refactor: Replace string reading methods with CString equivalents and improve error handling

lib/connector/meshcore_connector.dart

@@ -2127,9 +2127,7 @@ class MeshCoreConnector extends ChangeNotifier {
       outboundText,
       selfKey,
     );
-    final ackHashHex = ackHash
+    final ackHashHex = ackHashToHex(ackHash);
-        .map((b) => b.toRadixString(16).padLeft(2, '0'))
-        .join();
     final messageBytes = utf8.encode(outboundText).length;
     _pendingRepeaterAcks[ackHashHex]?.timeout?.cancel();
     _pendingRepeaterAcks[ackHashHex] = _RepeaterAckContext(
@@ -2901,7 +2899,7 @@ class MeshCoreConnector extends ChangeNotifier {
       _currentSf = reader.readByte();
       _currentCr = reader.readByte();
 
-      _selfName = reader.readString();
+      _selfName = reader.readCString();
     } catch (e) {
       _appDebugLogService?.error(
         'Error parsing SELF_INFO frame: $e',
@@ -3554,7 +3552,7 @@ class MeshCoreConnector extends ChangeNotifier {
         reader.skipBytes(4); // Skip extra 4 bytes for signed/plain variants
       }
 
-      final msgText = reader.readString();
+      final msgText = reader.readCString();
 
       final flags = txtType;
       final shiftedType = flags >> 2;
@@ -3724,10 +3722,9 @@ class MeshCoreConnector extends ChangeNotifier {
       final packet = _parseRawPacket(raw);
       if (packet == null || packet.payloadType != _payloadTypeGroupText) return;
 
-      final payload = packet.payload;
+      final payload = BufferReader(packet.payload);
-      if (payload.length <= _cipherMacSize) return;
+      final channelHash = payload.readByte();
-      final channelHash = payload[0];
+      final encrypted = Uint8List.fromList(payload.readRemainingBytes());
-      final encrypted = Uint8List.fromList(payload.sublist(1));
 
       // Use cached channels as fallback if live channels not yet loaded
       final channelsToSearch = _channels.isNotEmpty
@@ -3741,15 +3738,14 @@ class MeshCoreConnector extends ChangeNotifier {
           final decryptedBytes = _decryptPayload(channel.psk, encrypted);
           if (decryptedBytes == null || decryptedBytes.length < 6) return;
           final decrypted = BufferReader(decryptedBytes);
-          // Skip header + SNR + reserved (2)
+
-          decrypted.skipBytes(4);
+          final timestampRaw = decrypted.readUInt32LE();
           final txtType = decrypted.readByte();
           if ((txtType >> 2) != 0) {
             return;
           }
 
-          final timestampRaw = decrypted.readUInt32LE();
+          final text = decrypted.readCString();
-          final text = decrypted.readString();
           final parsed = _splitSenderText(text);
           final decodedText =
               Smaz.tryDecodePrefixed(parsed.text) ?? parsed.text;
@@ -3811,13 +3807,13 @@ class MeshCoreConnector extends ChangeNotifier {
 
     try {
       final reader = BufferReader(frame);
-      reader.skipBytes(2); // code + is_flood
+      reader.skipBytes(2); //Skip code and is_flood
       final ackHash = reader.readUInt32LE();
       final timeoutMs = reader.readUInt32LE();
 
       // Check if this is a CLI command ACK - if so, ignore it
       if (_lastSentWasCliCommand) {
-        final ackHashHex = ackHash.toRadixString(16).padLeft(8, '0');
+        final ackHashHex = ackHashToHex(ackHash);
         debugPrint('Ignoring CLI command ACK (sent): $ackHashHex');
         _lastSentWasCliCommand = false;
         return;
@@ -3949,7 +3945,7 @@ class MeshCoreConnector extends ChangeNotifier {
   }
 
   bool _handleRepeaterCommandSent(int ackHash, int timeoutMs) {
-    final ackHashHex = ackHash.toRadixString(16).padLeft(8, '0');
+    final ackHashHex = ackHashToHex(ackHash);
     final entry = _pendingRepeaterAcks[ackHashHex];
     if (entry == null) return false;
 
@@ -3968,7 +3964,7 @@ class MeshCoreConnector extends ChangeNotifier {
   }
 
   bool _handleRepeaterCommandAck(int ackHash, int tripTimeMs) {
-    final ackHashHex = ackHash.toRadixString(16).padLeft(8, '0');
+    final ackHashHex = ackHashToHex(ackHash);
     final entry = _pendingRepeaterAcks.remove(ackHashHex);
     if (entry == null) return false;
     entry.timeout?.cancel();
@@ -4319,36 +4315,34 @@ class MeshCoreConnector extends ChangeNotifier {
   }
 
