tiny_skia_path/floating_point.rs
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// Copyright 2006 The Android Open Source Project
// Copyright 2020 Yevhenii Reizner
//
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
use crate::scalar::Scalar;
pub use strict_num::{FiniteF32, NonZeroPositiveF32, NormalizedF32};
#[cfg(all(not(feature = "std"), feature = "no-std-float"))]
use crate::NoStdFloat;
pub(crate) const FLOAT_PI: f32 = 3.14159265;
const MAX_I32_FITS_IN_F32: f32 = 2147483520.0;
const MIN_I32_FITS_IN_F32: f32 = -MAX_I32_FITS_IN_F32;
// TODO: is there an std alternative?
/// Custom float to integer conversion routines.
pub trait SaturateCast<T>: Sized {
/// Return the closest integer for the given float.
fn saturate_from(n: T) -> Self;
}
impl SaturateCast<f32> for i32 {
/// Return the closest integer for the given float.
///
/// Returns MAX_I32_FITS_IN_F32 for NaN.
fn saturate_from(mut x: f32) -> Self {
x = if x < MAX_I32_FITS_IN_F32 {
x
} else {
MAX_I32_FITS_IN_F32
};
x = if x > MIN_I32_FITS_IN_F32 {
x
} else {
MIN_I32_FITS_IN_F32
};
x as i32
}
}
impl SaturateCast<f64> for i32 {
/// Return the closest integer for the given double.
///
/// Returns i32::MAX for NaN.
fn saturate_from(mut x: f64) -> Self {
x = if x < i32::MAX as f64 {
x
} else {
i32::MAX as f64
};
x = if x > i32::MIN as f64 {
x
} else {
i32::MIN as f64
};
x as i32
}
}
/// Custom float to integer rounding routines.
#[allow(missing_docs)]
pub trait SaturateRound<T>: SaturateCast<T> {
fn saturate_floor(n: T) -> Self;
fn saturate_ceil(n: T) -> Self;
fn saturate_round(n: T) -> Self;
}
impl SaturateRound<f32> for i32 {
fn saturate_floor(x: f32) -> Self {
Self::saturate_from(x.floor())
}
fn saturate_ceil(x: f32) -> Self {
Self::saturate_from(x.ceil())
}
fn saturate_round(x: f32) -> Self {
Self::saturate_from(x.floor() + 0.5)
}
}
/// Return the float as a 2s compliment int. Just to be used to compare floats
/// to each other or against positive float-bit-constants (like 0). This does
/// not return the int equivalent of the float, just something cheaper for
/// compares-only.
pub(crate) fn f32_as_2s_compliment(x: f32) -> i32 {
sign_bit_to_2s_compliment(bytemuck::cast(x))
}
/// Convert a sign-bit int (i.e. float interpreted as int) into a 2s compliement
/// int. This also converts -0 (0x80000000) to 0. Doing this to a float allows
/// it to be compared using normal C operators (<, <=, etc.)
fn sign_bit_to_2s_compliment(mut x: i32) -> i32 {
if x < 0 {
x &= 0x7FFFFFFF;
x = -x;
}
x
}
/// An immutable `f32` that is larger than 0 but less then 1.
#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Default, Debug)]
#[repr(transparent)]
pub struct NormalizedF32Exclusive(FiniteF32);
impl NormalizedF32Exclusive {
/// Just a random, valid number.
pub const ANY: Self = Self::HALF;
/// A predefined 0.5 value.
pub const HALF: Self = NormalizedF32Exclusive(unsafe { FiniteF32::new_unchecked(0.5) });
/// Creates a `NormalizedF32Exclusive`.
pub fn new(n: f32) -> Option<Self> {
if n > 0.0 && n < 1.0 {
// `n` is guarantee to be finite after the bounds check.
FiniteF32::new(n).map(NormalizedF32Exclusive)
} else {
None
}
}
/// Creates a `NormalizedF32Exclusive` clamping the given value.
///
/// Returns zero in case of NaN or infinity.
pub fn new_bounded(n: f32) -> Self {
let n = n.bound(f32::EPSILON, 1.0 - f32::EPSILON);
// `n` is guarantee to be finite after clamping.
debug_assert!(n.is_finite());
NormalizedF32Exclusive(unsafe { FiniteF32::new_unchecked(n) })
}
/// Returns the value as a primitive type.
pub fn get(self) -> f32 {
self.0.get()
}
/// Returns the value as a `FiniteF32`.
pub fn to_normalized(self) -> NormalizedF32 {
// NormalizedF32 is (0,1), while NormalizedF32 is [0,1], so it will always fit.
unsafe { NormalizedF32::new_unchecked(self.0.get()) }
}
}