debian man page for io_setcookie

io_setcookie(3) 					     Library Functions Manual						   io_setcookie(3)

NAME
       io_setcookie - associate cookie with descriptor

SYNTAX
       #include <io.h>

       void io_setcookie(int64 fd,void* cookie);

DESCRIPTION
       io_setcookie associates a cookie (pointer to some anonymous data structure) with this descriptor.  Only one cookie can be associated with a
       descriptor.

       Use io_getcookie(3) to retrieve the cookie for a descriptor (usually after io_canread or io_canwrite brought it to your attention).

       Please note that io_close does not deallocate your cookie.  You need to do that yourself.

       The idea is that you put the state associated with a TCP connection you serve in a common struct.  Then you do not need to  have  your  own
       data  structure to retrieve the state for a connection, you can just use the data structure io_wait already maintains.  The lookup works in
       constant time and should not cause any cache misses.

SEE ALSO
       io_wait(3), io_getcookie(3)

																   io_setcookie(3)