File : 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) 1992-2015, 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 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. --
17 -- --
18 -- --
19 -- --
20 -- --
21 -- --
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/>. --
26 -- --
27 -- GNAT was originally developed by the GNAT team at New York University. --
28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
29 -- --
30 ------------------------------------------------------------------------------
31
32 with System.Img_Int; use System.Img_Int;
33
34 package body System.Img_Dec is
35
36 -------------------
37 -- Image_Decimal --
38 -------------------
39
40 procedure Image_Decimal
41 (V : Integer;
42 S : in out String;
43 P : out Natural;
44 Scale : Integer)
45 is
46 pragma Assert (S'First = 1);
47
48 begin
49 -- Add space at start for non-negative numbers
50
51 if V >= 0 then
52 S (1) := ' ';
53 P := 1;
54 else
55 P := 0;
56 end if;
57
58 Set_Image_Decimal (V, S, P, Scale, 1, Integer'Max (1, Scale), 0);
59 end Image_Decimal;
60
61 ------------------------
62 -- Set_Decimal_Digits --
63 ------------------------
64
65 procedure Set_Decimal_Digits
66 (Digs : in out String;
67 NDigs : Natural;
68 S : out String;
69 P : in out Natural;
70 Scale : Integer;
71 Fore : Natural;
72 Aft : Natural;
73 Exp : Natural)
74 is
75 Minus : constant Boolean := (Digs (Digs'First) = '-');
76 -- Set True if input is negative
77
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.
82
83 FD : Natural := 2;
84 -- First digit position of digits remaining to be processed
85
86 LD : Natural := NDigs;
87 -- Last digit position of digits remaining to be processed
88
89 ND : Natural := NDigs - 1;
90 -- Number of digits remaining to be processed (LD - FD + 1)
91
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.
97
98 Digits_After_Point : constant Natural := Integer'Max (1, Aft);
99 -- Digit positions after decimal point in result string
100
101 Expon : Integer;
102 -- Integer value of exponent
103
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.
112
113 procedure Set (C : Character);
114 pragma Inline (Set);
115 -- Sets character C in output buffer
116
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.
122
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
126
127 procedure Set_Zeroes (N : Integer);
128 pragma Inline (Set_Zeroes);
129 -- Set N zeroes, no effect if N is negative
130
131 -----------
132 -- Round --
133 -----------
134
135 procedure Round (N : Integer) is
136 D : Character;
137
138 begin
139 -- Nothing to do if rounding past the last digit we have
140
141 if N >= LD then
142 return;
143
144 -- Cases of rounding before the initial digit
145
146 elsif N < FD then
147
148 -- The result is zero, unless we are rounding just before
149 -- the first digit, and the first digit is five or more.
150
151 if N = 1 and then Digs (Digs'First + 1) >= '5' then
152 Digs (Digs'First) := '1';
153 else
154 Digs (Digs'First) := '0';
155 Zero := True;
156 end if;
157
158 Digits_Before_Point := Digits_Before_Point + 1;
159 FD := 1;
160 LD := 1;
161 ND := 1;
162
163 -- Normal case of rounding an existing digit
164
165 else
166 LD := N;
167 ND := LD - 1;
168
169 if Digs (N + 1) >= '5' then
170 for J in reverse 2 .. N loop
171 D := Character'Succ (Digs (J));
172
173 if D <= '9' then
174 Digs (J) := D;
175 return;
176 else
177 Digs (J) := '0';
178 end if;
179 end loop;
180
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
184
185 Digs (Digs'First) := '1';
186 FD := 1;
187 ND := ND + 1;
188 Digits_Before_Point := Digits_Before_Point + 1;
189 end if;
190 end if;
191 end Round;
192
193 ---------
194 -- Set --
195 ---------
196
197 procedure Set (C : Character) is
198 begin
199 P := P + 1;
200 S (P) := C;
201 end Set;
202
203 -------------------------
204 -- Set_Blanks_And_Sign --
205 -------------------------
206
207 procedure Set_Blanks_And_Sign (N : Integer) is
208 W : Integer := N;
209
210 begin
211 if Minus then
212 W := W - 1;
213
214 for J in 1 .. W loop
215 Set (' ');
216 end loop;
217
218 Set ('-');
219
220 else
221 for J in 1 .. W loop
222 Set (' ');
223 end loop;
224 end if;
225 end Set_Blanks_And_Sign;
226
227 ----------------
228 -- Set_Digits --
229 ----------------
230
231 procedure Set_Digits (S, E : Natural) is
232 begin
233 for J in S .. E loop
234 Set (Digs (J));
235 end loop;
236 end Set_Digits;
237
238 ----------------
239 -- Set_Zeroes --
240 ----------------
241
242 procedure Set_Zeroes (N : Integer) is
243 begin
244 for J in 1 .. N loop
245 Set ('0');
246 end loop;
247 end Set_Zeroes;
248
249 -- Start of processing for Set_Decimal_Digits
250
251 begin
252 -- Case of exponent given
253
254 if Exp > 0 then
255 Set_Blanks_And_Sign (Fore - 1);
256 Round (Digits_After_Point + 2);
257 Set (Digs (FD));
258 FD := FD + 1;
259 ND := ND - 1;
260 Set ('.');
261
262 if ND >= Digits_After_Point then
263 Set_Digits (FD, FD + Digits_After_Point - 1);
264 else
265 Set_Digits (FD, LD);
266 Set_Zeroes (Digits_After_Point - ND);
267 end if;
268
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
274 -- exponent of +0.
