| 1 | /* |
| 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. |
| 6 | * |
| 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. |
| 12 | * |
| 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 |
| 18 | * when one completes. |
| 19 | */ |
| 20 | |
| 21 | /* |
| 22 | * TODO: |
| 23 | * |
| 24 | * - could do with some sort of private-data field in each handle |
| 25 | * structure. |
| 26 | */ |
| 27 | |
| 28 | #include <assert.h> |
| 29 | |
| 30 | #include "putty.h" |
| 31 | |
| 32 | /* ---------------------------------------------------------------------- |
| 33 | * Generic definitions. |
| 34 | */ |
| 35 | |
| 36 | /* |
| 37 | * Maximum amount of backlog we will allow to build up on an input |
| 38 | * handle before we stop reading from it. |
| 39 | */ |
| 40 | #define MAX_BACKLOG 32768 |
| 41 | |
| 42 | struct handle_generic { |
| 43 | /* |
| 44 | * Initial fields common to both handle_input and handle_output |
| 45 | * structures. |
| 46 | * |
| 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 |
| 52 | * thread. |
| 53 | */ |
| 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? */ |
| 61 | }; |
| 62 | |
| 63 | /* ---------------------------------------------------------------------- |
| 64 | * Input threads. |
| 65 | */ |
| 66 | |
| 67 | /* |
| 68 | * Data required by an input thread. |
| 69 | */ |
| 70 | struct handle_input { |
| 71 | /* |
| 72 | * Copy of the handle_generic structure. |
| 73 | */ |
| 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? */ |
| 81 | |
| 82 | /* |
| 83 | * Data set by the input thread before signalling ev_to_main, |
| 84 | * and read by the main thread after receiving that signal. |
| 85 | */ |
| 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 */ |
| 89 | |
| 90 | /* |
| 91 | * Callback function called by this module when data arrives on |
| 92 | * an input handle. |
| 93 | */ |
| 94 | handle_inputfn_t gotdata; |
| 95 | }; |
| 96 | |
| 97 | /* |
| 98 | * The actual thread procedure for an input thread. |
| 99 | */ |
| 100 | static DWORD WINAPI handle_input_threadfunc(void *param) |
| 101 | { |
| 102 | struct handle_input *ctx = (struct handle_input *) param; |
| 103 | |
| 104 | while (1) { |
| 105 | ctx->readret = ReadFile(ctx->h, ctx->buffer, sizeof(ctx->buffer), |
| 106 | &ctx->len, NULL); |
| 107 | if (!ctx->readret) |
| 108 | ctx->len = 0; |
| 109 | |
| 110 | SetEvent(ctx->ev_to_main); |
| 111 | |
| 112 | if (!ctx->len) |
| 113 | break; |
| 114 | |
| 115 | WaitForSingleObject(ctx->ev_from_main, INFINITE); |
| 116 | if (ctx->done) |
| 117 | break; /* main thread told us to shut down */ |
| 118 | } |
| 119 | |
| 120 | return 0; |
| 121 | } |
| 122 | |
| 123 | /* |
| 124 | * This is called after a succcessful read, or from the |
| 125 | * `unthrottle' function. It decides whether or not to begin a new |
| 126 | * read operation. |
| 127 | */ |
| 128 | static void handle_throttle(struct handle_input *ctx, int backlog) |
| 129 | { |
| 130 | assert(!ctx->defunct); |
| 131 | |
| 132 | /* |
| 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. |
| 136 | */ |
| 137 | if (ctx->busy) |
| 138 | return; |
| 139 | |
| 140 | /* |
| 141 | * Otherwise, we must decide whether to start a new read based |
| 142 | * on the size of the backlog. |
