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
25 /* ----------------------------------------------------------------------
26 * Generic definitions.
30 * Maximum amount of backlog we will allow to build up on an input
31 * handle before we stop reading from it.
33 #define MAX_BACKLOG 32768
35 struct handle_generic {
37 * Initial fields common to both handle_input and handle_output
40 * The three HANDLEs are set up at initialisation time and are
41 * thereafter read-only to both main thread and subthread.
42 * `moribund' is only used by the main thread; `done' is
43 * written by the main thread before signalling to the
44 * subthread. `defunct' and `busy' are used only by the main
47 HANDLE h; /* the handle itself */
48 HANDLE ev_to_main; /* event used to signal main thread */
49 HANDLE ev_from_main; /* event used to signal back to us */
50 int moribund; /* are we going to kill this soon? */
51 int done; /* request subthread to terminate */
52 int defunct; /* has the subthread already gone? */
53 int busy; /* operation currently in progress? */
54 void *privdata; /* for client to remember who they are */
57 /* ----------------------------------------------------------------------
62 * Data required by an input thread.
66 * Copy of the handle_generic structure.
68 HANDLE h; /* the handle itself */
69 HANDLE ev_to_main; /* event used to signal main thread */
70 HANDLE ev_from_main; /* event used to signal back to us */
71 int moribund; /* are we going to kill this soon? */
72 int done; /* request subthread to terminate */
73 int defunct; /* has the subthread already gone? */
74 int busy; /* operation currently in progress? */
75 void *privdata; /* for client to remember who they are */
78 * Data set at initialisation and then read-only.
83 * Data set by the input thread before signalling ev_to_main,
84 * and read by the main thread after receiving that signal.
86 char buffer[4096]; /* the data read from the handle */
87 DWORD len; /* how much data that was */
88 int readret; /* lets us know about read errors */
91 * Callback function called by this module when data arrives on
94 handle_inputfn_t gotdata;
98 * The actual thread procedure for an input thread.
100 static DWORD WINAPI handle_input_threadfunc(void *param)
102 struct handle_input *ctx = (struct handle_input *) param;
103 OVERLAPPED ovl, *povl;
107 if (ctx->flags & HANDLE_FLAG_OVERLAPPED) {
109 oev = CreateEvent(NULL, TRUE, FALSE, NULL);
114 if (ctx->flags & HANDLE_FLAG_UNITBUFFER)
117 readlen = sizeof(ctx->buffer);
121 memset(povl, 0, sizeof(OVERLAPPED));
124 ctx->readret = ReadFile(ctx->h, ctx->buffer, readlen,
126 if (povl && !ctx->readret && GetLastError() == ERROR_IO_PENDING) {
127 WaitForSingleObject(povl->hEvent, INFINITE);
128 ctx->readret = GetOverlappedResult(ctx->h, povl, &ctx->len, FALSE);
134 if (ctx->readret && ctx->len == 0 &&
135 (ctx->flags & HANDLE_FLAG_IGNOREEOF))
138 SetEvent(ctx->ev_to_main);
143 WaitForSingleObject(ctx->ev_from_main, INFINITE);
145 break; /* main thread told us to shut down */
155 * This is called after a succcessful read, or from the
156 * `unthrottle' function. It decides whether or not to begin a new
159 static void handle_throttle(struct handle_input *ctx, int backlog)
165 * If there's a read operation already in progress, do nothing:
166 * when that completes, we'll come back here and be in a
167 * position to make a better decision.
173 * Otherwise, we must decide whether to start a new read based
174 * on the size of the backlog.
176 if (backlog < MAX_BACKLOG) {
177 SetEvent(ctx->ev_from_main);
182 /* ----------------------------------------------------------------------
187 * Data required by an output thread.
189 struct handle_output {
191 * Copy of the handle_generic structure.
193 HANDLE h; /* the handle itself */
194 HANDLE ev_to_main; /* event used to signal main thread */
195 HANDLE ev_from_main; /* event used to signal back to us */
196 int moribund; /* are we going to kill this soon? */
197 int done; /* request subthread to terminate */
198 int defunct; /* has the subthread already gone? */
199 int busy; /* operation currently in progress? */
200 void *privdata; /* for client to remember who they are */
203 * Data set at initialisation and then read-only.
