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 by the input thread before signalling ev_to_main,
79 * and read by the main thread after receiving that signal.
81 char buffer[4096]; /* the data read from the handle */
82 DWORD len; /* how much data that was */
83 int readret; /* lets us know about read errors */
86 * Callback function called by this module when data arrives on
89 handle_inputfn_t gotdata;
93 * The actual thread procedure for an input thread.
95 static DWORD WINAPI handle_input_threadfunc(void *param)
97 struct handle_input *ctx = (struct handle_input *) param;
100 ctx->readret = ReadFile(ctx->h, ctx->buffer, sizeof(ctx->buffer),
105 SetEvent(ctx->ev_to_main);
110 WaitForSingleObject(ctx->ev_from_main, INFINITE);
112 break; /* main thread told us to shut down */
119 * This is called after a succcessful read, or from the
120 * `unthrottle' function. It decides whether or not to begin a new
123 static void handle_throttle(struct handle_input *ctx, int backlog)
125 assert(!ctx->defunct);
128 * If there's a read operation already in progress, do nothing:
129 * when that completes, we'll come back here and be in a
130 * position to make a better decision.
136 * Otherwise, we must decide whether to start a new read based
137 * on the size of the backlog.
139 if (backlog < MAX_BACKLOG) {
140 SetEvent(ctx->ev_from_main);
145 /* ----------------------------------------------------------------------
150 * Data required by an output thread.
152 struct handle_output {
154 * Copy of the handle_generic structure.
156 HANDLE h; /* the handle itself */
157 HANDLE ev_to_main; /* event used to signal main thread */
158 HANDLE ev_from_main; /* event used to signal back to us */
159 int moribund; /* are we going to kill this soon? */
160 int done; /* request subthread to terminate */
161 int defunct; /* has the subthread already gone? */
162 int busy; /* operation currently in progress? */
163 void *privdata; /* for client to remember who they are */
166 * Data set by the main thread before signalling ev_from_main,
167 * and read by the input thread after receiving that signal.
169 char *buffer; /* the data to write */
170 DWORD len; /* how much data there is */
173 * Data set by the input thread before signalling ev_to_main,
174 * and read by the main thread after receiving that signal.
176 DWORD lenwritten; /* how much data we actually wrote */
177 int writeret; /* return value from WriteFile */
180 * Data only ever read or written by the main thread.
182 bufchain queued_data; /* data still waiting to be written */
185 * Callback function called when the backlog in the bufchain
188 handle_outputfn_t sentdata;
191 static DWORD WINAPI handle_output_threadfunc(void *param)
193 struct handle_output *ctx = (struct handle_output *) param;
196 WaitForSingleObject(ctx->ev_from_main, INFINITE);
198 SetEvent(ctx->ev_to_main);
201 ctx->writeret = WriteFile(ctx->h, ctx->buffer, ctx->len,
202 &ctx->lenwritten, NULL);
203 SetEvent(ctx->ev_to_main);
211 static void handle_try_output(struct handle_output *ctx)
216 if (!ctx->busy && bufchain_size(&ctx->queued_data)) {
217 bufchain_prefix(&ctx->queued_data, &senddata, &sendlen);
218 ctx->buffer = senddata;
220 SetEvent(ctx->ev_from_main);
225 /* ----------------------------------------------------------------------
226 * Unified code handling both input and output threads.
