From 07009801171f3f8d45d8b0911bc540b470ac2acf Mon Sep 17 00:00:00 2001
From: Peter Butzhammer <peter.butzhammer@evopro-ag.de>
Date: Thu, 25 Apr 2024 13:47:24 +0200
Subject: [PATCH] Fix string to byte array encoding

---
 .../ValueConverterTests/WriteToBuffer.cs      | 25 ++++++++++++++++---
 Sharp7.Rx/ValueConverter.cs                   |  4 ++-
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/Sharp7.Rx.Tests/ValueConverterTests/WriteToBuffer.cs b/Sharp7.Rx.Tests/ValueConverterTests/WriteToBuffer.cs
index 0e8e15d..b316ae0 100644
--- a/Sharp7.Rx.Tests/ValueConverterTests/WriteToBuffer.cs
+++ b/Sharp7.Rx.Tests/ValueConverterTests/WriteToBuffer.cs
@@ -23,12 +23,31 @@ internal class WriteToBuffer : ConverterTestBase
 
     public static IEnumerable<ConverterTestCase> GetAdditinalWriteTestCases()
     {
+        yield return new ConverterTestCase("a", "DB0.Byte80.3", [0x61, 0x00, 0x00]); // short string
+        yield return new ConverterTestCase("abc", "DB0.Byte80.3", [0x61, 0x62, 0x63]); // matching string
+        yield return new ConverterTestCase("abcxx", "DB0.Byte80.3", [0x61, 0x62, 0x63]); // long string
+
+        yield return new ConverterTestCase("a", "DB0.string0.3", [0x03, 0x01, 0x61, 0x00, 0x00]); // short string
+        yield return new ConverterTestCase("abc", "DB0.string0.3", [0x03, 0x03, 0x61, 0x62, 0x63]); // matching string
+        yield return new ConverterTestCase("abcxx", "DB0.string0.3", [0x03, 0x03, 0x61, 0x62, 0x63]); // long string
+
+        yield return new ConverterTestCase("a", "DB0.wstring0.3", [0x00, 0x03, 0x00, 0x01, 0x00, 0x61, 0x00, 0x00, 0x00, 0x00]); // short string
+        yield return new ConverterTestCase("abc", "DB0.wstring0.3", [0x00, 0x03, 0x00, 0x03, 0x00, 0x61, 0x00, 0x62, 0x00, 0x63]); // matching string
+        yield return new ConverterTestCase("abcxx", "DB0.wstring0.3", [0x00, 0x03, 0x00, 0x03, 0x00, 0x61, 0x00, 0x62, 0x00, 0x63]); // long string
+
+
         yield return new ConverterTestCase("aaaaBCDE", "DB0.string0.4", [0x04, 0x04, 0x61, 0x61, 0x61, 0x61]); // Length in address exceeds PLC string length
         yield return new ConverterTestCase("aaaaBCDE", "DB0.WString0.4", [0x00, 0x04, 0x00, 0x04, 0x00, 0x61, 0x00, 0x61, 0x00, 0x61, 0x00, 0x61]); // Length in address exceeds PLC string length
         yield return new ConverterTestCase("aaaaBCDE", "DB0.DBB0.4", [0x61, 0x61, 0x61, 0x61]); // Length in address exceeds PLC array length
-        yield return new ConverterTestCase("\ud83d\udc69\ud83c\udffd\u200d\ud83d\ude80", "DB0.WString0.2", [0x00, 0x02, 0x00, 0x02, 0xD8, 0x3D, 0xDC, 0x69]); // Length in address exceeds PLC string length, multi char unicode point
-        yield return new ConverterTestCase("\ud83d\udc69\ud83c\udffd\u200d\ud83d\ude80", "DB0.String0.2", [0x02, 0x02, 0x3F, 0x3F]); // Length in address exceeds PLC string length, multi char unicode point
-        yield return new ConverterTestCase("\ud83d\udc69\ud83c\udffd\u200d\ud83d\ude80", "DB0.DBB0.4", [0x3F, 0x3F, 0x3F, 0x3F]); // Length in address exceeds PLC string length, multi char unicode point
+
+        // Length in address exceeds PLC string length, multi char unicode point
+        yield return new ConverterTestCase("\ud83d\udc69\ud83c\udffd\u200d\ud83d\ude80", "DB0.WString0.2", [0x00, 0x02, 0x00, 0x02, 0xD8, 0x3D, 0xDC, 0x69]);
+
+        // Length in address exceeds PLC string length, multi char unicode point
+        yield return new ConverterTestCase("\ud83d\udc69\ud83c\udffd\u200d\ud83d\ude80", "DB0.String0.2", [0x02, 0x02, 0x3F, 0x3F]);
+
+        // Length in address exceeds PLC string length, multi char unicode point
+        yield return new ConverterTestCase("\ud83d\udc69\ud83c\udffd\u200d\ud83d\ude80", "DB0.DBB0.4", [0x3F, 0x3F, 0x3F, 0x3F]);
     }
 
     [TestCase(18, "DB0.DInt12", 3)]
diff --git a/Sharp7.Rx/ValueConverter.cs b/Sharp7.Rx/ValueConverter.cs
index 97d4666..24f307b 100644
--- a/Sharp7.Rx/ValueConverter.cs
+++ b/Sharp7.Rx/ValueConverter.cs
@@ -54,7 +54,9 @@ internal static class ValueConverter
                         EncodeWString(data);
                         return;
                     case DbType.Byte:
-                        Encoding.ASCII.GetBytes(stringValue.AsSpan(0, address.Length), data);
+
+                        var readOnlySpan = stringValue.AsSpan(0, Math.Min(address.Length, stringValue.Length));
+                        Encoding.ASCII.GetBytes(readOnlySpan, data);
                         return;
                     default:
                         throw new DataTypeMissmatchException($"Cannot write string to {address.Type}", typeof(string), address);