- Move all serialization code to separate Serializer namespace and files.

- Generalize and improve JSON processing code.

- Prevent mesh passwords from containing " characters to avoid messing up the JSON processing.

- Improve documentation.

libraries/ESP8266WiFiMesh/examples/HelloEspnow/HelloEspnow.ino

@@ -19,7 +19,7 @@ namespace TypeCast = MeshTypeConversionFunctions;
    https://arduino-esp8266.readthedocs.io/en/latest/PROGMEM.html
 */
 constexpr char exampleMeshName[] PROGMEM = "MeshNode_"; // The name of the mesh network. Used as prefix for the node SSID and to find other network nodes in the example networkFilter and broadcastFilter functions below.
-constexpr char exampleWiFiPassword[] PROGMEM = "ChangeThisWiFiPassword_TODO"; // The password has to be min 8 and max 64 characters long, otherwise an AP which uses it will not be found during scans.
+constexpr char exampleWiFiPassword[] PROGMEM = "ChangeThisWiFiPassword_TODO"; // Note: " is an illegal character. The password has to be min 8 and max 64 characters long, otherwise an AP which uses it will not be found during scans.
 
 // A custom encryption key is required when using encrypted ESP-NOW transmissions. There is always a default Kok set, but it can be replaced if desired.
 // All ESP-NOW keys below must match in an encrypted connection pair for encrypted communication to be possible.

libraries/ESP8266WiFiMesh/examples/HelloMesh/HelloMesh.ino

@@ -26,7 +26,7 @@ namespace TypeCast = MeshTypeConversionFunctions;
    https://arduino-esp8266.readthedocs.io/en/latest/PROGMEM.html
 */
 constexpr char exampleMeshName[] PROGMEM = "MeshNode_"; // The name of the mesh network. Used as prefix for the node SSID and to find other network nodes in the example networkFilter and broadcastFilter functions below.
-constexpr char exampleWiFiPassword[] PROGMEM = "ChangeThisWiFiPassword_TODO"; // The password has to be min 8 and max 64 characters long, otherwise an AP which uses it will not be found during scans.
+constexpr char exampleWiFiPassword[] PROGMEM = "ChangeThisWiFiPassword_TODO"; // Note: " is an illegal character. The password has to be min 8 and max 64 characters long, otherwise an AP which uses it will not be found during scans.
 
 // A custom encryption key is required when using encrypted ESP-NOW transmissions. There is always a default Kok set, but it can be replaced if desired.
 // All ESP-NOW keys below must match in an encrypted connection pair for encrypted communication to be possible.

libraries/ESP8266WiFiMesh/examples/HelloTcpIp/HelloTcpIp.ino

@@ -19,7 +19,7 @@ namespace TypeCast = MeshTypeConversionFunctions;
    https://arduino-esp8266.readthedocs.io/en/latest/PROGMEM.html
 */
 constexpr char exampleMeshName[] PROGMEM = "MeshNode_";
-constexpr char exampleWiFiPassword[] PROGMEM = "ChangeThisWiFiPassword_TODO";
+constexpr char exampleWiFiPassword[] PROGMEM = "ChangeThisWiFiPassword_TODO"; // Note: " is an illegal character. The password has to be min 8 and max 64 characters long, otherwise an AP which uses it will not be found during scans.
 
 unsigned int requestNumber = 0;
 unsigned int responseNumber = 0;

libraries/ESP8266WiFiMesh/src/EncryptedConnectionData.cpp

@@ -27,6 +27,7 @@
 #include "TypeConversionFunctions.h"
 #include "JsonTranslator.h"
 #include "MeshCryptoInterface.h"
+#include "Serializer.h"
 
 namespace
 {
@@ -157,16 +158,8 @@ bool EncryptedConnectionData::desync() const { return _desync; }
 
 String EncryptedConnectionData::serialize() const
 {
-  // Returns: {"connectionState":{"duration":"123","password":"abc","ownSK":"1A2","peerSK":"3B4","peerStaMac":"F2","peerApMac":"E3"}}
+  return Serializer:: serializeEncryptedConnection((temporary() ? String(temporary()->remainingDuration()) : emptyString), String(desync()), TypeCast::uint64ToString(getOwnSessionKey()), 
-  
+                                                   TypeCast::uint64ToString(getPeerSessionKey()), TypeCast::macToString(_peerStaMac), TypeCast::macToString(_peerApMac));
-  return 
-  String(FPSTR(JsonTranslator::jsonConnectionState))
-  + (temporary() ? String(FPSTR(JsonTranslator::jsonDuration)) + '\"' + String(temporary()->remainingDuration()) + F("\",") : emptyString)
-  + FPSTR(JsonTranslator::jsonDesync) + '\"' + String(desync()) + F("\",") 
-  + FPSTR(JsonTranslator::jsonOwnSessionKey) + '\"' + TypeCast::uint64ToString(getOwnSessionKey()) + F("\",") 
-  + FPSTR(JsonTranslator::jsonPeerSessionKey) + '\"' + TypeCast::uint64ToString(getPeerSessionKey()) + F("\",") 
-  + FPSTR(JsonTranslator::jsonPeerStaMac) + '\"' + TypeCast::macToString(_peerStaMac) + F("\",") 
-  + FPSTR(JsonTranslator::jsonPeerApMac) + '\"' + TypeCast::macToString(_peerApMac) +  F("\"}}");
 }
 
 const ExpiringTimeTracker *EncryptedConnectionData::temporary() const

libraries/ESP8266WiFiMesh/src/EspnowMeshBackend.cpp

@@ -27,6 +27,8 @@ extern "C" {
 #include "MutexTracker.h"
 #include "JsonTranslator.h"
 #include "MeshCryptoInterface.h"
+#include "EspnowUtility.h"
+#include "Serializer.h"
 
