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
24 * - could do with some sort of private-data field in each handle
32 /* ----------------------------------------------------------------------
33 * Generic definitions.
37 * Maximum amount of backlog we will allow to build up on an input
38 * handle before we stop reading from it.
40 #define MAX_BACKLOG 32768
42 struct handle_generic {
44 * Initial fields common to both handle_input and handle_output
47 * The three HANDLEs are set up at initialisation time and are
48 * thereafter read-only to both main thread and subthread.
49 * `moribund' is only used by the main thread; `done' is
50 * written by the main thread before signalling to the
51 * subthread. `defunct' and `busy' are used only by the main
54 HANDLE h; /* the handle itself */
55 HANDLE ev_to_main; /* event used to signal main thread */
56 HANDLE ev_from_main; /* event used to signal back to us */
57 int moribund; /* are we going to kill this soon? */
58 int done; /* request subthread to terminate */
59 int defunct; /* has the subthread already gone? */
60 int busy; /* operation currently in progress? */
63 /* ----------------------------------------------------------------------
68 * Data required by an input thread.
72 * Copy of the handle_generic structure.
74 HANDLE h; /* the handle itself */
75 HANDLE ev_to_main; /* event used to signal main thread */
76 HANDLE ev_from_main; /* event used to signal back to us */
77 int moribund; /* are we going to kill this soon? */
78 int done; /* request subthread to terminate */
79 int defunct; /* has the subthread already gone? */
80 int busy; /* operation currently in progress? */
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;
105 ctx->readret = ReadFile(ctx->h, ctx->buffer, sizeof(ctx->buffer),
110 SetEvent(ctx->ev_to_main);
115 WaitForSingleObject(ctx->ev_from_main, INFINITE);
117 break; /* main thread told us to shut down */
124 * This is called after a succcessful read, or from the
125 * `unthrottle' function. It decides whether or not to begin a new
128 static void handle_throttle(struct handle_input *ctx, int backlog)
130 assert(!ctx->defunct);
133 * If there's a read operation already in progress, do nothing:
134 * when that completes, we'll come back here and be in a
135 * position to make a better decision.
141 * Otherwise, we must decide whether to start a new read based
142 * on the size of the backlog.
144 if (backlog < MAX_BACKLOG) {
145 SetEvent(ctx->ev_from_main);
150 /* ----------------------------------------------------------------------
155 * Data required by an output thread.
157 struct handle_output {
159 * Copy of the handle_generic structure.
161 HANDLE h; /* the handle itself */
162 HANDLE ev_to_main; /* event used to signal main thread */
163 HANDLE ev_from_main; /* event used to signal back to us */
164 int moribund; /* are we going to kill this soon? */
165 int done; /* request subthread to terminate */
166 int defunct; /* has the subthread already gone? */
167 int busy; /* operation currently in progress? */
170 * Data set by the main thread before signalling ev_from_main,
171 * and read by the input thread after receiving that signal.
173 char *buffer; /* the data to write */
174 DWORD len; /* how much data there is */
177 * Data set by the input thread before signalling ev_to_main,
178 * and read by the main thread after receiving that signal.
180 DWORD lenwritten; /* how much data we actually wrote */
181 int writeret; /* return value from WriteFile */
184 * Data only ever read or written by the main thread.
186 bufchain queued_data; /* data still waiting to be written */
189 * Callback function called when the backlog in the bufchain
192 handle_outputfn_t sentdata;
195 static DWORD WINAPI handle_output_threadfunc(void *param)
197 struct handle_output *ctx = (struct handle_output *) param;
200 WaitForSingleObject(ctx->ev_from_main, INFINITE);
202 SetEvent(ctx->ev_to_main);
205 ctx->writeret = WriteFile(ctx->h, ctx->buffer, ctx->len,
206 &ctx->lenwritten, NULL);
207 SetEvent(ctx->ev_to_main);
215 static void handle_try_output(struct handle_output *ctx)
220 if (!ctx->busy && bufchain_size(&ctx->queued_data)) {
221 bufchain_prefix(&ctx->queued_data, &senddata, &sendlen);
222 ctx->buffer = senddata;
224 SetEvent(ctx->ev_from_main);
229 /* ----------------------------------------------------------------------
230 * Unified code handling both input and output threads.
