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
;
267 if (ctx
->flags
& HANDLE_FLAG_OVERLAPPED
)
273 WaitForSingleObject(ctx
->ev_from_main
, INFINITE
);
275 SetEvent(ctx
->ev_to_main
);
279 memset(povl
, 0, sizeof(OVERLAPPED
));
280 writeret
= WriteFile(ctx
->h
, ctx
->buffer
, ctx
->len
,
281 &ctx
->lenwritten
, povl
);
283 ctx
->writeerr
= GetLastError();
286 if (povl
&& !writeret
&& GetLastError() == ERROR_IO_PENDING
) {
287 writeret
= GetOverlappedResult(ctx
->h
, povl
,
288 &ctx
->lenwritten
, TRUE
);
290 ctx
->writeerr
= GetLastError();
295 SetEvent(ctx
->ev_to_main
);
303 static void handle_try_output(struct handle_output
*ctx
)
308 if (!ctx
->busy
&& bufchain_size(&ctx
->queued_data
)) {
309 bufchain_prefix(&ctx
->queued_data
, &senddata
, &sendlen
);
310 ctx
->buffer
= senddata
;
312 SetEvent(ctx
->ev_from_main
);
317 /* ----------------------------------------------------------------------
318 * Unified code handling both input and output threads.
324 struct handle_generic g
;
325 struct handle_input i
;
326 struct handle_output o
;
330 static tree234
*handles_by_evtomain
;
332 static int handle_cmp_evtomain(void *av
, void *bv
)
334 struct handle
*a
= (struct handle
*)av
;
335 struct handle
*b
= (struct handle
*)bv
;
337 if ((unsigned)a
->u
.g
.ev_to_main
< (unsigned)b
->u
.g
.ev_to_main
)
339 else if ((unsigned)a
->u
.g
.ev_to_main
> (unsigned)b
->u
.g
.ev_to_main
)
345 static int handle_find_evtomain(void *av
, void *bv
)
347 HANDLE
*a
= (HANDLE
*)av
;
348 struct handle
*b
= (struct handle
*)bv
;
350 if ((unsigned)*a
< (unsigned)b
->u
.g
.ev_to_main
)
352 else if ((unsigned)*a
> (unsigned)b
->u
.g
.ev_to_main
)
358 struct handle
*handle_input_new(HANDLE handle
, handle_inputfn_t gotdata
,
359 void *privdata
, int flags
)
361 struct handle
*h
= snew(struct handle
);
362 DWORD in_threadid
; /* required for Win9x */
366 h
->u
.i
.ev_to_main
= CreateEvent(NULL
, FALSE
, FALSE
, NULL
);
367 h
->u
.i
.ev_from_main
= CreateEvent(NULL
, FALSE
, FALSE
, NULL
);
368 h
->u
.i
.gotdata
= gotdata
;
369 h
->u
.i
.defunct
= FALSE
;
370 h
->u
.i
.moribund
= FALSE
;
372 h
->u
.i
.privdata
= privdata
;
373 h
->u
.i
.flags
= flags
;
375 if (!handles_by_evtomain
)
376 handles_by_evtomain
= newtree234(handle_cmp_evtomain
);
377 add234(handles_by_evtomain
, h
);
379 CreateThread(NULL
, 0, handle_input_threadfunc
,
380 &h
->u
.i
, 0, &in_threadid
);
386 struct handle
*handle_output_new(HANDLE handle
, handle_outputfn_t sentdata
,
387 void *privdata
, int flags
)
389 struct handle
*h
= snew(struct handle
);
390 DWORD out_threadid
; /* required for Win9x */
394 h
->u
.o
.ev_to_main
= CreateEvent(NULL
, FALSE
, FALSE
, NULL
);
395 h
->u
.o
.ev_from_main
= CreateEvent(NULL
, FALSE
, FALSE
, NULL
);
397 h
->u
.o
.defunct
= FALSE
;
398 h
->u
.o
.moribund
= FALSE
;
400 h
->u
.o
.privdata
= privdata
;
401 bufchain_init(&h
->u
.o
.queued_data
);
402 h
->u
.o
.sentdata
= sentdata
;
403 h
->u
.o
.flags
= flags
;
405 if (!handles_by_evtomain
)
406 handles_by_evtomain
= newtree234(handle_cmp_evtomain
);
407 add234(handles_by_evtomain
, h
);
409 CreateThread(NULL
, 0, handle_output_threadfunc
,
410 &h
->u
.i
, 0, &out_threadid
);
415 int handle_write(struct handle
*h
, const void *data
, int len
)
418 bufchain_add(&h
->u
.o
.queued_data
, data
, len
);
419 handle_try_output(&h
->u
.o
);
420 return bufchain_size(&h
->u
.o
.queued_data
);
423 HANDLE
*handle_get_events(int *nevents
)
430 * Go through our tree counting the handle objects currently
431 * engaged in useful activity.
