simplify server, check that hashes match

server.go

@@ -87,54 +87,44 @@ func (s *Server) doError(conn net.Conn, e error) error {
 }
 
 func (s *Server) receiveBlob(conn net.Conn) error {
-	var sendRequest sendBlobRequest
+	blobSize, blobHash, err := s.readBlobRequest(conn)
-	dec := json.NewDecoder(conn)
-	err := dec.Decode(&sendRequest)
-	if err != nil {
-		return err
-	} else if sendRequest.BlobSize > BlobSize {
-		return fmt.Errorf("Blob size cannot be greater than " + strconv.Itoa(BlobSize) + " bytes")
-	}
-
-	// check if blob exists
-	haveBlob := false
-	sendResponse, err := json.Marshal(sendBlobResponse{SendBlob: !haveBlob})
 	if err != nil {
 		return err
 	}
 
-	_, err = conn.Write(sendResponse)
+	blobExists := false
+	blobPath := path.Join(s.BlobDir, blobHash)
+	if _, err := os.Stat(blobPath); !os.IsNotExist(err) {
+		blobExists = true
+	}
+
+	err = s.sendBlobResponse(conn, blobExists)
 	if err != nil {
 		return err
 	}
 
-	blob := make([]byte, sendRequest.BlobSize)
+	if blobExists {
+		return nil
+	}
+
+	blob := make([]byte, blobSize)
 	_, err = io.ReadFull(bufio.NewReader(conn), blob)
 	if err != nil {
 		return err
 	}
 
-	blobHash := getBlobHash(blob)
+	receivedBlobHash := getBlobHash(blob)
-	if sendRequest.BlobHash != blobHash {
+	if blobHash != receivedBlobHash {
-		return fmt.Errorf("Hash of received blob does not match hash from send request")
+		return fmt.Errorf("Hash of received blob data does not match hash from send request")
 	}
 	log.Println("Got blob " + blobHash[:8])
 
-	err = ioutil.WriteFile(path.Join(s.BlobDir, blobHash), blob, 0644)
+	err = ioutil.WriteFile(blobPath, blob, 0644)
 	if err != nil {
 		return err
 	}
 
-	transferResponse, err := json.Marshal(blobTransferResponse{ReceivedBlob: true})
+	return s.sendTransferResponse(conn, true)
-	if err != nil {
-		return err
-	}
-
-	_, err = conn.Write(transferResponse)
-	if err != nil {
-		return err
-	}
-	return nil
 }
 
 func (s *Server) doHandshake(conn net.Conn) error {
@@ -160,6 +150,42 @@ func (s *Server) doHandshake(conn net.Conn) error {
 	return nil
 }
 
+func (s *Server) readBlobRequest(conn net.Conn) (int, string, error) {
+	var sendRequest sendBlobRequest
+	dec := json.NewDecoder(conn)
+	err := dec.Decode(&sendRequest)
+	if err != nil {
+		return 0, "", err
+	} else if sendRequest.BlobSize > BlobSize {
+		return 0, "", fmt.Errorf("Blob size cannot be greater than " + strconv.Itoa(BlobSize) + " bytes")
+	}
+	return sendRequest.BlobSize, sendRequest.BlobHash, nil
+}
+
+func (s *Server) sendBlobResponse(conn net.Conn, blobExists bool) error {
+	sendResponse, err := json.Marshal(sendBlobResponse{SendBlob: !blobExists})
+	if err != nil {
+		return err
+	}
+	_, err = conn.Write(sendResponse)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func (s *Server) sendTransferResponse(conn net.Conn, receivedBlob bool) error {
+	transferResponse, err := json.Marshal(blobTransferResponse{ReceivedBlob: receivedBlob})
+	if err != nil {
+		return err
+	}
+	_, err = conn.Write(transferResponse)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
 func (s *Server) ensureBlobDirExists() error {
 	if stat, err := os.Stat(s.BlobDir); err != nil {
 		if os.IsNotExist(err) {