implemented Blob type

Author: kerryjiang

src/SciSharp.MySQL.Replication/Events/LogEvent.cs

@@ -74,6 +74,7 @@ static LogEvent()
             DataTypes[(int)ColumnType.TIMESTAMP_V2] = new TimestampV2Type();
             DataTypes[(int)ColumnType.ENUM] = new EnumType();
             DataTypes[(int)ColumnType.SET] = new SetType();
+            DataTypes[(int)ColumnType.BLOB] = new BlobType();
         }
 
         /// <summary>

src/SciSharp.MySQL.Replication/Types/BlobType.cs

@@ -5,14 +5,38 @@
 
 namespace SciSharp.MySQL.Replication.Types
 {
+    /// <summary>
+    /// Options specific to BLOB data type.
+    /// </summary>
+    class BlobOptions
+    {
+        /// <summary>
+        /// Gets or sets the number of bytes used to store the BLOB length (1, 2, 3, or 4).
+        /// </summary>
+        public int LengthBytes { get; set; }
+    }
+
     /// <summary>
     /// Represents the MySQL BLOB data type.
     /// </summary>
     /// <remarks>
     /// Handles the reading and conversion of MySQL BLOB values.
     /// </remarks>
-    class BlobType : IMySQLDataType
+    class BlobType : IMySQLDataType, IColumnMetadataLoader
     {
+        /// <summary>
+        /// Loads metadata for BLOB type.
+        /// </summary>
+        /// <param name="columnMetadata">The column metadata object.</param>
+        public void LoadMetadataValue(ColumnMetadata columnMetadata)
+        {
+            // The metadata value for BLOB is the length of the size field in bytes (1, 2, 3, or 4)
+            columnMetadata.Options = new BlobOptions
+            {
+                LengthBytes = columnMetadata.MetadataValue[0]
+            };
+        }
+        
         /// <summary>
         /// Reads a BLOB value from the binary log.
         /// </summary>
@@ -21,16 +45,34 @@ class BlobType : IMySQLDataType
         /// <returns>A byte array representing the MySQL BLOB value.</returns>
         public object ReadValue(ref SequenceReader<byte> reader, ColumnMetadata columnMetadata)
         {
-            int blobLength = reader.ReadInteger(columnMetadata.MetadataValue[0]);
-
-            try
+            // Get metadata length (bytes used for size field: 1, 2, 3, or 4) from Options
+            int lengthBytes = columnMetadata.Options is BlobOptions options ? options.LengthBytes : 0;
+            
+            // Read the length of the BLOB based on metadata
+            int blobLength = reader.ReadInteger(lengthBytes);
+            
+            // Validate blob length to prevent out-of-memory issues
+            if (blobLength < 0 || blobLength > 1_000_000_000) // 1GB limit as safety check
             {
-                return reader.Sequence.Slice(reader.Consumed, blobLength).ToArray();
+                throw new InvalidOperationException($"Invalid BLOB length: {blobLength}");
             }
-            finally
+            
+            // Handle empty BLOB
+            if (blobLength == 0)
             {
-                reader.Advance(blobLength);
+                return Array.Empty<byte>();
             }
+            
+            // Read the BLOB data
+            byte[] blobData = new byte[blobLength];
+
+            if (!reader.TryCopyTo(blobData.AsSpan()))
+            {
+                throw new InvalidOperationException($"Failed to read complete BLOB data (expected {blobLength} bytes)");
+            }
+
+            reader.Advance(blobLength);
+            return blobData;
         }
     }
 }

tests/Test/DataTypesTest.cs

@@ -161,7 +161,7 @@ await TestDataType<DateTime>("timestamp_table", currentValue, currentValue.AddHo
             });
         }
 
-        //[Fact]
+        [Fact]
         public async Task TestBlobType()
         {
             var currentValue = new byte[] { 0x01, 0x02, 0x03, 0x04, 0x05 };