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
;
277 h
->u
.i
.defunct
= FALSE
;
278 h
->u
.i
.moribund
= FALSE
;
280 h
->u
.i
.privdata
= privdata
;
282 if (!handles_by_evtomain
)
283 handles_by_evtomain
= newtree234(handle_cmp_evtomain
);
284 add234(handles_by_evtomain
, h
);
286 CreateThread(NULL
, 0, handle_input_threadfunc
,
289 handle_throttle(&h
->u
.i
, 0); /* start first read operation */
294 struct handle
*handle_output_new(HANDLE handle
, handle_outputfn_t sentdata
,
297 struct handle
*h
= snew(struct handle
);
301 h
->u
.o
.ev_to_main
= CreateEvent(NULL
, FALSE
, FALSE
, NULL
);
302 h
->u
.o
.ev_from_main
= CreateEvent(NULL
, FALSE
, FALSE
, NULL
);
304 h
->u
.o
.defunct
= FALSE
;
305 h
->u
.o
.moribund
= FALSE
;
307 h
->u
.o
.privdata
= privdata
;
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
);
488 void *handle_get_privdata(struct handle
*h
)
490 return h
->u
.g
.privdata
;