| // 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 crate::common::{log10_pow2, log10_pow5, pow5bits}; | 
 | #[cfg(not(feature = "small"))] | 
 | pub use crate::d2s_full_table::{DOUBLE_POW5_INV_SPLIT, DOUBLE_POW5_SPLIT}; | 
 | use crate::d2s_intrinsics::{ | 
 |     div10, div100, div5, mul_shift_all_64, multiple_of_power_of_2, multiple_of_power_of_5, | 
 | }; | 
 | #[cfg(feature = "small")] | 
 | pub use crate::d2s_small_table::{compute_inv_pow5, compute_pow5}; | 
 | use core::mem::MaybeUninit; | 
 |  | 
 | pub const DOUBLE_MANTISSA_BITS: u32 = 52; | 
 | pub const DOUBLE_EXPONENT_BITS: u32 = 11; | 
 | pub const DOUBLE_BIAS: i32 = 1023; | 
 | pub const DOUBLE_POW5_INV_BITCOUNT: i32 = 125; | 
 | pub const DOUBLE_POW5_BITCOUNT: i32 = 125; | 
 |  | 
 | #[cfg_attr(feature = "no-panic", inline)] | 
 | pub fn decimal_length17(v: u64) -> u32 { | 
 |     // This is slightly faster than a loop. | 
 |     // The average output length is 16.38 digits, so we check high-to-low. | 
 |     // Function precondition: v is not an 18, 19, or 20-digit number. | 
 |     // (17 digits are sufficient for round-tripping.) | 
 |     debug_assert!(v < 100000000000000000); | 
 |  | 
 |     if v >= 10000000000000000 { | 
 |         17 | 
 |     } else if v >= 1000000000000000 { | 
 |         16 | 
 |     } else if v >= 100000000000000 { | 
 |         15 | 
 |     } else if v >= 10000000000000 { | 
 |         14 | 
 |     } else if v >= 1000000000000 { | 
 |         13 | 
 |     } else if v >= 100000000000 { | 
 |         12 | 
 |     } else if v >= 10000000000 { | 
 |         11 | 
 |     } else if v >= 1000000000 { | 
 |         10 | 
 |     } else 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 | 
 |     } | 
 | } | 
 |  | 
 | // A floating decimal representing m * 10^e. | 
 | pub struct FloatingDecimal64 { | 
 |     pub mantissa: u64, | 
 |     // Decimal exponent's range is -324 to 308 | 
 |     // inclusive, and can fit in i16 if needed. | 
 |     pub exponent: i32, | 
 | } | 
 |  | 
 | #[cfg_attr(feature = "no-panic", inline)] | 
 | pub fn d2d(ieee_mantissa: u64, ieee_exponent: u32) -> FloatingDecimal64 { | 
 |     let (e2, m2) = if ieee_exponent == 0 { | 
 |         ( | 
 |             // We subtract 2 so that the bounds computation has 2 additional bits. | 
 |             1 - DOUBLE_BIAS - DOUBLE_MANTISSA_BITS as i32 - 2, | 
 |             ieee_mantissa, | 
 |         ) | 
 |     } else { | 
 |         ( | 
 |             ieee_exponent as i32 - DOUBLE_BIAS - DOUBLE_MANTISSA_BITS as i32 - 2, | 
 |             (1u64 << DOUBLE_MANTISSA_BITS) | ieee_mantissa, | 
 |         ) | 
 |     }; | 
 |     let even = (m2 & 1) == 0; | 
 |     let accept_bounds = even; | 
 |  | 
 |     // Step 2: Determine the interval of valid decimal representations. | 
 |     let mv = 4 * m2; | 
 |     // Implicit bool -> int conversion. True is 1, false is 0. | 
 |     let mm_shift = (ieee_mantissa != 0 || ieee_exponent <= 1) as u32; | 
 |     // We would compute mp and mm like this: | 
 |     // uint64_t mp = 4 * m2 + 2; | 
 |     // uint64_t mm = mv - 1 - mm_shift; | 
 |  | 
 |     // Step 3: Convert to a decimal power base using 128-bit arithmetic. | 
 |     let mut vr: u64; | 
 |     let mut vp: u64; | 
 |     let mut vm: u64; | 
 |     let mut vp_uninit: MaybeUninit<u64> = MaybeUninit::uninit(); | 
 |     let mut vm_uninit: MaybeUninit<u64> = MaybeUninit::uninit(); | 
 |     let e10: i32; | 
 |     let mut vm_is_trailing_zeros = false; | 
 |     let mut vr_is_trailing_zeros = false; | 
 |     if e2 >= 0 { | 
 |         // I tried special-casing q == 0, but there was no effect on performance. | 
 |         // This expression is slightly faster than max(0, log10_pow2(e2) - 1). | 
 |         let q = log10_pow2(e2) - (e2 > 3) as u32; | 
 |         e10 = q as i32; | 
 |         let k = DOUBLE_POW5_INV_BITCOUNT + pow5bits(q as i32) - 1; | 
 |         let i = -e2 + q as i32 + k; | 
 |         vr = unsafe { | 
 |             mul_shift_all_64( | 
 |                 m2, | 