 namespace
 {
@@ -1773,7 +1775,7 @@ EncryptedConnectionStatus EspnowMeshBackend::requestEncryptedConnectionKernel(co
       requestMessage = encryptionRequestBuilder(requestNonce, existingTimeTracker);
     else if(_ongoingPeerRequestResult == EncryptedConnectionStatus::SOFT_LIMIT_CONNECTION_ESTABLISHED)
       // We will only get a soft limit connection. Adjust future actions based on this.
-      requestMessage = JsonTranslator::createEncryptionRequestHmacMessage(FPSTR(temporaryEncryptionRequestHeader), requestNonce, getEspnowHashKey(), 
+      requestMessage = Serializer::createEncryptionRequestHmacMessage(FPSTR(temporaryEncryptionRequestHeader), requestNonce, getEspnowHashKey(), 
                                                                           hashKeyLength, getAutoEncryptionDuration());
     else
       assert(false && String(F("Unknown _ongoingPeerRequestResult during encrypted connection finalization!")));
@@ -1848,7 +1850,7 @@ String EspnowMeshBackend::defaultEncryptionRequestBuilder(const String &requestH
 {
   (void)existingTimeTracker; // This removes a "unused parameter" compiler warning. Does nothing else.
   
-  return JsonTranslator::createEncryptionRequestHmacMessage(requestHeader, requestNonce, hashKey, hashKeyLength, durationMs);
+  return Serializer::createEncryptionRequestHmacMessage(requestHeader, requestNonce, hashKey, hashKeyLength, durationMs);
 }
     
 String EspnowMeshBackend::flexibleEncryptionRequestBuilder(const uint32_t minDurationMs, const uint8_t *hashKey, 
@@ -1860,7 +1862,7 @@ String EspnowMeshBackend::flexibleEncryptionRequestBuilder(const uint32_t minDur
   uint32_t connectionDuration = minDurationMs >= existingTimeTracker.remainingDuration() ? 
                                 minDurationMs : existingTimeTracker.remainingDuration();
 
-  return createEncryptionRequestHmacMessage(FPSTR(temporaryEncryptionRequestHeader), requestNonce, hashKey, hashKeyLength, connectionDuration);
+  return Serializer::createEncryptionRequestHmacMessage(FPSTR(temporaryEncryptionRequestHeader), requestNonce, hashKey, hashKeyLength, connectionDuration);
 }
 
 EncryptedConnectionStatus EspnowMeshBackend::requestEncryptedConnection(const uint8_t *peerMac)
@@ -2437,13 +2439,13 @@ void EspnowMeshBackend::sendPeerRequestConfirmations(const ExpiringTimeTracker *
     if(!existingEncryptedConnection && 
        ((reciprocalPeerRequest && encryptedConnections.size() >= maxEncryptedConnections) || (!reciprocalPeerRequest && reservedEncryptedConnections() >= maxEncryptedConnections)))
     {
-      espnowSendToNodeUnsynchronized(JsonTranslator::createEncryptionRequestHmacMessage(FPSTR(maxConnectionsReachedHeader), 
+      espnowSendToNodeUnsynchronized(Serializer::createEncryptionRequestHmacMessage(FPSTR(maxConnectionsReachedHeader), 
                                                         confirmationsIterator->getPeerRequestNonce(), hashKey, hashKeyLength),
                                                         defaultBSSID, 'C', generateMessageID(nullptr)); // Generates a new message ID to avoid sending encrypted sessionKeys over unencrypted connections.
                                                         
       confirmationsIterator = peerRequestConfirmationsToSend.erase(confirmationsIterator);
     }
-    else if(espnowSendToNodeUnsynchronized(JsonTranslator::createEncryptionRequestHmacMessage(FPSTR(basicConnectionInfoHeader),
+    else if(espnowSendToNodeUnsynchronized(Serializer::createEncryptionRequestHmacMessage(FPSTR(basicConnectionInfoHeader),
                                                               confirmationsIterator->getPeerRequestNonce(), hashKey, hashKeyLength),
                                                               sendToDefaultBSSID ? defaultBSSID : unencryptedBSSID, 'C', generateMessageID(nullptr)) // Generates a new message ID to avoid sending encrypted sessionKeys over unencrypted connections.
                                                               == TransmissionStatusType::TRANSMISSION_COMPLETE)
@@ -2475,7 +2477,7 @@ void EspnowMeshBackend::sendPeerRequestConfirmations(const ExpiringTimeTracker *
       if(!existingEncryptedConnection)
       {
         // Send "node full" message
-        espnowSendToNodeUnsynchronized(JsonTranslator::createEncryptionRequestHmacMessage(FPSTR(maxConnectionsReachedHeader), 
+        espnowSendToNodeUnsynchronized(Serializer::createEncryptionRequestHmacMessage(FPSTR(maxConnectionsReachedHeader), 
                                                           confirmationsIterator->getPeerRequestNonce(), hashKey, hashKeyLength), 
                                                           defaultBSSID, 'C', generateMessageID(nullptr)); // Generates a new message ID to avoid sending encrypted sessionKeys over unencrypted connections.
       }
@@ -2503,7 +2505,7 @@ void EspnowMeshBackend::sendPeerRequestConfirmations(const ExpiringTimeTracker *
         
         // Send password and keys.
         // Probably no need to know which connection type to use, that is stored in request node and will be sent over for finalization.
-        espnowSendToNodeUnsynchronized(JsonTranslator::createEncryptedConnectionInfo(messageHeader,
+        espnowSendToNodeUnsynchronized(Serializer::createEncryptedConnectionInfo(messageHeader,
                                                           confirmationsIterator->getPeerRequestNonce(), confirmationsIterator->getAuthenticationPassword(), 
                                                           existingEncryptedConnection->getOwnSessionKey(), existingEncryptedConnection->getPeerSessionKey()),
                                                           defaultBSSID, 'C', generateMessageID(nullptr));  // Generates a new message ID to avoid sending encrypted sessionKeys over unencrypted connections.
@@ -2679,11 +2681,7 @@ void EspnowMeshBackend::resetTransmissionFailRate()
 
