gcc/ada/s-imgdec.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --                        S Y S T E M . I M G _ D E C                       --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2006, 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- --
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  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.Img_Int; use System.Img_Int;
  35
  36 package body System.Img_Dec is
  37
  38    -------------------
  39    -- Image_Decimal --
  40    -------------------
  41
  42    function Image_Decimal
  43      (V     : Integer;
  44       Scale : Integer) return String
  45    is
  46       P : Natural := 0;
  47       S : String (1 .. 64);
  48
  49    begin
  50       Set_Image_Decimal (V, S, P, Scale, 1, Integer'Max (1, Scale), 0);
  51
  52       --  Mess around to make sure we have the objectionable space at the
  53       --  start for positive numbers in accordance with the annoying rules!
  54
  55       if S (1) /= ' ' and then S (1) /= '-' then
  56          S (2 .. P + 1) := S (1 .. P);
  57          S (1) := ' ';
  58          return S (1 .. P + 1);
  59       else
  60          return S (1 .. P);
  61       end if;
  62    end Image_Decimal;
  63
  64    ------------------------
  65    -- Set_Decimal_Digits --
  66    ------------------------
  67
  68    procedure Set_Decimal_Digits
  69      (Digs  : in out String;
  70       NDigs : Natural;
  71       S     : out String;
  72       P     : in out Natural;
  73       Scale : Integer;
  74       Fore  : Natural;
  75       Aft   : Natural;
  76       Exp   : Natural)
  77    is
  78       Minus : constant Boolean := (Digs (Digs'First) = '-');
  79       --  Set True if input is negative
  80
  81       Zero : Boolean := (Digs (Digs'First + 1) = '0');
  82       --  Set True if input is exactly zero (only case when a leading zero
  83       --  is permitted in the input string given to this procedure). This
  84       --  flag can get set later if rounding causes the value to become zero.
  85
  86       FD : Natural := 2;
  87       --  First digit position of digits remaining to be processed
  88
  89       LD : Natural := NDigs;
  90       --  Last digit position of digits remaining to be processed
  91
  92       ND : Natural := NDigs - 1;
  93       --  Number of digits remaining to be processed (LD - FD + 1)
  94
  95       Digits_Before_Point : Integer := ND - Scale;
  96       --  Number of digits before decimal point in the input value. This
  97       --  value can be negative if the input value is less than 0.1, so
  98       --  it is an indication of the current exponent. Digits_Before_Point
  99       --  is adjusted if the rounding step generates an extra digit.
 100
 101       Digits_After_Point : constant Natural := Integer'Max (1, Aft);
 102       --  Digit positions after decimal point in result string
 103
 104       Expon : Integer;
 105       --  Integer value of exponent
 106
 107       procedure Round (N : Natural);
 108       --  Round the number in Digs. N is the position of the last digit to be
 109       --  retained in the rounded position (rounding is based on Digs (N + 1)
 110       --  FD, LD, ND are reset as necessary if required. Note that if the
 111       --  result value rounds up (e.g. 9.99 => 10.0), an extra digit can be
 112       --  placed in the sign position as a result of the rounding, this is
 113       --  the case in which FD is adjusted.
 114
 115       procedure Set (C : Character);
 116       pragma Inline (Set);
 117       --  Sets character C in output buffer
 118
 119       procedure Set_Blanks_And_Sign (N : Integer);
 120       --  Sets leading blanks and minus sign if needed. N is the number of
 121       --  positions to be filled (a minus sign is output even if N is zero
 122       --  or negative, For a positive value, if N is non-positive, then
 123       --  a leading blank is filled.
 124
 125       procedure Set_Digits (S, E : Natural);
 126       pragma Inline (Set_Digits);
 127       --  Set digits S through E from Digs, no effect if S > E
 128
 129       procedure Set_Zeroes (N : Integer);
 130       pragma Inline (Set_Zeroes);
 131       --  Set N zeroes, no effect if N is negative
 132
 133       procedure Round (N : Natural) is
 134          D : Character;
 135
 136       begin
 137          --  Nothing to do if rounding at or past last digit
 138
 139          if N >= LD then
 140             return;
 141
 142          --  Cases of rounding before the initial digit
 143
 144          elsif N < FD then
 145
 146             --  The result is zero, unless we are rounding just before
 147             --  the first digit, and the first digit is five or more.
