38 lines
992 B
Rust
38 lines
992 B
Rust
use std::fmt;
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/// Debug-formats the given slice, but only up to the first `max_len` elements.
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/// Any further elements are replaced by an ellipsis.
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///
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/// See also [`slice_truncated()`],
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pub struct TruncatedSlice<'a, T> {
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inner: &'a [T],
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max_len: usize,
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}
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impl<T: fmt::Debug> fmt::Debug for TruncatedSlice<'_, T> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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if self.inner.len() <= self.max_len {
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write!(f, "{:?}", self.inner)
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} else {
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f.debug_list()
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.entries(&self.inner[..self.max_len])
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.entry(&"...")
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.finish()
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}
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}
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}
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/// See [`TruncatedSlice`]. Useful for `#[instrument]`:
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///
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/// ```
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/// use conduwuit_core::utils::debug::slice_truncated;
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///
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/// #[tracing::instrument(fields(foos = slice_truncated(foos, 42)))]
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/// fn bar(foos: &[&str]);
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/// ```
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pub fn slice_truncated<T: fmt::Debug>(
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slice: &[T],
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max_len: usize,
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) -> tracing::field::DebugValue<TruncatedSlice<'_, T>> {
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tracing::field::debug(TruncatedSlice { inner: slice, max_len })
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}
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