 String EspnowMeshBackend::serializeUnencryptedConnection()
 {  
-  using namespace JsonTranslator;
+  return Serializer::serializeUnencryptedConnection(String(_unsynchronizedMessageID));
-  
-  // Returns: {"connectionState":{"unsyncMsgID":"123"}}
-  
-  return String(FPSTR(jsonConnectionState)) + createJsonEndPair(FPSTR(jsonUnsynchronizedMessageID), String(_unsynchronizedMessageID));
 }
 
 String EspnowMeshBackend::serializeEncryptedConnection(const uint8_t *peerMac)

libraries/ESP8266WiFiMesh/src/EspnowMeshBackend.h

@@ -1217,7 +1217,7 @@ private:
    * @param peerMac The MAC of the node with which an encrypted connection should be established.
    * @param encryptionRequestBuilder A function which is responsible for constructing the request message to send. 
    * Called twice when the request is successful. First to build the initial request message and then to build the connection verification message.
-   * The request message should typically be of the form: JsonTranslator::createEncryptionRequestIntro() + JsonTranslator::createEncryptionRequestEnding().
+   * The request message should typically be of the form found in Serializer::createEncryptionRequestHmacMessage.
    * @return The ultimate status of the requested encrypted connection, as EncryptedConnectionStatus.
    */
   EncryptedConnectionStatus requestEncryptedConnectionKernel(const uint8_t *peerMac, const encryptionRequestBuilderType &encryptionRequestBuilder);

libraries/ESP8266WiFiMesh/src/FloodingMesh.cpp

@@ -25,6 +25,7 @@
 #include "FloodingMesh.h"
 #include "TypeConversionFunctions.h"
 #include "JsonTranslator.h"
+#include "Serializer.h"
 
 namespace
 {
@@ -153,16 +154,11 @@ void FloodingMesh::performMeshInstanceMaintenance()
 
 String FloodingMesh::serializeMeshState() const
 {
-  using namespace JsonTranslator;
-  
-  // Returns: {"meshState":{"connectionState":{"unsyncMsgID":"123"},"meshMsgCount":"123"}}
-
   String connectionState = getEspnowMeshBackendConst().serializeUnencryptedConnection();
+  uint32_t unsyncMsgID = 0;
+  JsonTranslator::getUnsynchronizedMessageID(connectionState, unsyncMsgID);
   
-  return 
+  return Serializer::serializeMeshState(String(unsyncMsgID), String(_messageCount));
-  String(F("{\"meshState\":{"))
-  + connectionState.substring(1, connectionState.length() - 1) + String(',')
-  + createJsonEndPair(FPSTR(jsonMeshMessageCount), String(_messageCount));
 }
 
 void FloodingMesh::loadMeshState(const String &serializedMeshState)

libraries/ESP8266WiFiMesh/src/JsonTranslator.cpp

@@ -25,59 +25,171 @@
 #include "JsonTranslator.h"
 #include "EspnowProtocolInterpreter.h"
 #include "TypeConversionFunctions.h"
-#include "MeshCryptoInterface.h"
+#include "MeshCryptoInterface.h" // TODO: Remove?
 
 namespace
 {
   namespace TypeCast = MeshTypeConversionFunctions;
+  
+  bool getMac(const String &jsonString, const String &valueIdentifier, uint8_t *resultArray)
+  {
+    String jsonValue;
+    bool decoded = JsonTranslator::decode(jsonString, valueIdentifier, jsonValue);
+
+    if(jsonValue.length() != 12)
+      decoded = false; // Mac String is always 12 characters long
+    
+    if(decoded)
+      TypeCast::stringToMac(jsonValue, resultArray);
+  
+    return decoded;
+  }
 }
 
 namespace JsonTranslator
 {
-  String createJsonPair(const String &valueIdentifier, const String &value)
+  int32_t getStartIndex(const String &jsonString, const String &valueIdentifier, const int32_t searchStartIndex)
   {
-    return valueIdentifier + '\"' + value + F("\",");
+    int32_t startIndex = jsonString.indexOf(String('"') + valueIdentifier + F("\":"), searchStartIndex);
+    if(startIndex < 0)
+      return startIndex;
+  
+    startIndex += valueIdentifier.length() + 3; // Do not include valueIdentifier and associated characters
+    return startIndex;
   }
   
-  String createJsonEndPair(const String &valueIdentifier, const String &value)
+  int32_t getEndIndex(const String &jsonString, const int32_t searchStartIndex)
   {
-    return valueIdentifier + '\"' + value + F("\"}}");
+    int32_t endIndex = -1;
+    
+    if(jsonString[searchStartIndex] == '"')
+    {
+      endIndex = jsonString.indexOf('"', searchStartIndex + 1);
+    }
+    else if(jsonString[searchStartIndex] == '{')
+    {
+      uint32_t depth = 1;
+      bool withinString = false;
+      
+      for(uint32_t index = searchStartIndex + 1; depth != 0 && index < jsonString.length(); ++index)
+      {
+        if(jsonString[index] == '"')
+          withinString = !withinString;
+        else if(!withinString)
+        {
+          if(jsonString[index] == '{')
+            ++depth;
+          else if(jsonString[index] == '}')
+            --depth;
         }
 
-  String createEncryptedConnectionInfo(const String &infoHeader, const String &requestNonce, const String &authenticationPassword, const uint64_t ownSessionKey, const uint64_t peerSessionKey)
+        if(depth == 0)
         {
-    // Returns: Encrypted connection info:{"arguments":{"nonce":"1F2","password":"abc","ownSK":"3B4","peerSK":"1A2"}}
+          assert(index < 0x80000000); // Must avoid int32_t overflow
-
+          endIndex = index;
-    return
+        }
-    infoHeader + String(F("{\"arguments\":{")) 
+      }
-    + createJsonPair(FPSTR(jsonNonce), requestNonce)
-    + createJsonPair(FPSTR(jsonPassword), authenticationPassword)
-    + createJsonPair(FPSTR(jsonOwnSessionKey), TypeCast::uint64ToString(peerSessionKey))   // Exchanges session keys since it should be valid for the receiver.
-    + createJsonEndPair(FPSTR(jsonPeerSessionKey), TypeCast::uint64ToString(ownSessionKey));
     }
   