   _RawPacket? _parseRawPacket(Uint8List raw) {
-    if (raw.length < 3) return null;
+    try {
-    var index = 0;
+      final reader = BufferReader(raw);
-    final header = raw[index++];
+      final header = reader.readByte();
-    final routeType = header & _phRouteMask;
+      final routeType = header & _phRouteMask;
-    final hasTransport =
+      final hasTransport =
-        routeType == _routeTransportFlood || routeType == _routeTransportDirect;
+          routeType == _routeTransportFlood ||
-    if (hasTransport) {
+          routeType == _routeTransportDirect;
-      if (raw.length < index + 4) return null;
+      if (hasTransport) {
-      index += 4;
+        reader.skipBytes(2); // Skip reserved bytes in transport header
-    }
+      }
-    if (raw.length <= index) return null;
+      final pathLenRaw = reader.readByte();
-    final pathLenRaw = raw[index++];
+      final pathByteLen = _decodePathByteLen(pathLenRaw);
-    final pathByteLen = _decodePathByteLen(pathLenRaw);
+      final pathBytes = reader.readBytes(pathByteLen);
-    if (raw.length < index + pathByteLen) return null;
+      final payload = reader.readBytes(reader.remaining);
-    final pathBytes = Uint8List.fromList(
-      raw.sublist(index, index + pathByteLen),
-    );
-    index += pathByteLen;
-    if (raw.length <= index) return null;
-    final payload = Uint8List.fromList(raw.sublist(index));
 
-    return _RawPacket(
+      return _RawPacket(
-      header: header,
+        header: header,
-      routeType: routeType,
+        routeType: routeType,
-      payloadType: (header >> _phTypeShift) & _phTypeMask,
+        payloadType: (header >> _phTypeShift) & _phTypeMask,
-      payloadVer: (header >> _phVerShift) & _phVerMask,
+        payloadVer: (header >> _phVerShift) & _phVerMask,
-      pathLenRaw: pathLenRaw,
+        pathLenRaw: pathLenRaw,
-      pathBytes: pathBytes,
+        pathBytes: pathBytes,
-      payload: payload,
+        payload: payload,
-    );
+      );
+    } catch (e) {
+      appLogger.warn('Error parsing raw packet: $e');
+      return null;
+    }
   }
 
   int _computeChannelHash(Uint8List psk) {
@@ -4767,7 +4761,7 @@ class MeshCoreConnector extends ChangeNotifier {
   void _handleCustomVars(Uint8List frame) {
     final buf = BufferReader(frame.sublist(1));
     try {
-      _currentCustomVars = _parseKeyValueString(buf.readString());
+      _currentCustomVars = _parseKeyValueString(buf.readCString());
     } catch (e) {
       appLogger.warn('Malformed custom vars frame: $e', tag: 'Connector');
     }
@@ -4924,7 +4918,7 @@ class MeshCoreConnector extends ChangeNotifier {
         longitude = packet.readInt32LE() / 1e6;
       }
       if (hasName && packet.remaining > 0) {
-        name = packet.readString();
+        name = packet.readCString();
       }
     } catch (e) {
       appLogger.warn('Malformed advert frame: $e', tag: 'Connector');
@@ -4986,7 +4980,7 @@ class MeshCoreConnector extends ChangeNotifier {
         longitude = advert.readInt32LE() / 1e6;
       }
       if (hasName && advert.remaining > 0) {
-        name = advert.readString();
+        name = advert.readCString();
       }
     } catch (e) {
       appLogger.warn('Malformed advert frame: $e', tag: 'Connector');

lib/connector/meshcore_protocol.dart

@@ -1,6 +1,8 @@
 import 'dart:convert';
 import 'dart:typed_data';
 
+import 'package:flutter/widgets.dart';
+
 // Buffer Reader - sequential binary data reader with pointer tracking
 class BufferReader {
   int _pointer = 0;
@@ -37,16 +39,6 @@ class BufferReader {
 
   Uint8List readRemainingBytes() => readBytes(remaining);
 
-  String readString() {
-    _lastPointer = _pointer;
-    final value = readRemainingBytes();
-    try {
-      return utf8.decode(Uint8List.fromList(value), allowMalformed: true);
-    } catch (e) {
-      return String.fromCharCodes(value); // Latin-1 fallback
-    }
-  }
-
   String readCStringGreedy(int maxLength) {
     _lastPointer = _pointer;
     final value = <int>[];
@@ -62,11 +54,12 @@ class BufferReader {
     }
   }
 
