1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95
// 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. // Returns the number of decimal digits in v, which must not contain more than 9 // digits. #[cfg_attr(feature = "no-panic", inline)] pub fn decimal_length9(v: u32) -> u32 { // Function precondition: v is not a 10-digit number. // (f2s: 9 digits are sufficient for round-tripping.) debug_assert!(v < 1000000000); if v >= 100000000 { 9 } else if v >= 10000000 { 8 } else if v >= 1000000 { 7 } else if v >= 100000 { 6 } else if v >= 10000 { 5 } else if v >= 1000 { 4 } else if v >= 100 { 3 } else if v >= 10 { 2 } else { 1 } } // Returns e == 0 ? 1 : [log_2(5^e)]; requires 0 <= e <= 3528. #[cfg_attr(feature = "no-panic", inline)] #[allow(dead_code)] pub fn log2_pow5(e: i32) -> i32 /* or u32 -> 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) as i32 } // Returns e == 0 ? 1 : ceil(log_2(5^e)); requires 0 <= e <= 3528. #[cfg_attr(feature = "no-panic", inline)] pub fn pow5bits(e: i32) -> i32 /* or u32 -> 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) as i32 } #[cfg_attr(feature = "no-panic", inline)] #[allow(dead_code)] pub fn ceil_log2_pow5(e: i32) -> i32 /* or u32 -> u32 */ { log2_pow5(e) + 1 } // Returns floor(log_10(2^e)); requires 0 <= e <= 1650. #[cfg_attr(feature = "no-panic", inline)] pub fn log10_pow2(e: i32) -> u32 /* or u32 -> u32 */ { // 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 } // Returns floor(log_10(5^e)); requires 0 <= e <= 2620. #[cfg_attr(feature = "no-panic", inline)] pub fn log10_pow5(e: i32) -> u32 /* or u32 -> u32 */ { // 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 }