1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- S Y S T E M . I M G _ R E A L --
9 -- Copyright (C) 1992-2007, 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_LLU; use System.Img_LLU;
35 with System.Img_Uns; use System.Img_Uns;
36 with System.Powten_Table; use System.Powten_Table;
37 with System.Unsigned_Types; use System.Unsigned_Types;
39 package body System.Img_Real is
41 -- The following defines the maximum number of digits that we can convert
42 -- accurately. This is limited by the precision of Long_Long_Float, and
43 -- also by the number of digits we can hold in Long_Long_Unsigned, which
44 -- is the integer type we use as an intermediate for the result.
46 -- We assume that in practice, the limitation will come from the digits
47 -- value, rather than the integer value. This is true for typical IEEE
48 -- implementations, and at worst, the only loss is for some precision
49 -- in very high precision floating-point output.
51 -- Note that in the following, the "-2" accounts for the sign and one
52 -- extra digits, since we need the maximum number of 9's that can be
53 -- supported, e.g. for the normal 64 bit case, Long_Long_Integer'Width
54 -- is 21, since the maximum value (approx 1.6 * 10**19) has 20 digits,
55 -- but the maximum number of 9's that can be supported is 19.
59 (Long_Long_Unsigned'Width - 2, Long_Long_Float'Digits);
61 Unsdigs : constant := Unsigned'Width - 2;
62 -- Number of digits that can be converted using type Unsigned
63 -- See above for the explanation of the -2.
65 Maxscaling : constant := 5000;
66 -- Max decimal scaling required during conversion of floating-point
67 -- numbers to decimal. This is used to defend against infinite
68 -- looping in the conversion, as can be caused by erroneous executions.
69 -- The largest exponent used on any current system is 2**16383, which
70 -- is approximately 10**4932, and the highest number of decimal digits
71 -- is about 35 for 128-bit floating-point formats, so 5000 leaves
72 -- enough room for scaling such values
74 function Is_Negative (V : Long_Long_Float) return Boolean;
75 pragma Import (Intrinsic, Is_Negative);
77 --------------------------
78 -- Image_Floating_Point --
79 --------------------------
81 procedure Image_Floating_Point
87 pragma Assert (S'First = 1);
90 -- Decide wether a blank should be prepended before the call to
91 -- Set_Image_Real. We generate a blank for positive values, and
92 -- also for positive zeroes. For negative zeroes, we generate a
93 -- space only if Signed_Zeroes is True (the RM only permits the
94 -- output of -0.0 on targets where this is the case). We can of
95 -- course still see a -0.0 on a target where Signed_Zeroes is
96 -- False (since this attribute refers to the proper handling of
97 -- negative zeroes, not to their existence).
99 if not Is_Negative (V)
100 or else (not Long_Long_Float'Signed_Zeros and then V = -0.0)
108 Set_Image_Real (V, S, P, 1, Digs - 1, 3);
109 end Image_Floating_Point;
111 --------------------------------
112 -- Image_Ordinary_Fixed_Point --
113 --------------------------------
115 procedure Image_Ordinary_Fixed_Point
116 (V : Long_Long_Float;
121 pragma Assert (S'First = 1);
124 -- Output space at start if non-negative
133 Set_Image_Real (V, S, P, 1, Aft, 0);
134 end Image_Ordinary_Fixed_Point;
140 procedure Set_Image_Real
141 (V : Long_Long_Float;
149 pragma Import (C, Reset, "__gnat_init_float");
150 -- We import the floating-point processor reset routine so that we can
151 -- be sure the floating-point processor is properly set for conversion
152 -- calls (see description of Reset in GNAT.Float_Control (g-flocon.ads).
153 -- This is notably need on Windows, where calls to the operating system
154 -- randomly reset the processor into 64-bit mode.
156 NFrac : constant Natural := Natural'Max (Aft, 1);
158 X : aliased Long_Long_Float;
159 -- This is declared aliased because the expansion of X'Valid passes
160 -- X by access and JGNAT requires all access parameters to be aliased.
161 -- The Valid attribute probably needs to be handled via a different
162 -- expansion for JGNAT, and this use of aliased should be removed
163 -- once Valid is handled properly. ???
167 Field_Max : constant := 255;
168 -- This should be the same value as Ada.[Wide_]Text_IO.Field'Last.
169 -- It is not worth dragging in Ada.Text_IO to pick up this value,
170 -- since it really should never be necessary to change it!
172 Digs : String (1 .. 2 * Field_Max + 16);
173 -- Array used to hold digits of converted integer value. This is a
174 -- large enough buffer to accommodate ludicrous values of Fore and Aft.
