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Diffstat (limited to 'third_party/rust/dtoa/src/diyfp.rs')
| -rw-r--r-- | third_party/rust/dtoa/src/diyfp.rs | 253 |
1 files changed, 253 insertions, 0 deletions
diff --git a/third_party/rust/dtoa/src/diyfp.rs b/third_party/rust/dtoa/src/diyfp.rs new file mode 100644 index 0000000000..9d797657d6 --- /dev/null +++ b/third_party/rust/dtoa/src/diyfp.rs @@ -0,0 +1,253 @@ +// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or +// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license +// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. +// +// --- +// +// The C++ implementation preserved here in comments is licensed as follows: +// +// Tencent is pleased to support the open source community by making RapidJSON +// available. +// +// Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All +// rights reserved. +// +// Licensed under the MIT License (the "License"); you may not use this file +// except in compliance with the License. You may obtain a copy of the License +// at +// +// http://opensource.org/licenses/MIT +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT +// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the +// License for the specific language governing permissions and limitations under +// the License. + +use std::ops; + +#[derive(Copy, Clone, Debug)] +pub struct DiyFp<F, E> { + pub f: F, + pub e: E, +} + +impl<F, E> DiyFp<F, E> { + pub fn new(f: F, e: E) -> Self { + DiyFp { f: f, e: e } + } +} + +impl ops::Mul for DiyFp<u32, i32> { + type Output = Self; + fn mul(self, rhs: Self) -> Self { + let mut tmp = self.f as u64 * rhs.f as u64; + tmp += 1u64 << 31; // mult_round + DiyFp { + f: (tmp >> 32) as u32, + e: self.e + rhs.e + 32, + } + } +} + +impl ops::Mul for DiyFp<u64, isize> { + type Output = Self; + fn mul(self, rhs: Self) -> Self { + let m32 = 0xFFFFFFFFu64; + let a = self.f >> 32; + let b = self.f & m32; + let c = rhs.f >> 32; + let d = rhs.f & m32; + let ac = a * c; + let bc = b * c; + let ad = a * d; + let bd = b * d; + let mut tmp = (bd >> 32) + (ad & m32) + (bc & m32); + tmp += 1u64 << 31; // mult_round + DiyFp { + f: ac + (ad >> 32) + (bc >> 32) + (tmp >> 32), + e: self.e + rhs.e + 64, + } + } +} + +#[doc(hidden)] +#[macro_export] +macro_rules! diyfp {( + floating_type: $fty:ty, + significand_type: $sigty:ty, + exponent_type: $expty:ty, + + diy_significand_size: $diy_significand_size:expr, + significand_size: $significand_size:expr, + exponent_bias: $exponent_bias:expr, + mask_type: $mask_type:ty, + exponent_mask: $exponent_mask:expr, + significand_mask: $significand_mask:expr, + hidden_bit: $hidden_bit:expr, + cached_powers_f: $cached_powers_f:expr, + cached_powers_e: $cached_powers_e:expr, + min_power: $min_power:expr, +) => { + +type DiyFp = diyfp::DiyFp<$sigty, $expty>; + +impl DiyFp { + // Preconditions: + // `d` must have a positive sign and must not be infinity or NaN. + /* + explicit DiyFp(double d) { + union { + double d; + uint64_t u64; + } u = { d }; + + int biased_e = static_cast<int>((u.u64 & kDpExponentMask) >> kDpSignificandSize); + uint64_t significand = (u.u64 & kDpSignificandMask); + if (biased_e != 0) { + f = significand + kDpHiddenBit; + e = biased_e - kDpExponentBias; + } + else { + f = significand; + e = kDpMinExponent + 1; + } + } + */ + unsafe fn from(d: $fty) -> Self { + let u: $mask_type = mem::transmute(d); + + let biased_e = ((u & $exponent_mask) >> $significand_size) as $expty; + let significand = u & $significand_mask; + if biased_e != 0 { + DiyFp { + f: significand + $hidden_bit, + e: biased_e - $exponent_bias - $significand_size, + } + } else { + DiyFp { + f: significand, + e: 1 - $exponent_bias - $significand_size, + } + } + } + + // Normalizes so that the highest bit of the diy significand is 1. + /* + DiyFp Normalize() const { + DiyFp res = *this; + while (!