Fix exception when string value crosses a packet boundary.

Author: bgrainger

src/MySqlConnector/MySql.Data.MySqlClient/MySqlBulkCopy.cs

@@ -369,14 +369,13 @@ static bool WriteString(string value, Span<byte> output, out int bytesWritten)
 						var nextIndex = value.IndexOfAny(s_specialCharacters, index);
 						if (nextIndex == -1)
 							nextIndex = value.Length;
-						var encodedBytesWritten = Encoding.UTF8.GetBytes(value.AsSpan(index, nextIndex - index), output);
-						if (encodedBytesWritten == output.Length)
+						var encodedSize = Encoding.UTF8.GetByteCount(value.AsSpan(index, nextIndex - index));
+						if (encodedSize > output.Length)
 						{
-							// TODO: this isn't strictly an error
 							bytesWritten = 0;
 							return false;
 						}
-
+						var encodedBytesWritten = Encoding.UTF8.GetBytes(value.AsSpan(index, nextIndex - index), output);
 						bytesWritten += encodedBytesWritten;
 						output = output.Slice(encodedBytesWritten);
 						index = nextIndex;

src/MySqlConnector/Utilities/Utility.cs

@@ -44,6 +44,17 @@ public static string GetString(this Encoding encoding, ReadOnlySpan<byte> span)
 #endif
 		}
 
+		public static unsafe int GetByteCount(this Encoding encoding, ReadOnlySpan<char> chars)
+		{
+			if (chars.Length == 0)
+				return 0;
+
+			fixed (char* charsPtr = &MemoryMarshal.GetReference(chars))
+			{
+				return encoding.GetByteCount(charsPtr, chars.Length);
+			}
+		}
+
 		public static unsafe int GetBytes(this Encoding encoding, ReadOnlySpan<char> chars, Span<byte> bytes)
 		{
 			fixed (char* charsPtr = &MemoryMarshal.GetReference(chars))

tests/SideBySide/BulkLoaderSync.cs

@@ -529,8 +529,8 @@ public void BulkLoadDataReader()
 		}
 
 #if !NETCOREAPP1_1_2
-		[Fact]
-		public void BulkLoadDataTableWithLongData()
+		[SkippableFact(ServerFeatures.LargePackets)]
+		public void BulkLoadDataTableWithLongBlob()
 		{
 			var dataTable = new DataTable()
 			{
@@ -559,6 +559,48 @@ public void BulkLoadDataTableWithLongData()
 				DestinationTableName = "bulk_load_data_table",
 			};
 			bulkCopy.WriteToServer(dataTable);
+
+			using (var cmd = new MySqlCommand(@"select sum(length(b)) from bulk_load_data_table;", connection))
+			{
+				Assert.Equal(16_777_000m, cmd.ExecuteScalar());
+			}
+		}
+
+		[SkippableFact(ServerFeatures.LargePackets)]
+		public void BulkLoadDataTableWithLongString()
+		{
+			var dataTable = new DataTable()
+			{
+				Columns =
+				{
+					new DataColumn("id", typeof(int)),
+					new DataColumn("data", typeof(string)),
+				},
+				Rows =
+				{
+					new object[] { 1, new string('a', 16_777_000) },
+					new object[] { 2, new string('b', 16_777_000) },
+				},
+			};
+
+			using var connection = new MySqlConnection(GetLocalConnectionString());
+			connection.Open();
+			using (var cmd = new MySqlCommand(@"drop table if exists bulk_load_data_table;
+create table bulk_load_data_table(a int, b longtext);", connection))
+			{
+				cmd.ExecuteNonQuery();
+			}
+
+			var bulkCopy = new MySqlBulkCopy(connection)
+			{
+				DestinationTableName = "bulk_load_data_table",
+			};
+			bulkCopy.WriteToServer(dataTable);
+
+			using (var cmd = new MySqlCommand(@"select sum(length(b)) from bulk_load_data_table;", connection))
+			{
+				Assert.Equal(33_554_000m, cmd.ExecuteScalar());
+			}
 		}
 
 		[Fact]
@@ -605,7 +647,7 @@ public void BulkLoadDataTableWithSpecialCharacters()
 		}
 
 		[Fact]
-		public void BulkLoadDataTableWithTooLongData()
+		public void BulkLoadDataTableWithTooLongBlob()
 		{
 			var dataTable = new DataTable()
 			{
@@ -633,6 +675,36 @@ public void BulkLoadDataTableWithTooLongData()
 			};
 			Assert.Throws<MySqlException>(() => bulkCopy.WriteToServer(dataTable));
 		}
+
+		[Fact]
+		public void BulkLoadDataTableWithTooLongString()
+		{
+			var dataTable = new DataTable()
+			{
+				Columns =
+				{
+					new DataColumn("data", typeof(string)),
+				},
+				Rows =
+				{
+					new object[] { new string('a', 16_777_400) },
+				}
+			};
+
+			using var connection = new MySqlConnection(GetLocalConnectionString());
+			connection.Open();
+			using (var cmd = new MySqlCommand(@"drop table if exists bulk_load_data_table;
+create table bulk_load_data_table(a int, b longblob);", connection))
+			{
+				cmd.ExecuteNonQuery();
+			}
+
+			var bulkCopy = new MySqlBulkCopy(connection)
+			{
+				DestinationTableName = "bulk_load_data_table",
+			};
+			Assert.Throws<MySqlException>(() => bulkCopy.WriteToServer(dataTable));
+		}
 #endif
 #endif