-  String createEncryptionRequestIntro(const String &requestHeader, const uint32_t duration)
+    return endIndex;
-  {
-    return 
-    requestHeader + String(F("{\"arguments\":{")) 
-    + (requestHeader == FPSTR(EspnowProtocolInterpreter::temporaryEncryptionRequestHeader) ? createJsonPair(FPSTR(jsonDuration), String(duration)) : emptyString);
   }
   
-  String createEncryptionRequestEnding(const String &requestNonce)
+  String encode(std::initializer_list<String> identifiersAndValues)
   {
-    return createJsonEndPair(FPSTR(jsonNonce), requestNonce);
+    assert(identifiersAndValues.size() % 2 == 0); // List must consist of identifer-value pairs.
+    
+    String result = String('{');
+
+    bool isIdentifier = true;
+    for(String element : identifiersAndValues)
+    {
+      bool isObject = !isIdentifier && element[0] == '{';
+      if(isObject)
+        result += element;
+      else
+        result += String('"') + element + String('"');
+      
+      if(isIdentifier)
+        result += ':';
+      else
+        result += ',';
+
+      isIdentifier = !isIdentifier;
     }
 
-  String createEncryptionRequestHmacMessage(const String &requestHeader, const String &requestNonce, const uint8_t *hashKey, const uint8_t hashKeyLength, const uint32_t duration)
+    result[result.length() - 1] = '}';
-  {
+
-    String mainMessage = createEncryptionRequestIntro(requestHeader, duration) + createJsonPair(FPSTR(jsonNonce), requestNonce);
+    return result;
-    uint8_t staMac[6] {0};
-    uint8_t apMac[6] {0};
-    String requesterStaApMac = TypeCast::macToString(WiFi.macAddress(staMac)) + TypeCast::macToString(WiFi.softAPmacAddress(apMac));
-    String hmac = MeshCryptoInterface::createMeshHmac(requesterStaApMac + mainMessage, hashKey, hashKeyLength);
-    return mainMessage + createJsonEndPair(FPSTR(jsonHmac), hmac);
   }
 
+  String encodeLiterally(std::initializer_list<String> identifiersAndValues)
+  {
+    assert(identifiersAndValues.size() % 2 == 0); // List must consist of identifer-value pairs.
+    
+    String result = String('{');
+
+    bool isIdentifier = true;
+    for(String element : identifiersAndValues)
+    {
+      if(isIdentifier)
+        result += String('"') + element + String('"') + ':';
+      else
+        result += element + ',';
+
+      isIdentifier = !isIdentifier;
+    }
+
+    result[result.length() - 1] = '}';
+
+    return result;
+  }
+
+  bool decode(const String &jsonString, const String &valueIdentifier, String &value)
+  {
+    int32_t startIndex = getStartIndex(jsonString, valueIdentifier);
+    if(startIndex < 0)
+      return false;
+    
+    int32_t endIndex = getEndIndex(jsonString, startIndex);
+    if(endIndex < 0)
+      return false;
+
+    if(jsonString[startIndex] == '"')
+      ++startIndex; // Should not include starting "
+    else if(jsonString[startIndex] == '{')
+      ++endIndex; // Should include ending }
+    else
+      assert(false && F("Illegal JSON starting character!"));
+      
+    value = jsonString.substring(startIndex, endIndex);
+    return true;
+  }
+
+  bool decode(const String &jsonString, const String &valueIdentifier, uint32_t &value)
+  {
+    String jsonValue;
+    bool decoded = decode(jsonString, valueIdentifier, jsonValue);
+    
+    if(decoded)
+      value = strtoul(jsonValue.c_str(), nullptr, 0); // strtoul stops reading input when an invalid character is discovered.
+  
+    return decoded;
+  }
+
+  bool decodeRadix(const String &jsonString, const String &valueIdentifier, uint64_t &value, const uint8_t radix)
+  {
+    String jsonValue;
+    bool decoded = decode(jsonString, valueIdentifier, jsonValue);
+    
+    if(decoded)
+      value = TypeCast::stringToUint64(jsonValue, radix);
+  
+    return decoded;
+  }
+
+
+
+  // TODO: Move to encryptedEspnow class?
   bool verifyEncryptionRequestHmac(const String &encryptionRequestHmacMessage, const uint8_t *requesterStaMac, const uint8_t *requesterApMac, 
                                    const uint8_t *hashKey, const uint8_t hashKeyLength)
   {
@@ -86,7 +198,7 @@ namespace JsonTranslator
     String hmac;
     if(getHmac(encryptionRequestHmacMessage, hmac))
     {
-      int32_t hmacStartIndex = encryptionRequestHmacMessage.indexOf(FPSTR(jsonHmac));
+      int32_t hmacStartIndex = encryptionRequestHmacMessage.indexOf(String('"') + FPSTR(jsonHmac) + F("\":"));
       if(hmacStartIndex < 0)
         return false;
      
@@ -100,179 +212,78 @@ namespace JsonTranslator
     return false;
   }
 
-  int32_t getStartIndex(const String &jsonString, const String &valueIdentifier, const int32_t searchStartIndex)
-  {
-    int32_t startIndex = jsonString.indexOf(valueIdentifier, searchStartIndex);
-    if(startIndex < 0)
-      return startIndex;
-  
-    startIndex += valueIdentifier.length() + 1; // Do not include valueIdentifier and initial quotation mark
-    return startIndex;
-  }
-  
-  int32_t getEndIndex(const String &jsonString, const int32_t searchStartIndex)
-  {
-    int32_t endIndex = jsonString.indexOf(',', searchStartIndex);
-    if(endIndex < 0)
-      endIndex = jsonString.indexOf('}', searchStartIndex);
-  
-    endIndex -= 1; // End index will be at the character after the closing quotation mark, so need to subtract 1.
-  
-    return endIndex;
-  }
-
   bool getConnectionState(const String &jsonString, String &result)
   {
-    int32_t startIndex = jsonString.indexOf(FPSTR(jsonConnectionState));
+    return decode(jsonString, FPSTR(jsonConnectionState), result);
-    if(startIndex < 0)
-      return false;
-    
-    int32_t endIndex = jsonString.indexOf('}');
-    if(endIndex < 0)
-      return false;
-      
-    result = jsonString.substring(startIndex, endIndex + 1);
-    return true;
   }
   
