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) 1992-2008, 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 : not null 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       -----------
 104       -- Scanf --
 105       -----------
 106
 107       procedure Scanf is
 108          Digit : Natural;
 109
 110       begin
 111          loop
 112             Digit := Character'Pos (Str (P)) - Character'Pos ('0');
 113             P := P + 1;
 114
 115             --  Save up trailing zeroes after the decimal point
 116
 117             if Digit = 0 and After_Point = 1 then
 118                Num_Saved_Zeroes := Num_Saved_Zeroes + 1;
 119
 120             --  Here for a non-zero digit
 121
 122             else
 123                --  First deal with any previously saved zeroes
 124
 125                if Num_Saved_Zeroes /= 0 then
 126                   while Num_Saved_Zeroes > Maxpow loop
 127                      Uval := Uval * Powten (Maxpow);
 128                      Num_Saved_Zeroes := Num_Saved_Zeroes - Maxpow;
 129                      Scale := Scale - Maxpow;
 130                   end loop;
 131
 132                   Uval := Uval * Powten (Num_Saved_Zeroes);
 133                   Scale := Scale - Num_Saved_Zeroes;
 134
 135                   Num_Saved_Zeroes := 0;
 136                end if;
 137
 138                --  Accumulate new digit
 139
 140                Uval := Uval * 10.0 + Long_Long_Float (Digit);
 141                Scale := Scale - After_Point;
 142             end if;
 143
 144             --  Done if end of input field
 145
 146             if P > Max then
 147                return;
 148
 149             --  Check next character
 150
 151             elsif Str (P) not in Digs then
 152                if Str (P) = '_' then
 153                   Scan_Underscore (Str, P, Ptr, Max, False);
 154                else
 155                   return;
 156                end if;
 157             end if;
 158          end loop;
 159       end Scanf;
 160
 161    --  Start of processing for System.Scan_Real
 162
 163    begin
 164       Reset;
 165       Scan_Sign (Str, Ptr, Max, Minus, Start);
 166       P := Ptr.all;
 167       Ptr.all := Start;
 168
 169       --  If digit, scan numeral before point
 170
 171       if Str (P) in Digs then
 172          Uval := 0.0;
 173          Scanf;
 174
 175       --  Initial point, allowed only if followed by digit (RM 3.5(47))
 176
 177       elsif Str (P) = '.'
 178         and then P < Max
 179         and then Str (P + 1) in Digs
 180       then
 181          Uval := 0.0;
 182
 183       --  Any other initial character is an error
 184
 185       else
 186          raise Constraint_Error;
 187       end if;
 188
 189       --  Deal with based case
 190
 191       if P < Max and then (Str (P) = ':' or else Str (P) = '#') then
 192          declare
 193             Base_Char : constant Character := Str (P);
 194             Digit     : Natural;
 195             Fdigit    : Long_Long_Float;
 196
 197          begin
 198             --  Set bad base if out of range, and use safe base of 16.0,
 199             --  to guard against division by zero in the loop below.
 200
 201             if Uval < 2.0 or else Uval > 16.0 then
 202                Bad_Base := True;
 203                Uval := 16.0;
 204             end if;
 205
 206             Base := Uval;
 207             Uval := 0.0;
 208             P := P + 1;
 209
 210             --  Special check to allow initial point (RM 3.5(49))
 211
 212             if Str (P) = '.' then
 213                After_Point := 1;
 214                P := P + 1;
 215             end if;
 216
 217             --  Loop to scan digits of based number. On entry to the loop we
 218             --  must have a valid digit. If we don't, then we have an illegal
 219             --  floating-point value, and we raise Constraint_Error, note that
 220             --  Ptr at this stage was reset to the proper (Start) value.
