Adding upstream version 115.8.0esr.upstream/115.8.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

3 files changed, 967 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)
+}
+
+}}
diff --git a/third_party/rust/dtoa/src/dtoa.rs b/third_party/rust/dtoa/src/dtoa.rs
new file mode 100644
index 0000000000..8642a38920
--- /dev/null
+++ b/third_party/rust/dtoa/src/dtoa.rs
@@ -0,0 +1,509 @@
+// 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.
+
+#[doc(hidden)]
+#[macro_export]
+macro_rules! dtoa {(
+    floating_type: $fty:ty,
+    significand_type: $sigty:ty,
+    exponent_type: $expty:ty,
+    $($diyfp_param:ident: $diyfp_value:tt,)*
+) => {
+
+diyfp! {
+    floating_type: $fty,
+    significand_type: $sigty,
+    exponent_type: $expty,
+    $($diyfp_param: $diyfp_value,)*
+};
+
+/*
+inline void GrisuRound(char* buffer, int len, uint64_t delta, uint64_t rest, uint64_t ten_kappa, uint64_t wp_w) {
+    while (rest < wp_w && delta - rest >= ten_kappa &&
+           (rest + ten_kappa < wp_w ||  /// closer
+            wp_w - rest > rest + ten_kappa - wp_w)) {
+        buffer[len - 1]--;
+        rest += ten_kappa;
+    }
+}
+*/
+
+#[inline]
+unsafe fn grisu_round(buffer: *mut u8, len: isize, delta: $sigty, mut rest: $sigty, ten_kappa: $sigty, wp_w: $sigty) {
+    while rest < wp_w && delta - rest >= ten_kappa &&
+           (rest + ten_kappa < wp_w || // closer
+            wp_w - rest > rest + ten_kappa - wp_w) {
+        *buffer.offset(len - 1) -= 1;
+        rest += ten_kappa;
+    }
+}
+
+/*
+inline unsigned CountDecimalDigit32(uint32_t n) {
+    // Simple pure C++ implementation was faster than __builtin_clz version in this situation.
+    if (n < 10) return 1;
+    if (n < 100) return 2;
+    if (n < 1000) return 3;
+    if (n < 10000) return 4;
+    if (n < 100000) return 5;
+    if (n < 1000000) return 6;
+    if (n < 10000000) return 7;
+    if (n < 100000000) return 8;
+    // Will not reach 10 digits in DigitGen()
+    //if (n < 1000000000) return 9;
+    //return 10;
+    return 9;
+}
+*/
+
+#[inline]
+fn count_decimal_digit32(n: u32) -> usize {
+    if n < 10 { 1 }
+    else if n < 100 { 2 }
+    else if n < 1000 { 3 }
+    else if n < 10000 { 4 }
+    else if n < 100000 { 5 }
+    else if n < 1000000 { 6 }
+    else if n < 10000000 { 7 }
+    else if n < 100000000 { 8 }
+    // Will not reach 10 digits in digit_gen()
+    else { 9 }
+}
+
+/*
+inline void DigitGen(const DiyFp& W, const DiyFp& Mp, uint64_t delta, char* buffer, int* len, int* K) {
+    static const uint32_t kPow10[] = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000 };
+    const DiyFp one(uint64_t(1) << -Mp.e, Mp.e);
+    const DiyFp wp_w = Mp - W;
+    uint32_t p1 = static_cast<uint32_t>(Mp.f >> -one.e);
+    uint64_t p2 = Mp.f & (one.f - 1);
+    unsigned kappa = CountDecimalDigit32(p1); // kappa in [0, 9]
+    *len = 0;
+*/
+
+// Returns length and k.
