      (Str  : String;
  45       Ptr  : access Integer;
  46       Max  : Integer) return Long_Long_Float
  47    is
  48       procedure Reset;
  49       pragma Import (C, Reset, "__gnat_init_float");
  50       --  We import the floating-point processor reset routine so that we can
  51       --  be sure the floating-point processor is properly set for conversion
  52       --  calls (see description of Reset in GNAT.Float_Control (g-flocon.ads).
  53       --  This is notably need on Windows, where calls to the operating system
  54       --  randomly reset the processor into 64-bit mode.
  55
  56       P : Integer;
  57       --  Local copy of string pointer
  58
  59       Base   : Long_Long_Float;
  60       --  Base value
  61
  62       Uval : Long_Long_Float;
  63       --  Accumulated float result
  64
  65       subtype Digs is Character range '0' .. '9';
  66       --  Used to check for decimal digit
  67
  68       Scale : Integer := 0;
  69       --  Power of Base to multiply result by
  70
  71       Start : Positive;
  72       --  Position of starting non-blank character
  73
  74       Minus : Boolean;
  75       --  Set to True if minus sign is present, otherwise to False
  76
  77       Bad_Base : Boolean := False;
  78       --  Set True if Base out of range or if out of range digit
  79
  80       After_Point : Natural := 0;
  81       --  Set to 1 after the point
  82
  83       Num_Saved_Zeroes : Natural := 0;
  84       --  This counts zeroes after the decimal point. A non-zero value means
  85       --  that this number of previously scanned digits are zero. if the end
  86       --  of the number is reached, these zeroes are simply discarded, which
  87       --  ensures that trailing zeroes after the point never affect the value
  88       --  (which might otherwise happen as a result of rounding). With this
  89       --  processing in place, we can ensure that, for example, we get the
  90       --  same exact result from 1.0E+49 and 1.0000000E+49. This is not
  91       --  necessarily required in a case like this where the result is not
  92       --  a machine number, but it is certainly a desirable behavior.
  93
  94       procedure Scanf;
  95       --  Scans integer literal value starting at current character position.
  96       --  For each digit encountered, Uval is multiplied by 10.0, and the new
  97       --  digit value is incremented. In addition Scale is decremented for each
  98       --  digit encountered if we are after the point (After_Point = 1). The
  99       --  longest possible syntactically valid numeral is scanned out, and on
 100       --  return P points past the last character. On entry, the current
 101       --  character is known to be a digit, so a numeral is definitely present.
 102
 103       procedure Scanf is
 104          Digit : Natural;
 105
 106       begin
 107          loop
 108             Digit := Character'Pos (Str (P)) - Character'Pos ('0');
 109             P := P + 1;
 110
 111             --  Save up trailing zeroes after the decimal point
 112
 113             if Digit = 0 and After_Point = 1 then
 114                Num_Saved_Zeroes := Num_Saved_Zeroes + 1;
 115
 116             --  Here for a non-zero digit
 117
 118             else
 119                --  First deal with any previously saved zeroes
 120
 121                if Num_Saved_Zeroes /= 0 then
 122                   while Num_Saved_Zeroes > Maxpow loop
 123                      Uval := Uval * Powten (Maxpow);
 124                      Num_Saved_Zeroes := Num_Saved_Zeroes - Maxpow;
 125                      Scale := Scale - Maxpow;
 126                   end loop;
 127
 128                   Uval := Uval * Powten (Num_Saved_Zeroes);
 129                   Scale := Scale - Num_Saved_Zeroes;
 130
 131                   Num_Saved_Zeroes := 0;
 132                end if;
 133
 134                --  Accumulate new digit
 135
 136                Uval := Uval * 10.0 + Long_Long_Float (Digit);
 137                Scale := Scale - After_Point;
 138             end if;
 139
 140             --  Done if end of input field
 141
 142             if P > Max then
 143                return;
 144
 145             --  Check next character
 146
 147             elsif Str (P) not in Digs then
 148                if Str (P) = '_' then
 149                   Scan_Underscore (Str, P, Ptr, Max, False);
 150                else
 151                   return;
 152                end if;
 153             end if;
 154          end loop;
 155       end Scanf;
 156
 157    --  Start of processing for System.Scan_Real
 158
 159    begin
 160       Reset;
 161       Scan_Sign (Str, Ptr, Max, Minus, Start);
 162       P := Ptr.all;
 163       Ptr.all := Start;
 164
 165       --  If digit, scan numeral before point
 166
 167       if Str (P) in Digs then
 168          Uval := 0.0;
 169          Scanf;
 170
 171       --  Initial point, allowed only if followed by digit (RM 3.5(47))
 172
 173       elsif Str (P) = '.'
 174         and then P < Max
 175         and then Str (P + 1) in Digs
 176       then
 177          Uval := 0.0;
 178
 179       --  Any other initial character is an error
 180
 181       else
 182          raise Constraint_Error;
 183       end if;
 184
 185       --  Deal with based case
 186
 187       if P < Max and then (Str (P) = ':' or else Str (P) = '#') then
 188          declare
 189             Base_Char : constant Character := Str (P);
 190             Digit     : Natural;
 191             Fdigit    : Long_Long_Float;
 192
 193          begin
 194             --  Set bad base if out of range, and use safe base of 16.0,
 195             --  to guard against division by zero in the loop below.
 196
 197             if Uval < 2.0 or else Uval > 16.0 then
 198                Bad_Base := True;
 199                Uval := 16.0;
 200             end if;
 201
 202             Base := Uval;
 203             Uval := 0.0;
 204             P := P + 1;
 205
 206             --  Special check to allow initial point (RM 3.5(49))
 207
 208             if Str (P) = '.' then
 209                After_Point := 1;
 210                P := P + 1;
 211             end if;
 212
 213             --  Loop to scan digits of based number. On entry to the loop we
 214             --  must have a valid digit. If we don't, then we have an illegal
 215             --  floating-point value, and we raise Constraint_Error, note that
 216             --  Ptr at this stage was reset to the proper (Start) value.
