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#[cfg(test)] mod tests; /// Uses a sorted slice `data: &[E]` as a kind of "multi-map". The /// `key_fn` extracts a key of type `K` from the data, and this /// function finds the range of elements that match the key. `data` /// must have been sorted as if by a call to `sort_by_key` for this to /// work. pub fn binary_search_slice<E, K>(data: &'d [E], key_fn: impl Fn(&E) -> K, key: &K) -> &'d [E] where K: Ord, { let mid = match data.binary_search_by_key(key, &key_fn) { Ok(mid) => mid, Err(_) => return &[], }; // We get back *some* element with the given key -- so // search backwards to find the *first* one. // // (It'd be more efficient to use a "galloping" search // here, but it's not really worth it for small-ish // amounts of data.) let mut start = mid; while start > 0 { if key_fn(&data[start - 1]) == *key { start -= 1; } else { break; } } // Now search forward to find the *last* one. // // (It'd be more efficient to use a "galloping" search // here, but it's not really worth it for small-ish // amounts of data.) let mut end = mid + 1; let max = data.len(); while end < max { if key_fn(&data[end]) == *key { end += 1; } else { break; } } &data[start..end] }