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 --          Copyright (C) 1992-2002 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,  59 Temple Place - Suite 330,  Boston, --
  20 -- MA 02111-1307, 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)
  45       return  String
  46    is
  47       P : Natural := 0;
  48       S : String (1 .. 64);
  49
  50    begin
  51       Set_Image_Decimal (V, S, P, Scale, 1, Integer'Max (1, Scale), 0);
  52
  53       --  Mess around to make sure we have the objectionable space at the
  54       --  start for positive numbers in accordance with the annoying rules!
  55
  56       if S (1) /= ' ' and then S (1) /= '-' then
  57          S (2 .. P + 1) := S (1 .. P);
  58          S (1) := ' ';
  59          return S (1 .. P + 1);
  60       else
  61          return S (1 .. P);
  62       end if;
  63    end Image_Decimal;
  64
  65    ------------------------
  66    -- Set_Decimal_Digits --
  67    ------------------------
  68
  69    procedure Set_Decimal_Digits
  70      (Digs  : in out String;
  71       NDigs : Natural;
  72       S     : out String;
  73       P     : in out Natural;
  74       Scale : Integer;
  75       Fore  : Natural;
  76       Aft   : Natural;
  77       Exp   : Natural)
  78    is
  79       Minus : constant Boolean := (Digs (1) = '-');
  80       --  Set True if input is negative
  81
  82       Zero : Boolean := (Digs (2) = '0');
  83       --  Set True if input is exactly zero (only case when a leading zero
  84       --  is permitted in the input string given to this procedure). This
  85       --  flag can get set later if rounding causes the value to become zero.
  86
  87       FD : Natural := 2;
  88       --  First digit position of digits remaining to be processed
  89
  90       LD : Natural := NDigs;
  91       --  Last digit position of digits remaining to be processed
  92
  93       ND : Natural := NDigs - 1;
  94       --  Number of digits remaining to be processed (LD - FD + 1)
  95
  96       Digits_Before_Point : Integer := ND - Scale;
  97       --  Number of digits before decimal point in the input value. This
  98       --  value can be negative if the input value is less than 0.1, so
  99       --  it is an indication of the current exponent. Digits_Before_Point
 100       --  is adjusted if the rounding step generates an extra digit.
 101
 102       Digits_After_Point : constant Natural := Integer'Max (1, Aft);
 103       --  Digit positions after decimal point in result string
 104
 105       Expon : Integer;
 106       --  Integer value of exponent
 107
 108       procedure Round (N : Natural);
 109       --  Round the number in Digs. N is the position of the last digit to be
 110       --  retained in the rounded position (rounding is based on Digs (N + 1)
 111       --  FD, LD, ND are reset as necessary if required. Note that if the
 112       --  result value rounds up (e.g. 9.99 => 10.0), an extra digit can be
 113       --  placed in the sign position as a result of the rounding, this is
 114       --  the case in which FD is adjusted.
 115
 116       procedure Set (C : Character);
 117       pragma Inline (Set);
 118       --  Sets character C in output buffer
 119
 120       procedure Set_Blanks_And_Sign (N : Integer);
 121       --  Sets leading blanks and minus sign if needed. N is the number of
 122       --  positions to be filled (a minus sign is output even if N is zero
 123       --  or negative, For a positive value, if N is non-positive, then
 124       --  a leading blank is filled.
 125
 126       procedure Set_Digits (S, E : Natural);
 127       pragma Inline (Set_Digits);
 128       --  Set digits S through E from Digs, no effect if S > E
 129
 130       procedure Set_Zeroes (N : Integer);
 131       pragma Inline (Set_Zeroes);
 132       --  Set N zeroes, no effect if N is negative
 133
 134       procedure Round (N : Natural) is
 135          D : Character;
 136
 137       begin
 138          --  Nothing to do if rounding at or past last digit
 139
 140          if N >= LD then
 141             return;
 142
 143          --  Cases of rounding before the initial digit
 144
 145          elsif N < FD then
 146
 147             --  The result is zero, unless we are rounding just before
 148             --  the first digit, and the first digit is five or more.