232 struct handle_generic g;
233 struct handle_input i;
234 struct handle_output o;
238 static tree234 *handles_by_evtomain;
240 static int handle_cmp_evtomain(void *av, void *bv)
242 struct handle *a = (struct handle *)av;
243 struct handle *b = (struct handle *)bv;
245 if ((unsigned)a->u.g.ev_to_main < (unsigned)b->u.g.ev_to_main)
247 else if ((unsigned)a->u.g.ev_to_main > (unsigned)b->u.g.ev_to_main)
253 static int handle_find_evtomain(void *av, void *bv)
255 HANDLE *a = (HANDLE *)av;
256 struct handle *b = (struct handle *)bv;
258 if ((unsigned)*a < (unsigned)b->u.g.ev_to_main)
260 else if ((unsigned)*a > (unsigned)b->u.g.ev_to_main)
266 struct handle *handle_input_new(HANDLE handle, handle_inputfn_t gotdata,
269 struct handle *h = snew(struct handle);
273 h->u.i.ev_to_main = CreateEvent(NULL, FALSE, FALSE, NULL);
274 h->u.i.ev_from_main = CreateEvent(NULL, FALSE, FALSE, NULL);
275 h->u.i.gotdata = gotdata;
276 h->u.i.defunct = FALSE;
277 h->u.i.moribund = FALSE;
279 h->u.i.privdata = privdata;
281 if (!handles_by_evtomain)
282 handles_by_evtomain = newtree234(handle_cmp_evtomain);
283 add234(handles_by_evtomain, h);
285 CreateThread(NULL, 0, handle_input_threadfunc,
292 struct handle *handle_output_new(HANDLE handle, handle_outputfn_t sentdata,
295 struct handle *h = snew(struct handle);
299 h->u.o.ev_to_main = CreateEvent(NULL, FALSE, FALSE, NULL);
300 h->u.o.ev_from_main = CreateEvent(NULL, FALSE, FALSE, NULL);
302 h->u.o.defunct = FALSE;
303 h->u.o.moribund = FALSE;
305 h->u.o.privdata = privdata;
306 bufchain_init(&h->u.o.queued_data);
307 h->u.o.sentdata = sentdata;
309 if (!handles_by_evtomain)
310 handles_by_evtomain = newtree234(handle_cmp_evtomain);
311 add234(handles_by_evtomain, h);
313 CreateThread(NULL, 0, handle_output_threadfunc,
319 int handle_write(struct handle *h, const void *data, int len)
322 bufchain_add(&h->u.o.queued_data, data, len);
323 handle_try_output(&h->u.o);
324 return bufchain_size(&h->u.o.queued_data);
327 HANDLE *handle_get_events(int *nevents)
334 * Go through our tree counting the handle objects currently
335 * engaged in useful activity.
339 if (handles_by_evtomain) {
340 for (i = 0; (h = index234(handles_by_evtomain, i)) != NULL; i++) {
344 ret = sresize(ret, size, HANDLE);
346 ret[n++] = h->u.g.ev_to_main;
355 static void handle_destroy(struct handle *h)
358 bufchain_clear(&h->u.o.queued_data);
359 CloseHandle(h->u.g.ev_from_main);
360 CloseHandle(h->u.g.ev_to_main);
361 del234(handles_by_evtomain, h);
365 void handle_free(struct handle *h)
368 * If the handle is currently busy, we cannot immediately free
369 * it. Instead we must wait until it's finished its current
370 * operation, because otherwise the subthread will write to
371 * invalid memory after we free its context from under it.
373 assert(h && !h->u.g.moribund);
376 * Just set the moribund flag, which will be noticed next
377 * time an operation completes.
379 h->u.g.moribund = TRUE;
380 } else if (h->u.g.defunct) {
382 * There isn't even a subthread; we can go straight to
388 * The subthread is alive but not busy, so we now signal it
389 * to die. Set the moribund flag to indicate that it will
390 * want destroying after that.
392 h->u.g.moribund = TRUE;
395 SetEvent(h->u.g.ev_from_main);
399 void handle_got_event(HANDLE event)
403 assert(handles_by_evtomain);
404 h = find234(handles_by_evtomain, &event, handle_find_evtomain);
407 * This isn't an error condition. If two or more event
408 * objects were signalled during the same select operation,
409 * and processing of the first caused the second handle to
410 * be closed, then it will sometimes happen that we receive
411 * an event notification here for a handle which is already
412 * deceased. In that situation we simply do nothing.
417 if (h->u.g.moribund) {
419 * A moribund handle is already treated as dead from the
420 * external user's point of view, so do nothing with the
421 * actual event. Just signal the thread to die if
422 * 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);
488 void *handle_get_privdata(struct handle *h)
490 return h->u.g.privdata;