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;
106 if (ctx->flags & HANDLE_FLAG_OVERLAPPED) {
108 oev = CreateEvent(NULL, TRUE, FALSE, NULL);
115 memset(povl, 0, sizeof(OVERLAPPED));
118 ctx->readret = ReadFile(ctx->h, ctx->buffer, sizeof(ctx->buffer),
120 if (povl && !ctx->readret && GetLastError() == ERROR_IO_PENDING) {
121 WaitForSingleObject(povl->hEvent, INFINITE);
122 ctx->readret = GetOverlappedResult(ctx->h, povl, &ctx->len, FALSE);
128 if (ctx->readret && ctx->len == 0 &&
129 (ctx->flags & HANDLE_FLAG_IGNOREEOF))
132 SetEvent(ctx->ev_to_main);
137 WaitForSingleObject(ctx->ev_from_main, INFINITE);
139 break; /* main thread told us to shut down */
149 * This is called after a succcessful read, or from the
150 * `unthrottle' function. It decides whether or not to begin a new
153 static void handle_throttle(struct handle_input *ctx, int backlog)
159 * If there's a read operation already in progress, do nothing:
160 * when that completes, we'll come back here and be in a
161 * position to make a better decision.
167 * Otherwise, we must decide whether to start a new read based
168 * on the size of the backlog.
170 if (backlog < MAX_BACKLOG) {
171 SetEvent(ctx->ev_from_main);
176 /* ----------------------------------------------------------------------
181 * Data required by an output thread.
183 struct handle_output {
185 * Copy of the handle_generic structure.
187 HANDLE h; /* the handle itself */
188 HANDLE ev_to_main; /* event used to signal main thread */
189 HANDLE ev_from_main; /* event used to signal back to us */
190 int moribund; /* are we going to kill this soon? */
191 int done; /* request subthread to terminate */
192 int defunct; /* has the subthread already gone? */
193 int busy; /* operation currently in progress? */
194 void *privdata; /* for client to remember who they are */
197 * Data set at initialisation and then read-only.
202 * Data set by the main thread before signalling ev_from_main,
203 * and read by the input thread after receiving that signal.
205 char *buffer; /* the data to write */
206 DWORD len; /* how much data there is */
209 * Data set by the input thread before signalling ev_to_main,
210 * and read by the main thread after receiving that signal.
212 DWORD lenwritten; /* how much data we actually wrote */
213 int writeret; /* return value from WriteFile */
216 * Data only ever read or written by the main thread.
218 bufchain queued_data; /* data still waiting to be written */
221 * Callback function called when the backlog in the bufchain
224 handle_outputfn_t sentdata;
227 static DWORD WINAPI handle_output_threadfunc(void *param)
229 struct handle_output *ctx = (struct handle_output *) param;
230 OVERLAPPED ovl, *povl;
232 if (ctx->flags & HANDLE_FLAG_OVERLAPPED)
238 WaitForSingleObject(ctx->ev_from_main, INFINITE);
240 SetEvent(ctx->ev_to_main);
244 memset(povl, 0, sizeof(OVERLAPPED));
245 ctx->writeret = WriteFile(ctx->h, ctx->buffer, ctx->len,
246 &ctx->lenwritten, povl);
247 if (povl && !ctx->writeret && GetLastError() == ERROR_IO_PENDING)
248 ctx->writeret = GetOverlappedResult(ctx->h, povl,
249 &ctx->lenwritten, TRUE);
251 SetEvent(ctx->ev_to_main);
259 static void handle_try_output(struct handle_output *ctx)
264 if (!ctx->busy && bufchain_size(&ctx->queued_data)) {
265 bufchain_prefix(&ctx->queued_data, &senddata, &sendlen);
266 ctx->buffer = senddata;
268 SetEvent(ctx->ev_from_main);
273 /* ----------------------------------------------------------------------
274 * Unified code handling both input and output threads.