208 * Data set by the main thread before signalling ev_from_main,
209 * and read by the input thread after receiving that signal.
211 char *buffer; /* the data to write */
212 DWORD len; /* how much data there is */
215 * Data set by the input thread before signalling ev_to_main,
216 * and read by the main thread after receiving that signal.
218 DWORD lenwritten; /* how much data we actually wrote */
219 int writeret; /* return value from WriteFile */
222 * Data only ever read or written by the main thread.
224 bufchain queued_data; /* data still waiting to be written */
227 * Callback function called when the backlog in the bufchain
230 handle_outputfn_t sentdata;
233 static DWORD WINAPI handle_output_threadfunc(void *param)
235 struct handle_output *ctx = (struct handle_output *) param;
236 OVERLAPPED ovl, *povl;
238 if (ctx->flags & HANDLE_FLAG_OVERLAPPED)
244 WaitForSingleObject(ctx->ev_from_main, INFINITE);
246 SetEvent(ctx->ev_to_main);
250 memset(povl, 0, sizeof(OVERLAPPED));
251 ctx->writeret = WriteFile(ctx->h, ctx->buffer, ctx->len,
252 &ctx->lenwritten, povl);
253 if (povl && !ctx->writeret && GetLastError() == ERROR_IO_PENDING)
254 ctx->writeret = GetOverlappedResult(ctx->h, povl,
255 &ctx->lenwritten, TRUE);
257 SetEvent(ctx->ev_to_main);
265 static void handle_try_output(struct handle_output *ctx)
270 if (!ctx->busy && bufchain_size(&ctx->queued_data)) {
271 bufchain_prefix(&ctx->queued_data, &senddata, &sendlen);
272 ctx->buffer = senddata;
274 SetEvent(ctx->ev_from_main);
279 /* ----------------------------------------------------------------------
280 * Unified code handling both input and output threads.
286 struct handle_generic g;
287 struct handle_input i;
288 struct handle_output o;
292 static tree234 *handles_by_evtomain;
294 static int handle_cmp_evtomain(void *av, void *bv)
296 struct handle *a = (struct handle *)av;
297 struct handle *b = (struct handle *)bv;
299 if ((unsigned)a->u.g.ev_to_main < (unsigned)b->u.g.ev_to_main)
301 else if ((unsigned)a->u.g.ev_to_main > (unsigned)b->u.g.ev_to_main)
307 static int handle_find_evtomain(void *av, void *bv)
309 HANDLE *a = (HANDLE *)av;
310 struct handle *b = (struct handle *)bv;
312 if ((unsigned)*a < (unsigned)b->u.g.ev_to_main)
314 else if ((unsigned)*a > (unsigned)b->u.g.ev_to_main)
320 struct handle *handle_input_new(HANDLE handle, handle_inputfn_t gotdata,
321 void *privdata, int flags)
323 struct handle *h = snew(struct handle);
327 h->u.i.ev_to_main = CreateEvent(NULL, FALSE, FALSE, NULL);
328 h->u.i.ev_from_main = CreateEvent(NULL, FALSE, FALSE, NULL);
329 h->u.i.gotdata = gotdata;
330 h->u.i.defunct = FALSE;
331 h->u.i.moribund = FALSE;
333 h->u.i.privdata = privdata;
334 h->u.i.flags = flags;
336 if (!handles_by_evtomain)
337 handles_by_evtomain = newtree234(handle_cmp_evtomain);
338 add234(handles_by_evtomain, h);
340 CreateThread(NULL, 0, handle_input_threadfunc,
347 struct handle *handle_output_new(HANDLE handle, handle_outputfn_t sentdata,
348 void *privdata, int flags)
350 struct handle *h = snew(struct handle);
354 h->u.o.ev_to_main = CreateEvent(NULL, FALSE, FALSE, NULL);
355 h->u.o.ev_from_main = CreateEvent(NULL, FALSE, FALSE, NULL);
357 h->u.o.defunct = FALSE;
358 h->u.o.moribund = FALSE;
360 h->u.o.privdata = privdata;
361 bufchain_init(&h->u.o.queued_data);
362 h->u.o.sentdata = sentdata;
363 h->u.o.flags = flags;
365 if (!handles_by_evtomain)
366 handles_by_evtomain = newtree234(handle_cmp_evtomain);
367 add234(handles_by_evtomain, h);
369 CreateThread(NULL, 0, handle_output_threadfunc,
375 int handle_write(struct handle *h, const void *data, int len)
378 bufchain_add(&h->u.o.queued_data, data, len);
379 handle_try_output(&h->u.o);
380 return bufchain_size(&h->u.o.queued_data);
383 HANDLE *handle_get_events(int *nevents)
390 * Go through our tree counting the handle objects currently
391 * engaged in useful activity.
