use sha256 digest as cache keys (#135)

* use sha256 digest as cache keys

* rebasing master

libp2p/protocols/pubsub/gossipsub.nim

@@ -391,7 +391,7 @@ method publish*(g: GossipSub,
   await procCall PubSub(g).publish(topic, data)
 
   trace "about to publish message on topic", name = topic,
-                                             data = data.toHex()
+                                             data = data.shortLog
   if data.len > 0 and topic.len > 0:
     var peers: HashSet[string]
     if topic in g.topics: # if we're subscribed to the topic attempt to build a mesh

libp2p/protocols/pubsub/pubsubpeer.nim

@@ -8,7 +8,7 @@
 ## those terms.
 
 import options, hashes, strutils, tables, hashes
-import chronos, chronicles
+import chronos, chronicles, nimcrypto/sha2
 import rpc/[messages, message, protobuf],
        timedcache,
        ../../peer,
@@ -57,9 +57,9 @@ proc handle*(p: PubSubPeer, conn: Connection) {.async.} =
     while not conn.closed:
       trace "waiting for data", peer = p.id, closed = conn.closed
       let data = await conn.readLp(64 * 1024)
-      let hexData = data.toHex()
+      let digest = $(sha256.digest(data))
       trace "read data from peer", peer = p.id, data = data.shortLog
-      if $hexData.hash in p.recvdRpcCache:
+      if digest in p.recvdRpcCache:
         trace "message already received, skipping", peer = p.id
         continue
 
@@ -69,7 +69,7 @@ proc handle*(p: PubSubPeer, conn: Connection) {.async.} =
       for obs in p.observers[]:
         obs.onRecv(p, msg)
       await p.handler(p, @[msg])
-      p.recvdRpcCache.put($hexData.hash)
+      p.recvdRpcCache.put(digest)
   except CatchableError as exc:
     trace "Exception occurred in PubSubPeer.handle", exc = exc.msg
   finally:
@@ -87,19 +87,21 @@ proc send*(p: PubSubPeer, msgs: seq[RPCMsg]) {.async.} =
         var mm = m
         for obs in p.observers[]:
           obs.onSend(p, mm)
-      let encodedHex = encoded.buffer.toHex()
+
       if encoded.buffer.len <= 0:
         trace "empty message, skipping", peer = p.id
         return
 
-      if $encodedHex.hash in p.sentRpcCache:
+      let digest = $(sha256.digest(encoded.buffer))
+      if digest in p.sentRpcCache:
         trace "message already sent to peer, skipping", peer = p.id
         continue
 
       proc sendToRemote() {.async.} =
-        trace "sending encoded msgs to peer", peer = p.id, encoded = encoded.buffer.shortLog
+        trace "sending encoded msgs to peer", peer = p.id,
+                                              encoded = encoded.buffer.shortLog
         await p.sendConn.writeLp(encoded.buffer)
-        p.sentRpcCache.put($encodedHex.hash)
+        p.sentRpcCache.put(digest)
 
       # if no connection has been set,
       # queue messages untill a connection