2 * winhandl.c: Module to give Windows front ends the general
3 * ability to deal with consoles, pipes, serial ports, or any other
4 * type of data stream accessed through a Windows API HANDLE rather
5 * than a WinSock SOCKET.
7 * We do this by spawning a subthread to continuously try to read
8 * from the handle. Every time a read successfully returns some
9 * data, the subthread sets an event object which is picked up by
10 * the main thread, and the main thread then sets an event in
11 * return to instruct the subthread to resume reading.
13 * Output works precisely the other way round, in a second
14 * subthread. The output subthread should not be attempting to
15 * write all the time, because it hasn't always got data _to_
16 * write; so the output thread waits for an event object notifying
17 * it to _attempt_ a write, and then it sets an event in return
20 * (It's terribly annoying having to spawn a subthread for each
21 * direction of each handle. Technically it isn't necessary for
22 * serial ports, since we could use overlapped I/O within the main
23 * thread and wait directly on the event objects in the OVERLAPPED
24 * structures. However, we can't use this trick for some types of
25 * file handle at all - for some reason Windows restricts use of
26 * OVERLAPPED to files which were opened with the overlapped flag -
27 * and so we must use threads for those. This being the case, it's
28 * simplest just to use threads for everything rather than trying
29 * to keep track of multiple completely separate mechanisms.)
36 /* ----------------------------------------------------------------------
37 * Generic definitions.
41 * Maximum amount of backlog we will allow to build up on an input
42 * handle before we stop reading from it.
44 #define MAX_BACKLOG 32768
46 struct handle_generic {
48 * Initial fields common to both handle_input and handle_output
51 * The three HANDLEs are set up at initialisation time and are
52 * thereafter read-only to both main thread and subthread.
53 * `moribund' is only used by the main thread; `done' is
54 * written by the main thread before signalling to the
55 * subthread. `defunct' and `busy' are used only by the main
58 HANDLE h; /* the handle itself */
59 HANDLE ev_to_main; /* event used to signal main thread */
60 HANDLE ev_from_main; /* event used to signal back to us */
61 int moribund; /* are we going to kill this soon? */
62 int done; /* request subthread to terminate */
63 int defunct; /* has the subthread already gone? */
64 int busy; /* operation currently in progress? */
65 void *privdata; /* for client to remember who they are */
68 /* ----------------------------------------------------------------------
73 * Data required by an input thread.
77 * Copy of the handle_generic structure.
79 HANDLE h; /* the handle itself */
80 HANDLE ev_to_main; /* event used to signal main thread */
81 HANDLE ev_from_main; /* event used to signal back to us */
82 int moribund; /* are we going to kill this soon? */
83 int done; /* request subthread to terminate */
84 int defunct; /* has the subthread already gone? */
85 int busy; /* operation currently in progress? */
86 void *privdata; /* for client to remember who they are */
89 * Data set at initialisation and then read-only.
94 * Data set by the input thread before signalling ev_to_main,
95 * and read by the main thread after receiving that signal.
97 char buffer[4096]; /* the data read from the handle */
98 DWORD len; /* how much data that was */
99 int readerr; /* lets us know about read errors */
102 * Callback function called by this module when data arrives on
105 handle_inputfn_t gotdata;
109 * The actual thread procedure for an input thread.
111 static DWORD WINAPI handle_input_threadfunc(void *param)
113 struct handle_input *ctx = (struct handle_input *) param;
114 OVERLAPPED ovl, *povl;
116 int readret, readlen;
118 if (ctx->flags & HANDLE_FLAG_OVERLAPPED) {
120 oev = CreateEvent(NULL, TRUE, FALSE, NULL);
125 if (ctx->flags & HANDLE_FLAG_UNITBUFFER)
128 readlen = sizeof(ctx->buffer);
132 memset(povl, 0, sizeof(OVERLAPPED));
135 readret = ReadFile(ctx->h, ctx->buffer,readlen, &ctx->len, povl);
137 ctx->readerr = GetLastError();
140 if (povl && !readret && ctx->readerr == ERROR_IO_PENDING) {
141 WaitForSingleObject(povl->hEvent, INFINITE);
142 readret = GetOverlappedResult(ctx->h, povl, &ctx->len, FALSE);
144 ctx->readerr = GetLastError();
151 * Windows apparently sends ERROR_BROKEN_PIPE when a
152 * pipe we're reading from is closed normally from the
153 * writing end. This is ludicrous; if that situation
154 * isn't a natural EOF, _nothing_ is. So if we get that
155 * particular error, we pretend it's EOF.