   bool getPassword(const String &jsonString, String &result)
   {
-    int32_t startIndex = getStartIndex(jsonString, FPSTR(jsonPassword));
+    return decode(jsonString, FPSTR(jsonPassword), result);
-    if(startIndex < 0)
-      return false;
-    
-    int32_t endIndex = getEndIndex(jsonString, startIndex);
-    if(endIndex < 0)
-      return false;
-  
-    result = jsonString.substring(startIndex, endIndex);
-    return true;
   }
   
   bool getOwnSessionKey(const String &jsonString, uint64_t &result)
   {
-    int32_t startIndex = getStartIndex(jsonString, FPSTR(jsonOwnSessionKey));
+    return decodeRadix(jsonString, FPSTR(jsonOwnSessionKey), result);
-    if(startIndex < 0)
-      return false;
-    
-    int32_t endIndex = getEndIndex(jsonString, startIndex);
-    if(endIndex < 0)
-      return false;
-  
-    result = TypeCast::stringToUint64(jsonString.substring(startIndex, endIndex));
-    return true;
   }
   
   bool getPeerSessionKey(const String &jsonString, uint64_t &result)
   {
-    int32_t startIndex = getStartIndex(jsonString, FPSTR(jsonPeerSessionKey));
+    return decodeRadix(jsonString, FPSTR(jsonPeerSessionKey), result);
-    if(startIndex < 0)
-      return false;
-    
-    int32_t endIndex = getEndIndex(jsonString, startIndex);
-    if(endIndex < 0)
-      return false;
-    
-    result = TypeCast::stringToUint64(jsonString.substring(startIndex, endIndex));
-    return true;
   }
   
   bool getPeerStaMac(const String &jsonString, uint8_t *resultArray)
   {  
-    int32_t startIndex = getStartIndex(jsonString, FPSTR(jsonPeerStaMac));
+    return getMac(jsonString, FPSTR(jsonPeerStaMac), resultArray);
-    if(startIndex < 0)
-      return false;
-  
-    int32_t endIndex = getEndIndex(jsonString, startIndex);
-    if(endIndex < 0 || endIndex - startIndex != 12) // Mac String is always 12 characters long
-      return false;
-    
-    TypeCast::stringToMac(jsonString.substring(startIndex, endIndex), resultArray);
-    return true;
   }
   
   bool getPeerApMac(const String &jsonString, uint8_t *resultArray)
   {
-    int32_t startIndex = getStartIndex(jsonString, FPSTR(jsonPeerApMac));
+    return getMac(jsonString, FPSTR(jsonPeerApMac), resultArray);
-    if(startIndex < 0)
-      return false;
-      
-    int32_t endIndex = getEndIndex(jsonString, startIndex);
-    if(endIndex < 0 || endIndex - startIndex != 12) // Mac String is always 12 characters long
-      return false;
-    
-    TypeCast::stringToMac(jsonString.substring(startIndex, endIndex), resultArray);
-    return true;
   }
   
   bool getDuration(const String &jsonString, uint32_t &result)
   {  
-    int32_t startIndex = getStartIndex(jsonString, FPSTR(jsonDuration));
+    return decode(jsonString, FPSTR(jsonDuration), result);
-    if(startIndex < 0)
-      return false;
-    
-    result = strtoul(jsonString.substring(startIndex).c_str(), nullptr, 0); // strtoul stops reading input when an invalid character is discovered.
-    return true;
   }
   
   bool getNonce(const String &jsonString, String &result)
   {
-    int32_t startIndex = getStartIndex(jsonString, FPSTR(jsonNonce));
+    return decode(jsonString, FPSTR(jsonNonce), result);
-    if(startIndex < 0)
-      return false;
-    
-    int32_t endIndex = getEndIndex(jsonString, startIndex);
-    if(endIndex < 0)
-      return false;
-      
-    result = jsonString.substring(startIndex, endIndex);
-    return true;
   }
 
   bool getHmac(const String &jsonString, String &result)
   {
-    int32_t startIndex = getStartIndex(jsonString, FPSTR(jsonHmac));
+    return decode(jsonString, FPSTR(jsonHmac), result);
-    if(startIndex < 0)
-      return false;
-    
-    int32_t endIndex = getEndIndex(jsonString, startIndex);
-    if(endIndex < 0)
-      return false;
-      
-    result = jsonString.substring(startIndex, endIndex);
-    return true;
   }
 
   bool getDesync(const String &jsonString, bool &result)
   {  
-    int32_t startIndex = getStartIndex(jsonString, FPSTR(jsonDesync));
+    String jsonValue;
-    if(startIndex < 0)
+    bool decoded = decode(jsonString, FPSTR(jsonDesync), jsonValue);
-      return false;
     
-    result = bool(strtoul(jsonString.substring(startIndex).c_str(), nullptr, 0)); // strtoul stops reading input when an invalid character is discovered.
+    if(decoded)
-    return true;
+      result = bool(strtoul(jsonValue.c_str(), nullptr, 0)); // strtoul stops reading input when an invalid character is discovered.
+  
+    return decoded;
   }
 
   bool getUnsynchronizedMessageID(const String &jsonString, uint32_t &result)
   {
-    int32_t startIndex = getStartIndex(jsonString, FPSTR(jsonUnsynchronizedMessageID));
+    return decode(jsonString, FPSTR(jsonUnsynchronizedMessageID), result);
-    if(startIndex < 0)
-      return false;
-    
-    result = strtoul(jsonString.substring(startIndex).c_str(), nullptr, 0); // strtoul stops reading input when an invalid character is discovered.
-    return true;
   }
 
   bool getMeshMessageCount(const String &jsonString, uint16_t &result)
   {  
-    int32_t startIndex = getStartIndex(jsonString, FPSTR(jsonMeshMessageCount));
+    uint32_t longResult = 0;
-    if(startIndex < 0)
+    bool decoded = decode(jsonString, FPSTR(jsonMeshMessageCount), longResult);
-      return false;
 
