gcc/ada/s-imgdec.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUNTIME COMPONENTS                          --
   4 --                                                                          --
   5 --                        S Y S T E M . I M G _ D E C                       --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --                            $Revision: 1.16 $
  10 --                                                                          --
  11 --          Copyright (C) 1992-2001 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- --
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  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 -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
  33 --                                                                          --
  34 ------------------------------------------------------------------------------
  35
  36 with System.Img_Int; use System.Img_Int;
  37
  38 package body System.Img_Dec is
  39
  40    -------------------
  41    -- Image_Decimal --
  42    -------------------
  43
  44    function Image_Decimal
  45      (V     : Integer;
  46       Scale : Integer)
  47       return  String
  48    is
  49       P : Natural := 0;
  50       S : String (1 .. 64);
  51
  52    begin
  53       Set_Image_Decimal (V, S, P, Scale, 1, Integer'Max (1, Scale), 0);
  54
  55       --  Mess around to make sure we have the objectionable space at the
  56       --  start for positive numbers in accordance with the annoying rules!
  57
  58       if S (1) /= ' ' and then S (1) /= '-' then
  59          S (2 .. P + 1) := S (1 .. P);
  60          S (1) := ' ';
  61          return S (1 .. P + 1);
  62       else
  63          return S (1 .. P);
  64       end if;
  65    end Image_Decimal;
  66
  67    ------------------------
  68    -- Set_Decimal_Digits --
  69    ------------------------
  70
  71    procedure Set_Decimal_Digits
  72      (Digs  : in out String;
  73       NDigs : Natural;
  74       S     : out String;
  75       P     : in out Natural;
  76       Scale : Integer;
  77       Fore  : Natural;
  78       Aft   : Natural;
  79       Exp   : Natural)
  80    is
  81       Minus : constant Boolean := (Digs (1) = '-');
  82       --  Set True if input is negative
  83
  84       Zero : Boolean := (Digs (2) = '0');
  85       --  Set True if input is exactly zero (only case when a leading zero
  86       --  is permitted in the input string given to this procedure). This
  87       --  flag can get set later if rounding causes the value to become zero.
  88
  89       FD : Natural := 2;
  90       --  First digit position of digits remaining to be processed
  91
  92       LD : Natural := NDigs;
  93       --  Last digit position of digits remaining to be processed
  94
  95       ND : Natural := NDigs - 1;
  96       --  Number of digits remaining to be processed (LD - FD + 1)
  97
  98       Digits_Before_Point : Integer := ND - Scale;
  99       --  Number of digits before decimal point in the input value. This
 100       --  value can be negative if the input value is less than 0.1, so
 101       --  it is an indication of the current exponent. Digits_Before_Point
 102       --  is adjusted if the rounding step generates an extra digit.
 103
 104       Digits_After_Point : constant Natural := Integer'Max (1, Aft);
 105       --  Digit positions after decimal point in result string
 106
 107       Expon : Integer;
 108       --  Integer value of exponent
 109
 110       procedure Round (N : Natural);
 111       --  Round the number in Digs. N is the position of the last digit to be
 112       --  retained in the rounded position (rounding is based on Digs (N + 1)
 113       --  FD, LD, ND are reset as necessary if required. Note that if the
 114       --  result value rounds up (e.g. 9.99 => 10.0), an extra digit can be
 115       --  placed in the sign position as a result of the rounding, this is
 116       --  the case in which FD is adjusted.
 117
 118       procedure Set (C : Character);
 119       pragma Inline (Set);
 120       --  Sets character C in output buffer
 121
 122       procedure Set_Blanks_And_Sign (N : Integer);
 123       --  Sets leading blanks and minus sign if needed. N is the number of
 124       --  positions to be filled (a minus sign is output even if N is zero
 125       --  or negative, For a positive value, if N is non-positive, then
 126       --  a leading blank is filled.
 127
 128       procedure Set_Digits (S, E : Natural);
 129       pragma Inline (Set_Digits);
 130       --  Set digits S through E from Digs, no effect if S > E
 131
 132       procedure Set_Zeroes (N : Integer);
 133       pragma Inline (Set_Zeroes);
 134       --  Set N zeroes, no effect if N is negative
 135
 136       procedure Round (N : Natural) is
 137          D : Character;
 138
 139       begin
 140          --  Nothing to do if rounding at or past last digit
 141
 142          if N >= LD then
 143             return;
 144
 145          --  Cases of rounding before the initial digit
 146
 147          elsif N < FD then
 148
 149             --  The result is zero, unless we are rounding just before
 150             --  the first digit, and the first digit is five or more.