177 -- Number of digits stored in Digs (and also subscript of last digit)
179 procedure Adjust_Scale (S : Natural);
180 -- Adjusts the value in X by multiplying or dividing by a power of
181 -- ten so that it is in the range 10**(S-1) <= X < 10**S. Includes
182 -- adding 0.5 to round the result, readjusting if the rounding causes
183 -- the result to wander out of the range. Scale is adjusted to reflect
184 -- the power of ten used to divide the result (i.e. one is added to
185 -- the scale value for each division by 10.0, or one is subtracted
186 -- for each multiplication by 10.0).
188 procedure Convert_Integer;
189 -- Takes the value in X, outputs integer digits into Digs. On return,
190 -- Ndigs is set to the number of digits stored. The digits are stored
191 -- in Digs (1 .. Ndigs),
193 procedure Set (C : Character);
194 -- Sets character C in output buffer
196 procedure Set_Blanks_And_Sign (N : Integer);
197 -- Sets leading blanks and minus sign if needed. N is the number of
198 -- positions to be filled (a minus sign is output even if N is zero
199 -- or negative, but for a positive value, if N is non-positive, then
200 -- the call has no effect).
202 procedure Set_Digs (S, E : Natural);
203 -- Set digits S through E from Digs buffer. No effect if S > E
205 procedure Set_Special_Fill (N : Natural);
206 -- After outputting +Inf, -Inf or NaN, this routine fills out the
207 -- rest of the field with * characters. The argument is the number
208 -- of characters output so far (either 3 or 4)
210 procedure Set_Zeros (N : Integer);
211 -- Set N zeros, no effect if N is negative
214 pragma Inline (Set_Digs);
215 pragma Inline (Set_Zeros);
221 procedure Adjust_Scale (S : Natural) is
225 XP : Long_Long_Float;
228 -- Cases where scaling up is required
230 if X < Powten (S - 1) then
232 -- What we are looking for is a power of ten to multiply X by
233 -- so that the result lies within the required range.
236 XP := X * Powten (Maxpow);
237 exit when XP >= Powten (S - 1) or Scale < -Maxscaling;
239 Scale := Scale - Maxpow;
242 -- The following exception is only raised in case of erroneous
243 -- execution, where a number was considered valid but still
244 -- fails to scale up. One situation where this can happen is
245 -- when a system which is supposed to be IEEE-compliant, but
246 -- has been reconfigured to flush denormals to zero.
248 if Scale < -Maxscaling then
249 raise Constraint_Error;
252 -- Here we know that we must multiply by at least 10**1 and that
253 -- 10**Maxpow takes us too far: binary search to find right one.
255 -- Because of roundoff errors, it is possible for the value
256 -- of XP to be just outside of the interval when Lo >= Hi. In
257 -- that case we adjust explicitly by a factor of 10. This
258 -- can only happen with a value that is very close to an
259 -- exact power of 10.
265 Mid := (Lo + Hi) / 2;
266 XP := X * Powten (Mid);
268 if XP < Powten (S - 1) then
279 elsif XP >= Powten (S) then
296 Scale := Scale - Mid;
298 -- Cases where scaling down is required
300 elsif X >= Powten (S) then
302 -- What we are looking for is a power of ten to divide X by
303 -- so that the result lies within the required range.
306 XP := X / Powten (Maxpow);
307 exit when XP < Powten (S) or Scale > Maxscaling;
309 Scale := Scale + Maxpow;
312 -- The following exception is only raised in case of erroneous
313 -- execution, where a number was considered valid but still
314 -- fails to scale up. One situation where this can happen is
315 -- when a system which is supposed to be IEEE-compliant, but
316 -- has been reconfigured to flush denormals to zero.
318 if Scale > Maxscaling then
319 raise Constraint_Error;
322 -- Here we know that we must divide by at least 10**1 and that
323 -- 10**Maxpow takes us too far, binary search to find right one.
329 Mid := (Lo + Hi) / 2;
330 XP := X / Powten (Mid);
332 if XP < Powten (S - 1) then
343 elsif XP >= Powten (S) then
360 Scale := Scale + Mid;
362 -- Here we are already scaled right
368 -- Round, readjusting scale if needed. Note that if a readjustment
369 -- occurs, then it is never necessary to round again, because there
370 -- is no possibility of such a second rounding causing a change.
374 if X >= Powten (S) then
381 ---------------------
382 -- Convert_Integer --
383 ---------------------
385 procedure Convert_Integer is
387 -- Use Unsigned routine if possible, since on many machines it will
388 -- be significantly more efficient than the Long_Long_Unsigned one.
390 if X < Powten (Unsdigs) then
393 (Unsigned (Long_Long_Float'Truncation (X)),
396 -- But if we want more digits than fit in Unsigned, we have to use
397 -- the Long_Long_Unsigned routine after all.
