1 /* Copyright (C) 2003 Russ Cox, Massachusetts Institute of Technology */
5 * Generic RPC packet multiplexor. Inspired by but not derived from
6 * Plan 9 kernel. Originally developed as part of Tra, later used in
7 * libnventi, and then finally split out into a generic library.
14 static int gettag(Mux*, Muxrpc*);
15 static void puttag(Mux*, Muxrpc*);
16 static void enqueue(Mux*, Muxrpc*);
17 static void dequeue(Mux*, Muxrpc*);
22 memset(&mux->lk, 0, sizeof(Mux)-offsetof(Mux, lk));
23 mux->tagrend.l = &mux->lk;
24 mux->rpcfork.l = &mux->lk;
25 mux->sleep.next = &mux->sleep;
26 mux->sleep.prev = &mux->sleep;
30 muxrpc(Mux *mux, void *tx)
36 /* must malloc because stack could be private */
37 r = mallocz(sizeof(Muxrpc), 1);
39 werrstr("mallocz: %r");
44 /* assign the tag, add selves to response queue */
47 /*print("gettag %p %d\n", r, tag); */
51 /* actually send the packet */
52 if(tag < 0 || mux->settag(mux, tx, tag) < 0 || _muxsend(mux, tx) < 0){
53 werrstr("settag/send tag %d: %r", tag);
63 /* wait for our packet */
64 while(mux->muxer && !r->p){
68 /* if not done, there's no muxer: start muxing */
77 tag = mux->gettag(mux, p) - mux->mintag;
80 /*print("mux tag %d\n", tag); */
82 if(p == nil){ /* eof -- just give up and pass the buck */
86 /* hand packet to correct sleeper */
87 if(tag < 0 || tag >= mux->mwait){
88 fprint(2, "%s: bad rpc tag %ux\n", argv0, tag);
89 /* must leak packet! don't know how to free it! */
93 if(r2 == nil || r2->prev == nil){
94 fprint(2, "%s: bad rpc tag %ux (no one waiting on that tag)\n", argv0, tag);
95 /* must leak packet! don't know how to free it! */
104 /* if there is anyone else sleeping, wake them to mux */
105 if(mux->sleep.next != &mux->sleep)
106 rwakeup(&mux->sleep.next->r);
108 /*print("finished %p\n", r); */
113 werrstr("unexpected eof");
118 enqueue(Mux *mux, Muxrpc *r)
120 r->next = mux->sleep.next;
121 r->prev = &mux->sleep;
127 dequeue(Mux *mux, Muxrpc *r)
129 r->next->prev = r->prev;
130 r->prev->next = r->next;
136 gettag(Mux *mux, Muxrpc *r)
142 /* wait for a free tag */
143 while(mux->nwait == mux->mwait){
144 if(mux->mwait < mux->maxtag-mux->mintag){
150 w = realloc(mux->wait, mw*sizeof(w[0]));
153 memset(w+mux->mwait, 0, (mw-mux->mwait)*sizeof(w[0]));
155 mux->freetag = mux->mwait;
159 rsleep(&mux->tagrend);
163 if(mux->wait[i] == 0)
165 for(; i<mux->mwait; i++)
166 if(mux->wait[i] == 0)
168 for(i=0; i<mux->freetag; i++)
169 if(mux->wait[i] == 0)
171 /* should not fall out of while without free tag */
172 fprint(2, "libfs: nwait botch\n");
179 r->tag = i+mux->mintag;
184 puttag(Mux *mux, Muxrpc *r)
188 i = r->tag - mux->mintag;
189 assert(mux->wait[i] == r);
193 rwakeup(&mux->tagrend);