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#![doc = include_str!("../README.md")]
use std::fmt;
pub struct TruncatedSlice<'a, T> {
max_len: usize,
inner: &'a [T],
}
impl<'a, T> TruncatedSlice<'a, T> {
pub fn new(wrapped: &'a [T], max_len: usize) -> Self {
Self {
max_len,
inner: wrapped,
}
}
}
impl<'a, T> fmt::Debug for TruncatedSlice<'a, T>
where
T: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let dbg_len = std::cmp::min(self.inner.len(), self.max_len);
let is_truncated = dbg_len < self.inner.len();
f.write_str("[")?;
for (i, entry) in self.inner[..dbg_len].iter().enumerate() {
f.write_fmt(format_args!("{:?}", &entry))?;
if i != dbg_len - 1 {
f.write_str(", ")?;
}
}
if is_truncated {
f.write_fmt(format_args!(", ...({} more)", self.inner.len() - dbg_len))?;
}
f.write_str("]")
}
}
pub trait TruncateSliceDebug<'a, T>
where
T: fmt::Debug,
{
fn truncate_debug(&self, max_len: usize) -> TruncatedSlice<'a, T>;
}
impl<'a, T> TruncateSliceDebug<'a, T> for &'a [T]
where
T: fmt::Debug,
{
fn truncate_debug(&self, max_len: usize) -> TruncatedSlice<'a, T> {
TruncatedSlice::new(self, max_len)
}
}
#[test]
fn test_truncated_slice() {
let values = vec![7; 10];
let dbg10 = format!("{:?}", TruncatedSlice::new(&values, 5));
assert_eq!(&dbg10, "[7, 7, 7, 7, 7, ...(5 more)]");
let dbg10 = format!("{:?}", TruncatedSlice::new(&values, 20));
assert_eq!(&dbg10, "[7, 7, 7, 7, 7, 7, 7, 7, 7, 7]");
}