395 if (handles_by_evtomain) {
396 for (i = 0; (h = index234(handles_by_evtomain, i)) != NULL; i++) {
400 ret = sresize(ret, size, HANDLE);
402 ret[n++] = h->u.g.ev_to_main;
411 static void handle_destroy(struct handle *h)
414 bufchain_clear(&h->u.o.queued_data);
415 CloseHandle(h->u.g.ev_from_main);
416 CloseHandle(h->u.g.ev_to_main);
417 del234(handles_by_evtomain, h);
421 void handle_free(struct handle *h)
424 * If the handle is currently busy, we cannot immediately free
425 * it. Instead we must wait until it's finished its current
426 * operation, because otherwise the subthread will write to
427 * invalid memory after we free its context from under it.
429 assert(h && !h->u.g.moribund);
432 * Just set the moribund flag, which will be noticed next
433 * time an operation completes.
435 h->u.g.moribund = TRUE;
436 } else if (h->u.g.defunct) {
438 * There isn't even a subthread; we can go straight to
444 * The subthread is alive but not busy, so we now signal it
445 * to die. Set the moribund flag to indicate that it will
446 * want destroying after that.
448 h->u.g.moribund = TRUE;
451 SetEvent(h->u.g.ev_from_main);
455 void handle_got_event(HANDLE event)
459 assert(handles_by_evtomain);
460 h = find234(handles_by_evtomain, &event, handle_find_evtomain);
463 * This isn't an error condition. If two or more event
464 * objects were signalled during the same select operation,
465 * and processing of the first caused the second handle to
466 * be closed, then it will sometimes happen that we receive
467 * an event notification here for a handle which is already
468 * deceased. In that situation we simply do nothing.
473 if (h->u.g.moribund) {
475 * A moribund handle is already treated as dead from the
476 * external user's point of view, so do nothing with the
477 * actual event. Just signal the thread to die if
478 * necessary, or destroy the handle if not.
485 SetEvent(h->u.g.ev_from_main);
496 * A signal on an input handle means data has arrived.
498 if (h->u.i.len == 0) {
500 * EOF, or (nearly equivalently) read error.
502 h->u.i.gotdata(h, NULL, (h->u.i.readret ? 0 : -1));
503 h->u.i.defunct = TRUE;
505 backlog = h->u.i.gotdata(h, h->u.i.buffer, h->u.i.len);
506 handle_throttle(&h->u.i, backlog);
512 * A signal on an output handle means we have completed a
513 * write. Call the callback to indicate that the output
514 * buffer size has decreased, or to indicate an error.
516 if (!h->u.o.writeret) {
518 * Write error. Send a negative value to the callback,
519 * and mark the thread as defunct (because the output
520 * thread is terminating by now).
522 h->u.o.sentdata(h, -1);
523 h->u.o.defunct = TRUE;
525 bufchain_consume(&h->u.o.queued_data, h->u.o.lenwritten);
526 h->u.o.sentdata(h, bufchain_size(&h->u.o.queued_data));
527 handle_try_output(&h->u.o);
532 void handle_unthrottle(struct handle *h, int backlog)
535 handle_throttle(&h->u.i, backlog);
538 int handle_backlog(struct handle *h)
541 return bufchain_size(&h->u.o.queued_data);
544 void *handle_get_privdata(struct handle *h)
546 return h->u.g.privdata;