| // Translated from C to Rust. The original C code can be found at |
| // https://github.com/ulfjack/ryu and carries the following license: |
| // |
| // Copyright 2018 Ulf Adams |
| // |
| // The contents of this file may be used under the terms of the Apache License, |
| // Version 2.0. |
| // |
| // (See accompanying file LICENSE-Apache or copy at |
| // http://www.apache.org/licenses/LICENSE-2.0) |
| // |
| // Alternatively, the contents of this file may be used under the terms of |
| // the Boost Software License, Version 1.0. |
| // (See accompanying file LICENSE-Boost or copy at |
| // https://www.boost.org/LICENSE_1_0.txt) |
| // |
| // Unless required by applicable law or agreed to in writing, this software |
| // is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| // KIND, either express or implied. |
| |
| use core::ptr; |
| |
| // Returns e == 0 ? 1 : ceil(log_2(5^e)). |
| #[cfg_attr(feature = "no-panic", inline)] |
| pub fn pow5bits(e: i32) -> u32 { |
| // This approximation works up to the point that the multiplication overflows at e = 3529. |
| // If the multiplication were done in 64 bits, it would fail at 5^4004 which is just greater |
| // than 2^9297. |
| debug_assert!(e >= 0); |
| debug_assert!(e <= 3528); |
| ((e as u32 * 1217359) >> 19) + 1 |
| } |
| |
| // Returns floor(log_10(2^e)). |
| #[cfg_attr(feature = "no-panic", inline)] |
| pub fn log10_pow2(e: i32) -> i32 { |
| // The first value this approximation fails for is 2^1651 which is just greater than 10^297. |
| debug_assert!(e >= 0); |
| debug_assert!(e <= 1650); |
| ((e as u32 * 78913) >> 18) as i32 |
| } |
| |
| // Returns floor(log_10(5^e)). |
| #[cfg_attr(feature = "no-panic", inline)] |
| pub fn log10_pow5(e: i32) -> i32 { |
| // The first value this approximation fails for is 5^2621 which is just greater than 10^1832. |
| debug_assert!(e >= 0); |
| debug_assert!(e <= 2620); |
| ((e as u32 * 732923) >> 20) as i32 |
| } |
| |
| #[cfg_attr(feature = "no-panic", inline)] |
| pub unsafe fn copy_special_str( |
| result: *mut u8, |
| sign: bool, |
| exponent: bool, |
| mantissa: bool, |
| ) -> usize { |
| if mantissa { |
| ptr::copy_nonoverlapping(b"NaN".as_ptr(), result, 3); |
| return 3; |
| } |
| if sign { |
| *result = b'-'; |
| } |
| if exponent { |
| ptr::copy_nonoverlapping(b"Infinity".as_ptr(), result.offset(sign as isize), 8); |
| return sign as usize + 8; |
| } |
| ptr::copy_nonoverlapping(b"0E0".as_ptr(), result.offset(sign as isize), 3); |
| sign as usize + 3 |
| } |