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use crate::mem::MaybeUninit;
/// Trait used to describe the maximum number of digits in decimal base of the implemented integer.
#[unstable(feature = "int_format_into", issue = "138215")]
pub trait NumBufferTrait {
/// Maximum number of digits in decimal base of the implemented integer.
const BUF_SIZE: usize;
}
macro_rules! impl_NumBufferTrait {
($($signed:ident, $unsigned:ident,)*) => {
$(
#[unstable(feature = "int_format_into", issue = "138215")]
impl NumBufferTrait for $signed {
// `+ 2` and not `+ 1` to include the `-` character.
const BUF_SIZE: usize = $signed::MAX.ilog(10) as usize + 2;
}
#[unstable(feature = "int_format_into", issue = "138215")]
impl NumBufferTrait for $unsigned {
const BUF_SIZE: usize = $unsigned::MAX.ilog(10) as usize + 1;
}
)*
}
}
impl_NumBufferTrait! {
i8, u8,
i16, u16,
i32, u32,
i64, u64,
isize, usize,
i128, u128,
}
/// A buffer wrapper of which the internal size is based on the maximum
/// number of digits the associated integer can have.
#[unstable(feature = "int_format_into", issue = "138215")]
#[derive(Debug)]
pub struct NumBuffer<T: NumBufferTrait> {
// FIXME: Once const generics feature is working, use `T::BUF_SIZE` instead of 40.
pub(crate) buf: [MaybeUninit<u8>; 40],
// FIXME: Remove this field once we can actually use `T`.
phantom: core::marker::PhantomData<T>,
}
#[unstable(feature = "int_format_into", issue = "138215")]
impl<T: NumBufferTrait> NumBuffer<T> {
/// Initializes internal buffer.
#[unstable(feature = "int_format_into", issue = "138215")]
pub const fn new() -> Self {
// FIXME: Once const generics feature is working, use `T::BUF_SIZE` instead of 40.
NumBuffer { buf: [MaybeUninit::<u8>::uninit(); 40], phantom: core::marker::PhantomData }
}
/// Returns the length of the internal buffer.
#[unstable(feature = "int_format_into", issue = "138215")]
pub const fn capacity(&self) -> usize {
self.buf.len()
}
}
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