Feature/fix go errors in examples (#516)

* Fixing annoying errors Go errors showing in example code

* Fixed further Go warnings

clients/native/examples/go-examples/websocket/binary/binarysend.go

@@ -0,0 +1,217 @@
+package main
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io/ioutil"
+
+	"github.com/gorilla/websocket"
+)
+
+// request tags
+const sendRequestTag = 0x00
+const replyRequestTag = 0x01
+const selfAddressRequestTag = 0x02
+
+// response tags
+const errorResponseTag = 0x00
+const receivedResponseTag = 0x01
+const selfAddressResponseTag = 0x02
+
+func makeSelfAddressRequest() []byte {
+	return []byte{selfAddressRequestTag}
+}
+
+func parseSelfAddressResponse(rawResponse []byte) []byte {
+	if len(rawResponse) != 97 || rawResponse[0] != selfAddressResponseTag {
+		panic("Received invalid response")
+	}
+	return rawResponse[1:]
+}
+
+func makeSendRequest(recipient []byte, message []byte, withReplySurb bool) []byte {
+	messageLen := make([]byte, 8)
+	binary.BigEndian.PutUint64(messageLen, uint64(len(message)))
+
+	surbByte := byte(0)
+	if withReplySurb {
+		surbByte = 1
+	}
+
+	out := []byte{sendRequestTag, surbByte}
+	out = append(out, recipient...)
+	out = append(out, messageLen...)
+	out = append(out, message...)
+
+	return out
+}
+
+func makeReplyRequest(message []byte, replySURB []byte) []byte {
+	messageLen := make([]byte, 8)
+	binary.BigEndian.PutUint64(messageLen, uint64(len(message)))
+
+	surbLen := make([]byte, 8)
+	binary.BigEndian.PutUint64(surbLen, uint64(len(replySURB)))
+
+	out := []byte{replyRequestTag}
+	out = append(out, surbLen...)
+	out = append(out, replySURB...)
+	out = append(out, messageLen...)
+	out = append(out, message...)
+
+	return out
+}
+
+func parseReceived(rawResponse []byte) ([]byte, []byte) {
+	if rawResponse[0] != receivedResponseTag {
+		panic("Received invalid response!")
+	}
+
+	hasSurb := false
+	if rawResponse[1] == 1 {
+		hasSurb = true
+	} else if rawResponse[1] == 0 {
+		hasSurb = false
+	} else {
+		panic("malformed received response!")
+	}
+
+	data := rawResponse[2:]
+	if hasSurb {
+		surbLen := binary.BigEndian.Uint64(data[:8])
+		other := data[8:]
+
+		surb := other[:surbLen]
+		msgLen := binary.BigEndian.Uint64(other[surbLen : surbLen+8])
+
+		if len(other[surbLen+8:]) != int(msgLen) {
+			panic("invalid msg len")
+		}
+
+		msg := other[surbLen+8:]
+		return msg, surb
+	} else {
+		msgLen := binary.BigEndian.Uint64(data[:8])
+		other := data[8:]
+
+		if len(other) != int(msgLen) {
+			panic("invalid msg len")
+		}
+
+		msg := other[:msgLen]
+		return msg, nil
+	}
+}
+
+func sendBinaryWithoutReply() {
+	uri := "ws://localhost:1977"
+
+	conn, _, err := websocket.DefaultDialer.Dial(uri, nil)
+	if err != nil {
+		panic(err)
+	}
+	defer conn.Close()
+
+	selfAddressRequest := makeSelfAddressRequest()
+	if err = conn.WriteMessage(websocket.BinaryMessage, selfAddressRequest); err != nil {
+		panic(err)
+	}
+	_, receivedResponse, err := conn.ReadMessage()
+	if err != nil {
+		panic(err)
+	}
+	selfAddress := parseSelfAddressResponse(receivedResponse)
+
+	readData, err := ioutil.ReadFile("dummy_file")
+	if err != nil {
+		panic(err)
+	}
+
+	sendRequest := makeSendRequest(selfAddress, readData, false)
+	fmt.Printf("sending content of 'dummy file' over the mix network...\n")
+	if err = conn.WriteMessage(websocket.BinaryMessage, sendRequest); err != nil {
+		panic(err)
+	}
+
+	fmt.Printf("waiting to receive a message from the mix network...\n")
+	_, receivedResponse, err = conn.ReadMessage()
+	if err != nil {
+		panic(err)
+	}
+
+	fileData, replySURB := parseReceived(receivedResponse)
+	if replySURB != nil {
+		panic("did not expect a replySURB!")
+	}
+	fmt.Printf("writing the file back to the disk!\n")
+	ioutil.WriteFile("received_file_no_reply", fileData, 0644)
+}
+
+func sendBinaryWithReply() {
+	uri := "ws://localhost:1977"
+
+	conn, _, err := websocket.DefaultDialer.Dial(uri, nil)
+	if err != nil {
+		panic(err)
+	}
+	defer conn.Close()
+
+	selfAddressRequest := makeSelfAddressRequest()
+	if err = conn.WriteMessage(websocket.BinaryMessage, selfAddressRequest); err != nil {
+		panic(err)
+	}
+	_, receivedResponse, err := conn.ReadMessage()
+	if err != nil {
+		panic(err)
+	}
+	selfAddress := parseSelfAddressResponse(receivedResponse)
+
+	readData, err := ioutil.ReadFile("dummy_file")
+	if err != nil {
+		panic(err)
+	}
+
+	sendRequest := makeSendRequest(selfAddress, readData, true)
+	fmt.Printf("sending content of 'dummy file' over the mix network...\n")
+	if err = conn.WriteMessage(websocket.BinaryMessage, sendRequest); err != nil {
+		panic(err)
+	}
+
+	fmt.Printf("waiting to receive a message from the mix network...\n")
+	_, receivedResponse, err = conn.ReadMessage()
+	if err != nil {
+		panic(err)
+	}
+
+	fileData, replySURB := parseReceived(receivedResponse)
+
+	fmt.Printf("writing the file back to the disk!\n")
+	ioutil.WriteFile("received_file_withreply", fileData, 0644)
+
+	replyMessage := []byte("hello from reply SURB! - thanks for sending me the file!")
+	replyRequest := makeReplyRequest(replyMessage, replySURB)
+
+	fmt.Printf("sending '%v' (using reply SURB) over the mix network...\n", string(replyMessage))
+	if err = conn.WriteMessage(websocket.BinaryMessage, replyRequest); err != nil {
+		panic(err)
+	}
+
+	fmt.Printf("waiting to receive a message from the mix network...\n")
+	_, receivedResponse, err = conn.ReadMessage()
+	if err != nil {
+		panic(err)
+	}
+
+	receivedMessage, replySURB := parseReceived(receivedResponse)
+	if replySURB != nil {
+		panic("did not expect a replySURB!")
+	}
+
+	fmt.Printf("received %v from the mix network!\n", string(receivedMessage))
+
+}
+
+func main() {
+	// sendBinaryWithoutReply()
+	sendBinaryWithReply()
+}