 |                 #[cfg(feature = "small")] | 
 |                 &compute_inv_pow5(q), | 
 |                 #[cfg(not(feature = "small"))] | 
 |                 { | 
 |                     debug_assert!(q < DOUBLE_POW5_INV_SPLIT.len() as u32); | 
 |                     DOUBLE_POW5_INV_SPLIT.get_unchecked(q as usize) | 
 |                 }, | 
 |                 i as u32, | 
 |                 vp_uninit.as_mut_ptr(), | 
 |                 vm_uninit.as_mut_ptr(), | 
 |                 mm_shift, | 
 |             ) | 
 |         }; | 
 |         vp = unsafe { vp_uninit.assume_init() }; | 
 |         vm = unsafe { vm_uninit.assume_init() }; | 
 |         if q <= 21 { | 
 |             // This should use q <= 22, but I think 21 is also safe. Smaller values | 
 |             // may still be safe, but it's more difficult to reason about them. | 
 |             // Only one of mp, mv, and mm can be a multiple of 5, if any. | 
 |             let mv_mod5 = (mv as u32).wrapping_sub(5u32.wrapping_mul(div5(mv) as u32)); | 
 |             if mv_mod5 == 0 { | 
 |                 vr_is_trailing_zeros = multiple_of_power_of_5(mv, q); | 
 |             } else if accept_bounds { | 
 |                 // Same as min(e2 + (~mm & 1), pow5_factor(mm)) >= q | 
 |                 // <=> e2 + (~mm & 1) >= q && pow5_factor(mm) >= q | 
 |                 // <=> true && pow5_factor(mm) >= q, since e2 >= q. | 
 |                 vm_is_trailing_zeros = multiple_of_power_of_5(mv - 1 - mm_shift as u64, q); | 
 |             } else { | 
 |                 // Same as min(e2 + 1, pow5_factor(mp)) >= q. | 
 |                 vp -= multiple_of_power_of_5(mv + 2, q) as u64; | 
 |             } | 
 |         } | 
 |     } else { | 
 |         // This expression is slightly faster than max(0, log10_pow5(-e2) - 1). | 
 |         let q = log10_pow5(-e2) - (-e2 > 1) as u32; | 
 |         e10 = q as i32 + e2; | 
 |         let i = -e2 - q as i32; | 
 |         let k = pow5bits(i) - DOUBLE_POW5_BITCOUNT; | 
 |         let j = q as i32 - k; | 
 |         vr = unsafe { | 
 |             mul_shift_all_64( | 
 |                 m2, | 
 |                 #[cfg(feature = "small")] | 
 |                 &compute_pow5(i as u32), | 
 |                 #[cfg(not(feature = "small"))] | 
 |                 { | 
 |                     debug_assert!(i < DOUBLE_POW5_SPLIT.len() as i32); | 
 |                     DOUBLE_POW5_SPLIT.get_unchecked(i as usize) | 
 |                 }, | 
 |                 j as u32, | 
 |                 vp_uninit.as_mut_ptr(), | 
 |                 vm_uninit.as_mut_ptr(), | 
 |                 mm_shift, | 
 |             ) | 
 |         }; | 
 |         vp = unsafe { vp_uninit.assume_init() }; | 
 |         vm = unsafe { vm_uninit.assume_init() }; | 
 |         if q <= 1 { | 
 |             // {vr,vp,vm} is trailing zeros if {mv,mp,mm} has at least q trailing 0 bits. | 
 |             // mv = 4 * m2, so it always has at least two trailing 0 bits. | 
 |             vr_is_trailing_zeros = true; | 
 |             if accept_bounds { | 
 |                 // mm = mv - 1 - mm_shift, so it has 1 trailing 0 bit iff mm_shift == 1. | 
 |                 vm_is_trailing_zeros = mm_shift == 1; | 
 |             } else { | 
 |                 // mp = mv + 2, so it always has at least one trailing 0 bit. | 
 |                 vp -= 1; | 
 |             } | 
 |         } else if q < 63 { | 
 |             // TODO(ulfjack): Use a tighter bound here. | 
 |             // We want to know if the full product has at least q trailing zeros. | 
 |             // We need to compute min(p2(mv), p5(mv) - e2) >= q | 
 |             // <=> p2(mv) >= q && p5(mv) - e2 >= q | 
 |             // <=> p2(mv) >= q (because -e2 >= q) | 
 |             vr_is_trailing_zeros = multiple_of_power_of_2(mv, q); | 
 |         } | 
 |     } | 
 |  | 
 |     // Step 4: Find the shortest decimal representation in the interval of valid representations. | 
 |     let mut removed = 0i32; | 
 |     let mut last_removed_digit = 0u8; | 
