do only one hash lookup

Author: iunanua

opentelemetry-http/src/lib.rs

@@ -46,17 +46,12 @@ impl Extractor for HeaderExtractor<'_> {
 
     /// Get all the values for a key from the HeaderMap
     fn get_all(&self, key: &str) -> Option<Vec<&str>> {
-        if !self.0.contains_key(key) {
+        let all_iter = self.0.get_all(key).iter();
+        if let (0, Some(0)) = all_iter.size_hint() {
             return None;
         }
 
-        Some(
-            self.0
-                .get_all(key)
-                .iter()
-                .filter_map(|value| value.to_str().ok())
-                .collect(),
-        )
+        Some(all_iter.filter_map(|value| value.to_str().ok()).collect())
     }
 }