1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- S Y S T E M . I M G _ D E C --
9 -- Copyright (C) 1992-2008, Free Software Foundation, Inc. --
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. --
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. --
29 -- GNAT was originally developed by the GNAT team at New York University. --
30 -- Extensive contributions were provided by Ada Core Technologies Inc. --
32 ------------------------------------------------------------------------------
34 with System.Img_Int; use System.Img_Int;
36 package body System.Img_Dec is
42 procedure Image_Decimal
48 pragma Assert (S'First = 1);
51 -- Add space at start for non-negative numbers
60 Set_Image_Decimal (V, S, P, Scale, 1, Integer'Max (1, Scale), 0);
63 ------------------------
64 -- Set_Decimal_Digits --
65 ------------------------
67 procedure Set_Decimal_Digits
68 (Digs : in out String;
77 Minus : constant Boolean := (Digs (Digs'First) = '-');
78 -- Set True if input is negative
80 Zero : Boolean := (Digs (Digs'First + 1) = '0');
81 -- Set True if input is exactly zero (only case when a leading zero
82 -- is permitted in the input string given to this procedure). This
83 -- flag can get set later if rounding causes the value to become zero.
86 -- First digit position of digits remaining to be processed
88 LD : Natural := NDigs;
89 -- Last digit position of digits remaining to be processed
91 ND : Natural := NDigs - 1;
92 -- Number of digits remaining to be processed (LD - FD + 1)
94 Digits_Before_Point : Integer := ND - Scale;
95 -- Number of digits before decimal point in the input value. This
96 -- value can be negative if the input value is less than 0.1, so
97 -- it is an indication of the current exponent. Digits_Before_Point
98 -- is adjusted if the rounding step generates an extra digit.
100 Digits_After_Point : constant Natural := Integer'Max (1, Aft);
101 -- Digit positions after decimal point in result string
104 -- Integer value of exponent
106 procedure Round (N : Natural);
107 -- Round the number in Digs. N is the position of the last digit to be
108 -- retained in the rounded position (rounding is based on Digs (N + 1)
109 -- FD, LD, ND are reset as necessary if required. Note that if the
110 -- result value rounds up (e.g. 9.99 => 10.0), an extra digit can be
111 -- placed in the sign position as a result of the rounding, this is
112 -- the case in which FD is adjusted.
114 procedure Set (C : Character);
116 -- Sets character C in output buffer
118 procedure Set_Blanks_And_Sign (N : Integer);
119 -- Sets leading blanks and minus sign if needed. N is the number of
120 -- positions to be filled (a minus sign is output even if N is zero
121 -- or negative, For a positive value, if N is non-positive, then
122 -- a leading blank is filled.
124 procedure Set_Digits (S, E : Natural);
125 pragma Inline (Set_Digits);
126 -- Set digits S through E from Digs, no effect if S > E
128 procedure Set_Zeroes (N : Integer);
129 pragma Inline (Set_Zeroes);
130 -- Set N zeroes, no effect if N is negative
136 procedure Round (N : Natural) is
140 -- Nothing to do if rounding at or past last digit
145 -- Cases of rounding before the initial digit
149 -- The result is zero, unless we are rounding just before
150 -- the first digit, and the first digit is five or more.
152 if N = 1 and then Digs (Digs'First + 1) >= '5' then
153 Digs (Digs'First) := '1';
155 Digs (Digs'First) := '0';
159 Digits_Before_Point := Digits_Before_Point + 1;
164 -- Normal case of rounding an existing digit
170 if Digs (N + 1) >= '5' then
171 for J in reverse 2 .. N loop
172 D := Character'Succ (Digs (J));
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
186 Digs (Digs'First) := '1';
189 Digits_Before_Point := Digits_Before_Point + 1;
198 procedure Set (C : Character) is
204 -------------------------
205 -- Set_Blanks_And_Sign --
206 -------------------------
208 procedure Set_Blanks_And_Sign (N : Integer) is
226 end Set_Blanks_And_Sign;
232 procedure Set_Digits (S, E : Natural) is
243 procedure Set_Zeroes (N : Integer) is
250 -- Start of processing for Set_Decimal_Digits
253 -- Case of exponent given
256 Set_Blanks_And_Sign (Fore - 1);
257 Round (Digits_After_Point + 2);
263 if ND >= Digits_After_Point then
264 Set_Digits (FD, FD + Digits_After_Point - 1);
267 Set_Zeroes (Digits_After_Point - ND);
270 -- Calculate exponent. The number of digits before the decimal point
271 -- in the input is Digits_Before_Point, and the number of digits
272 -- before the decimal point in the output is 1, so we can get the
273 -- exponent as the difference between these two values. The one
274 -- exception is for the value zero, which by convention has an
280 Expon := Digits_Before_Point - 1;
288 Set_Image_Integer (Expon, Digs, ND);
291 Set_Image_Integer (-Expon, Digs, ND);
294 Set_Zeroes (Exp - ND - 1);
298 -- Case of no exponent given. To make these cases clear, we use
299 -- examples. For all the examples, we assume Fore = 2, Aft = 3.
300 -- A P in the example input string is an implied zero position,
301 -- not included in the input string.
304 -- Round at correct position
305 -- Input: 4PP => unchanged
306 -- Input: 400.03 => unchanged
307 -- Input 3.4567 => 3.457
308 -- Input: 9.9999 => 10.000
309 -- Input: 0.PPP5 => 0.001
310 -- Input: 0.PPP4 => 0
311 -- Input: 0.00003 => 0
313 Round (LD - (Scale - Digits_After_Point));
315 -- No digits before point in input
316 -- Input: .123 Output: 0.123
317 -- Input: .PP3 Output: 0.003
319 if Digits_Before_Point <= 0 then
320 Set_Blanks_And_Sign (Fore - 1);
323 Set_Zeroes (-Digits_Before_Point);
325 Set_Zeroes (Digits_After_Point - Scale);
327 -- At least one digit before point in input
330 -- Less digits in input than are needed before point
331 -- Input: 1PP Output: 100.000
333 if ND < Digits_Before_Point then
335 -- Special case, if the input is the single digit 0, then we
336 -- do not want 000.000, but instead 0.000.
338 if ND = 1 and then Digs (FD) = '0' then
339 Set_Blanks_And_Sign (Fore - 1);
342 -- Normal case where we need to output scaling zeroes
345 Set_Blanks_And_Sign (Fore - Digits_Before_Point);
347 Set_Zeroes (Digits_Before_Point - ND);
350 -- Set period and zeroes after the period
353 Set_Zeroes (Digits_After_Point);
355 -- Input has full amount of digits before decimal point
358 Set_Blanks_And_Sign (Fore - Digits_Before_Point);
359 Set_Digits (FD, FD + Digits_Before_Point - 1);
361 Set_Digits (FD + Digits_Before_Point, LD);
362 Set_Zeroes (Digits_After_Point - (ND - Digits_Before_Point));
366 end Set_Decimal_Digits;
368 -----------------------
369 -- Set_Image_Decimal --
370 -----------------------
372 procedure Set_Image_Decimal
381 Digs : String := Integer'Image (V);
382 -- Sign and digits of decimal value
385 Set_Decimal_Digits (Digs, Digs'Length, S, P, Scale, Fore, Aft, Exp);
386 end Set_Image_Decimal;