 151
 152             if N = 1 and then Digs (2) >= '5' then
 153                Digs (1) := '1';
 154             else
 155                Digs (1) := '0';
 156                Zero := True;
 157             end if;
 158
 159             Digits_Before_Point := Digits_Before_Point + 1;
 160             FD := 1;
 161             LD := 1;
 162             ND := 1;
 163
 164          --  Normal case of rounding an existing digit
 165
 166          else
 167             LD := N;
 168             ND := LD - 1;
 169
 170             if Digs (N + 1) >= '5' then
 171                for J in reverse 2 .. N loop
 172                   D := Character'Succ (Digs (J));
 173
 174                   if D <= '9' then
 175                      Digs (J) := D;
 176                      return;
 177                   else
 178                      Digs (J) := '0';
 179                   end if;
 180                end loop;
 181
 182                --  Here the rounding overflows into the sign position. That's
 183                --  OK, because we already captured the value of the sign and
 184                --  we are in any case destroying the value in the Digs buffer
 185
 186                Digs (1) := '1';
 187                FD := 1;
 188                ND := ND + 1;
 189                Digits_Before_Point := Digits_Before_Point + 1;
 190             end if;
 191          end if;
 192       end Round;
 193
 194       procedure Set (C : Character) is
 195       begin
 196          P := P + 1;
 197          S (P) := C;
 198       end Set;
 199
 200       procedure Set_Blanks_And_Sign (N : Integer) is
 201          W : Integer := N;
 202
 203       begin
 204          if Minus then
 205             W := W - 1;
 206
 207             for J in 1 .. W loop
 208                Set (' ');
 209             end loop;
 210
 211             Set ('-');
 212
 213          else
 214             for J in 1 .. W loop
 215                Set (' ');
 216             end loop;
 217          end if;
 218       end Set_Blanks_And_Sign;
 219
 220       procedure Set_Digits (S, E : Natural) is
 221       begin
 222          for J in S .. E loop
 223             Set (Digs (J));
 224          end loop;
 225       end Set_Digits;
 226
 227       procedure Set_Zeroes (N : Integer) is
 228       begin
 229          for J in 1 .. N loop
 230             Set ('0');
 231          end loop;
 232       end Set_Zeroes;
 233
 234    --  Start of processing for Set_Decimal_Digits
 235
 236    begin
 237       --  Case of exponent given
 238
 239       if Exp > 0 then
 240          Set_Blanks_And_Sign (Fore - 1);
 241          Round (Aft + 2);
 242          Set (Digs (FD));
 243          FD := FD + 1;
 244          ND := ND - 1;
 245          Set ('.');
 246
 247          if ND >= Digits_After_Point then
 248             Set_Digits (FD, FD + Digits_After_Point - 1);
 249
 250          else
 251             Set_Digits (FD, LD);
 252             Set_Zeroes (Digits_After_Point - ND);
 253          end if;
 254
 255          --  Calculate exponent. The number of digits before the decimal point
 256          --  in the input is Digits_Before_Point, and the number of digits
 257          --  before the decimal point in the output is 1, so we can get the
 258          --  exponent as the difference between these two values. The one
 259          --  exception is for the value zero, which by convention has an
 260          --  exponent of +0.
 261
 262          if Zero then
 263             Expon := 0;
 264          else
 265             Expon := Digits_Before_Point - 1;
 266          end if;
 267
 268          Set ('E');
 269          ND := 0;
 270
 271          if Expon >= 0 then
 272             Set ('+');
 273             Set_Image_Integer (Expon, Digs, ND);
 274          else
 275             Set ('-');
 276             Set_Image_Integer (-Expon, Digs, ND);
 277          end if;
 278
 279          Set_Zeroes (Exp - ND - 1);
 280          Set_Digits (1, ND);
 281          return;
 282
 283       --  Case of no exponent given. To make these cases clear, we use
 284       --  examples. For all the examples, we assume Fore = 2, Aft = 3.
 285       --  A P in the example input string is an implied zero position,
 286       --  not included in the input string.
 287
 288       else
 289          --  Round at correct position
 290          --    Input: 4PP      => unchanged
 291          --    Input: 400.03   => unchanged
 292          --    Input  3.4567   => 3.457
 293          --    Input: 9.9999   => 10.000
 294          --    Input: 0.PPP5   => 0.001
 295          --    Input: 0.PPP4   => 0
 296          --    Input: 0.00003  => 0
 297
 298          Round (LD - (Scale - Digits_After_Point));
 299
 300          --  No digits before point in input
 301          --    Input: .123   Output: 0.123
 302          --    Input: .PP3   Output: 0.003
 303
 304          if Digits_Before_Point <= 0 then
 305             Set_Blanks_And_Sign (Fore - 1);
 306             Set ('0');
 307             Set ('.');
 308
 309             Set_Zeroes (Digits_After_Point - ND);
 310             Set_Digits (FD, LD);
 311
 312          --  At least one digit before point in input
 313
 314          else
 315             Set_Blanks_And_Sign (Fore - Digits_Before_Point);
 316
 317             --  Less digits in input than are needed before point
 318             --    Input: 1PP  Output: 100.000
 319
 320             if ND < Digits_Before_Point then
 321                Set_Digits (FD, LD);
 322                Set_Zeroes (Digits_Before_Point - ND);
 323                Set ('.');
 324                Set_Zeroes (Digits_After_Point);
 325
 326             --  Input has full amount of digits before decimal point
 327
 328             else
 329                Set_Digits (FD, FD + Digits_Before_Point - 1);
 330                Set ('.');
 331                Set_Digits (FD + Digits_Before_Point, LD);
 332                Set_Zeroes (Digits_After_Point - (ND - Digits_Before_Point));
 333             end if;
 334          end if;
 335       end if;
 336
 337    end Set_Decimal_Digits;
 338
 339    -----------------------
 340    -- Set_Image_Decimal --
 341    -----------------------
 342
 343    procedure Set_Image_Decimal
 344      (V     : Integer;
 345       S     : out String;
 346       P     : in out Natural;
 347       Scale : Integer;
 348       Fore  : Natural;
 349       Aft   : Natural;
 350       Exp   : Natural)
 351    is
 352       Digs : String := Image_Integer (V);
 353       --  Sign and digits of decimal value
 354
 355    begin
 356       Set_Decimal_Digits (Digs, Digs'Length, S, P, Scale, Fore, Aft, Exp);
 357    end Set_Image_Decimal;
 358
 359 end System.Img_Dec;