Function for getting character frequencies

src/hufftree/base.rs

@@ -69,6 +69,20 @@ impl Hufftree {
     }
 }
 
+pub fn get_char_frequencies(text: String) -> HashMap<char, i32> {
+    let mut map = HashMap::new();
+
+    for character in text.chars() {
+        if map.contains_key(&character) {
+            map.entry(character).and_modify(|e| *e += 1);
+        } else {
+            map.insert(character, 1);
+        }
+    }
+
+    map
+}
+
 #[cfg(test)]
 mod test {
     use super::*;
@@ -104,4 +118,15 @@ mod test {
         assert_eq!(b_code.to_string(), "01");
         assert_eq!(c_code.to_string(), "00");
     }
+
+    #[test]
+    fn get_charcter_freq() {
+        let text = String::from("aaaaaabb cc");
+        let freq = get_char_frequencies(text);
+
+        assert_eq!(freq.get(&'a').unwrap(), &6);
+        assert_eq!(freq.get(&'b').unwrap(), &2);
+        assert_eq!(freq.get(&'c').unwrap(), &2);
+        assert_eq!(freq.get(&' ').unwrap(), &1);
+    }
 }