280 struct handle_generic g;
281 struct handle_input i;
282 struct handle_output o;
286 static tree234 *handles_by_evtomain;
288 static int handle_cmp_evtomain(void *av, void *bv)
290 struct handle *a = (struct handle *)av;
291 struct handle *b = (struct handle *)bv;
293 if ((unsigned)a->u.g.ev_to_main < (unsigned)b->u.g.ev_to_main)
295 else if ((unsigned)a->u.g.ev_to_main > (unsigned)b->u.g.ev_to_main)
301 static int handle_find_evtomain(void *av, void *bv)
303 HANDLE *a = (HANDLE *)av;
304 struct handle *b = (struct handle *)bv;
306 if ((unsigned)*a < (unsigned)b->u.g.ev_to_main)
308 else if ((unsigned)*a > (unsigned)b->u.g.ev_to_main)
314 struct handle *handle_input_new(HANDLE handle, handle_inputfn_t gotdata,
315 void *privdata, int flags)
317 struct handle *h = snew(struct handle);
321 h->u.i.ev_to_main = CreateEvent(NULL, FALSE, FALSE, NULL);
322 h->u.i.ev_from_main = CreateEvent(NULL, FALSE, FALSE, NULL);
323 h->u.i.gotdata = gotdata;
324 h->u.i.defunct = FALSE;
325 h->u.i.moribund = FALSE;
327 h->u.i.privdata = privdata;
328 h->u.i.flags = flags;
330 if (!handles_by_evtomain)
331 handles_by_evtomain = newtree234(handle_cmp_evtomain);
332 add234(handles_by_evtomain, h);
334 CreateThread(NULL, 0, handle_input_threadfunc,
341 struct handle *handle_output_new(HANDLE handle, handle_outputfn_t sentdata,
342 void *privdata, int flags)
344 struct handle *h = snew(struct handle);
348 h->u.o.ev_to_main = CreateEvent(NULL, FALSE, FALSE, NULL);
349 h->u.o.ev_from_main = CreateEvent(NULL, FALSE, FALSE, NULL);
351 h->u.o.defunct = FALSE;
352 h->u.o.moribund = FALSE;
354 h->u.o.privdata = privdata;
355 bufchain_init(&h->u.o.queued_data);
356 h->u.o.sentdata = sentdata;
357 h->u.o.flags = flags;
359 if (!handles_by_evtomain)
360 handles_by_evtomain = newtree234(handle_cmp_evtomain);
361 add234(handles_by_evtomain, h);
363 CreateThread(NULL, 0, handle_output_threadfunc,
369 int handle_write(struct handle *h, const void *data, int len)
372 bufchain_add(&h->u.o.queued_data, data, len);
373 handle_try_output(&h->u.o);
374 return bufchain_size(&h->u.o.queued_data);
377 HANDLE *handle_get_events(int *nevents)
384 * Go through our tree counting the handle objects currently
385 * engaged in useful activity.
389 if (handles_by_evtomain) {
390 for (i = 0; (h = index234(handles_by_evtomain, i)) != NULL; i++) {
394 ret = sresize(ret, size, HANDLE);
396 ret[n++] = h->u.g.ev_to_main;
405 static void handle_destroy(struct handle *h)
408 bufchain_clear(&h->u.o.queued_data);
409 CloseHandle(h->u.g.ev_from_main);
410 CloseHandle(h->u.g.ev_to_main);
411 del234(handles_by_evtomain, h);
415 void handle_free(struct handle *h)
418 * If the handle is currently busy, we cannot immediately free
419 * it. Instead we must wait until it's finished its current
420 * operation, because otherwise the subthread will write to
421 * invalid memory after we free its context from under it.
423 assert(h && !h->u.g.moribund);
426 * Just set the moribund flag, which will be noticed next
427 * time an operation completes.
429 h->u.g.moribund = TRUE;
430 } else if (h->u.g.defunct) {
432 * There isn't even a subthread; we can go straight to
438 * The subthread is alive but not busy, so we now signal it
439 * to die. Set the moribund flag to indicate that it will
440 * want destroying after that.
442 h->u.g.moribund = TRUE;
445 SetEvent(h->u.g.ev_from_main);
449 void handle_got_event(HANDLE event)
453 assert(handles_by_evtomain);
454 h = find234(handles_by_evtomain, &event, handle_find_evtomain);
457 * This isn't an error condition. If two or more event
458 * objects were signalled during the same select operation,
459 * and processing of the first caused the second handle to
460 * be closed, then it will sometimes happen that we receive
461 * an event notification here for a handle which is already
462 * deceased. In that situation we simply do nothing.
467 if (h->u.g.moribund) {
469 * A moribund handle is already treated as dead from the
470 * external user's point of view, so do nothing with the
471 * actual event. Just signal the thread to die if
472 * necessary, or destroy the handle if not.
479 SetEvent(h->u.g.ev_from_main);
490 * A signal on an input handle means data has arrived.
492 if (h->u.i.len == 0) {
494 * EOF, or (nearly equivalently) read error.
496 h->u.i.gotdata(h, NULL, (h->u.i.readret ? 0 : -1));
497 h->u.i.defunct = TRUE;
499 backlog = h->u.i.gotdata(h, h->u.i.buffer, h->u.i.len);
500 handle_throttle(&h->u.i, backlog);
506 * A signal on an output handle means we have completed a
507 * write. Call the callback to indicate that the output
508 * buffer size has decreased, or to indicate an error.
510 if (!h->u.o.writeret) {
512 * Write error. Send a negative value to the callback,
513 * and mark the thread as defunct (because the output
514 * thread is terminating by now).
516 h->u.o.sentdata(h, -1);
517 h->u.o.defunct = TRUE;
519 bufchain_consume(&h->u.o.queued_data, h->u.o.lenwritten);
520 h->u.o.sentdata(h, bufchain_size(&h->u.o.queued_data));
521 handle_try_output(&h->u.o);
526 void handle_unthrottle(struct handle *h, int backlog)
529 handle_throttle(&h->u.i, backlog);
532 int handle_backlog(struct handle *h)
535 return bufchain_size(&h->u.o.queued_data);
538 void *handle_get_privdata(struct handle *h)
540 return h->u.g.privdata;