Question

I have a MySQL database with a table containing a BINARY(16) column.

When I write binary data via ODBC from my C++ application, the data is treated like a Null-terminated string, i.e. it is truncated at the first Null byte in the data.

In my C++ application I bind an unsigned char [16] array using SQLBindParameter like this:

SQLBindParameter(statementHandler, paramCount, SQL_PARAM_INPUT, SQL_C_BINARY, SQL_BINARY, MAX_NOTIFICATION_OUT_IP_BIN_LEN, 0, _notificationOutDstIP, MAX_NOTIFICATION_OUT_IP_BIN_LEN, 0);

MAX_NOTIFICATION_OUT_IP_BIN_LEN is 16.

How can I make sure that 16 bytes are written to the database, even if the binary data contains Null values?

Answer 1

From the MSDN documentation for SQLBindParameter:

If StrLen_or_IndPtr is a null pointer, the driver assumes that all input parameter values are non-NULL and that character and binary data is null-terminated.

Instead, set that argument to be a pointer to the data length:

SQLBindParameter(statementHandler,
                 paramCount,
                 SQL_PARAM_INPUT,
                 SQL_C_BINARY, SQL_BINARY,
                 MAX_NOTIFICATION_OUT_IP_BIN_LEN,
                 0,
                 _notificationOutDstIP,
                 MAX_NOTIFICATION_OUT_IP_BIN_LEN,
                 &MAX_NOTIFICATION_OUT_IP_BIN_LEN
);