-    uint32_t longResult = strtoul(jsonString.substring(startIndex).c_str(), nullptr, 0); // strtoul stops reading input when an invalid character is discovered.
+    if(longResult > 65535) // Must fit within uint16_t
-    assert(longResult <= 65535); // Must fit within uint16_t
+      decoded = false;
 
+    if(decoded)
       result = longResult;
-    return true;
+      
+    return decoded;
   }
 }

libraries/ESP8266WiFiMesh/src/JsonTranslator.h

@@ -26,34 +26,29 @@
 #define __ESPNOWJSONTRANSLATOR_H__
 
 #include <WString.h>
+#include <initializer_list>
 
 namespace JsonTranslator 
 {
-  constexpr char jsonConnectionState[] PROGMEM = "{\"connectionState\":{";
+  constexpr char jsonConnectionState[] PROGMEM = "connectionState";
-  constexpr char jsonPassword[] PROGMEM = "\"password\":";
+  constexpr char jsonMeshState[] PROGMEM = "meshState";
-  constexpr char jsonOwnSessionKey[] PROGMEM = "\"ownSK\":";
+  constexpr char jsonPassword[] PROGMEM = "password";
-  constexpr char jsonPeerSessionKey[] PROGMEM = "\"peerSK\":";
+  constexpr char jsonOwnSessionKey[] PROGMEM = "ownSK";
-  constexpr char jsonPeerStaMac[] PROGMEM = "\"peerStaMac\":";
+  constexpr char jsonPeerSessionKey[] PROGMEM = "peerSK";
-  constexpr char jsonPeerApMac[] PROGMEM = "\"peerApMac\":";
+  constexpr char jsonPeerStaMac[] PROGMEM = "peerStaMac";
-  constexpr char jsonDuration[] PROGMEM = "\"duration\":";
+  constexpr char jsonPeerApMac[] PROGMEM = "peerApMac";
-  constexpr char jsonNonce[] PROGMEM = "\"nonce\":";
+  constexpr char jsonDuration[] PROGMEM = "duration";
-  constexpr char jsonHmac[] PROGMEM = "\"hmac\":";
+  constexpr char jsonNonce[] PROGMEM = "nonce";
-  constexpr char jsonDesync[] PROGMEM = "\"desync\":";
+  constexpr char jsonHmac[] PROGMEM = "hmac";
-  constexpr char jsonUnsynchronizedMessageID[] PROGMEM = "\"unsyncMsgID\":";
+  constexpr char jsonDesync[] PROGMEM = "desync";
-  constexpr char jsonMeshMessageCount[] PROGMEM = "\"meshMsgCount\":";
+  constexpr char jsonUnsynchronizedMessageID[] PROGMEM = "unsyncMsgID";
+  constexpr char jsonMeshMessageCount[] PROGMEM = "meshMsgCount";
+  constexpr char jsonArguments[] PROGMEM = "arguments";
 
-  String createJsonPair(const String &valueIdentifier, const String &value);
-  String createJsonEndPair(const String &valueIdentifier, const String &value);
-  
-  String createEncryptedConnectionInfo(const String &infoHeader, const String &requestNonce, const String &authenticationPassword, const uint64_t ownSessionKey, const uint64_t peerSessionKey);
-  String createEncryptionRequestIntro(const String &requestHeader, const uint32_t duration = 0);
-  String createEncryptionRequestEnding(const String &requestNonce);
-  String createEncryptionRequestHmacMessage(const String &requestHeader, const String &requestNonce, const uint8_t *hashKey, const uint8_t hashKeyLength, const uint32_t duration = 0);
-
-  bool verifyEncryptionRequestHmac(const String &encryptionRequestHmacMessage, const uint8_t *requesterStaMac, const uint8_t *requesterApMac, const uint8_t *hashKey, const uint8_t hashKeyLength);
   
   /**
    * Provides the index within jsonString where the value of valueIdentifier starts.
+   * Note that including " within a JSON string value will result in errors.
    *
    * @param jsonString The String to search within.
    * @param valueIdentifier The identifier to search for.
@@ -64,15 +59,87 @@ namespace JsonTranslator
   int32_t getStartIndex(const String &jsonString, const String &valueIdentifier, const int32_t searchStartIndex = 0);
   
   /**
-   * Provides the index within jsonString where the next JSON termination character (',' or '}') is found, starting from searchStartIndex.
+   * Provides the index within jsonString where the JSON object or JSON string value ends, starting the search from searchStartIndex.
+   * Note that including " within a JSON string value will result in errors.
+   * 
+   * The character at searchStartIndex must be either " (for a string) or { (for an object), otherwise the search fails.
    *
    * @param jsonString The String to search within.
-   * @param searchStartIndex The index of jsonString where the search will start.
+   * @param searchStartIndex The index of jsonString where the search will start. The index position should contain either " or {.
    *          
-   * @return An int32_t containing the index within jsonString where the next JSON termination character is found, or a negative value if no such character was found.
+   * @return An int32_t containing the index within jsonString where the JSON string/object ends, or a negative value if no such character was found.
    */
   int32_t getEndIndex(const String &jsonString, const int32_t searchStartIndex);
 
