[protocol] added ALREADYHAVE packet; [node] fixed logical path error when receiving a single file; ALREADY HAVE FILE FEATURE

src/node/node.go

@@ -40,7 +40,8 @@ type sending struct {
 	Recursive    bool   // recursively send directory
 	CanSendBytes bool   // is the other node ready to receive another piece
 	FilesToSend  []*fsys.File
-	CurrentFileIndex uint64 // an id of a file that is currently being transported
+	// CurrentFileIndex uint64 // an index of a file with a specific ID that is currently being transported
+	CurrentFileID uint64 // an id of a file that is currently being transported
 }
 
 // Receiving-side node information
@@ -313,7 +314,7 @@ func (node *Node) Start() {
 						node.transferInfo.Sending.FilesToSend = append(node.transferInfo.Sending.FilesToSend, file)
 
 						// set current file id to the first file
-						node.transferInfo.Sending.CurrentFileIndex = 0
+						node.transferInfo.Sending.CurrentFileID = 0
 
 						filePacket, err := protocol.CreateFilePacket(file)
 						if err != nil {
@@ -342,7 +343,7 @@ func (node *Node) Start() {
 					node.transferInfo.Sending.FilesToSend = append(node.transferInfo.Sending.FilesToSend, fileToSend)
 
 					// set current file index to the first and only file
-					node.transferInfo.Sending.CurrentFileIndex = 0
+					node.transferInfo.Sending.CurrentFileID = 0
 
 					filePacket, err := protocol.CreateFilePacket(node.transferInfo.Sending.FilesToSend[0])
 					if err != nil {
@@ -373,6 +374,23 @@ func (node *Node) Start() {
 			case protocol.HeaderDisconnecting:
 				node.state.Stopped = true
 				fmt.Printf("%s disconnected\n", node.netInfo.Conn.RemoteAddr())
+
+			case protocol.HeaderAlreadyHave:
+				// the other node already has a file with such ID.
+				// do not send it
+
+				fileIDReader := bytes.NewReader(incomingPacket.Body)
+				var fileID uint64
+				binary.Read(fileIDReader, binary.BigEndian, &fileID)
+
+				for index, fileToSend := range node.transferInfo.Sending.FilesToSend {
+					if fileToSend.ID == fileID {
+						node.transferInfo.Sending.FilesToSend = append(node.transferInfo.Sending.FilesToSend[:index], node.transferInfo.Sending.FilesToSend[index+1:]...)
+
+						node.transferInfo.Sending.CurrentFileID++
+					}
+				}
+
 			}
 
 			// Transfer section
@@ -386,6 +404,8 @@ func (node *Node) Start() {
 				fmt.Printf("Transfer ended successfully\n")
 
 				node.state.Stopped = true
+
+				continue
 			}
 
 			// if allowed to transfer and the other node is ready to receive packets - send one piece
@@ -394,7 +414,15 @@ func (node *Node) Start() {
 
 				// sending a piece of a single file
 
-				currentFileIndex := node.transferInfo.Sending.CurrentFileIndex
+				// determine an index of a file with current ID
+				var currentFileIndex uint64 = 0
+				for index, fileToSend := range node.transferInfo.Sending.FilesToSend {
+					if fileToSend.ID == node.transferInfo.Sending.CurrentFileID {
+						currentFileIndex = uint64(index)
+						break
+					}
+				}
+
 				err = protocol.SendPiece(node.transferInfo.Sending.FilesToSend[currentFileIndex], node.netInfo.Conn, node.netInfo.EncryptionKey)
 				switch err {
 				case protocol.ErrorSentAll:
@@ -419,21 +447,10 @@ func (node *Node) Start() {
 
 					protocol.SendPacket(node.netInfo.Conn, endFilePacket)
 
-					// start sending the next file
-					if uint64(len(node.transferInfo.Sending.FilesToSend)) == (node.transferInfo.Sending.CurrentFileIndex + 1) {
-						// all files has been sent
-						node.state.Stopped = true
-
-						// send DONE packet
-						donePacket := protocol.Packet{
-							Header: protocol.HeaderDone,
-						}
-
-						protocol.SendPacket(node.netInfo.Conn, donePacket)
+					node.transferInfo.Sending.FilesToSend = append(node.transferInfo.Sending.FilesToSend[:currentFileIndex], node.transferInfo.Sending.FilesToSend[currentFileIndex+1:]...)
 
