| Szabolcs Nagy | 2eaed46 | 2013-09-04 15:52:54 +0000 | [diff] [blame] | 1 | #include <math.h> |
| 2 | #include <stdint.h> | ||||
| Rich Felker | b69f695 | 2012-03-13 01:17:53 -0400 | [diff] [blame] | 3 | |
| Rich Felker | b69f695 | 2012-03-13 01:17:53 -0400 | [diff] [blame] | 4 | double scalbn(double x, int n) |
| 5 | { | ||||
| Szabolcs Nagy | 2eaed46 | 2013-09-04 15:52:54 +0000 | [diff] [blame] | 6 | union {double f; uint64_t i;} u; |
| 7 | double_t y = x; | ||||
| Rich Felker | b69f695 | 2012-03-13 01:17:53 -0400 | [diff] [blame] | 8 | |
| nsz | 8051e08 | 2012-03-19 10:54:07 +0100 | [diff] [blame] | 9 | if (n > 1023) { |
| Szabolcs Nagy | 2eaed46 | 2013-09-04 15:52:54 +0000 | [diff] [blame] | 10 | y *= 0x1p1023; |
| nsz | 8051e08 | 2012-03-19 10:54:07 +0100 | [diff] [blame] | 11 | n -= 1023; |
| 12 | if (n > 1023) { | ||||
| Szabolcs Nagy | 2eaed46 | 2013-09-04 15:52:54 +0000 | [diff] [blame] | 13 | y *= 0x1p1023; |
| nsz | 8051e08 | 2012-03-19 10:54:07 +0100 | [diff] [blame] | 14 | n -= 1023; |
| Szabolcs Nagy | 1b77b90 | 2013-08-15 10:07:46 +0000 | [diff] [blame] | 15 | if (n > 1023) |
| 16 | n = 1023; | ||||
| nsz | 8051e08 | 2012-03-19 10:54:07 +0100 | [diff] [blame] | 17 | } |
| 18 | } else if (n < -1022) { | ||||
| Szabolcs Nagy | 2eaed46 | 2013-09-04 15:52:54 +0000 | [diff] [blame] | 19 | y *= 0x1p-1022; |
| nsz | 8051e08 | 2012-03-19 10:54:07 +0100 | [diff] [blame] | 20 | n += 1022; |
| 21 | if (n < -1022) { | ||||
| Szabolcs Nagy | 2eaed46 | 2013-09-04 15:52:54 +0000 | [diff] [blame] | 22 | y *= 0x1p-1022; |
| nsz | 8051e08 | 2012-03-19 10:54:07 +0100 | [diff] [blame] | 23 | n += 1022; |
| Szabolcs Nagy | 1b77b90 | 2013-08-15 10:07:46 +0000 | [diff] [blame] | 24 | if (n < -1022) |
| 25 | n = -1022; | ||||
| nsz | 8051e08 | 2012-03-19 10:54:07 +0100 | [diff] [blame] | 26 | } |
| Rich Felker | b69f695 | 2012-03-13 01:17:53 -0400 | [diff] [blame] | 27 | } |
| Szabolcs Nagy | 2eaed46 | 2013-09-04 15:52:54 +0000 | [diff] [blame] | 28 | u.i = (uint64_t)(0x3ff+n)<<52; |
| 29 | x = y * u.f; | ||||
| Szabolcs Nagy | c4359e0 | 2012-11-13 10:55:35 +0100 | [diff] [blame] | 30 | return x; |
| Rich Felker | b69f695 | 2012-03-13 01:17:53 -0400 | [diff] [blame] | 31 | } |