Is count of un acknowldged bytes maitained anywhere in kernel data structures for TCP socket ?

Hi all
What i am trying to do is : get data that is lying in the TCP
send buffer.
I need the count first and then the actual data. I dont know if this
count is already calculatated and stored somewhere ?? For data i
*think* , i need to traverse the sk_write_queue list for all the
sk_buff structs and pick up if there is any data in it . Currently my
code traveses this list twice . Once for count and once for data. want
to optimize that.

Thanks,
Rohit