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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// 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
//
//
// 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)
}
}}