401 Set_Image_Long_Long_Unsigned
402 (Long_Long_Unsigned (Long_Long_Float'Truncation (X)),
411 procedure Set (C : Character) is
417 -------------------------
418 -- Set_Blanks_And_Sign --
419 -------------------------
421 procedure Set_Blanks_And_Sign (N : Integer) is
424 for J in 1 .. N - 1 loop
435 end Set_Blanks_And_Sign;
441 procedure Set_Digs (S, E : Natural) is
448 ----------------------
449 -- Set_Special_Fill --
450 ----------------------
452 procedure Set_Special_Fill (N : Natural) is
456 F := Fore + 1 + Aft - N;
465 end Set_Special_Fill;
471 procedure Set_Zeros (N : Integer) is
478 -- Start of processing for Set_Image_Real
484 -- Deal with invalid values first,
488 -- Note that we're taking our chances here, as V might be
489 -- an invalid bit pattern resulting from erroneous execution
490 -- (caused by using uninitialized variables for example).
492 -- No matter what, we'll at least get reasonable behaviour,
493 -- converting to infinity or some other value, or causing an
494 -- exception to be raised is fine.
496 -- If the following test succeeds, then we definitely have
497 -- an infinite value, so we print Inf.
499 if V > Long_Long_Float'Last then
504 Set_Special_Fill (4);
506 -- In all other cases we print NaN
508 elsif V < Long_Long_Float'First then
513 Set_Special_Fill (4);
519 Set_Special_Fill (3);
540 if Long_Long_Float'Signed_Zeros and then Is_Negative (V) then
546 Set_Blanks_And_Sign (Fore - 1);
554 Set_Zeros (Natural'Max (1, Exp - 1));
560 -- It should not be possible for a NaN to end up here.
561 -- Either the 'Valid test has failed, or we have some form
562 -- of erroneous execution. Raise Constraint_Error instead of
563 -- attempting to go ahead printing the value.
565 raise Constraint_Error;
568 -- X and Sign are set here, and X is known to be a valid,
569 -- non-zero floating-point number.
571 -- Case of non-zero value with Exp = 0
575 -- First step is to multiply by 10 ** Nfrac to get an integer
576 -- value to be output, an then add 0.5 to round the result.
579 NF : Natural := NFrac;
583 -- If we are larger than Powten (Maxdigs) now, then
584 -- we have too many significant digits, and we have
585 -- not even finished multiplying by NFrac (NF shows
586 -- the number of unaccounted-for digits).
588 if X >= Powten (Maxdigs) then
590 -- In this situation, we only to generate a reasonable
591 -- number of significant digits, and then zeroes after.
592 -- So first we rescale to get:
594 -- 10 ** (Maxdigs - 1) <= X < 10 ** Maxdigs
596 -- and then convert the resulting integer
598 Adjust_Scale (Maxdigs);
601 -- If that caused rescaling, then add zeros to the end
602 -- of the number to account for this scaling. Also add
603 -- zeroes to account for the undone multiplications
605 for J in 1 .. Scale + NF loop
612 -- If multiplication is complete, then convert the resulting
613 -- integer after rounding (note that X is non-negative)
620 -- Otherwise we can go ahead with the multiplication. If it
621 -- can be done in one step, then do it in one step.
623 elsif NF < Maxpow then
624 X := X * Powten (NF);
627 -- If it cannot be done in one step, then do partial scaling
630 X := X * Powten (Maxpow);
636 -- If number of available digits is less or equal to NFrac,
637 -- then we need an extra zero before the decimal point.
639 if Ndigs <= NFrac then
640 Set_Blanks_And_Sign (Fore - 1);
643 Set_Zeros (NFrac - Ndigs);
646 -- Normal case with some digits before the decimal point
649 Set_Blanks_And_Sign (Fore - (Ndigs - NFrac));
650 Set_Digs (1, Ndigs - NFrac);
652 Set_Digs (Ndigs - NFrac + 1, Ndigs);
655 -- Case of non-zero value with non-zero Exp value
658 -- If NFrac is less than Maxdigs, then all the fraction digits are
659 -- significant, so we can scale the resulting integer accordingly.
661 if NFrac < Maxdigs then
662 Adjust_Scale (NFrac + 1);
665 -- Otherwise, we get the maximum number of digits available
668 Adjust_Scale (Maxdigs);
671 for J in 1 .. NFrac - Maxdigs + 1 loop
678 Set_Blanks_And_Sign (Fore - 1);
683 -- The exponent is the scaling factor adjusted for the digits
684 -- that we output after the decimal point, since these were
685 -- included in the scaled digits that we output.
687 Expon := Scale + NFrac;
694 Set_Image_Unsigned (Unsigned (Expon), Digs, Ndigs);
697 Set_Image_Unsigned (Unsigned (-Expon), Digs, Ndigs);
700 Set_Zeros (Exp - Ndigs - 1);