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|
//! Identifier newtype primitives and helpers for defining and working with
//! them.
use core::hash::Hash;
/// Numeric identifier representation.
///
/// Most implementors of this should be defined using the `id` macro for
/// consistency in their implementations.
pub trait Id:
Copy + Clone + PartialEq + Eq + PartialOrd + Ord + Hash + Send + Sync
{
/// The backing integer type for this identifier.
type Integer: Integer;
/// Instantiate a new identifier from its underlying representation.
#[must_use]
fn new(v: Self::Integer) -> Self;
}
//NOTE: we don't use the same [`Integer`] trait in `numerics` here as there
// is specific behavior desired in an "integer backing an id"---such as
// checked overflow---that may not be wanted in more general arithmetic
// operations.
/// Valid integer types backing an [`Id`].
pub trait Integer:
Copy
+ Clone
+ PartialEq
+ Eq
+ PartialOrd
+ Ord
+ Hash
+ Send
+ Sync
+ sealed::Sealed
{
/// Zero value of the integer type.
const ZERO: Self;
/// Convert this integer into a `usize`.
fn into_usize(self) -> usize;
/// Construct an integer from a `usize`.
///
/// Returns `None` if no corresponding integer exists.
fn from_usize(v: usize) -> Option<Self>;
/// Returns the successor value of this integer.
///
/// If this would have overflowed, `None` is returned.
fn increment(self) -> Option<Self>;
//// Returns the predecessor value of this integer.
///
/// If this would have overflowed, `None` is returned.
fn decrement(self) -> Option<Self>;
}
macro_rules! integer_impl {
($t:ty) => {
impl sealed::Sealed for $t {}
impl Integer for $t {
const ZERO: Self = 0;
#[allow(trivial_numeric_casts, clippy::cast_possible_truncation)]
fn into_usize(self) -> usize {
//NOTE: truncation never happens as `Integer` implementations
// are gated behind `target_pointer_width`.
self as usize
}
#[allow(trivial_numeric_casts, clippy::cast_possible_truncation)]
fn from_usize(v: usize) -> Option<Self> {
//NOTE: truncation can't happen, see above.
if v <= Self::MAX as usize {
//NOTE: we just checked this exists and doesn't truncate.
Some(v as $t)
} else {
None
}
}
fn increment(self) -> Option<Self> {
self.checked_add(1)
}
fn decrement(self) -> Option<Self> {
self.checked_sub(1)
}
}
};
}
integer_impl!(usize);
#[cfg(target_pointer_width = "64")]
integer_impl!(u64);
#[cfg(any(target_pointer_width = "64", target_pointer_width = "32"))]
integer_impl!(u32);
integer_impl!(u16);
integer_impl!(u8);
mod sealed {
pub trait Sealed {}
}
|
