MySQL c++ connector: what is the correct way to use SetBlob() to set multiple blob data in a query?

I asked the same question on stackexchange db admin, that seems to be the proper place for the question, but the problem is no one even view the question. So I post the same question here again:

I am working on Mysql table insertion. The table creation statement is like:

CREATE TABLE files_table (fid INT NOT NULL AUTO_INCREMENT, idx TINYBLOB, head TINYBLOB, size BLOB, PRIMARY KEY(fid));

I could insert record manually

mysql> select * from files_table order by fid asc;
+-----+------+------+------------+
| fid | idx  | head | size       |
+-----+------+------+------------+
|   1 | 1    | 1    | 1          |
+-----+------+------+------------+

But when I use the connector to add the next value by using c++ connector:

class StreamBufferData : public std::streambuf
{
public:
    StreamBufferData(const char *in_data, size_t in_size)
    {
        setg(in_data, in_data, in_data + in_size);
    }
};

enum{QUERY_SIZE=256;}
char ins[QUERY_SIZE];

strcpy(ins, "INSERT INTO files_table (idx, head, size) VALUES (?,?,?)");

try
{
    std::unique_ptr<sql::PreparedStatement> statement(ptr_connection->prepareStatement(ins));

    char test_data[2] = "0";
    StreamBufferData buffer0(test_data, 2);
    std::istream test_s0(&buffer0);
    statement->setBlob(1, &test_s0);

    strcpy(test_data, "1");
    StreamBufferData buffer1(test_data, 2);
    std::istream test_s1(&buffer1);
    statement->setBlob(2, &test_s1);

    strcpy(test_data, "2");
    StreamBufferData buffer2(test_data, 2);
    std::istream test_s2(&buffer2);
    statement->setBlob(3, &test_s2);

    statement->executeUpdate();
}
catch(sql::SQLException &e)
{
    std::cout << e.what() << ‘\n’; 
    return;
}

The result is :

+-----+------+------+------------+
| fid | idx  | head | size       |
+-----+------+------+------------+
|   1 | 1    | 1    | 1          |
|   2 | 2    | 2    | 2          |
+-----+------+------+------------+

Only the last value is correctly inserted into the table. My question is: what is the proper way to user msql::PreparedStatement::setBlob() to set multiple blobs in a query?

[environment]
Ubuntu 16.04.2
MySQL 5.7
MySQL connector version: 7.1.1.7
boost 1.58.0
g++ 5.4.0

Thanks for your help

Rong