Decoding name now also supports strings without padding nulls. (#194)

#193 non-breaking Co-authored-by: Menno Lodder <menno@lodder>
sharpbrick · Jan 14, 2024 · f07713c · f07713c
1 parent 24bcfaf
commit f07713c
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diff --git a/src/SharpBrick.PoweredUp/Protocol/Formatter/PortModeInformationEncoder.cs b/src/SharpBrick.PoweredUp/Protocol/Formatter/PortModeInformationEncoder.cs
@@ -18,7 +18,8 @@ public LegoWirelessMessage Decode(byte hubId, in Span<byte> data)
 
         var message = informationType switch
         {
-            PortModeInformationType.Name => new PortModeInformationForNameMessage(portId, mode, Encoding.ASCII.GetString(payload.Slice(0, payload.IndexOf<byte>(0x00)))),
+            // Here the specs say to use the length field and just pick the remainder of the bytes, no termination.
+            PortModeInformationType.Name => new PortModeInformationForNameMessage(portId, mode, ParseStringIgnoringTrainingNullCharacters(payload)),
             PortModeInformationType.Raw => new PortModeInformationForRawMessage(portId, mode, RawMin: BitConverter.ToSingle(payload.Slice(0, 4)), RawMax: BitConverter.ToSingle(payload.Slice(4, 4))),
             PortModeInformationType.Pct => new PortModeInformationForPctMessage(portId, mode, PctMin: BitConverter.ToSingle(payload.Slice(0, 4)), PctMax: BitConverter.ToSingle(payload.Slice(4, 4))),
             PortModeInformationType.SI => new PortModeInformationForSIMessage(portId, mode, SIMin: BitConverter.ToSingle(payload.Slice(0, 4)), SIMax: BitConverter.ToSingle(payload.Slice(4, 4))),
@@ -34,6 +35,18 @@ public LegoWirelessMessage Decode(byte hubId, in Span<byte> data)
         return message;
     }
 
+    private static string ParseStringIgnoringTrainingNullCharacters(Span<byte> data)
+    {
+        // Most devices pad the name with 0x00
+        var firstNullCharIndex = data.IndexOf<byte>(0x00);
+        var dataToDecode = data;
+        if (firstNullCharIndex != -1) {
+            // Trim everything after the last 0x00.
+            dataToDecode = data.Slice(0, firstNullCharIndex);
+        }
+
+        return Encoding.ASCII.GetString(dataToDecode);
+    }
     private PortModeInformationMessage DecodeMapping(byte portId, byte mode, in Span<byte> data)
         => new PortModeInformationForMappingMessage(
             portId,

diff --git a/test/SharpBrick.PoweredUp.Test/Protocol/Formatter/PortModeInformationEncoderTest.cs b/test/SharpBrick.PoweredUp.Test/Protocol/Formatter/PortModeInformationEncoderTest.cs
@@ -14,6 +14,8 @@ public class PortModeInformationEncoderTest
     [InlineData("11-00-44-00-03-00-41-50-4F-53-00-00-00-00-00-00-00", 0x00, 0x03, PortModeInformationType.Name, "APOS")]
     [InlineData("11-00-44-00-04-00-4C-4F-41-44-00-00-00-00-00-00-00", 0x00, 0x04, PortModeInformationType.Name, "LOAD")]
     [InlineData("11-00-44-00-05-00-43-41-4C-49-42-00-00-00-00-00-00", 0x00, 0x05, PortModeInformationType.Name, "CALIB")]
+    // WeDo 2.0 actually uses full name length
+    [InlineData("11-00-44-00-00-00-4C-50-46-32-2D-4D-4D-4F-54-4F-52", 0x00, 0x00, PortModeInformationType.Name, "LPF2-MMOTOR")]
     public void PortModeInformationEncoder_Decode_Name(string data, byte expectedPort, byte expectedMode, PortModeInformationType expectedType, string expectedText)
     {
         var message = Decode<PortModeInformationForNameMessage>(data);