 221
 222             loop
 223                if P > Max then
 224                   raise Constraint_Error;
 225
 226                elsif Str (P) in Digs then
 227                   Digit := Character'Pos (Str (P)) - Character'Pos ('0');
 228
 229                elsif Str (P) in 'A' .. 'F' then
 230                   Digit :=
 231                     Character'Pos (Str (P)) - (Character'Pos ('A') - 10);
 232
 233                elsif Str (P) in 'a' .. 'f' then
 234                   Digit :=
 235                     Character'Pos (Str (P)) - (Character'Pos ('a') - 10);
 236
 237                else
 238                   raise Constraint_Error;
 239                end if;
 240
 241                --  Save up trailing zeroes after the decimal point
 242
 243                if Digit = 0 and After_Point = 1 then
 244                   Num_Saved_Zeroes := Num_Saved_Zeroes + 1;
 245
 246                --  Here for a non-zero digit
 247
 248                else
 249                   --  First deal with any previously saved zeroes
 250
 251                   if Num_Saved_Zeroes /= 0 then
 252                      Uval := Uval * Base ** Num_Saved_Zeroes;
 253                      Scale := Scale - Num_Saved_Zeroes;
 254                      Num_Saved_Zeroes := 0;
 255                   end if;
 256
 257                   --  Now accumulate the new digit
 258
 259                   Fdigit := Long_Long_Float (Digit);
 260
 261                   if Fdigit >= Base then
 262                      Bad_Base := True;
 263                   else
 264                      Scale := Scale - After_Point;
 265                      Uval := Uval * Base + Fdigit;
 266                   end if;
 267                end if;
 268
 269                P := P + 1;
 270
 271                if P > Max then
 272                   raise Constraint_Error;
 273
 274                elsif Str (P) = '_' then
 275                   Scan_Underscore (Str, P, Ptr, Max, True);
 276
 277                else
 278                   --  Skip past period after digit. Note that the processing
 279                   --  here will permit either a digit after the period, or the
 280                   --  terminating base character, as allowed in (RM 3.5(48))
 281
 282                   if Str (P) = '.' and then After_Point = 0 then
 283                      P := P + 1;
 284                      After_Point := 1;
 285
 286                      if P > Max then
 287                         raise Constraint_Error;
 288                      end if;
 289                   end if;
 290
 291                   exit when Str (P) = Base_Char;
 292                end if;
 293             end loop;
 294
 295             --  Based number successfully scanned out (point was found)
 296
 297             Ptr.all := P + 1;
 298          end;
 299
 300       --  Non-based case, check for being at decimal point now. Note that
 301       --  in Ada 95, we do not insist on a decimal point being present
 302
 303       else
 304          Base := 10.0;
 305          After_Point := 1;
 306
 307          if P <= Max and then Str (P) = '.' then
 308             P := P + 1;
 309
 310             --  Scan digits after point if any are present (RM 3.5(46))
 311
 312             if P <= Max and then Str (P) in Digs then
 313                Scanf;
 314             end if;
 315          end if;
 316
 317          Ptr.all := P;
 318       end if;
 319
 320       --  At this point, we have Uval containing the digits of the value as
 321       --  an integer, and Scale indicates the negative of the number of digits
 322       --  after the point. Base contains the base value (an integral value in
 323       --  the range 2.0 .. 16.0). Test for exponent, must be at least one
 324       --  character after the E for the exponent to be valid.
 325
 326       Scale := Scale + Scan_Exponent (Str, Ptr, Max, Real => True);
 327
 328       --  At this point the exponent has been scanned if one is present and
 329       --  Scale is adjusted to include the exponent value. Uval contains the
 330       --  the integral value which is to be multiplied by Base ** Scale.
 331
 332       --  If base is not 10, use exponentiation for scaling
 333
 334       if Base /= 10.0 then
 335          Uval := Uval * Base ** Scale;
 336
 337       --  For base 10, use power of ten table, repeatedly if necessary
 338
 339       elsif Scale > 0 then
 340          while Scale > Maxpow loop
 341             Uval := Uval * Powten (Maxpow);
 342             Scale := Scale - Maxpow;
 343          end loop;
 344
 345          if Scale > 0 then
 346             Uval := Uval * Powten (Scale);
 347          end if;
 348
 349       elsif Scale < 0 then
 350          while (-Scale) > Maxpow loop
 351             Uval := Uval / Powten (Maxpow);
 352             Scale := Scale + Maxpow;
 353          end loop;
 354
 355          if Scale < 0 then
 356             Uval := Uval / Powten (-Scale);
 357          end if;
 358       end if;
 359
 360       --  Here is where we check for a bad based number
 361
 362       if Bad_Base then
 363          raise Constraint_Error;
 364
 365       --  If OK, then deal with initial minus sign, note that this processing
 366       --  is done even if Uval is zero, so that -0.0 is correctly interpreted.
 367
 368       else
 369          if Minus then
 370             return -Uval;
 371          else
 372             return Uval;
 373          end if;
 374       end if;
 375    end Scan_Real;
 376
 377    ----------------
 378    -- Value_Real --
 379    ----------------
 380
 381    function Value_Real (Str : String) return Long_Long_Float is
 382       V : Long_Long_Float;
 383       P : aliased Integer := Str'First;
 384    begin
 385       V := Scan_Real (Str, P'Access, Str'Last);
 386       Scan_Trailing_Blanks (Str, P);
 387       return V;
 388    end Value_Real;
 389
 390 end System.Val_Real;