Resolve the issue of Chinese truncation during varchar insertion

column.go

@@ -17,7 +17,7 @@ import (
 type BufferLen api.SQLLEN
 
 func (l *BufferLen) IsNull() bool {
-	return *l == api.SQL_NULL_DATA
+	return *l == api.SQL_NULL_DATA || int64(*l) == 0x00000000ffffffff
 }
 
 func (l *BufferLen) GetData(h api.SQLHSTMT, idx int, ctype api.SQLSMALLINT, buf []byte) api.SQLRETURN {

column_test.go

@@ -0,0 +1,49 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+
+// Use of this source code is governed by a BSD-style
+
+// license that can be found in the LICENSE file.
+
+package odbc
+
+import (
+	"fmt"
+	"testing"
+	"unsafe"
+)
+
+func TestBufferLen_IsNull(t *testing.T) {
+	tests := []struct {
+		name string
+		i    interface{}
+		l    BufferLen
+		want bool
+	}{
+		// TODO: Add test cases.
+		{name: "IsNull ", i: int64(-1), want: true},
+		{name: "IsNull ", i: int32(-1), want: true},
+		{name: "IsNull ", i: int64(0x00000000ffffffff), want: true},
+
+		{name: "NotNull ", i: int32(1)},
+		{name: "NotNull ", i: int32(0x7fffffff)},
+		{name: "NotNull ", i: int64(0x1ffffffff)},
+	}
+	for _, tt := range tests {
+		switch i := tt.i.(type) {
+		case int64:
+			if unsafe.Sizeof(tt.l) != 8 {
+				continue
+			}
+			tt.l = BufferLen(i)
+			tt.name += fmt.Sprintf("0x%016x", uint64(i))
+		case int32:
+			tt.l = BufferLen(i)
+			tt.name += fmt.Sprintf("0x%08x", uint32(i))
+		}
+		t.Run(tt.name, func(t *testing.T) {
+			if got := tt.l.IsNull(); got != tt.want {
+				t.Errorf("BufferLen.IsNull() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

mssql_test.go

@@ -620,6 +620,8 @@ var typeTests = []typeTest{
 	{"select cast('abcde' as nvarchar(3))", match([]byte("abc"))},
 	{"select cast('' as nvarchar(5))", match([]byte(""))},
 	{"select cast(NULL as nvarchar(5))", match(nil)},
+	{"select cast('你好世界' as varchar(21))", match([]byte("你好世界"))},
+	{"select cast('Γεια σου κόσμε' as varchar(21))", match([]byte("Γεια σου κόσμε"))},
 
 	// datetime, smalldatetime
 	{"select cast('20151225' as datetime)", match(time.Date(2015, 12, 25, 0, 0, 0, 0, time.Local))},

param.go

@@ -80,6 +80,9 @@ func (p *Parameter) BindValue(h api.SQLHSTMT, idx int, v driver.Value, conn *Con
 			// https://docs.microsoft.com/en-us/sql/odbc/microsoft/microsoft-access-data-types
 			sqltype = api.SQL_WLONGVARCHAR
 		}
+		if p.isDescribed && p.Size > 0 {
+			size = p.Size
+		}
 	case int64:
 		if -0x80000000 < d && d < 0x7fffffff {
 			// Some ODBC drivers do not support SQL_BIGINT.
@@ -156,6 +159,9 @@ func (p *Parameter) BindValue(h api.SQLHSTMT, idx int, v driver.Value, conn *Con
 		default:
 			sqltype = api.SQL_BINARY
 		}
+		if p.isDescribed && p.Size > 0 {
+			size = p.Size
+		}
 	default:
 		return fmt.Errorf("unsupported type %T", v)
 	}