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implement Messages;
#
# message queues and their users
#
include "messages.m";
clientidgen := 1;
init()
{
clientidgen = 1;
}
Msglist.new(): ref Msglist
{
msgs := ref Msglist;
msgs.tail = ref Msg; # valid Msg when .next != nil
return msgs;
}
Msglist.queue(msgs: self ref Msglist): ref Msg
{
return msgs.tail;
}
Msglist.wait(msgs: self ref Msglist, u: ref User, rd: ref Readreq)
{
msgs.readers = (u, rd) :: msgs.readers; # list reversed, but currently does not matter
}
Msglist.write(msgs: self ref Msglist, m: ref Msg): list of (ref User, ref Readreq)
{
tail := msgs.tail;
tail.from = m.from;
tail.data = m.data;
tail.next = ref Msg(nil, nil, nil);
msgs.tail = tail.next; # next message will be formed in tail.next
rl := msgs.readers;
msgs.readers = nil;
return rl;
}
Msglist.flushtag(msgs: self ref Msglist, tag: int)
{
rl := msgs.readers;
msgs.readers = nil;
for(; rl != nil; rl = tl rl){
(nil, req) := hd rl;
if(req.tag != tag)
msgs.readers = hd rl :: msgs.readers;
}
}
Msglist.flushfid(msgs: self ref Msglist, fid: int)
{
rl := msgs.readers;
msgs.readers = nil;
for(; rl != nil; rl = tl rl){
(nil, req) := hd rl;
if(req.fid != fid)
msgs.readers = hd rl :: msgs.readers;
}
}
User.new(fid: int, name: string): ref User
{
return ref User(clientidgen++, fid, name, nil);
}
User.initqueue(u: self ref User, msgs: ref Msglist)
{
u.queue = msgs.tail;
}
User.read(u: self ref User): ref Msg
{
if((m := u.queue).next != nil){
u.queue = m.next;
m = ref *m; # copy to ensure no aliasing
m.next = nil;
return m;
}
return nil;
}
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