 |     // On average, we remove ~2 digits. | 
 |     let output = if vm_is_trailing_zeros || vr_is_trailing_zeros { | 
 |         // General case, which happens rarely (~0.7%). | 
 |         loop { | 
 |             let vp_div10 = div10(vp); | 
 |             let vm_div10 = div10(vm); | 
 |             if vp_div10 <= vm_div10 { | 
 |                 break; | 
 |             } | 
 |             let vm_mod10 = (vm as u32).wrapping_sub(10u32.wrapping_mul(vm_div10 as u32)); | 
 |             let vr_div10 = div10(vr); | 
 |             let vr_mod10 = (vr as u32).wrapping_sub(10u32.wrapping_mul(vr_div10 as u32)); | 
 |             vm_is_trailing_zeros &= vm_mod10 == 0; | 
 |             vr_is_trailing_zeros &= last_removed_digit == 0; | 
 |             last_removed_digit = vr_mod10 as u8; | 
 |             vr = vr_div10; | 
 |             vp = vp_div10; | 
 |             vm = vm_div10; | 
 |             removed += 1; | 
 |         } | 
 |         if vm_is_trailing_zeros { | 
 |             loop { | 
 |                 let vm_div10 = div10(vm); | 
 |                 let vm_mod10 = (vm as u32).wrapping_sub(10u32.wrapping_mul(vm_div10 as u32)); | 
 |                 if vm_mod10 != 0 { | 
 |                     break; | 
 |                 } | 
 |                 let vp_div10 = div10(vp); | 
 |                 let vr_div10 = div10(vr); | 
 |                 let vr_mod10 = (vr as u32).wrapping_sub(10u32.wrapping_mul(vr_div10 as u32)); | 
 |                 vr_is_trailing_zeros &= last_removed_digit == 0; | 
 |                 last_removed_digit = vr_mod10 as u8; | 
 |                 vr = vr_div10; | 
 |                 vp = vp_div10; | 
 |                 vm = vm_div10; | 
 |                 removed += 1; | 
 |             } | 
 |         } | 
 |         if vr_is_trailing_zeros && last_removed_digit == 5 && vr % 2 == 0 { | 
 |             // Round even if the exact number is .....50..0. | 
 |             last_removed_digit = 4; | 
 |         } | 
 |         // We need to take vr + 1 if vr is outside bounds or we need to round up. | 
 |         vr + ((vr == vm && (!accept_bounds || !vm_is_trailing_zeros)) || last_removed_digit >= 5) | 
 |             as u64 | 
 |     } else { | 
 |         // Specialized for the common case (~99.3%). Percentages below are relative to this. | 
 |         let mut round_up = false; | 
 |         let vp_div100 = div100(vp); | 
 |         let vm_div100 = div100(vm); | 
 |         // Optimization: remove two digits at a time (~86.2%). | 
 |         if vp_div100 > vm_div100 { | 
 |             let vr_div100 = div100(vr); | 
 |             let vr_mod100 = (vr as u32).wrapping_sub(100u32.wrapping_mul(vr_div100 as u32)); | 
 |             round_up = vr_mod100 >= 50; | 
 |             vr = vr_div100; | 
 |             vp = vp_div100; | 
 |             vm = vm_div100; | 
 |             removed += 2; | 
 |         } | 
 |         // Loop iterations below (approximately), without optimization above: | 
 |         // 0: 0.03%, 1: 13.8%, 2: 70.6%, 3: 14.0%, 4: 1.40%, 5: 0.14%, 6+: 0.02% | 
 |         // Loop iterations below (approximately), with optimization above: | 
 |         // 0: 70.6%, 1: 27.8%, 2: 1.40%, 3: 0.14%, 4+: 0.02% | 
 |         loop { | 
 |             let vp_div10 = div10(vp); | 
 |             let vm_div10 = div10(vm); | 
 |             if vp_div10 <= vm_div10 { | 
 |                 break; | 
 |             } | 
 |             let vr_div10 = div10(vr); | 
 |             let vr_mod10 = (vr as u32).wrapping_sub(10u32.wrapping_mul(vr_div10 as u32)); | 
 |             round_up = vr_mod10 >= 5; | 
 |             vr = vr_div10; | 
 |             vp = vp_div10; | 
 |             vm = vm_div10; | 
 |             removed += 1; | 
 |         } | 
 |         // We need to take vr + 1 if vr is outside bounds or we need to round up. | 
 |         vr + (vr == vm || round_up) as u64 | 
 |     }; | 
 |     let exp = e10 + removed; | 
 |  | 
 |     FloatingDecimal64 { | 
 |         exponent: exp, | 
 |         mantissa: output, | 
 |     } | 
 | } |