+#[inline]
+unsafe fn digit_gen(w: DiyFp, mp: DiyFp, mut delta: $sigty, buffer: *mut u8, mut k: isize) -> (isize, isize) {
+    static POW10: [$sigty; 10] = [ 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000 ];
+    let one = DiyFp::new(1 << -mp.e, mp.e);
+    let wp_w = mp - w;
+    let mut p1 = (mp.f >> -one.e) as u32;
+    let mut p2 = mp.f & (one.f - 1);
+    let mut kappa = count_decimal_digit32(p1); // kappa in [0, 9]
+    let mut len = 0;
+
+    /*
+    while (kappa > 0) {
+        uint32_t d = 0;
+        switch (kappa) {
+            case  9: d = p1 /  100000000; p1 %=  100000000; break;
+            case  8: d = p1 /   10000000; p1 %=   10000000; break;
+            case  7: d = p1 /    1000000; p1 %=    1000000; break;
+            case  6: d = p1 /     100000; p1 %=     100000; break;
+            case  5: d = p1 /      10000; p1 %=      10000; break;
+            case  4: d = p1 /       1000; p1 %=       1000; break;
+            case  3: d = p1 /        100; p1 %=        100; break;
+            case  2: d = p1 /         10; p1 %=         10; break;
+            case  1: d = p1;              p1 =           0; break;
+            default:;
+        }
+        if (d || *len)
+            buffer[(*len)++] = static_cast<char>('0' + static_cast<char>(d));
+        kappa--;
+        uint64_t tmp = (static_cast<uint64_t>(p1) << -one.e) + p2;
+        if (tmp <= delta) {
+            *K += kappa;
+            GrisuRound(buffer, *len, delta, tmp, static_cast<uint64_t>(kPow10[kappa]) << -one.e, wp_w.f);
+            return;
+        }
+    }
+    */
+    while kappa > 0 {
+        let mut d = 0u32;
+        match kappa {
+            9 => { d = p1 /  100000000; p1 %=  100000000; }
+            8 => { d = p1 /   10000000; p1 %=   10000000; }
+            7 => { d = p1 /    1000000; p1 %=    1000000; }
+            6 => { d = p1 /     100000; p1 %=     100000; }
+            5 => { d = p1 /      10000; p1 %=      10000; }
+            4 => { d = p1 /       1000; p1 %=       1000; }
+            3 => { d = p1 /        100; p1 %=        100; }
+            2 => { d = p1 /         10; p1 %=         10; }
+            1 => { d = p1;              p1 =           0; }
+            _ => {}
+        }
+        if d != 0 || len != 0 {
+            *buffer.offset(len) = b'0' + d as u8;
+            len += 1;
+        }
+        kappa -= 1;
+        let tmp = (p1 as $sigty << -one.e) + p2;
+        if tmp <= delta {
+            k += kappa as isize;
+            grisu_round(buffer, len, delta, tmp, POW10[kappa] << -one.e, wp_w.f);
+            return (len, k);
+        }
+    }
+
+    // kappa = 0
+    /*
+    for (;;) {
+        p2 *= 10;
+        delta *= 10;
+        char d = static_cast<char>(p2 >> -one.e);
+        if (d || *len)
+            buffer[(*len)++] = static_cast<char>('0' + d);
+        p2 &= one.f - 1;
+        kappa--;
+        if (p2 < delta) {
+            *K += kappa;
+            int index = -static_cast<int>(kappa);
+            GrisuRound(buffer, *len, delta, p2, one.f, wp_w.f * (index < 9 ? kPow10[-static_cast<int>(kappa)] : 0));
+            return;
+        }
+    }
+    */
+    loop {
+        p2 *= 10;
+        delta *= 10;
+        let d = (p2 >> -one.e) as u8;
+        if d != 0 || len != 0 {
+            *buffer.offset(len) = b'0' + d;
+            len += 1;
+        }
+        p2 &= one.f - 1;
+        kappa = kappa.wrapping_sub(1);
+        if p2 < delta {
+            k += kappa as isize;
+            let index = -(kappa as isize);
+            grisu_round(buffer, len, delta, p2, one.f, wp_w.f * if index < 9 { POW10[-(kappa as isize) as usize] } else { 0 });
+            return (len, k);
+        }
+    }
+}
+
+/*
+inline void Grisu2(double value, char* buffer, int* length, int* K) {
+    const DiyFp v(value);
+    DiyFp w_m, w_p;
+    v.NormalizedBoundaries(&w_m, &w_p);
+
+    const DiyFp c_mk = GetCachedPower(w_p.e, K);
+    const DiyFp W = v.Normalize() * c_mk;
+    DiyFp Wp = w_p * c_mk;
+    DiyFp Wm = w_m * c_mk;
+    Wm.f++;
+    Wp.f--;
+    DigitGen(W, Wp, Wp.f - Wm.f, buffer, length, K);
+}
+*/
+
+// Returns length and k.