-  String readCString(int maxLength) {
+  String readCString({int maxLength = -1}) {
     final backupPointer = _pointer;
     final value = <int>[];
     int counter = 0;
-    while (counter < maxLength) {
+    final maxLen = maxLength >= 0 ? maxLength : remaining;
+    while (counter < maxLen) {
       final byte = readByte();
       if (byte == 0) break;
       value.add(byte);
@@ -409,48 +402,40 @@ ParsedContactText? parseContactMessageText(Uint8List frame) {
       // Signed messages have a 4-byte signature after the timestamp, before the text
       message.skipBytes(4);
     }
-    final text = message.readString();
+    final text = message.readCString();
     if (text.isEmpty) return null;
 
     return ParsedContactText(senderPrefix: senderPrefix, text: text);
   } catch (e) {
+    debugPrint('Error parsing contact message text: $e');
     return null;
   }
 }
 
-// // Helper to read uint32 little-endian
+// Helper to read uint32 little-endian
-// int readUint32LE(Uint8List data, int offset) {
+int readUint32LE(Uint8List data, int offset) {
-//   return data[offset] |
+  return data[offset] |
-//       (data[offset + 1] << 8) |
+      (data[offset + 1] << 8) |
-//       (data[offset + 2] << 16) |
+      (data[offset + 2] << 16) |
-//       (data[offset + 3] << 24);
+      (data[offset + 3] << 24);
-// }
+}
 
-// // Helper to read uint16 little-endian
+// Helper to read uint16 little-endian
-// int readUint16LE(Uint8List data, int offset) {
+int readUint16LE(Uint8List data, int offset) {
-//   return data[offset] | (data[offset + 1] << 8);
+  return data[offset] | (data[offset + 1] << 8);
-// }
+}
 
-// // Helper to read int32 little-endian
+// Helper to read int32 little-endian
-// int readInt32LE(Uint8List data, int offset) {
+int readInt32LE(Uint8List data, int offset) {
-//   int val = readUint32LE(data, offset);
+  int val = readUint32LE(data, offset);
-//   if (val >= 0x80000000) val -= 0x100000000;
+  if (val >= 0x80000000) val -= 0x100000000;
-//   return val;
+  return val;
-// }
+}
 
-// // Helper to read null-terminated UTF-8 string
+// Helper to convert uint32 to hex string
-// String readCString(Uint8List data, int offset, int maxLen) {
+String ackHashToHex(int ackHash) {
-//   int end = offset;
+  return ackHash.toRadixString(16).padLeft(8, '0');
-//   while (end < offset + maxLen && end < data.length && data[end] != 0) {
+}
-//     end++;
-//   }
-//   try {
-//     return utf8.decode(data.sublist(offset, end), allowMalformed: true);
-//   } catch (e) {
-//     // Fallback to Latin-1 if UTF-8 decoding fails
-//     return String.fromCharCodes(data.sublist(offset, end));
-//   }
-// }
 
 // Helper to convert public key to hex string
 String pubKeyToHex(Uint8List pubKey) {

lib/models/channel_message.dart

@@ -2,6 +2,7 @@ import 'dart:typed_data';
 import '../connector/meshcore_protocol.dart';
 import '../helpers/reaction_helper.dart';
 import '../helpers/smaz.dart';
+import '../utils/app_logger.dart';
 
 enum ChannelMessageStatus { pending, sent, failed }
 
@@ -114,8 +115,8 @@ class ChannelMessage {
     // V3: [0]=code [1]=SNR [2]=rsv1 [3]=rsv2 [4]=channel_idx [5]=path_len [path... optional] [txt_type] [timestamp x4] [text...]
     // Non-V3: [0]=code [1]=channel_idx [2]=path_len [3]=txt_type [4-7]=timestamp [8+]=text
     if (frame.length < 8) return null;
-    final reader = BufferReader(frame);
     try {
+      final reader = BufferReader(frame);
       final code = reader.readByte();
       if (code != respCodeChannelMsgRecv && code != respCodeChannelMsgRecvV3) {
         return null;
@@ -133,11 +134,9 @@ class ChannelMessage {
         pathLen = reader.readByte();
         txtType = reader.readByte();
         final hasPath = (flags & 0x01) != 0;
-        if (hasPath) {
+        if (hasPath && pathLen > 0) {
           reader.rewind(); // Rewind to read path length again for pathBytes
           pathBytes = reader.readBytes(pathLen);
-          // Force text type to plain if path is present
-          txtType = txtTypePlain;
         } else {
           pathLen = 0;
         }
@@ -152,7 +151,7 @@ class ChannelMessage {
         return null;
       }
 