+  /*
+   * Create a JSON String based on the identifiers and values given.
+   * 
+   * Assumes all values are either strings or JSON objects. A value is interpreted as a JSON object if it starts with {
+   * Assumes all identifiers are strings.
+   * 
+   * @param identifiersAndValues Any even number of String arguments. It is assumed that the identifiers and values are given in an alternating manner, as in encode({Identifier1, Value1, Identifier2, Value2, ...})
+   */
+  String encode(std::initializer_list<String> identifiersAndValues);
+
+  /*
+   * Create a JSON String based on the identifiers and values given.
+   * 
+   * Does not make any assumptions regarding value types. " must be added manually around string values.
+   * Useful for example if your JSON values can contain starting { characters, since the regular encode() will then interpret them as JSON objects.
+   * Assumes all identifiers are strings.
+   * 
+   * @param identifiersAndValues Any even number of String arguments. It is assumed that the identifiers and values are given in an alternating manner, as in encodeLiterally({Identifier1, Value1, Identifier2, Value2, ...})
+   */
+  String encodeLiterally(std::initializer_list<String> identifiersAndValues);
+  
+  /*
+   * Get a value from a JSON String.
+   * Assumes all values are either JSON strings ( starting with " ) or JSON objects ( starting with { ).
+   * 
+   * Note that including " within a JSON string value will result in errors.
+   * Escape characters are not supported at this moment, since we do not want string length modification to occur during ESP-NOW protocol transmissions.
+   * 
+   * @param jsonString The String to search within.
+   * @param valueIdentifier The identifier to search for.
+   * @param value The String variable to put the result in.
+   * 
+   * @return True if a value was found. False otherwise. The value argument is not modified if false is returned.
+   */
+  bool decode(const String &jsonString, const String &valueIdentifier, String &value);
+
+  /*
+   * Get a value from a JSON String.
+   * Assumes all values are stored as strings in standard C-format (i.e. decimal by default).
+   * 
+   * Note that including " within a JSON string value will result in errors.
+   * Escape characters are not supported at this moment, since we do not want string length modification to occur during ESP-NOW protocol transmissions.
+   * 
+   * @param jsonString The String to search within.
+   * @param valueIdentifier The identifier to search for.
+   * @param value The uint32_t variable to put the result in.
+   * 
+   * @return True if a value was found. False otherwise. The value argument is not modified if false is returned.
+   */
+  bool decode(const String &jsonString, const String &valueIdentifier, uint32_t &value);
+
+  /*
+   * Get a value from a JSON String.
+   * Assumes all values are stored as strings encoded in the specified radix. Hexadecimal encoding is the default.
+   * 
+   * Note that including " within a JSON string value will result in errors.
+   * Escape characters are not supported at this moment, since we do not want string length modification to occur during ESP-NOW protocol transmissions.
+   * 
+   * @param jsonString The String to search within.
+   * @param valueIdentifier The identifier to search for.
+   * @param value The uint64_t variable to put the result in.
+   * @param radix The base to use when converting the string value to uint64_t. Must be between 2 and 36.
+   * 
+   * @return True if a value was found. False otherwise. The value argument is not modified if false is returned.
+   */
+  bool decodeRadix(const String &jsonString, const String &valueIdentifier, uint64_t &value, const uint8_t radix = 16);
+  
+  bool verifyEncryptionRequestHmac(const String &encryptionRequestHmacMessage, const uint8_t *requesterStaMac, const uint8_t *requesterApMac, const uint8_t *hashKey, const uint8_t hashKeyLength);
+  
   bool getConnectionState(const String &jsonString, String &result);
   /**
    * Stores the value of the password field within jsonString into the result variable. 

libraries/ESP8266WiFiMesh/src/MeshBackendBase.cpp

@@ -203,6 +203,7 @@ String MeshBackendBase::getNodeID() const {return getSSIDSuffix();}
 void MeshBackendBase::setMeshPassword(const String &newMeshPassword)
 {
   assert(8 <= newMeshPassword.length() && newMeshPassword.length() <= 64); // Limited by the ESP8266 API.
+  assert(newMeshPassword.indexOf('"') == -1); // " is not allowed in passwords to allow for easier JSON parsing and predictable password length (no need for extra escape characters).
   
   _meshPassword = newMeshPassword;
 

libraries/ESP8266WiFiMesh/src/MeshBackendBase.h

@@ -194,7 +194,7 @@ public:
    * Will also change the setting for the active AP (via an AP restart)
    * if this MeshBackendBase instance is the current AP controller.
    * 
-   * @param newMeshPassword The password to use.
+   * @param newMeshPassword The password to use. Must be between 8 and 64 characters long. " is an illegal character because of JSON parsing requirements.
    */
   void setMeshPassword(const String &newMeshPassword);
   String getMeshPassword() const;