+#[inline]
+unsafe fn grisu2(value: $fty, buffer: *mut u8) -> (isize, isize) {
+    let v = DiyFp::from(value);
+    let (w_m, w_p) = v.normalized_boundaries();
+
+    let (c_mk, k) = get_cached_power(w_p.e);
+    let w = v.normalize() * c_mk;
+    let mut wp = w_p * c_mk;
+    let mut wm = w_m * c_mk;
+    wm.f += 1;
+    wp.f -= 1;
+    digit_gen(w, wp, wp.f - wm.f, buffer, k)
+}
+
+/*
+inline char* WriteExponent(int K, char* buffer) {
+    if (K < 0) {
+        *buffer++ = '-';
+        K = -K;
+    }
+
+    if (K >= 100) {
+        *buffer++ = static_cast<char>('0' + static_cast<char>(K / 100));
+        K %= 100;
+        const char* d = GetDigitsLut() + K * 2;
+        *buffer++ = d[0];
+        *buffer++ = d[1];
+    }
+    else if (K >= 10) {
+        const char* d = GetDigitsLut() + K * 2;
+        *buffer++ = d[0];
+        *buffer++ = d[1];
+    }
+    else
+        *buffer++ = static_cast<char>('0' + static_cast<char>(K));
+
+    return buffer;
+}
+*/
+
+#[inline]
+unsafe fn write_exponent(mut k: isize, mut buffer: *mut u8) -> *mut u8 {
+    if k < 0 {
+        *buffer = b'-';
+        buffer = buffer.offset(1);
+        k = -k;
+    }
+
+    if k >= 100 {
+        *buffer = b'0' + (k / 100) as u8;
+        k %= 100;
+        let d = DEC_DIGITS_LUT.get_unchecked(k as usize * 2);
+        ptr::copy_nonoverlapping(d, buffer.offset(1), 2);
+        buffer.offset(3)
+    } else if k >= 10 {
+        let d = DEC_DIGITS_LUT.get_unchecked(k as usize * 2);
+        ptr::copy_nonoverlapping(d, buffer, 2);
+        buffer.offset(2)
+    } else {
+        *buffer = b'0' + k as u8;
+        buffer.offset(1)
+    }
+}
+
+/*
+inline char* Prettify(char* buffer, int length, int k, int maxDecimalPlaces) {
+    const int kk = length + k;  // 10^(kk-1) <= v < 10^kk
+*/
+
+#[inline]
+unsafe fn prettify(buffer: *mut u8, length: isize, k: isize) -> *mut u8 {
+    let kk = length + k; // 10^(kk-1) <= v < 10^kk
+
+    /*
+    if (0 <= k && kk <= 21) {
+        // 1234e7 -> 12340000000
+        for (int i = length; i < kk; i++)
+            buffer[i] = '0';
+        buffer[kk] = '.';
+        buffer[kk + 1] = '0';
+        return &buffer[kk + 2];
+    }
+    */
+    if 0 <= k && kk <= 21 {
+        // 1234e7 -> 12340000000
+        for i in length..kk {
+            *buffer.offset(i) = b'0';
+        }
+        *buffer.offset(kk) = b'.';
+        *buffer.offset(kk + 1) = b'0';
+        buffer.offset(kk + 2)
+    }
+
+    /*
+    else if (0 < kk && kk <= 21) {
+        // 1234e-2 -> 12.34
+        std::memmove(&buffer[kk + 1], &buffer[kk], static_cast<size_t>(length - kk));
+        buffer[kk] = '.';
+        if (0 > k + maxDecimalPlaces) {
+            // When maxDecimalPlaces = 2, 1.2345 -> 1.23, 1.102 -> 1.1
+            // Remove extra trailing zeros (at least one) after truncation.