 148
 149             if N = 1 and then Digs (Digs'First + 1) >= '5' then
 150                Digs (Digs'First) := '1';
 151             else
 152                Digs (Digs'First) := '0';
 153                Zero := True;
 154             end if;
 155
 156             Digits_Before_Point := Digits_Before_Point + 1;
 157             FD := 1;
 158             LD := 1;
 159             ND := 1;
 160
 161          --  Normal case of rounding an existing digit
 162
 163          else
 164             LD := N;
 165             ND := LD - 1;
 166
 167             if Digs (N + 1) >= '5' then
 168                for J in reverse 2 .. N loop
 169                   D := Character'Succ (Digs (J));
 170
 171                   if D <= '9' then
 172                      Digs (J) := D;
 173                      return;
 174                   else
 175                      Digs (J) := '0';
 176                   end if;
 177                end loop;
 178
 179                --  Here the rounding overflows into the sign position. That's
 180                --  OK, because we already captured the value of the sign and
 181                --  we are in any case destroying the value in the Digs buffer
 182
 183                Digs (Digs'First) := '1';
 184                FD := 1;
 185                ND := ND + 1;
 186                Digits_Before_Point := Digits_Before_Point + 1;
 187             end if;
 188          end if;
 189       end Round;
 190
 191       procedure Set (C : Character) is
 192       begin
 193          P := P + 1;
 194          S (P) := C;
 195       end Set;
 196
 197       procedure Set_Blanks_And_Sign (N : Integer) is
 198          W : Integer := N;
 199
 200       begin
 201          if Minus then
 202             W := W - 1;
 203
 204             for J in 1 .. W loop
 205                Set (' ');
 206             end loop;
 207
 208             Set ('-');
 209
 210          else
 211             for J in 1 .. W loop
 212                Set (' ');
 213             end loop;
 214          end if;
 215       end Set_Blanks_And_Sign;
 216
 217       procedure Set_Digits (S, E : Natural) is
 218       begin
 219          for J in S .. E loop
 220             Set (Digs (J));
 221          end loop;
 222       end Set_Digits;
 223
 224       procedure Set_Zeroes (N : Integer) is
 225       begin
 226          for J in 1 .. N loop
 227             Set ('0');
 228          end loop;
 229       end Set_Zeroes;
 230
 231    --  Start of processing for Set_Decimal_Digits
 232
 233    begin
 234       --  Case of exponent given
 235
 236       if Exp > 0 then
 237          Set_Blanks_And_Sign (Fore - 1);
 238          Round (Aft + 2);
 239          Set (Digs (FD));
 240          FD := FD + 1;
 241          ND := ND - 1;
 242          Set ('.');
 243
 244          if ND >= Digits_After_Point then
 245             Set_Digits (FD, FD + Digits_After_Point - 1);
 246
 247          else
 248             Set_Digits (FD, LD);
 249             Set_Zeroes (Digits_After_Point - ND);
 250          end if;
 251
 252          --  Calculate exponent. The number of digits before the decimal point
 253          --  in the input is Digits_Before_Point, and the number of digits
 254          --  before the decimal point in the output is 1, so we can get the
 255          --  exponent as the difference between these two values. The one
 256          --  exception is for the value zero, which by convention has an
 257          --  exponent of +0.
 258
 259          if Zero then
 260             Expon := 0;
 261          else
 262             Expon := Digits_Before_Point - 1;
 263          end if;
 264
 265          Set ('E');
 266          ND := 0;
 267
 268          if Expon >= 0 then
 269             Set ('+');
 270             Set_Image_Integer (Expon, Digs, ND);
 271          else
 272             Set ('-');
 273             Set_Image_Integer (-Expon, Digs, ND);
 274          end if;
 275
 276          Set_Zeroes (Exp - ND - 1);
 277          Set_Digits (1, ND);
 278          return;
 279
 280       --  Case of no exponent given. To make these cases clear, we use
 281       --  examples. For all the examples, we assume Fore = 2, Aft = 3.
 282       --  A P in the example input string is an implied zero position,
 283       --  not included in the input string.
 284
 285       else
 286          --  Round at correct position
 287          --    Input: 4PP      => unchanged
 288          --    Input: 400.03   => unchanged
 289          --    Input  3.4567   => 3.457
 290          --    Input: 9.9999   => 10.000
 291          --    Input: 0.PPP5   => 0.001
 292          --    Input: 0.PPP4   => 0
 293          --    Input: 0.00003  => 0
 294
 295          Round (LD - (Scale - Digits_After_Point));
 296
 297          --  No digits before point in input
 298          --    Input: .123   Output: 0.123
 299          --    Input: .PP3   Output: 0.003
 300
 301          if Digits_Before_Point <= 0 then
 302             Set_Blanks_And_Sign (Fore - 1);
 303             Set ('0');
 304             Set ('.');
 305
 306             Set_Zeroes (Digits_After_Point - ND);
 307             Set_Digits (FD, LD);
 308
 309          --  At least one digit before point in input
 310
 311          else
 312             Set_Blanks_And_Sign (Fore - Digits_Before_Point);
 313
 314             --  Less digits in input than are needed before point
 315             --    Input: 1PP  Output: 100.000
 316
 317             if ND < Digits_Before_Point then
 318                Set_Digits (FD, LD);
 319                Set_Zeroes (Digits_Before_Point - ND);
 320                Set ('.');
 321                Set_Zeroes (Digits_After_Point);
 322
 323             --  Input has full amount of digits before decimal point
 324
 325             else
 326                Set_Digits (FD, FD + Digits_Before_Point - 1);
 327                Set ('.');
 328                Set_Digits (FD + Digits_Before_Point, LD);
 329                Set_Zeroes (Digits_After_Point - (ND - Digits_Before_Point));
 330             end if;
 331          end if;
 332       end if;
 333
 334    end Set_Decimal_Digits;
 335
 336    -----------------------
 337    -- Set_Image_Decimal --
 338    -----------------------
 339
 340    procedure Set_Image_Decimal
 341      (V     : Integer;
 342       S     : out String;
 343       P     : in out Natural;
 344       Scale : Integer;
 345       Fore  : Natural;
 346       Aft   : Natural;
 347       Exp   : Natural)
 348    is
 349       Digs : String := Image_Integer (V);
 350       --  Sign and digits of decimal value
 351
 352    begin
 353       Set_Decimal_Digits (Digs, Digs'Length, S, P, Scale, Fore, Aft, Exp);
 354    end Set_Image_Decimal;
 355
 356 end System.Img_Dec;