56 lines
1.7 KiB
Rust
56 lines
1.7 KiB
Rust
// Copyright (c) 2018 Jorge Aparicio
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// Copyright © 2005-2020 Rich Felker, et al.
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// Copyright © 1993,2004 Sun Microsystems or
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// Copyright © 2003-2011 David Schultz or
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// Copyright © 2003-2009 Steven G. Kargl or
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// Copyright © 2003-2009 Bruce D. Evans or
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// Copyright © 2008 Stephen L. Moshier or
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// Copyright © 2017-2018 Arm Limited
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// SPDX-License-Identifier: MIT
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// This file is licensed solely under the terms discussed in LICENSE-LIBM-MIT at the crate root.
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// See the package-level README for full details.
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// Taken from https://github.com/rust-lang/libm/blob/master/src/math/mod.rs#L1
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macro_rules! force_eval {
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($e:expr) => {
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unsafe { ::core::ptr::read_volatile(&$e) }
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};
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}
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// Taken from https://github.com/rust-lang/libm/blob/libm-v0.2.11/src/math/round.rs
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pub(crate) fn round(x: f64) -> f64 {
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trunc(x + copysign(0.5 - 0.25 * f64::EPSILON, x))
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}
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// Adapted from: https://github.com/rust-lang/libm/blob/libm-v0.2.11/src/math/trunc.rs#L8-L12
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#[allow(clippy::needless_late_init /*, reason = "The original libm code uses this style" */)]
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fn trunc(x: f64) -> f64 {
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let x1p120 = f64::from_bits(0x4770000000000000); // 0x1p120f === 2 ^ 120
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let mut i: u64 = x.to_bits();
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let mut e: i64 = ((i >> 52) & 0x7ff) as i64 - 0x3ff + 12;
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let m: u64;
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if e >= 52 + 12 {
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return x;
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}
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if e < 12 {
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e = 1;
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}
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m = -1i64 as u64 >> e;
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if (i & m) == 0 {
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return x;
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}
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force_eval!(x + x1p120);
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i &= !m;
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f64::from_bits(i)
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}
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// Taken from https://github.com/rust-lang/libm/blob/libm-v0.2.11/src/math/copysign.rs
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fn copysign(x: f64, y: f64) -> f64 {
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let mut ux = x.to_bits();
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let uy = y.to_bits();
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ux &= (!0) >> 1;
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ux |= uy & (1 << 63);
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f64::from_bits(ux)
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}
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