+            for (int i = kk + maxDecimalPlaces; i > kk + 1; i--)
+                if (buffer[i] != '0')
+                    return &buffer[i + 1];
+            return &buffer[kk + 2]; // Reserve one zero
+        }
+        else
+            return &buffer[length + 1];
+    }
+    */
+    else if 0 < kk && kk <= 21 {
+        // 1234e-2 -> 12.34
+        ptr::copy(buffer.offset(kk), buffer.offset(kk + 1), (length - kk) as usize);
+        *buffer.offset(kk) = b'.';
+        if 0 > k + MAX_DECIMAL_PLACES {
+            // When MAX_DECIMAL_PLACES = 2, 1.2345 -> 1.23, 1.102 -> 1.1
+            // Remove extra trailing zeros (at least one) after truncation.
+            for i in (kk + 2 .. kk + MAX_DECIMAL_PLACES + 1).rev() {
+                if *buffer.offset(i) != b'0' {
+                    return buffer.offset(i + 1);
+                }
+            }
+            buffer.offset(kk + 2) // Reserve one zero
+        } else {
+            buffer.offset(length + 1)
+        }
+    }
+
+    /*
+    else if (-6 < kk && kk <= 0) {
+        // 1234e-6 -> 0.001234
+        const int offset = 2 - kk;
+        std::memmove(&buffer[offset], &buffer[0], static_cast<size_t>(length));
+        buffer[0] = '0';
+        buffer[1] = '.';
+        for (int i = 2; i < offset; i++)
+            buffer[i] = '0';
+        if (length - kk > maxDecimalPlaces) {
+            // When maxDecimalPlaces = 2, 0.123 -> 0.12, 0.102 -> 0.1
+            // Remove extra trailing zeros (at least one) after truncation.
+            for (int i = maxDecimalPlaces + 1; i > 2; i--)
+                if (buffer[i] != '0')
+                    return &buffer[i + 1];
+            return &buffer[3]; // Reserve one zero
+        }
+        else
+            return &buffer[length + offset];
+    }
+    */
+    else if -6 < kk && kk <= 0 {
+        // 1234e-6 -> 0.001234
+        let offset = 2 - kk;
+        ptr::copy(buffer, buffer.offset(offset), length as usize);
+        *buffer = b'0';
+        *buffer.offset(1) = b'.';
+        for i in 2..offset {
+            *buffer.offset(i) = b'0';
+        }
+        if length - kk > MAX_DECIMAL_PLACES {
+            // When MAX_DECIMAL_PLACES = 2, 0.123 -> 0.12, 0.102 -> 0.1
+            // Remove extra trailing zeros (at least one) after truncation.
+            for i in (3 .. MAX_DECIMAL_PLACES + 2).rev() {
+                if *buffer.offset(i) != b'0' {
+                    return buffer.offset(i + 1);
+                }
+            }
+            buffer.offset(3) // Reserve one zero
+        } else {
+            buffer.offset(length + offset)
+        }
+    }
+
+    /*
+    else if (kk < -maxDecimalPlaces) {
+        // Truncate to zero
+        buffer[0] = '0';
+        buffer[1] = '.';
+        buffer[2] = '0';
+        return &buffer[3];
+    }
+    */
+    else if kk < -MAX_DECIMAL_PLACES {
+        *buffer = b'0';
+        *buffer.offset(1) = b'.';
+        *buffer.offset(2) = b'0';
+        buffer.offset(3)
+    }
+
+    /*
+    else if (length == 1) {
+        // 1e30
+        buffer[1] = 'e';
+        return WriteExponent(kk - 1, &buffer[2]);
+    }
+    */
+    else if length == 1 {
+        // 1e30
+        *buffer.offset(1) = b'e';
+        write_exponent(kk - 1, buffer.offset(2))
+    }
+
+    /*
+    else {
+        // 1234e30 -> 1.234e33
+        std::memmove(&buffer[2], &buffer[1], static_cast<size_t>(length - 1));
+        buffer[1] = '.';
+        buffer[length + 1] = 'e';
+        return WriteExponent(kk - 1, &buffer[0 + length + 2]);
+    }
+    */
+    else {
+        // 1234e30 -> 1.234e33
+        ptr::copy(buffer.offset(1), buffer.offset(2), (length - 1) as usize);