435 if (handles_by_evtomain
) {
436 for (i
= 0; (h
= index234(handles_by_evtomain
, i
)) != NULL
; i
++) {
440 ret
= sresize(ret
, size
, HANDLE
);
442 ret
[n
++] = h
->u
.g
.ev_to_main
;
451 static void handle_destroy(struct handle
*h
)
454 bufchain_clear(&h
->u
.o
.queued_data
);
455 CloseHandle(h
->u
.g
.ev_from_main
);
456 CloseHandle(h
->u
.g
.ev_to_main
);
457 del234(handles_by_evtomain
, h
);
461 void handle_free(struct handle
*h
)
464 * If the handle is currently busy, we cannot immediately free
465 * it. Instead we must wait until it's finished its current
466 * operation, because otherwise the subthread will write to
467 * invalid memory after we free its context from under it.
469 assert(h
&& !h
->u
.g
.moribund
);
472 * Just set the moribund flag, which will be noticed next
473 * time an operation completes.
475 h
->u
.g
.moribund
= TRUE
;
476 } else if (h
->u
.g
.defunct
) {
478 * There isn't even a subthread; we can go straight to
484 * The subthread is alive but not busy, so we now signal it
485 * to die. Set the moribund flag to indicate that it will
486 * want destroying after that.
488 h
->u
.g
.moribund
= TRUE
;
491 SetEvent(h
->u
.g
.ev_from_main
);
495 void handle_got_event(HANDLE event
)
499 assert(handles_by_evtomain
);
500 h
= find234(handles_by_evtomain
, &event
, handle_find_evtomain
);
503 * This isn't an error condition. If two or more event
504 * objects were signalled during the same select operation,
505 * and processing of the first caused the second handle to
506 * be closed, then it will sometimes happen that we receive
507 * an event notification here for a handle which is already
508 * deceased. In that situation we simply do nothing.
513 if (h
->u
.g
.moribund
) {
515 * A moribund handle is already treated as dead from the
516 * external user's point of view, so do nothing with the
517 * actual event. Just signal the thread to die if
518 * necessary, or destroy the handle if not.
525 SetEvent(h
->u
.g
.ev_from_main
);
536 * A signal on an input handle means data has arrived.
538 if (h
->u
.i
.len
== 0) {
540 * EOF, or (nearly equivalently) read error.
542 h
->u
.i
.gotdata(h
, NULL
, -h
->u
.i
.readerr
);
543 h
->u
.i
.defunct
= TRUE
;
545 backlog
= h
->u
.i
.gotdata(h
, h
->u
.i
.buffer
, h
->u
.i
.len
);
546 handle_throttle(&h
->u
.i
, backlog
);
552 * A signal on an output handle means we have completed a
553 * write. Call the callback to indicate that the output
554 * buffer size has decreased, or to indicate an error.
556 if (h
->u
.o
.writeerr
) {
558 * Write error. Send a negative value to the callback,
559 * and mark the thread as defunct (because the output
560 * thread is terminating by now).
562 h
->u
.o
.sentdata(h
, -h
->u
.o
.writeerr
);
563 h
->u
.o
.defunct
= TRUE
;
565 bufchain_consume(&h
->u
.o
.queued_data
, h
->u
.o
.lenwritten
);
566 h
->u
.o
.sentdata(h
, bufchain_size(&h
->u
.o
.queued_data
));
567 handle_try_output(&h
->u
.o
);
572 void handle_unthrottle(struct handle
*h
, int backlog
)
575 handle_throttle(&h
->u
.i
, backlog
);
578 int handle_backlog(struct handle
*h
)
581 return bufchain_size(&h
->u
.o
.queued_data
);
584 void *handle_get_privdata(struct handle
*h
)
586 return h
->u
.g
.privdata
;