| yuezonghe | 824eb0c | 2024-06-27 02:32:26 -0700 | [diff] [blame] | 1 | /* Round double to integer away from zero. |
| 2 | Copyright (C) 1997 Free Software Foundation, Inc. |
| 3 | This file is part of the GNU C Library. |
| 4 | Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997. |
| 5 | |
| 6 | The GNU C Library is free software; you can redistribute it and/or |
| 7 | modify it under the terms of the GNU Lesser General Public |
| 8 | License as published by the Free Software Foundation; either |
| 9 | version 2.1 of the License, or (at your option) any later version. |
| 10 | |
| 11 | The GNU C Library is distributed in the hope that it will be useful, |
| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 14 | Lesser General Public License for more details. |
| 15 | |
| 16 | You should have received a copy of the GNU Lesser General Public |
| 17 | License along with the GNU C Library; if not, write to the Free |
| 18 | Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
| 19 | 02111-1307 USA. */ |
| 20 | |
| 21 | #include <math.h> |
| 22 | #include "math_private.h" |
| 23 | |
| 24 | static const double huge = 1.0e300; |
| 25 | |
| 26 | double |
| 27 | round (double x) |
| 28 | { |
| 29 | int32_t i0, j0; |
| 30 | u_int32_t i1; |
| 31 | |
| 32 | EXTRACT_WORDS (i0, i1, x); |
| 33 | j0 = ((i0 >> 20) & 0x7ff) - 0x3ff; |
| 34 | if (j0 < 20) |
| 35 | { |
| 36 | if (j0 < 0) |
| 37 | { |
| 38 | if (huge + x > 0.0) |
| 39 | { |
| 40 | i0 &= 0x80000000; |
| 41 | if (j0 == -1) |
| 42 | i0 |= 0x3ff00000; |
| 43 | i1 = 0; |
| 44 | } |
| 45 | } |
| 46 | else |
| 47 | { |
| 48 | u_int32_t i = 0x000fffff >> j0; |
| 49 | if (((i0 & i) | i1) == 0) |
| 50 | /* X is integral. */ |
| 51 | return x; |
| 52 | if (huge + x > 0.0) |
| 53 | { |
| 54 | /* Raise inexact if x != 0. */ |
| 55 | i0 += 0x00080000 >> j0; |
| 56 | i0 &= ~i; |
| 57 | i1 = 0; |
| 58 | } |
| 59 | } |
| 60 | } |
| 61 | else if (j0 > 51) |
| 62 | { |
| 63 | if (j0 == 0x400) |
| 64 | /* Inf or NaN. */ |
| 65 | return x + x; |
| 66 | else |
| 67 | return x; |
| 68 | } |
| 69 | else |
| 70 | { |
| 71 | u_int32_t i = 0xffffffff >> (j0 - 20); |
| 72 | if ((i1 & i) == 0) |
| 73 | /* X is integral. */ |
| 74 | return x; |
| 75 | |
| 76 | if (huge + x > 0.0) |
| 77 | { |
| 78 | /* Raise inexact if x != 0. */ |
| 79 | u_int32_t j = i1 + (1 << (51 - j0)); |
| 80 | if (j < i1) |
| 81 | i0 += 1; |
| 82 | i1 = j; |
| 83 | } |
| 84 | i1 &= ~i; |
| 85 | } |
| 86 | |
| 87 | INSERT_WORDS (x, i0, i1); |
| 88 | return x; |
| 89 | } |
| 90 | libm_hidden_def(round) |