+        *buffer.offset(1) = b'.';
+        *buffer.offset(length + 1) = b'e';
+        write_exponent(kk - 1, buffer.offset(length + 2))
+    }
+}
+
+/*
+inline char* dtoa(double value, char* buffer, int maxDecimalPlaces = 324) {
+    RAPIDJSON_ASSERT(maxDecimalPlaces >= 1);
+    Double d(value);
+    if (d.IsZero()) {
+        if (d.Sign())
+            *buffer++ = '-';     // -0.0, Issue #289
+        buffer[0] = '0';
+        buffer[1] = '.';
+        buffer[2] = '0';
+        return &buffer[3];
+    }
+    else {
+        if (value < 0) {
+            *buffer++ = '-';
+            value = -value;
+        }
+        int length, K;
+        Grisu2(value, buffer, &length, &K);
+        return Prettify(buffer, length, K, maxDecimalPlaces);
+    }
+}
+*/
+
+#[allow(deprecated)]
+#[inline]
+unsafe fn dtoa<W: io::Write>(mut wr: W, mut value: $fty) -> io::Result<usize> {
+    if value == 0.0 {
+        if value.is_sign_negative() {
+            match wr.write_all(b"-0.0") {
+                Ok(()) => Ok(4),
+                Err(e) => Err(e),
+            }
+        } else {
+            match wr.write_all(b"0.0") {
+                Ok(()) => Ok(3),
+                Err(e) => Err(e),
+            }
+        }
+    } else {
+        let negative = value < 0.0;
+        if negative {
+            if let Err(e) = wr.write_all(b"-") {
+                return Err(e);
+            }
+            value = -value;
+        }
+        let mut buffer: [u8; 24] = mem::uninitialized();
+        let buf_ptr = buffer.as_mut_ptr();
+        let (length, k) = grisu2(value, buf_ptr);
+        let end = prettify(buf_ptr, length, k);
+        let len = end as usize - buf_ptr as usize;
+        if let Err(e) = wr.write_all(slice::from_raw_parts(buf_ptr, len)) {
+            return Err(e);
+        }
+        if negative {
+            Ok(len + 1)
+        } else {
+            Ok(len)
+        }
+    }
+}
+
+}}
diff --git a/third_party/rust/dtoa/src/lib.rs b/third_party/rust/dtoa/src/lib.rs
new file mode 100644
index 0000000000..aed62f500b
--- /dev/null
+++ b/third_party/rust/dtoa/src/lib.rs
@@ -0,0 +1,205 @@
+//! [![github]](https://github.com/dtolnay/dtoa)&ensp;[![crates-io]](https://crates.io/crates/dtoa)&ensp;[![docs-rs]](https://docs.rs/dtoa)
+//!
+//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
+//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
+//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logoColor=white&logo=data:image/svg+xml;base64,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
+//!
+//! <br>
+//!
+//! This crate provides fast functions for printing floating-point primitives to
+//! an [`io::Write`]. The implementation is a straightforward Rust port of [Milo
+//! Yip]'s C++ implementation [dtoa.h]. The original C++ code of each function
+//! is included in comments.
+//!
+//! See also [`itoa`] for printing integer primitives.
+//!
+//! [`io::Write`]: https://doc.rust-lang.org/std/io/trait.Write.html
+//! [Milo Yip]: https://github.com/miloyip
+//! [dtoa.h]: https://github.com/miloyip/rapidjson/blob/master/include/rapidjson/internal/dtoa.h
+//! [`itoa`]: https://github.com/dtolnay/itoa
+//!
+//! <br>
+//!
+//! ## Performance (lower is better)
+//!
+//! ![performance](https://raw.githubusercontent.com/dtolnay/dtoa/master/performance.png)
+//!
+//! <br>
+//!
+//! # Examples
+//!
+//! ```edition2018
+//! use std::io;
+//!
+//! fn main() -> io::Result<()> {
+//!     // Write to a vector or other io::Write.
+//!     let mut buf = Vec::new();
+//!     dtoa::write(&mut buf, 2.71828f64)?;
+//!     println!("{:?}", buf);
+//!
+//!     // Write to a stack buffer.