236 struct handle_generic g;
237 struct handle_input i;
238 struct handle_output o;
242 static tree234 *handles_by_evtomain;
244 static int handle_cmp_evtomain(void *av, void *bv)
246 struct handle *a = (struct handle *)av;
247 struct handle *b = (struct handle *)bv;
249 if ((unsigned)a->u.g.ev_to_main < (unsigned)b->u.g.ev_to_main)
251 else if ((unsigned)a->u.g.ev_to_main > (unsigned)b->u.g.ev_to_main)
257 static int handle_find_evtomain(void *av, void *bv)
259 HANDLE *a = (HANDLE *)av;
260 struct handle *b = (struct handle *)bv;
262 if ((unsigned)*a < (unsigned)b->u.g.ev_to_main)
264 else if ((unsigned)*a > (unsigned)b->u.g.ev_to_main)
270 struct handle *handle_input_new(HANDLE handle, handle_inputfn_t gotdata)
272 struct handle *h = snew(struct handle);
276 h->u.i.ev_to_main = CreateEvent(NULL, FALSE, FALSE, NULL);
277 h->u.i.ev_from_main = CreateEvent(NULL, FALSE, FALSE, NULL);
278 h->u.i.gotdata = gotdata;
280 h->u.i.defunct = FALSE;
281 h->u.i.moribund = FALSE;
284 if (!handles_by_evtomain)
285 handles_by_evtomain = newtree234(handle_cmp_evtomain);
286 add234(handles_by_evtomain, h);
288 CreateThread(NULL, 0, handle_input_threadfunc,
291 handle_throttle(&h->u.i, 0); /* start first read operation */
296 struct handle *handle_output_new(HANDLE handle, handle_outputfn_t sentdata)
298 struct handle *h = snew(struct handle);
302 h->u.o.ev_to_main = CreateEvent(NULL, FALSE, FALSE, NULL);
303 h->u.o.ev_from_main = CreateEvent(NULL, FALSE, FALSE, NULL);
305 h->u.o.defunct = FALSE;
306 h->u.o.moribund = FALSE;
308 bufchain_init(&h->u.o.queued_data);
309 h->u.o.sentdata = sentdata;
311 if (!handles_by_evtomain)
312 handles_by_evtomain = newtree234(handle_cmp_evtomain);
313 add234(handles_by_evtomain, h);
315 CreateThread(NULL, 0, handle_output_threadfunc,
321 int handle_write(struct handle *h, const void *data, int len)
324 bufchain_add(&h->u.o.queued_data, data, len);
325 handle_try_output(&h->u.o);
326 return bufchain_size(&h->u.o.queued_data);
329 HANDLE *handle_get_events(int *nevents)
336 * Go through our tree counting the handle objects currently
337 * engaged in useful activity.
341 if (handles_by_evtomain) {
342 for (i = 0; (h = index234(handles_by_evtomain, i)) != NULL; i++) {
346 ret = sresize(ret, size, HANDLE);
348 ret[n++] = h->u.g.ev_to_main;
357 static void handle_destroy(struct handle *h)
360 bufchain_clear(&h->u.o.queued_data);
361 CloseHandle(h->u.g.ev_from_main);
362 CloseHandle(h->u.g.ev_to_main);
363 del234(handles_by_evtomain, h);
367 void handle_free(struct handle *h)
370 * If the handle is currently busy, we cannot immediately free
371 * it. Instead we must wait until it's finished its current
372 * operation, because otherwise the subthread will write to
373 * invalid memory after we free its context from under it.
375 assert(h && !h->u.g.moribund);
378 * Just set the moribund flag, which will be noticed next
379 * time an operation completes.
381 h->u.g.moribund = TRUE;
382 } else if (h->u.g.defunct) {
384 * There isn't even a subthread; we can go straight to
390 * The subthread is alive but not busy, so we now signal it
391 * to die. Set the moribund flag to indicate that it will
392 * want destroying after that.
394 h->u.g.moribund = TRUE;
396 SetEvent(h->u.g.ev_from_main);
400 void handle_got_event(HANDLE event)
404 assert(handles_by_evtomain);
405 h = find234(handles_by_evtomain, &event, handle_find_evtomain);
408 * This isn't an error condition. If two or more event
409 * objects were signalled during the same select operation,
410 * and processing of the first caused the second handle to
411 * be closed, then it will sometimes happen that we receive
412 * an event notification here for a handle which is already
413 * deceased. In that situation we simply do nothing.
418 if (h->u.g.moribund) {
420 * A moribund handle is already treated as dead from the
421 * external user's point of view, so do nothing with the
422 * actual event. Just signal the thread to die if
423 * necessary, or destroy the handle if not.
429 SetEvent(h->u.g.ev_from_main);
440 * A signal on an input handle means data has arrived.
442 if (h->u.i.len == 0) {
444 * EOF, or (nearly equivalently) read error.
446 h->u.i.gotdata(h, NULL, (h->u.i.readret ? 0 : -1));
447 h->u.i.defunct = TRUE;
449 backlog = h->u.i.gotdata(h, h->u.i.buffer, h->u.i.len);
450 handle_throttle(&h->u.i, backlog);
456 * A signal on an output handle means we have completed a
457 * write. Call the callback to indicate that the output
458 * buffer size has decreased, or to indicate an error.
460 if (!h->u.o.writeret) {
462 * Write error. Send a negative value to the callback,
463 * and mark the thread as defunct (because the output
464 * thread is terminating by now).
466 h->u.o.sentdata(h, -1);
467 h->u.o.defunct = TRUE;
469 bufchain_consume(&h->u.o.queued_data, h->u.o.lenwritten);
470 h->u.o.sentdata(h, bufchain_size(&h->u.o.queued_data));
471 handle_try_output(&h->u.o);
476 void handle_unthrottle(struct handle *h, int backlog)
479 handle_throttle(&h->u.i, backlog);
482 int handle_backlog(struct handle *h)
485 return bufchain_size(&h->u.o.queued_data);