iroh_metrics/iterable.rs
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//! Traits for iterating over the fields of structs.
use std::fmt;
/// Derives [`Iterable`] for a struct.
///
/// You can use this derive instead of [`MetricsGroup`] if you want to implement `Default`
/// and `MetricsGroup` manually, but still use a derived `Iterable` impl.
///
/// [`Iterable`]: ::iroh_metrics::iterable::Iterable
/// [`MetricsGroup`]: ::iroh_metrics::MetricsGroup
pub use iroh_metrics_derive::Iterable;
use crate::MetricItem;
/// Trait for iterating over the fields of a struct.
pub trait Iterable {
/// Returns the number of fields in the struct.
fn field_count(&self) -> usize;
/// Returns the field name and dyn reference to the field.
fn field_ref(&self, n: usize) -> Option<MetricItem<'_>>;
}
/// Helper trait to convert from `self` to `dyn Iterable`.
pub trait IntoIterable {
/// Returns `self` as `dyn Iterable`
fn as_iterable(&self) -> &dyn Iterable;
/// Returns an iterator over the fields of the struct.
fn field_iter(&self) -> FieldIter<'_> {
FieldIter::new(self.as_iterable())
}
}
impl<T> IntoIterable for T
where
T: Iterable,
{
fn as_iterable(&self) -> &dyn Iterable {
self
}
}
/// Iterator over the fields of a struct.
///
/// Returned from [`IntoIterable::field_iter`].
pub struct FieldIter<'a> {
pos: usize,
inner: &'a dyn Iterable,
}
impl fmt::Debug for FieldIter<'_> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "FieldIter")
}
}
impl<'a> FieldIter<'a> {
pub(crate) fn new(inner: &'a dyn Iterable) -> Self {
Self { pos: 0, inner }
}
}
impl<'a> Iterator for FieldIter<'a> {
type Item = MetricItem<'a>;
fn next(&mut self) -> Option<Self::Item> {
if self.pos == self.inner.field_count() {
None
} else {
let out = self.inner.field_ref(self.pos);
self.pos += 1;
out
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
let n = self.inner.field_count() - self.pos;
(n, Some(n))
}
}