+//!     let mut bytes = [b'\0'; 20];
+//!     let n = dtoa::write(&mut bytes[..], 2.71828f64)?;
+//!     println!("{:?}", &bytes[..n]);
+//!
+//!     Ok(())
+//! }
+//! ```
+
+#![doc(html_root_url = "https://docs.rs/dtoa/0.4.8")]
+#![cfg_attr(feature = "cargo-clippy", allow(renamed_and_removed_lints))]
+#![cfg_attr(
+    feature = "cargo-clippy",
+    allow(
+        cast_lossless,
+        cast_possible_truncation,
+        if_not_else,
+        missing_errors_doc,
+        range_plus_one,
+        shadow_unrelated,
+        transmute_float_to_int,
+        unreadable_literal,
+        unseparated_literal_suffix
+    )
+)]
+
+#[macro_use] mod diyfp;
+#[macro_use] mod dtoa;
+
+use std::{io, mem, ops, ptr, slice};
+
+/// Write float to an `io::Write`.
+#[inline]
+pub fn write<W: io::Write, V: Floating>(wr: W, value: V) -> io::Result<usize> {
+    value.write(wr)
+}
+
+/// An floating point number that can be formatted by `dtoa::write`.
+pub trait Floating {
+    fn write<W: io::Write>(self, wr: W) -> io::Result<usize>;
+}
+
+impl Floating for f32 {
+    fn write<W: io::Write>(self, wr: W) -> io::Result<usize> {
+        dtoa! {
+            floating_type: f32,
+            significand_type: u32,
+            exponent_type: i32,
+
+            diy_significand_size: 32,
+            significand_size: 23,
+            exponent_bias: 0x7F,
+            mask_type: u32,
+            exponent_mask: 0x7F800000,
+            significand_mask: 0x007FFFFF,
+            hidden_bit: 0x00800000,
+            cached_powers_f: CACHED_POWERS_F_32,
+            cached_powers_e: CACHED_POWERS_E_32,
+            min_power: (-36),
+        };
+        unsafe { dtoa(wr, self) }
+    }
+}
+
+impl Floating for f64 {
+    fn write<W: io::Write>(self, wr: W) -> io::Result<usize> {
+        dtoa! {
+            floating_type: f64,
+            significand_type: u64,
+            exponent_type: isize,
+
+            diy_significand_size: 64,
+            significand_size: 52,
+            exponent_bias: 0x3FF,
+            mask_type: u64,
+            exponent_mask: 0x7FF0000000000000,
+            significand_mask: 0x000FFFFFFFFFFFFF,
+            hidden_bit: 0x0010000000000000,
+            cached_powers_f: CACHED_POWERS_F_64,
+            cached_powers_e: CACHED_POWERS_E_64,
+            min_power: (-348),
+        };
+        unsafe { dtoa(wr, self) }
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+const MAX_DECIMAL_PLACES: isize = 324;
+
+static DEC_DIGITS_LUT: [u8; 200] = *b"\
+    0001020304050607080910111213141516171819\
+    2021222324252627282930313233343536373839\
+    4041424344454647484950515253545556575859\
+    6061626364656667686970717273747576777879\
+    8081828384858687888990919293949596979899";
+
+// 10^-36, 10^-28, ..., 10^52
+static CACHED_POWERS_F_32: [u32; 12] = [
+    0xaa242499, 0xfd87b5f3, 0xbce50865, 0x8cbccc09,
+    0xd1b71759, 0x9c400000, 0xe8d4a510, 0xad78ebc6,
