| #[inline] |
| #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] |
| pub fn scalbn(x: f64, mut n: i32) -> f64 { |
| let x1p1023 = f64::from_bits(0x7fe0000000000000); // 0x1p1023 === 2 ^ 1023 |
| let x1p53 = f64::from_bits(0x4340000000000000); // 0x1p53 === 2 ^ 53 |
| let x1p_1022 = f64::from_bits(0x0010000000000000); // 0x1p-1022 === 2 ^ (-1022) |
| |
| let mut y = x; |
| |
| if n > 1023 { |
| y *= x1p1023; |
| n -= 1023; |
| if n > 1023 { |
| y *= x1p1023; |
| n -= 1023; |
| if n > 1023 { |
| n = 1023; |
| } |
| } |
| } else if n < -1022 { |
| /* make sure final n < -53 to avoid double |
| rounding in the subnormal range */ |
| y *= x1p_1022 * x1p53; |
| n += 1022 - 53; |
| if n < -1022 { |
| y *= x1p_1022 * x1p53; |
| n += 1022 - 53; |
| if n < -1022 { |
| n = -1022; |
| } |
| } |
| } |
| y * f64::from_bits(((0x3ff + n) as u64) << 52) |
| } |