 217
 218             loop
 219                if P > Max then
 220                   raise Constraint_Error;
 221
 222                elsif Str (P) in Digs then
 223                   Digit := Character'Pos (Str (P)) - Character'Pos ('0');
 224
 225                elsif Str (P) in 'A' .. 'F' then
 226                   Digit :=
 227                     Character'Pos (Str (P)) - (Character'Pos ('A') - 10);
 228
 229                elsif Str (P) in 'a' .. 'f' then
 230                   Digit :=
 231                     Character'Pos (Str (P)) - (Character'Pos ('a') - 10);
 232
 233                else
 234                   raise Constraint_Error;
 235                end if;
 236
 237                --  Save up trailing zeroes after the decimal point
 238
 239                if Digit = 0 and After_Point = 1 then
 240                   Num_Saved_Zeroes := Num_Saved_Zeroes + 1;
 241
 242                --  Here for a non-zero digit
 243
 244                else
 245                   --  First deal with any previously saved zeroes
 246
 247                   if Num_Saved_Zeroes /= 0 then
 248                      Uval := Uval * Base ** Num_Saved_Zeroes;
 249                      Scale := Scale - Num_Saved_Zeroes;
 250                      Num_Saved_Zeroes := 0;
 251                   end if;
 252
 253                   --  Now accumulate the new digit
 254
 255                   Fdigit := Long_Long_Float (Digit);
 256
 257                   if Fdigit >= Base then
 258                      Bad_Base := True;
 259                   else
 260                      Scale := Scale - After_Point;
 261                      Uval := Uval * Base + Fdigit;
 262                   end if;
 263                end if;
 264
 265                P := P + 1;
 266
 267                if P > Max then
 268                   raise Constraint_Error;
 269
 270                elsif Str (P) = '_' then
 271                   Scan_Underscore (Str, P, Ptr, Max, True);
 272
 273                else
 274                   --  Skip past period after digit. Note that the processing
 275                   --  here will permit either a digit after the period, or the
 276                   --  terminating base character, as allowed in (RM 3.5(48))
 277
 278                   if Str (P) = '.' and then After_Point = 0 then
 279                      P := P + 1;
 280                      After_Point := 1;
 281
 282                      if P > Max then
 283                         raise Constraint_Error;
 284                      end if;
 285                   end if;
 286
 287                   exit when Str (P) = Base_Char;
 288                end if;
 289             end loop;
 290
 291             --  Based number successfully scanned out (point was found)
 292
 293             Ptr.all := P + 1;
 294          end;
 295
 296       --  Non-based case, check for being at decimal point now. Note that
 297       --  in Ada 95, we do not insist on a decimal point being present
 298
 299       else
 300          Base := 10.0;
 301          After_Point := 1;
 302
 303          if P <= Max and then Str (P) = '.' then
 304             P := P + 1;
 305
 306             --  Scan digits after point if any are present (RM 3.5(46))
 307
 308             if P <= Max and then Str (P) in Digs then
 309                Scanf;
 310             end if;
 311          end if;
 312
 313          Ptr.all := P;
 314       end if;
 315
 316       --  At this point, we have Uval containing the digits of the value as
 317       --  an integer, and Scale indicates the negative of the number of digits
 318       --  after the point. Base contains the base value (an integral value in
 319       --  the range 2.0 .. 16.0). Test for exponent, must be at least one
 320       --  character after the E for the exponent to be valid.
 321
 322       Scale := Scale + Scan_Exponent (Str, Ptr, Max, Real => True);
 323
 324       --  At this point the exponent has been scanned if one is present and
 325       --  Scale is adjusted to include the exponent value. Uval contains the
 326       --  the integral value which is to be multiplied by Base ** Scale.
 327
 328       --  If base is not 10, use exponentiation for scaling
 329
 330       if Base /= 10.0 then
 331          Uval := Uval * Base ** Scale;
 332
 333       --  For base 10, use power of ten table, repeatedly if necessary.
 334
 335       elsif Scale > 0 then
 336          while Scale > Maxpow loop
 337             Uval := Uval * Powten (Maxpow);
 338             Scale := Scale - Maxpow;
 339          end loop;
 340
 341          if Scale > 0 then
 342             Uval := Uval * Powten (Scale);
 343          end if;
 344
 345       elsif Scale < 0 then
 346          while (-Scale) > Maxpow loop
 347             Uval := Uval / Powten (Maxpow);
 348             Scale := Scale + Maxpow;
 349          end loop;
 350
 351          if Scale < 0 then
 352             Uval := Uval / Powten (-Scale);
 353          end if;
 354       end if;
 355
 356       --  Here is where we check for a bad based number
 357
 358       if Bad_Base then
 359          raise Constraint_Error;
 360
 361       --  If OK, then deal with initial minus sign, note that this processing
 362       --  is done even if Uval is zero, so that -0.0 is correctly interpreted.
 363
 364       else
 365          if Minus then
 366             return -Uval;
 367          else
 368             return Uval;
 369          end if;
 370       end if;
 371    end Scan_Real;
 372
 373    ----------------
 374    -- Value_Real --
 375    ----------------
 376
 377    function Value_Real (Str : String) return Long_Long_Float is
 378       V : Long_Long_Float;
 379       P : aliased Integer := Str'First;
 380
 381    begin
 382       V := Scan_Real (Str, P'Access, Str'Last);
 383       Scan_Trailing_Blanks (Str, P);
 384       return V;
 385    end Value_Real;
 386
 387 end System.Val_Real;