+    0x813f3979, 0xc097ce7c, 0x8f7e32ce, 0xd5d238a5,
+];
+
+static CACHED_POWERS_E_32: [i16; 12] = [
+    -151, -125, -98, -71, -45, -18, 8, 35, 62, 88, 115, 141,
+];
+
+// 10^-348, 10^-340, ..., 10^340
+static CACHED_POWERS_F_64: [u64; 87] = [
+    0xfa8fd5a0081c0288, 0xbaaee17fa23ebf76,
+    0x8b16fb203055ac76, 0xcf42894a5dce35ea,
+    0x9a6bb0aa55653b2d, 0xe61acf033d1a45df,
+    0xab70fe17c79ac6ca, 0xff77b1fcbebcdc4f,
+    0xbe5691ef416bd60c, 0x8dd01fad907ffc3c,
+    0xd3515c2831559a83, 0x9d71ac8fada6c9b5,
+    0xea9c227723ee8bcb, 0xaecc49914078536d,
+    0x823c12795db6ce57, 0xc21094364dfb5637,
+    0x9096ea6f3848984f, 0xd77485cb25823ac7,
+    0xa086cfcd97bf97f4, 0xef340a98172aace5,
+    0xb23867fb2a35b28e, 0x84c8d4dfd2c63f3b,
+    0xc5dd44271ad3cdba, 0x936b9fcebb25c996,
+    0xdbac6c247d62a584, 0xa3ab66580d5fdaf6,
+    0xf3e2f893dec3f126, 0xb5b5ada8aaff80b8,
+    0x87625f056c7c4a8b, 0xc9bcff6034c13053,
+    0x964e858c91ba2655, 0xdff9772470297ebd,
+    0xa6dfbd9fb8e5b88f, 0xf8a95fcf88747d94,
+    0xb94470938fa89bcf, 0x8a08f0f8bf0f156b,
+    0xcdb02555653131b6, 0x993fe2c6d07b7fac,
+    0xe45c10c42a2b3b06, 0xaa242499697392d3,
+    0xfd87b5f28300ca0e, 0xbce5086492111aeb,
+    0x8cbccc096f5088cc, 0xd1b71758e219652c,
+    0x9c40000000000000, 0xe8d4a51000000000,
+    0xad78ebc5ac620000, 0x813f3978f8940984,
+    0xc097ce7bc90715b3, 0x8f7e32ce7bea5c70,
+    0xd5d238a4abe98068, 0x9f4f2726179a2245,
+    0xed63a231d4c4fb27, 0xb0de65388cc8ada8,
+    0x83c7088e1aab65db, 0xc45d1df942711d9a,
+    0x924d692ca61be758, 0xda01ee641a708dea,
+    0xa26da3999aef774a, 0xf209787bb47d6b85,
+    0xb454e4a179dd1877, 0x865b86925b9bc5c2,
+    0xc83553c5c8965d3d, 0x952ab45cfa97a0b3,
+    0xde469fbd99a05fe3, 0xa59bc234db398c25,
+    0xf6c69a72a3989f5c, 0xb7dcbf5354e9bece,
+    0x88fcf317f22241e2, 0xcc20ce9bd35c78a5,
+    0x98165af37b2153df, 0xe2a0b5dc971f303a,
+    0xa8d9d1535ce3b396, 0xfb9b7cd9a4a7443c,
+    0xbb764c4ca7a44410, 0x8bab8eefb6409c1a,
+    0xd01fef10a657842c, 0x9b10a4e5e9913129,
+    0xe7109bfba19c0c9d, 0xac2820d9623bf429,
+    0x80444b5e7aa7cf85, 0xbf21e44003acdd2d,
+    0x8e679c2f5e44ff8f, 0xd433179d9c8cb841,
+    0x9e19db92b4e31ba9, 0xeb96bf6ebadf77d9,
+    0xaf87023b9bf0ee6b,
+];
+static CACHED_POWERS_E_64: [i16; 87] = [
+    -1220, -1193, -1166, -1140, -1113, -1087, -1060, -1034, -1007,  -980,
+    -954,   -927,  -901,  -874,  -847,  -821,  -794,  -768,  -741,  -715,
+    -688,   -661,  -635,  -608,  -582,  -555,  -529,  -502,  -475,  -449,
+    -422,   -396,  -369,  -343,  -316,  -289,  -263,  -236,  -210,  -183,
+    -157,   -130,  -103,   -77,   -50,   -24,     3,    30,    56,    83,
+     109,    136,   162,   189,   216,   242,   269,   295,   322,   348,
+     375,    402,   428,   455,   481,   508,   534,   561,   588,   614,
+     641,    667,   694,   720,   747,   774,   800,   827,   853,   880,
+     907,    933,   960,   986,  1013,  1039,  1066,
+];