1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- S Y S T E M . I M G _ D E C --
9 -- Copyright (C) 1992-2009, 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 3, 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. --
18 -- As a special exception under Section 7 of GPL version 3, you are granted --
19 -- additional permissions described in the GCC Runtime Library Exception, --
20 -- version 3.1, as published by the Free Software Foundation. --
22 -- You should have received a copy of the GNU General Public License and --
23 -- a copy of the GCC Runtime Library Exception along with this program; --
24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
25 -- <http://www.gnu.org/licenses/>. --
27 -- GNAT was originally developed by the GNAT team at New York University. --
28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
30 ------------------------------------------------------------------------------
32 with System.Img_Int; use System.Img_Int;
34 package body System.Img_Dec is
40 procedure Image_Decimal
46 pragma Assert (S'First = 1);
49 -- Add space at start for non-negative numbers
58 Set_Image_Decimal (V, S, P, Scale, 1, Integer'Max (1, Scale), 0);
61 ------------------------
62 -- Set_Decimal_Digits --
63 ------------------------
65 procedure Set_Decimal_Digits
66 (Digs : in out String;
75 Minus : constant Boolean := (Digs (Digs'First) = '-');
76 -- Set True if input is negative
78 Zero : Boolean := (Digs (Digs'First + 1) = '0');
79 -- Set True if input is exactly zero (only case when a leading zero
80 -- is permitted in the input string given to this procedure). This
81 -- flag can get set later if rounding causes the value to become zero.
84 -- First digit position of digits remaining to be processed
86 LD : Natural := NDigs;
87 -- Last digit position of digits remaining to be processed
89 ND : Natural := NDigs - 1;
90 -- Number of digits remaining to be processed (LD - FD + 1)
92 Digits_Before_Point : Integer := ND - Scale;
93 -- Number of digits before decimal point in the input value. This
94 -- value can be negative if the input value is less than 0.1, so
95 -- it is an indication of the current exponent. Digits_Before_Point
96 -- is adjusted if the rounding step generates an extra digit.
98 Digits_After_Point : constant Natural := Integer'Max (1, Aft);
99 -- Digit positions after decimal point in result string
102 -- Integer value of exponent
104 procedure Round (N : Integer);
105 -- Round the number in Digs. N is the position of the last digit to be
106 -- retained in the rounded position (rounding is based on Digs (N + 1)
107 -- FD, LD, ND are reset as necessary if required. Note that if the
108 -- result value rounds up (e.g. 9.99 => 10.0), an extra digit can be
109 -- placed in the sign position as a result of the rounding, this is
110 -- the case in which FD is adjusted. The call to Round has no effect
111 -- if N is outside the range FD .. LD.
113 procedure Set (C : Character);
115 -- Sets character C in output buffer
117 procedure Set_Blanks_And_Sign (N : Integer);
118 -- Sets leading blanks and minus sign if needed. N is the number of
119 -- positions to be filled (a minus sign is output even if N is zero
120 -- or negative, For a positive value, if N is non-positive, then
121 -- a leading blank is filled.
123 procedure Set_Digits (S, E : Natural);
124 pragma Inline (Set_Digits);
125 -- Set digits S through E from Digs, no effect if S > E
127 procedure Set_Zeroes (N : Integer);
128 pragma Inline (Set_Zeroes);
129 -- Set N zeroes, no effect if N is negative
135 procedure Round (N : Integer) is
139 -- Nothing to do if rounding past the last digit we have
144 -- Cases of rounding before the initial digit
148 -- The result is zero, unless we are rounding just before
149 -- the first digit, and the first digit is five or more.
