Put non-continous headers to header_cache, and re-check it after head…

…er_process success

sync/src/synchronizer/headers_process.rs

@@ -136,6 +136,7 @@ impl<'a> HeadersProcess<'a> {
 
         if !self.is_parent_exists(&headers[0]) {
             // put the headers into a memory cache
+            self.synchronizer.header_cache.insert(headers[0].parent_hash, headers);
             // verify them later
             return Status::ok();
         }
@@ -222,6 +223,14 @@ impl<'a> HeadersProcess<'a> {
             }
         }
 
+        {
+            // these headers verify success
+            // may the headers's tail header_hash exist in headers_cahce?
+            if let Some(headers) = self.synchronizer.headers_cache.get(headers.last().expect("last header must exist").hash){
+                HeadersProcess::new().execute();
+            }
+        }
+
         Status::ok()
     }
 }

sync/src/synchronizer/mod.rs

@@ -301,6 +301,9 @@ pub struct Synchronizer {
     pub(crate) chain: ChainController,
     /// Sync shared state
     pub shared: Arc<SyncShared>,
+
+    // First Headers's parent_hash -> Headers
+    pub(crate) header_cache: HashMap<Byte32, Vec<Header>>,
     fetch_channel: Option<channel::Sender<FetchCMD>>,
 }