(res.f & (static_cast<uint64_t>(1) << 63))) { + res.f <<= 1; + res.e--; + } + return res; + } + */ + fn normalize(self) -> DiyFp { + let mut res = self; + while (res.f & (1 << ($diy_significand_size - 1))) == 0 { + res.f <<= 1; + res.e -= 1; + } + res + } + + // Normalizes so that the highest bit of the diy significand is 1. + // + // Precondition: + // `self.f` must be no more than 2 bits longer than the f64 significand. + /* + DiyFp NormalizeBoundary() const { + DiyFp res = *this; + while (!(res.f & (kDpHiddenBit << 1))) { + res.f <<= 1; + res.e--; + } + res.f <<= (kDiySignificandSize - kDpSignificandSize - 2); + res.e = res.e - (kDiySignificandSize - kDpSignificandSize - 2); + return res; + } + */ + fn normalize_boundary(self) -> DiyFp { + let mut res = self; + while (res.f & $hidden_bit << 1) == 0 { + res.f <<= 1; + res.e -= 1; + } + res.f <<= $diy_significand_size - $significand_size - 2; + res.e -= $diy_significand_size - $significand_size - 2; + res + } + + // Normalizes `self - e` and `self + e` where `e` is half of the least + // significant digit of `self`. The plus is normalized so that the highest + // bit of the diy significand is 1. The minus is normalized so that it has + // the same exponent as the plus. + // + // Preconditions: + // `self` must have been returned directly from `DiyFp::from_f64`. + // `self.f` must not be zero. + /* + void NormalizedBoundaries(DiyFp* minus, DiyFp* plus) const { + DiyFp pl = DiyFp((f << 1) + 1, e - 1).NormalizeBoundary(); + DiyFp mi = (f == kDpHiddenBit) ? DiyFp((f << 2) - 1, e - 2) : DiyFp((f << 1) - 1, e - 1); + mi.f <<= mi.e - pl.e; + mi.e = pl.e; + *plus = pl; + *minus = mi; + } + */ + fn normalized_boundaries(self) -> (DiyFp, DiyFp) { + let pl = DiyFp::new((self.f << 1) + 1, self.e - 1).normalize_boundary(); + let mut mi = if self.f == $hidden_bit { + DiyFp::new((self.f << 2) - 1, self.e - 2) + } else { + DiyFp::new((self.f << 1) - 1, self.e - 1) + }; + mi.f <<= mi.e - pl.e; + mi.e = pl.e; + (mi, pl) + } +} + +impl ops::Sub for DiyFp { + type Output = Self; + fn sub(self, rhs: Self) -> Self { + DiyFp { + f: self.f - rhs.f, + e: self.e, + } + } +} + +/* +inline DiyFp GetCachedPower(int e, int* K) { + //int k = static_cast<int>(ceil((-61 - e) * 0.30102999566398114)) + 374; + double dk = (-61 - e) * 0.30102999566398114 + 347; // dk must be positive, so can do ceiling in positive + int k = static_cast<int>(dk); + if (dk - k > 0.0) + k++; + + unsigned index = static_cast<unsigned>((k >> 3) + 1); + *K = -(-348 + static_cast<int>(index << 3)); // decimal exponent no need lookup table + + return GetCachedPowerByIndex(index); +} +*/ +#[inline] +fn get_cached_power(e: $expty) -> (DiyFp, isize) { + let dk = (3 - $diy_significand_size - e) as f64 * 0.30102999566398114f64 - ($min_power + 1) as f64; + let mut k = dk as isize; + if dk - k as f64 > 0.0 { + k += 1; + } + + let index = ((k >> 3) + 1) as usize; + let k = -($min_power + (index << 3) as isize); + + (DiyFp::new($cached_powers_f[index], $cached_powers_e[index] as $expty), k) +} + +}} |