151 if N = 1 and then Digs (Digs'First + 1) >= '5' then
152 Digs (Digs'First) := '1';
154 Digs (Digs'First) := '0';
158 Digits_Before_Point := Digits_Before_Point + 1;
163 -- Normal case of rounding an existing digit
169 if Digs (N + 1) >= '5' then
170 for J in reverse 2 .. N loop
171 D := Character'Succ (Digs (J));
181 -- Here the rounding overflows into the sign position. That's
182 -- OK, because we already captured the value of the sign and
183 -- we are in any case destroying the value in the Digs buffer
185 Digs (Digs'First) := '1';
188 Digits_Before_Point := Digits_Before_Point + 1;
197 procedure Set (C : Character) is
203 -------------------------
204 -- Set_Blanks_And_Sign --
205 -------------------------
207 procedure Set_Blanks_And_Sign (N : Integer) is
225 end Set_Blanks_And_Sign;
231 procedure Set_Digits (S, E : Natural) is
242 procedure Set_Zeroes (N : Integer) is
249 -- Start of processing for Set_Decimal_Digits
252 -- Case of exponent given
255 Set_Blanks_And_Sign (Fore - 1);
256 Round (Digits_After_Point + 2);
262 if ND >= Digits_After_Point then
263 Set_Digits (FD, FD + Digits_After_Point - 1);
266 Set_Zeroes (Digits_After_Point - ND);
269 -- Calculate exponent. The number of digits before the decimal point
270 -- in the input is Digits_Before_Point, and the number of digits
271 -- before the decimal point in the output is 1, so we can get the
272 -- exponent as the difference between these two values. The one
273 -- exception is for the value zero, which by convention has an
279 Expon := Digits_Before_Point - 1;
287 Set_Image_Integer (Expon, Digs, ND);
290 Set_Image_Integer (-Expon, Digs, ND);
293 Set_Zeroes (Exp - ND - 1);
297 -- Case of no exponent given. To make these cases clear, we use
298 -- examples. For all the examples, we assume Fore = 2, Aft = 3.
299 -- A P in the example input string is an implied zero position,
300 -- not included in the input string.
303 -- Round at correct position
304 -- Input: 4PP => unchanged
305 -- Input: 400.03 => unchanged
306 -- Input 3.4567 => 3.457
307 -- Input: 9.9999 => 10.000
308 -- Input: 0.PPP5 => 0.001
309 -- Input: 0.PPP4 => 0
310 -- Input: 0.00003 => 0
312 Round (LD - (Scale - Digits_After_Point));
314 -- No digits before point in input
315 -- Input: .123 Output: 0.123
316 -- Input: .PP3 Output: 0.003
318 if Digits_Before_Point <= 0 then
319 Set_Blanks_And_Sign (Fore - 1);
324 DA : Natural := Digits_After_Point;
325 -- Digits remaining to output after point
327 LZ : constant Integer :=
328 Integer'Max (0, Integer'Min (DA, -Digits_Before_Point));
329 -- Number of leading zeroes after point
336 Set_Digits (FD, FD + DA - 1);
340 Set_Zeroes (DA - ND);
344 -- At least one digit before point in input
347 -- Less digits in input than are needed before point
348 -- Input: 1PP Output: 100.000
350 if ND < Digits_Before_Point then
352 -- Special case, if the input is the single digit 0, then we
353 -- do not want 000.000, but instead 0.000.
355 if ND = 1 and then Digs (FD) = '0' then
356 Set_Blanks_And_Sign (Fore - 1);
359 -- Normal case where we need to output scaling zeroes
362 Set_Blanks_And_Sign (Fore - Digits_Before_Point);
364 Set_Zeroes (Digits_Before_Point - ND);
367 -- Set period and zeroes after the period
370 Set_Zeroes (Digits_After_Point);
372 -- Input has full amount of digits before decimal point
375 Set_Blanks_And_Sign (Fore - Digits_Before_Point);
376 Set_Digits (FD, FD + Digits_Before_Point - 1);
378 Set_Digits (FD + Digits_Before_Point, LD);
379 Set_Zeroes (Digits_After_Point - (ND - Digits_Before_Point));
383 end Set_Decimal_Digits;
385 -----------------------
386 -- Set_Image_Decimal --
387 -----------------------
389 procedure Set_Image_Decimal
398 Digs : String := Integer'Image (V);
399 -- Sign and digits of decimal value
402 Set_Decimal_Digits (Digs, Digs'Length, S, P, Scale, Fore, Aft, Exp);
403 end Set_Image_Decimal;