Using bcp_collen and bcp_moretext

[GraemeS]

I'm using C++ (VS2005) on Windows (XP and 2003 server) to code a database application (SQL 2005) using the bulk copy functions available with the SQL Native Client.
Initially I coded it so that I was calling bcp_bind for every column for every new row. I've now modified it so that I avoid bcp_bind unless I have to change the data pointer, and use bcp_collen where it's simply a data length change.
This seems to work OK except for one field which is a binary data field which could contain quite large amounts of data (>4K). To copy this field I have used bcp_moretext. This only seems to work if I call bcp_bind for every row, even if the data pointer and data length haven't changed.

For bcp_bind I do: -

bcp_bind(handle, NULL, 0, length, NULL, 0, SQLIMAGE, col)

for bcp_collen(handle, length, col)

and for the bcp_moretext after calling 'bcp_sendrow' loop: -

while (length > 0)
{
int sendLen = __min(length, 4096);
bcp_moretext(handle, sendLen, dataPtr);
dataPtr += sendLen;
length -= sendLen;
}

Any ideas or do I have to do the bcp_bind calls everytime?