libraries/ESP8266WiFiMesh/src/Serializer.cpp

@@ -0,0 +1,122 @@
+/*
+ * Copyright (C) 2020 Anders Löfgren
+ *
+ * License (MIT license):
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+ 
+#include "Serializer.h"
+#include "JsonTranslator.h"
+#include "TypeConversionFunctions.h"
+#include "MeshCryptoInterface.h" 
+
+namespace
+{
+  namespace TypeCast = MeshTypeConversionFunctions;
+
+  String createJsonEndPair(const String &valueIdentifier, const String &value)
+  {
+    const String q = String('"');
+    return q + valueIdentifier + q + ':' + q + value + F("\"}}");
+  }
+}
+
+namespace Serializer
+{
+  /*
+   * NOTE: The internal states may be changed in future updates, so the function signatures here are not guaranteed to be stable.
+   */
+  
+  String serializeMeshState(const String &unsyncMsgID, const String &meshMsgCount)
+  {
+    using namespace JsonTranslator;
+
+    // Returns: {"meshState":{"connectionState":{"unsyncMsgID":"123"},"meshMsgCount":"123"}}
+    return encode({FPSTR(jsonMeshState), encode({FPSTR(jsonConnectionState), encode({FPSTR(jsonUnsynchronizedMessageID), unsyncMsgID}), FPSTR(jsonMeshMessageCount), meshMsgCount})});
+  }
+
+  String serializeUnencryptedConnection(const String &unsyncMsgID)
+  {
+    using namespace JsonTranslator;
+
+    // Returns: {"connectionState":{"unsyncMsgID":"123"}}
+    return encode({FPSTR(jsonConnectionState), encode({FPSTR(jsonUnsynchronizedMessageID), unsyncMsgID})});
+  }
+
+  String serializeEncryptedConnection(const String &duration, const String &desync, const String &ownSK, const String &peerSK, const String &peerStaMac, const String &peerApMac)
+  {
+    using namespace JsonTranslator;
+
+    if(duration.isEmpty())
+    {
+      // Returns: {"connectionState":{"desync":"0","ownSK":"1A2","peerSK":"3B4","peerStaMac":"F2","peerApMac":"E3"}}
+      return encode({FPSTR(jsonConnectionState), encode({FPSTR(jsonDesync), desync, FPSTR(jsonOwnSessionKey), ownSK, FPSTR(jsonPeerSessionKey), peerSK, 
+                     FPSTR(jsonPeerStaMac), peerStaMac, FPSTR(jsonPeerApMac), peerApMac})});
+    }
+    
+    // Returns: {"connectionState":{"duration":"123","desync":"0","ownSK":"1A2","peerSK":"3B4","peerStaMac":"F2","peerApMac":"E3"}}
+    return encode({FPSTR(jsonConnectionState), encode({FPSTR(jsonDuration), duration, FPSTR(jsonDesync), desync, FPSTR(jsonOwnSessionKey), ownSK, FPSTR(jsonPeerSessionKey), peerSK, 
+                   FPSTR(jsonPeerStaMac), peerStaMac, FPSTR(jsonPeerApMac), peerApMac})});
+  }
+    
+  String createEncryptedConnectionInfo(const String &infoHeader, const String &requestNonce, const String &authenticationPassword, const uint64_t ownSessionKey, const uint64_t peerSessionKey)
+  {
+    using namespace JsonTranslator;
+
+    const String q = String('"');
+
+    // Returns: infoHeader{"arguments":{"nonce":"1F2","password":"abc","ownSK":"3B4","peerSK":"1A2"}}
+    return 
+    infoHeader + 
+    encode({FPSTR(jsonArguments), 
+    encodeLiterally({FPSTR(jsonNonce), q + requestNonce + q, 
+                     FPSTR(jsonPassword), q + authenticationPassword + q, 
+                     FPSTR(jsonOwnSessionKey), q + TypeCast::uint64ToString(peerSessionKey) + q,   // Exchanges session keys since it should be valid for the receiver.
+                     FPSTR(jsonPeerSessionKey), q + TypeCast::uint64ToString(ownSessionKey) + q})});
+  }
+  
+  String createEncryptionRequestHmacMessage(const String &requestHeader, const String &requestNonce, const uint8_t *hashKey, const uint8_t hashKeyLength, const uint32_t duration)
+  {
+    using namespace JsonTranslator;
+
+    String mainMessage = requestHeader;
+
+    if(requestHeader == FPSTR(EspnowProtocolInterpreter::temporaryEncryptionRequestHeader))
+    {
+      mainMessage += encode({FPSTR(jsonArguments), encode({FPSTR(jsonDuration), String(duration), FPSTR(jsonNonce), requestNonce})});
+    }
+    else
+    {
+      mainMessage += encode({FPSTR(jsonArguments), encode({FPSTR(jsonNonce), requestNonce})});
+    }
+
+    // We need to have an open JSON object so we can add the HMAC later.
+    mainMessage.remove(mainMessage.length() - 2);
+    mainMessage += ',';
+
+    uint8_t staMac[6] {0};
+    uint8_t apMac[6] {0};
+    String requesterStaApMac = TypeCast::macToString(WiFi.macAddress(staMac)) + TypeCast::macToString(WiFi.softAPmacAddress(apMac));
+    String hmac = MeshCryptoInterface::createMeshHmac(requesterStaApMac + mainMessage, hashKey, hashKeyLength);
+
+    // Returns: requestHeader{"arguments":{"duration":"123","nonce":"1F2","hmac":"3B4"}}
+    return mainMessage + createJsonEndPair(FPSTR(jsonHmac), hmac);
+  }
+}

libraries/ESP8266WiFiMesh/src/Serializer.h

@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2020 Anders Löfgren
+ *
+ * License (MIT license):
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef __ESP8266MESHSERIALIZER_H__
+#define __ESP8266MESHSERIALIZER_H__
+
+#include <WString.h>
+
+namespace Serializer 
+{
+  /*
+   * NOTE: The internal states may be changed in future updates, so the function signatures here are not guaranteed to be stable.
+   */
+   
+  String serializeMeshState(const String &unsyncMsgID, const String &meshMsgCount);
+  String serializeUnencryptedConnection(const String &unsyncMsgID);
+  String serializeEncryptedConnection(const String &duration, const String &desync, const String &ownSK, const String &peerSK, const String &peerStaMac, const String &peerApMac);
+  
+  String createEncryptedConnectionInfo(const String &infoHeader, const String &requestNonce, const String &authenticationPassword, const uint64_t ownSessionKey, const uint64_t peerSessionKey);
+  String createEncryptionRequestHmacMessage(const String &requestHeader, const String &requestNonce, const uint8_t *hashKey, const uint8_t hashKeyLength, const uint32_t duration = 0);
+}
+
+#endif

libraries/ESP8266WiFiMesh/src/TypeConversionFunctions.h

@@ -42,7 +42,7 @@ namespace MeshTypeConversionFunctions
    * @param base The radix to convert "number" into. Must be between 2 and 36.
    * @return A string of "number" encoded in radix "base".
    */
-  String uint64ToString(uint64_t number, const byte base = 16);
+  String uint64ToString(uint64_t number, const uint8_t base = 16);
   
   /**
    * Note that using base 10 instead of 16 increases conversion time by roughly a factor of 2, due to unfavourable 64-bit arithmetic.
@@ -52,7 +52,7 @@ namespace MeshTypeConversionFunctions
    * @param base The radix of "string". Must be between 2 and 36.
    * @return A uint64_t of the string, using radix "base" during decoding.
    */
-  uint64_t stringToUint64(const String &string, const byte base = 16);
+  uint64_t stringToUint64(const String &string, const uint8_t base = 16);
   
   /** 
    *  Convert the contents of a uint8_t array to a String in HEX format. The resulting String starts from index 0 of the array.