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6c9b0f68 | 1 | /* Handle floating-point rounding mode within libc. |
f7a9f785 | 2 | Copyright (C) 2012-2016 Free Software Foundation, Inc. |
6c9b0f68 JM |
3 | This file is part of the GNU C Library. |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
16 | License along with the GNU C Library; if not, see | |
17 | <http://www.gnu.org/licenses/>. */ | |
18 | ||
19 | #ifndef _ROUNDING_MODE_H | |
20 | #define _ROUNDING_MODE_H 1 | |
21 | ||
22 | #include <fenv.h> | |
23 | #include <stdbool.h> | |
24 | #include <stdlib.h> | |
25 | ||
26 | /* Get the architecture-specific definition of how to determine the | |
27 | rounding mode in libc. This header must also define the FE_* | |
28 | macros for any standard rounding modes the architecture does not | |
29 | have in <fenv.h>, to arbitrary distinct values. */ | |
30 | #include <get-rounding-mode.h> | |
31 | ||
32 | /* Return true if a number should be rounded away from zero in | |
33 | rounding mode MODE, false otherwise. NEGATIVE is true if the | |
34 | number is negative, false otherwise. LAST_DIGIT_ODD is true if the | |
35 | last digit of the truncated value (last bit for binary) is odd, | |
36 | false otherwise. HALF_BIT is true if the number is at least half | |
37 | way from the truncated value to the next value with the | |
38 | least-significant digit in the same place, false otherwise. | |
39 | MORE_BITS is true if the number is not exactly equal to the | |
40 | truncated value or the half-way value, false otherwise. */ | |
41 | ||
f1d70dad | 42 | static bool |
6c9b0f68 JM |
43 | round_away (bool negative, bool last_digit_odd, bool half_bit, bool more_bits, |
44 | int mode) | |
45 | { | |
46 | switch (mode) | |
47 | { | |
48 | case FE_DOWNWARD: | |
49 | return negative && (half_bit || more_bits); | |
50 | ||
51 | case FE_TONEAREST: | |
52 | return half_bit && (last_digit_odd || more_bits); | |
53 | ||
54 | case FE_TOWARDZERO: | |
55 | return false; | |
56 | ||
57 | case FE_UPWARD: | |
58 | return !negative && (half_bit || more_bits); | |
59 | ||
60 | default: | |
61 | abort (); | |
62 | } | |
63 | } | |
64 | ||
65 | #endif /* rounding-mode.h */ |