serialize from and to file

.gitignore

@@ -1,2 +1,3 @@
 /target
 debug.png
+*.messagepack

src/main.rs

@@ -8,29 +8,30 @@ fn main() {
     //Init all descriptors:
     let desc = Median;
 
-    //Pre-allocate hashmap to right size:
+    //Initialize hashmap, empty or from cached file:
     let count = fs::read_dir("img").unwrap().count();
-    let mut map: HashMap<String, u64> = HashMap::with_capacity(count);
+    let map_file = fs::read("map.messagepack");
+    let mut map: HashMap<String, u64> = match map_file {
+        Ok(f) => rmp_serde::from_slice(&f).unwrap(),
+        Err(_e) => HashMap::with_capacity(count),
+    };
 
     //Calculate phashes for all images
     for node in fs::read_dir("img").unwrap() {
         let file = node.expect("Error walking directory");
-        let img = image::open(file.path()).expect("Unable to open file");
-        let phash = desc.describe(img);
         let name = file.file_name().into_string().expect("Issue with filename");
-        map.insert(name, phash);
+        if !map.contains_key(&name) {
+            let img = image::open(file.path()).expect("Unable to open file");
+            let phash = desc.describe(img);
+            map.insert(name, phash);
+        }
     }
 
     for (key, val) in map.iter() {
         println!("{key}: {val}");
     }
 
-    //Test (de)serialize to vector with MessagePack:
+    //Serialize hashmap with MessagePack:
     let serialized: Vec<u8> = rmp_serde::to_vec(&map).unwrap();
-
+    fs::write("map.messagepack",&serialized).unwrap();
-    let x: HashMap<String, u64> = rmp_serde::from_slice(&serialized).unwrap();
-
-    for (key, val) in x.iter() {
-        println!("{key}: {val}");
-    }
 }