157 if (ctx->readerr == ERROR_BROKEN_PIPE)
162 if (readret && ctx->len == 0 &&
163 (ctx->flags & HANDLE_FLAG_IGNOREEOF))
166 SetEvent(ctx->ev_to_main);
171 WaitForSingleObject(ctx->ev_from_main, INFINITE);
173 break; /* main thread told us to shut down */
183 * This is called after a succcessful read, or from the
184 * `unthrottle' function. It decides whether or not to begin a new
187 static void handle_throttle(struct handle_input *ctx, int backlog)
193 * If there's a read operation already in progress, do nothing:
194 * when that completes, we'll come back here and be in a
195 * position to make a better decision.
201 * Otherwise, we must decide whether to start a new read based
202 * on the size of the backlog.
204 if (backlog < MAX_BACKLOG) {
205 SetEvent(ctx->ev_from_main);
210 /* ----------------------------------------------------------------------
215 * Data required by an output thread.
217 struct handle_output {
219 * Copy of the handle_generic structure.
221 HANDLE h; /* the handle itself */
222 HANDLE ev_to_main; /* event used to signal main thread */
223 HANDLE ev_from_main; /* event used to signal back to us */
224 int moribund; /* are we going to kill this soon? */
225 int done; /* request subthread to terminate */
226 int defunct; /* has the subthread already gone? */
227 int busy; /* operation currently in progress? */
228 void *privdata; /* for client to remember who they are */
231 * Data set at initialisation and then read-only.
236 * Data set by the main thread before signalling ev_from_main,
237 * and read by the input thread after receiving that signal.
239 char *buffer; /* the data to write */
240 DWORD len; /* how much data there is */
243 * Data set by the input thread before signalling ev_to_main,
244 * and read by the main thread after receiving that signal.
246 DWORD lenwritten; /* how much data we actually wrote */
247 int writeerr; /* return value from WriteFile */
250 * Data only ever read or written by the main thread.
252 bufchain queued_data; /* data still waiting to be written */
255 * Callback function called when the backlog in the bufchain
258 handle_outputfn_t sentdata;
261 static DWORD WINAPI handle_output_threadfunc(void *param)
263 struct handle_output *ctx = (struct handle_output *) param;
264 OVERLAPPED ovl, *povl;
268 if (ctx->flags & HANDLE_FLAG_OVERLAPPED) {
270 oev = CreateEvent(NULL, TRUE, FALSE, NULL);
276 WaitForSingleObject(ctx->ev_from_main, INFINITE);
278 SetEvent(ctx->ev_to_main);
282 memset(povl, 0, sizeof(OVERLAPPED));
286 writeret = WriteFile(ctx->h, ctx->buffer, ctx->len,
287 &ctx->lenwritten, povl);
289 ctx->writeerr = GetLastError();
292 if (povl && !writeret && GetLastError() == ERROR_IO_PENDING) {
293 writeret = GetOverlappedResult(ctx->h, povl,
294 &ctx->lenwritten, TRUE);
296 ctx->writeerr = GetLastError();
301 SetEvent(ctx->ev_to_main);
312 static void handle_try_output(struct handle_output *ctx)
317 if (!ctx->busy && bufchain_size(&ctx->queued_data)) {
318 bufchain_prefix(&ctx->queued_data, &senddata, &sendlen);
319 ctx->buffer = senddata;
321 SetEvent(ctx->ev_from_main);
326 /* ----------------------------------------------------------------------
327 * Unified code handling both input and output threads.
333 struct handle_generic g;
334 struct handle_input i;
335 struct handle_output o;
339 static tree234 *handles_by_evtomain;
341 static int handle_cmp_evtomain(void *av, void *bv)
343 struct handle *a = (struct handle *)av;
344 struct handle *b = (struct handle *)bv;
346 if ((unsigned)a->u.g.ev_to_main < (unsigned)b->u.g.ev_to_main)
348 else if ((unsigned)a->u.g.ev_to_main > (unsigned)b->u.g.ev_to_main)
354 static int handle_find_evtomain(void *av, void *bv)
356 HANDLE *a = (HANDLE *)av;
357 struct handle *b = (struct handle *)bv;
359 if ((unsigned)*a < (unsigned)b->u.g.ev_to_main)
361 else if ((unsigned)*a > (unsigned)b->u.g.ev_to_main)
367 struct handle *handle_input_new(HANDLE handle, handle_inputfn_t gotdata,
368 void *privdata, int flags)
370 struct handle *h = snew(struct handle);
371 DWORD in_threadid; /* required for Win9x */
375 h->u.i.ev_to_main = CreateEvent(NULL, FALSE, FALSE, NULL);
376 h->u.i.ev_from_main = CreateEvent(NULL, FALSE, FALSE, NULL);
377 h->u.i.gotdata = gotdata;
378 h->u.i.defunct = FALSE;
379 h->u.i.moribund = FALSE;
381 h->u.i.privdata = privdata;
382 h->u.i.flags = flags;
