Compress snapshot files

Fix: ##220

Author: baumstern

Cargo.lock

@@ -18,6 +18,7 @@ parking_lot = "0.5"
 patricia-trie = { path = "../util/patricia_trie" }
 rand = "0.5.3"
 rlp = { path = "../util/rlp" }
+snap = "0.2"
 time = "0.1"
 triehash = { path = "../util/triehash" }
 

sync/Cargo.toml

@@ -30,6 +30,7 @@ extern crate patricia_trie as trie;
 extern crate rand;
 #[cfg_attr(test, macro_use)]
 extern crate rlp;
+extern crate snap;
 extern crate time;
 extern crate triehash;
 

sync/src/lib.rs

@@ -91,7 +91,7 @@ fn write_snapshot(db: Arc<KeyValueDB>, path: PathBuf, root: &H256) -> Result<(),
     }
 
     {
-        let mut file = File::create(path.join("head"))?;
+        let file = File::create(path.join("head"))?;
         let mut snappy = snap::Writer::new(file);
 
         let mut stream = RlpStream::new();
@@ -108,7 +108,7 @@ fn write_snapshot(db: Arc<KeyValueDB>, path: PathBuf, root: &H256) -> Result<(),
 
     for (grandchild, _) in &grandchildren {
         let nodes = enumerate_subtree(&db, grandchild)?;
-        let mut file = File::create(path.join(format!("{:x}", grandchild)))?;
+        let file = File::create(path.join(format!("{:x}", grandchild)))?;
         let mut snappy = snap::Writer::new(file);
 
         let mut stream = RlpStream::new();
@@ -119,7 +119,7 @@ fn write_snapshot(db: Arc<KeyValueDB>, path: PathBuf, root: &H256) -> Result<(),
             stream.append(&value);
         }
         stream.complete_unbounded_list();
-        
+
         snappy.write(&stream.drain())?;
     }