-					} else {
-						node.transferInfo.Sending.CurrentFileIndex++
-					}
+					// start sending the next file
+					node.transferInfo.Sending.CurrentFileID++
 
 				case nil:
 					node.transferInfo.Sending.CanSendBytes = false
@@ -441,8 +458,7 @@ func (node *Node) Start() {
 				default:
 					node.state.Stopped = true
 
-					CurrentFileIndex := node.transferInfo.Sending.CurrentFileIndex
-					fmt.Printf("An error occured while sending a piece of \"%s\": %s\n", node.transferInfo.Sending.FilesToSend[CurrentFileIndex].Name, err)
+					fmt.Printf("An error occured while sending a piece of \"%s\": %s\n", node.transferInfo.Sending.FilesToSend[currentFileIndex].Name, err)
 					panic(err)
 				}
 
@@ -585,7 +601,12 @@ func (node *Node) Start() {
 					panic(err)
 				}
 
+				if file.RelativeParentPath == "" {
+					// does not have a parent dir
+					file.Path = filepath.Join(node.transferInfo.Receiving.DownloadsPath, file.Name)
+				} else {
 					file.Path = filepath.Join(node.transferInfo.Receiving.DownloadsPath, file.RelativeParentPath)
+				}
 
 				// create all underlying directories right ahead
 				err = os.MkdirAll(filepath.Dir(file.Path), os.ModePerm)
@@ -593,17 +614,54 @@ func (node *Node) Start() {
 					panic(err)
 				}
 
-				// check if the file already exists; if yes - remove it and replace with a new one
+				// check if the file already exists
 				_, err = os.Stat(file.Path)
 				if err == nil {
 					// exists
-					// remove it
+					// check if it is the exact file
+					existingFileHandler, err := os.Open(file.Path)
+					if err != nil {
+						os.Remove(file.Path)
+					}
+
+					existingFileChecksum, _ := checksum.GetPartialCheckSum(existingFileHandler)
+
+					if existingFileChecksum == file.Checksum {
+						// it`s the exact same file. No need to receive it again
+						// notify the other node
+
+						fmt.Printf("Already have \"%s\". Skipping...\n\n", file.Name)
+
+						alreadyHavePacketBodyBuffer := new(bytes.Buffer)
+						binary.Write(alreadyHavePacketBodyBuffer, binary.BigEndian, file.ID)
+
+						alreadyHavePacket := protocol.Packet{
+							Header: protocol.HeaderAlreadyHave,
+							Body:   alreadyHavePacketBodyBuffer.Bytes(),
+						}
+
+						encryptedBody, err := encryption.Encrypt(node.netInfo.EncryptionKey, alreadyHavePacket.Body)
+						if err != nil {
+							panic(err)
+						}
+
+						alreadyHavePacket.Body = encryptedBody
+
+						protocol.SendPacket(node.netInfo.Conn, alreadyHavePacket)
+
+					} else {
+						// not the same file. Remove it and await new bytes
 						os.Remove(file.Path)
 					}
 
+					existingFileHandler.Close()
+				} else {
+					// does not exist
+
 					node.mutex.Lock()
 					node.transferInfo.Receiving.AcceptedFiles = append(node.transferInfo.Receiving.AcceptedFiles, file)
 					node.mutex.Unlock()
+				}
 
 			case protocol.HeaderFileBytes:
 				// check if this file has been accepted to receive
@@ -632,17 +690,6 @@ func (node *Node) Start() {
 						wrote, err := acceptedFile.Handler.WriteAt(fileBytes, int64(acceptedFile.SentBytes))
 						if err != nil {
 							panic(err)
-							// // fmt.Printf("[Debug] %+v\n", acceptedFile)
-
-							// // this file won`t be completed, so it`ll be ignored
-
-							// // remove this file from the pool
-							// node.transferInfo.Receiving.AcceptedFiles = append(node.transferInfo.Receiving.AcceptedFiles[:index], node.transferInfo.Receiving.AcceptedFiles[index+1:]...)
-
-							// fmt.Printf("[ERROR] an error occured when receiving a file \"%s\": %s. This file will not be completed", acceptedFile.Name, err)
-
-							// // remove it from the filesystem
-							// os.Remove(acceptedFile.Path)
 						}
 						acceptedFile.SentBytes += uint64(wrote)
 

src/protocol/headers.go

@@ -87,3 +87,10 @@ const HeaderEndfile Header = "ENDFILE"
 // between a file and a directory.
 // ie: DIRECTORY~(dirname size in binary)(dirname)(dirsize)
 const HeaderDirectory Header = "DIRECTORY"
+
+// ALREADYHAVE
+// Sent by receiver in case there is the same file that already exists.
+// Sender upon receiving such packet with specified file ID must not send it.
+// Body must contain a file ID.
+// ie: ALREADYHAVE~(file ID in binary)
+const HeaderAlreadyHave Header = "ALREADYHAVE"