 149
 150             if N = 1 and then Digs (2) >= '5' then
 151                Digs (1) := '1';
 152             else
 153                Digs (1) := '0';
 154                Zero := True;
 155             end if;
 156
 157             Digits_Before_Point := Digits_Before_Point + 1;
 158             FD := 1;
 159             LD := 1;
 160             ND := 1;
 161
 162          --  Normal case of rounding an existing digit
 163
 164          else
 165             LD := N;
 166             ND := LD - 1;
 167
 168             if Digs (N + 1) >= '5' then
 169                for J in reverse 2 .. N loop
 170                   D := Character'Succ (Digs (J));
 171
 172                   if D <= '9' then
 173                      Digs (J) := D;
 174                      return;
 175                   else
 176                      Digs (J) := '0';
 177                   end if;
 178                end loop;
 179
 180                --  Here the rounding overflows into the sign position. That's
 181                --  OK, because we already captured the value of the sign and
 182                --  we are in any case destroying the value in the Digs buffer
 183
 184                Digs (1) := '1';
 185                FD := 1;
 186                ND := ND + 1;
 187                Digits_Before_Point := Digits_Before_Point + 1;
 188             end if;
 189          end if;
 190       end Round;
 191
 192       procedure Set (C : Character) is
 193       begin
 194          P := P + 1;
 195          S (P) := C;
 196       end Set;
 197
 198       procedure Set_Blanks_And_Sign (N : Integer) is
 199          W : Integer := N;
 200
 201       begin
 202          if Minus then
 203             W := W - 1;
 204
 205             for J in 1 .. W loop
 206                Set (' ');
 207             end loop;
 208
 209             Set ('-');
 210
 211          else
 212             for J in 1 .. W loop
 213                Set (' ');
 214             end loop;
 215          end if;
 216       end Set_Blanks_And_Sign;
 217
 218       procedure Set_Digits (S, E : Natural) is
 219       begin
 220          for J in S .. E loop
 221             Set (Digs (J));
 222          end loop;
 223       end Set_Digits;
 224
 225       procedure Set_Zeroes (N : Integer) is
 226       begin
 227          for J in 1 .. N loop
 228             Set ('0');
 229          end loop;
 230       end Set_Zeroes;
 231
 232    --  Start of processing for Set_Decimal_Digits
 233
 234    begin
 235       --  Case of exponent given
 236
 237       if Exp > 0 then
 238          Set_Blanks_And_Sign (Fore - 1);
 239          Round (Aft + 2);
 240          Set (Digs (FD));
 241          FD := FD + 1;
 242          ND := ND - 1;
 243          Set ('.');
 244
 245          if ND >= Digits_After_Point then
 246             Set_Digits (FD, FD + Digits_After_Point - 1);
 247
 248          else
 249             Set_Digits (FD, LD);
 250             Set_Zeroes (Digits_After_Point - ND);
 251          end if;
 252
 253          --  Calculate exponent. The number of digits before the decimal point
 254          --  in the input is Digits_Before_Point, and the number of digits
 255          --  before the decimal point in the output is 1, so we can get the
 256          --  exponent as the difference between these two values. The one
 257          --  exception is for the value zero, which by convention has an
 258          --  exponent of +0.
 259
 260          if Zero then
 261             Expon := 0;
 262          else
 263             Expon := Digits_Before_Point - 1;
 264          end if;
 265
 266          Set ('E');
 267          ND := 0;
 268
 269          if Expon >= 0 then
 270             Set ('+');
 271             Set_Image_Integer (Expon, Digs, ND);
 272          else
 273             Set ('-');
 274             Set_Image_Integer (-Expon, Digs, ND);
 275          end if;
 276
 277          Set_Zeroes (Exp - ND - 1);
 278          Set_Digits (1, ND);
 279          return;
 280
 281       --  Case of no exponent given. To make these cases clear, we use
 282       --  examples. For all the examples, we assume Fore = 2, Aft = 3.
 283       --  A P in the example input string is an implied zero position,
 284       --  not included in the input string.
 285
 286       else
 287          --  Round at correct position
 288          --    Input: 4PP      => unchanged
 289          --    Input: 400.03   => unchanged
 290          --    Input  3.4567   => 3.457
 291          --    Input: 9.9999   => 10.000
 292          --    Input: 0.PPP5   => 0.001
 293          --    Input: 0.PPP4   => 0
 294          --    Input: 0.00003  => 0
 295
 296          Round (LD - (Scale - Digits_After_Point));
 297
 298          --  No digits before point in input
 299          --    Input: .123   Output: 0.123
 300          --    Input: .PP3   Output: 0.003
 301
 302          if Digits_Before_Point <= 0 then
 303             Set_Blanks_And_Sign (Fore - 1);
 304             Set ('0');
 305             Set ('.');
 306
 307             Set_Zeroes (Digits_After_Point - ND);
 308             Set_Digits (FD, LD);
 309
 310          --  At least one digit before point in input
 311
 312          else
 313             Set_Blanks_And_Sign (Fore - Digits_Before_Point);
 314
 315             --  Less digits in input than are needed before point
 316             --    Input: 1PP  Output: 100.000
 317
 318             if ND < Digits_Before_Point then
 319                Set_Digits (FD, LD);
 320                Set_Zeroes (Digits_Before_Point - ND);
 321                Set ('.');
 322                Set_Zeroes (Digits_After_Point);
 323
 324             --  Input has full amount of digits before decimal point
 325
 326             else
 327                Set_Digits (FD, FD + Digits_Before_Point - 1);
 328                Set ('.');
 329                Set_Digits (FD + Digits_Before_Point, LD);
 330                Set_Zeroes (Digits_After_Point - (ND - Digits_Before_Point));
 331             end if;
 332          end if;
 333       end if;
 334
 335    end Set_Decimal_Digits;
 336
 337    -----------------------
 338    -- Set_Image_Decimal --
 339    -----------------------
 340
 341    procedure Set_Image_Decimal
 342      (V     : Integer;
 343       S     : out String;
 344       P     : in out Natural;
 345       Scale : Integer;
 346       Fore  : Natural;
 347       Aft   : Natural;
 348       Exp   : Natural)
 349    is
 350       Digs : String := Image_Integer (V);
 351       --  Sign and digits of decimal value
 352
 353    begin
 354       Set_Decimal_Digits (Digs, Digs'Length, S, P, Scale, Fore, Aft, Exp);
 355    end Set_Image_Decimal;
 356
 357 end System.Img_Dec;