Add meta section len() and to_bytes()

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/vm/obj/obj.rs

@@ -205,11 +205,21 @@ pub struct MetaSection {
 
 impl MetaSection {
     pub fn len(&self) -> usize {
-        todo!() // 8 + ...
+        8 + self.entries.iter()
+            .map(|(k, _)| 8 + k.as_bytes().len() + 8)
+            .sum::<usize>()
     }
 
     pub fn to_bytes(&self) -> Vec<u8> {
-        todo!()
+        let mut cursor = Cursor::new(Vec::new());
+        cursor.write_u64::<LE>(self.entries.len() as u64).unwrap();
+        for (k, v) in self.entries.iter() {
+            let key_len = k.as_bytes().len();
+            cursor.write_u64::<LE>(key_len as u64).unwrap();
+            cursor.write(k.as_bytes()).unwrap();
+            cursor.write_u64::<LE>(*v).unwrap();
+        }
+        cursor.into_inner()
     }
 
     pub fn from_bytes(bytes: &[u8]) -> Result<Self> {
@@ -246,6 +256,9 @@ mod test {
                     len: 16,
                     contents: vec!(0u8; 16),
                 }),
+                Section::Meta(MetaSection {
+                    entries: Default::default(),
+                })
             ],
         };