-      final text = reader.readString();
+      final text = reader.readCString();
 
       // Extract sender name and actual message from "name: msg" format
       String senderName = 'Unknown';
@@ -185,6 +184,7 @@ class ChannelMessage {
         channelIndex: channelIdx,
       );
     } catch (e) {
+      appLogger.error('Error parsing channel message frame: $e');
       // If parsing fails, return null to avoid crashes
       return null;
     }

lib/models/message.dart

@@ -105,7 +105,7 @@ class Message {
       if ((flags >> 2) != txtTypePlain) {
         return null;
       }
-      final text = reader.readString();
+      final text = reader.readCString();
 
       return Message(
         senderKey: senderKey,

lib/services/ble_debug_log_service.dart

@@ -245,19 +245,6 @@ class BleDebugLogService extends ChangeNotifier {
     }
   }
 
-  // Helper to read uint32 little-endian
-  int readUint32LE(Uint8List data, int offset) {
-    return data[offset] |
-        (data[offset + 1] << 8) |
-        (data[offset + 2] << 16) |
-        (data[offset + 3] << 24);
-  }
-
-  // // Helper to read uint16 little-endian
-  int readUint16LE(Uint8List data, int offset) {
-    return data[offset] | (data[offset + 1] << 8);
-  }
-
   String _frameDetail(int code, Uint8List frame) {
     switch (code) {
       case respCodeSent:

lib/services/message_retry_service.dart

@@ -98,7 +98,7 @@ class MessageRetryService extends ChangeNotifier {
 
   /// Compute expected ACK hash using same algorithm as firmware:
   /// SHA256([timestamp(4)][attempt(1)][text][sender_pubkey(32)]) -> first 4 bytes
-  static Uint8List computeExpectedAckHash(
+  static int computeExpectedAckHash(
     int timestampSeconds,
     int attempt,
     String text,
@@ -126,7 +126,8 @@ class MessageRetryService extends ChangeNotifier {
 
     // Compute SHA256 and return first 4 bytes
     final hash = sha256.convert(buffer);
-    return Uint8List.fromList(hash.bytes.sublist(0, 4));
+    final bytes = Uint8List.fromList(hash.bytes.sublist(0, 4));
+    return (bytes[3] << 24) | (bytes[2] << 16) | (bytes[1] << 8) | bytes[0];
   }
 
   Future<void> sendMessageWithRetry({
@@ -324,9 +325,7 @@ class MessageRetryService extends ChangeNotifier {
         outboundText,
         selfPubKey,
       );
-      final expectedHashHex = expectedHash
+      final expectedHashHex = expectedHash.toRadixString(16).padLeft(8, '0');
-          .map((b) => b.toRadixString(16).padLeft(2, '0'))
-          .join();
       _expectedHashToMessageId[expectedHashHex] = messageId;
 
       final shortText = message.text.length > 20

lib/widgets/debug_frame_viewer.dart

@@ -10,14 +10,6 @@ class DebugFrameViewer {
     Uint8List frame,
     String title,
   ) {
-    // Helper to read uint32 little-endian
-    int readUint32LE(Uint8List data, int offset) {
-      return data[offset] |
-          (data[offset + 1] << 8) |
-          (data[offset + 2] << 16) |
-          (data[offset + 3] << 24);
-    }
-
     final hexString = frame
         .map((b) => b.toRadixString(16).padLeft(2, '0'))
         .join(' ');

test/services/retry_and_protocol_test.dart

@@ -169,16 +169,6 @@ void main() {
       expect(first, equals(second));
     });
 
-    test('hash is exactly 4 bytes long', () {
-      final hash = MessageRetryService.computeExpectedAckHash(
-        fixedTs,
-        0,
-        fixedText,
-        fixedKey,
-      );
-      expect(hash.length, equals(4));
-    });
-
     test('hash matches manual SHA-256 computation', () {
       for (int attempt = 0; attempt < 4; attempt++) {
         final actual = MessageRetryService.computeExpectedAckHash(
@@ -509,7 +499,7 @@ void main() {
           fixedText,
           fixedKey,
         );
-        final hex = hash.map((b) => b.toRadixString(16).padLeft(2, '0')).join();
+        final hex = hash.toRadixString(16).padLeft(8, '0');
         expect(
           hashes.containsKey(hex),
           isFalse,