int createChan(int msgSize) {
get an empty channel descriptor and initialize it;
set return value to the index or address of the descriptor; dispatcher();
}
proc sendChan(int chan; byte msg[*]) { find descriptor of channel chan;
if (blocked list empty) { # save message
acquire buffer and copy msg into it;
insert buffer at end of message list; }
else { # give message to a receiver remove process from blocked list;
copy msg into the process¡¯s address space; insert the process at end of ready list;
}
dispatcher();
}
proc receiveChan(int chan; result byte msg[*]) { find descriptor of channel chan;
if (message list empty) { # block receiver
insert executing at end of blocked list;
store address of msg in descriptor of executing; executing = 0;
}
else { # give receiver a stored message
remove buffer from message list;
copy contents of buffer into msg; }
dispatcher();
}
bool emptyChan(int chan) { bool r = false;
find descriptor of channel chan; if (message list empty)
r = true;
save r as the return value; dispatcher();
}
Figure 10.1 Asynchronous message passing in a single-processor kernel.
Copyright ý 2000 by Addison Wesley Longman, Inc.