polyfill.rs

// Copyright 2015-2016 Brian Smith.
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

//! Polyfills for functionality that will (hopefully) be added to Rust's
//! standard library soon.

#[cfg(any(target_pointer_width = "32", target_pointer_width = "64"))]
#[inline(always)]
pub const fn u64_from_usize(x: usize) -> u64 {
    x as u64
}

#[cfg(any(target_pointer_width = "32", target_pointer_width = "64"))]
pub fn usize_from_u32(x: u32) -> usize {
    x as usize
}

#[cfg(all(target_arch = "aarch64", target_pointer_width = "64"))]
#[allow(clippy::cast_possible_truncation)]
pub fn usize_from_u64(x: u64) -> usize {
    x as usize
}

/// const-capable `x.try_into().unwrap_or(usize::MAX)`
#[allow(clippy::cast_possible_truncation)]
#[inline(always)]
pub const fn usize_from_u64_saturated(x: u64) -> usize {
    const USIZE_MAX: u64 = u64_from_usize(usize::MAX);
    if x < USIZE_MAX {
        x as usize
    } else {
        usize::MAX
    }
}

mod array_flat_map;
mod array_flatten;
mod array_split_map;

pub mod sliceutil;

#[cfg(feature = "alloc")]
mod leading_zeros_skipped;

pub mod ptr;

pub mod slice;

#[cfg(test)]
mod test;

mod unwrap_const;

pub use self::{
    array_flat_map::ArrayFlatMap, array_flatten::ArrayFlatten, array_split_map::ArraySplitMap,
    unwrap_const::unwrap_const,
};

#[cfg(feature = "alloc")]
pub use leading_zeros_skipped::LeadingZerosStripped;

#[cfg(test)]
mod tests {
    use super::*;
    #[test]
    fn test_usize_from_u64_saturated() {
        const USIZE_MAX: u64 = u64_from_usize(usize::MAX);
        assert_eq!(usize_from_u64_saturated(u64::MIN), usize::MIN);
        assert_eq!(usize_from_u64_saturated(USIZE_MAX), usize::MAX);
        assert_eq!(usize_from_u64_saturated(USIZE_MAX - 1), usize::MAX - 1);

        #[cfg(not(target_pointer_width = "64"))]
        {
            assert_eq!(usize_from_u64_saturated(USIZE_MAX + 1), usize::MAX);
        }
    }
}