275
276 Expon := (if Zero then 0 else Digits_Before_Point - 1);
277 Set ('E');
278 ND := 0;
279
280 if Expon >= 0 then
281 Set ('+');
282 Set_Image_Integer (Expon, Digs, ND);
283 else
284 Set ('-');
285 Set_Image_Integer (-Expon, Digs, ND);
286 end if;
287
288 Set_Zeroes (Exp - ND - 1);
289 Set_Digits (1, ND);
290 return;
291
292 -- Case of no exponent given. To make these cases clear, we use
293 -- examples. For all the examples, we assume Fore = 2, Aft = 3.
294 -- A P in the example input string is an implied zero position,
295 -- not included in the input string.
296
297 else
298 -- Round at correct position
299 -- Input: 4PP => unchanged
300 -- Input: 400.03 => unchanged
301 -- Input 3.4567 => 3.457
302 -- Input: 9.9999 => 10.000
303 -- Input: 0.PPP5 => 0.001
304 -- Input: 0.PPP4 => 0
305 -- Input: 0.00003 => 0
306
307 Round (LD - (Scale - Digits_After_Point));
308
309 -- No digits before point in input
310 -- Input: .123 Output: 0.123
311 -- Input: .PP3 Output: 0.003
312
313 if Digits_Before_Point <= 0 then
314 Set_Blanks_And_Sign (Fore - 1);
315 Set ('0');
316 Set ('.');
317
318 declare
319 DA : Natural := Digits_After_Point;
320 -- Digits remaining to output after point
321
322 LZ : constant Integer := Integer'Min (DA, -Digits_Before_Point);
323 -- Number of leading zeroes after point. Note: there used to be
324 -- a Max of this result with zero, but that's redundant, since
325 -- we know DA is positive, and because of the test above, we
326 -- know that -Digits_Before_Point >= 0.
327
328 begin
329 Set_Zeroes (LZ);
330 DA := DA - LZ;
331
332 if DA < ND then
333
334 -- Note: it is definitely possible for the above condition
335 -- to be True, for example:
336
337 -- V => 1234, Scale => 5, Fore => 0, After => 1, Exp => 0
338
339 -- but in this case DA = 0, ND = 1, FD = 1, FD + DA-1 = 0
340 -- so the arguments in the call are (1, 0) meaning that no
341 -- digits are output.
342
343 -- No obvious example exists where the following call to
344 -- Set_Digits actually outputs some digits, but we lack a
345 -- proof that no such example exists.
346
347 -- So it is safer to retain this call, even though as a
348 -- result it is hard (or perhaps impossible) to create a
349 -- coverage test for the inlined code of the call.
350
351 Set_Digits (FD, FD + DA - 1);
352
353 else
354 Set_Digits (FD, LD);
355 Set_Zeroes (DA - ND);
356 end if;
357 end;
358
359 -- At least one digit before point in input
360
361 else
362 -- Less digits in input than are needed before point
363 -- Input: 1PP Output: 100.000
364
365 if ND < Digits_Before_Point then
366
367 -- Special case, if the input is the single digit 0, then we
368 -- do not want 000.000, but instead 0.000.
369
370 if ND = 1 and then Digs (FD) = '0' then
371 Set_Blanks_And_Sign (Fore - 1);
372 Set ('0');
373
374 -- Normal case where we need to output scaling zeroes
375
376 else
377 Set_Blanks_And_Sign (Fore - Digits_Before_Point);
378 Set_Digits (FD, LD);
379 Set_Zeroes (Digits_Before_Point - ND);
380 end if;
381
382 -- Set period and zeroes after the period
383
384 Set ('.');
385 Set_Zeroes (Digits_After_Point);
386
387 -- Input has full amount of digits before decimal point
388
389 else
390 Set_Blanks_And_Sign (Fore - Digits_Before_Point);
391 Set_Digits (FD, FD + Digits_Before_Point - 1);
392 Set ('.');
393 Set_Digits (FD + Digits_Before_Point, LD);
394 Set_Zeroes (Digits_After_Point - (ND - Digits_Before_Point));
395 end if;
396 end if;
397 end if;
398 end Set_Decimal_Digits;
399
400 -----------------------
401 -- Set_Image_Decimal --
402 -----------------------
403
404 procedure Set_Image_Decimal
405 (V : Integer;
406 S : in out String;
407 P : in out Natural;
408 Scale : Integer;
409 Fore : Natural;
410 Aft : Natural;
411 Exp : Natural)
412 is
413 Digs : String := Integer'Image (V);
414 -- Sign and digits of decimal value
415
416 begin
417 Set_Decimal_Digits (Digs, Digs'Length, S, P, Scale, Fore, Aft, Exp);
418 end Set_Image_Decimal;
419
420 end System.Img_Dec;