384 if (!handles_by_evtomain)
385 handles_by_evtomain = newtree234(handle_cmp_evtomain);
386 add234(handles_by_evtomain, h);
388 CreateThread(NULL, 0, handle_input_threadfunc,
389 &h->u.i, 0, &in_threadid);
395 struct handle *handle_output_new(HANDLE handle, handle_outputfn_t sentdata,
396 void *privdata, int flags)
398 struct handle *h = snew(struct handle);
399 DWORD out_threadid; /* required for Win9x */
403 h->u.o.ev_to_main = CreateEvent(NULL, FALSE, FALSE, NULL);
404 h->u.o.ev_from_main = CreateEvent(NULL, FALSE, FALSE, NULL);
406 h->u.o.defunct = FALSE;
407 h->u.o.moribund = FALSE;
409 h->u.o.privdata = privdata;
410 bufchain_init(&h->u.o.queued_data);
411 h->u.o.sentdata = sentdata;
412 h->u.o.flags = flags;
414 if (!handles_by_evtomain)
415 handles_by_evtomain = newtree234(handle_cmp_evtomain);
416 add234(handles_by_evtomain, h);
418 CreateThread(NULL, 0, handle_output_threadfunc,
419 &h->u.o, 0, &out_threadid);
424 int handle_write(struct handle *h, const void *data, int len)
427 bufchain_add(&h->u.o.queued_data, data, len);
428 handle_try_output(&h->u.o);
429 return bufchain_size(&h->u.o.queued_data);
432 HANDLE *handle_get_events(int *nevents)
439 * Go through our tree counting the handle objects currently
440 * engaged in useful activity.
444 if (handles_by_evtomain) {
445 for (i = 0; (h = index234(handles_by_evtomain, i)) != NULL; i++) {
449 ret = sresize(ret, size, HANDLE);
451 ret[n++] = h->u.g.ev_to_main;
460 static void handle_destroy(struct handle *h)
463 bufchain_clear(&h->u.o.queued_data);
464 CloseHandle(h->u.g.ev_from_main);
465 CloseHandle(h->u.g.ev_to_main);
466 del234(handles_by_evtomain, h);
470 void handle_free(struct handle *h)
473 * If the handle is currently busy, we cannot immediately free
474 * it. Instead we must wait until it's finished its current
475 * operation, because otherwise the subthread will write to
476 * invalid memory after we free its context from under it.
478 assert(h && !h->u.g.moribund);
481 * Just set the moribund flag, which will be noticed next
482 * time an operation completes.
484 h->u.g.moribund = TRUE;
485 } else if (h->u.g.defunct) {
487 * There isn't even a subthread; we can go straight to
493 * The subthread is alive but not busy, so we now signal it
494 * to die. Set the moribund flag to indicate that it will
495 * want destroying after that.
497 h->u.g.moribund = TRUE;
500 SetEvent(h->u.g.ev_from_main);
504 void handle_got_event(HANDLE event)
508 assert(handles_by_evtomain);
509 h = find234(handles_by_evtomain, &event, handle_find_evtomain);
512 * This isn't an error condition. If two or more event
513 * objects were signalled during the same select operation,
514 * and processing of the first caused the second handle to
515 * be closed, then it will sometimes happen that we receive
516 * an event notification here for a handle which is already
517 * deceased. In that situation we simply do nothing.
522 if (h->u.g.moribund) {
524 * A moribund handle is already treated as dead from the
525 * external user's point of view, so do nothing with the
526 * actual event. Just signal the thread to die if
527 * necessary, or destroy the handle if not.
534 SetEvent(h->u.g.ev_from_main);
545 * A signal on an input handle means data has arrived.
547 if (h->u.i.len == 0) {
549 * EOF, or (nearly equivalently) read error.
551 h->u.i.gotdata(h, NULL, -h->u.i.readerr);
552 h->u.i.defunct = TRUE;
554 backlog = h->u.i.gotdata(h, h->u.i.buffer, h->u.i.len);
555 handle_throttle(&h->u.i, backlog);
561 * A signal on an output handle means we have completed a
562 * write. Call the callback to indicate that the output
563 * buffer size has decreased, or to indicate an error.
565 if (h->u.o.writeerr) {
567 * Write error. Send a negative value to the callback,
568 * and mark the thread as defunct (because the output
569 * thread is terminating by now).
571 h->u.o.sentdata(h, -h->u.o.writeerr);
572 h->u.o.defunct = TRUE;
574 bufchain_consume(&h->u.o.queued_data, h->u.o.lenwritten);
575 h->u.o.sentdata(h, bufchain_size(&h->u.o.queued_data));
576 handle_try_output(&h->u.o);
581 void handle_unthrottle(struct handle *h, int backlog)
584 handle_throttle(&h->u.i, backlog);
587 int handle_backlog(struct handle *h)
590 return bufchain_size(&h->u.o.queued_data);
593 void *handle_get_privdata(struct handle *h)
595 return h->u.g.privdata;