| 143 | */ |
| 144 | if (backlog < MAX_BACKLOG) { |
| 145 | SetEvent(ctx->ev_from_main); |
| 146 | ctx->busy = TRUE; |
| 147 | } |
| 148 | } |
| 149 | |
| 150 | /* ---------------------------------------------------------------------- |
| 151 | * Output threads. |
| 152 | */ |
| 153 | |
| 154 | /* |
| 155 | * Data required by an output thread. |
| 156 | */ |
| 157 | struct handle_output { |
| 158 | /* |
| 159 | * Copy of the handle_generic structure. |
| 160 | */ |
| 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? */ |
| 168 | |
| 169 | /* |
| 170 | * Data set by the main thread before signalling ev_from_main, |
| 171 | * and read by the input thread after receiving that signal. |
| 172 | */ |
| 173 | char *buffer; /* the data to write */ |
| 174 | DWORD len; /* how much data there is */ |
| 175 | |
| 176 | /* |
| 177 | * Data set by the input thread before signalling ev_to_main, |
| 178 | * and read by the main thread after receiving that signal. |
| 179 | */ |
| 180 | DWORD lenwritten; /* how much data we actually wrote */ |
| 181 | int writeret; /* return value from WriteFile */ |
| 182 | |
| 183 | /* |
| 184 | * Data only ever read or written by the main thread. |
| 185 | */ |
| 186 | bufchain queued_data; /* data still waiting to be written */ |
| 187 | |
| 188 | /* |
| 189 | * Callback function called when the backlog in the bufchain |
| 190 | * drops. |
| 191 | */ |
| 192 | handle_outputfn_t sentdata; |
| 193 | }; |
| 194 | |
| 195 | static DWORD WINAPI handle_output_threadfunc(void *param) |
| 196 | { |
| 197 | struct handle_output *ctx = (struct handle_output *) param; |
| 198 | |
| 199 | while (1) { |
| 200 | WaitForSingleObject(ctx->ev_from_main, INFINITE); |
| 201 | if (ctx->done) { |
| 202 | SetEvent(ctx->ev_to_main); |
| 203 | break; |
| 204 | } |
| 205 | ctx->writeret = WriteFile(ctx->h, ctx->buffer, ctx->len, |
| 206 | &ctx->lenwritten, NULL); |
| 207 | SetEvent(ctx->ev_to_main); |
| 208 | if (!ctx->writeret) |
| 209 | break; |
| 210 | } |
| 211 | |
| 212 | return 0; |
| 213 | } |
| 214 | |
| 215 | static void handle_try_output(struct handle_output *ctx) |
| 216 | { |
| 217 | void *senddata; |
| 218 | int sendlen; |
| 219 | |
| 220 | if (!ctx->busy && bufchain_size(&ctx->queued_data)) { |
| 221 | bufchain_prefix(&ctx->queued_data, &senddata, &sendlen); |
| 222 | ctx->buffer = senddata; |
| 223 | ctx->len = sendlen; |
| 224 | SetEvent(ctx->ev_from_main); |
| 225 | ctx->busy = TRUE; |
| 226 | } |
| 227 | } |
| 228 | |
| 229 | /* ---------------------------------------------------------------------- |
| 230 | * Unified code handling both input and output threads. |
| 231 | */ |
| 232 | |
| 233 | struct handle { |
| 234 | int output; |
| 235 | union { |
| 236 | struct handle_generic g; |
| 237 | struct handle_input i; |
| 238 | struct handle_output o; |
| 239 | } u; |
| 240 | }; |
| 241 | |
| 242 | static tree234 *handles_by_evtomain; |
| 243 | |
| 244 | static int handle_cmp_evtomain(void *av, void *bv) |
| 245 | { |
| 246 | struct handle *a = (struct handle *)av; |
| 247 | struct handle *b = (struct handle *)bv; |
| 248 | |
| 249 | if ((unsigned)a->u.g.ev_to_main < (unsigned)b->u.g.ev_to_main) |
| 250 | return -1; |
| 251 | else if ((unsigned)a->u.g.ev_to_main > (unsigned)b->u.g.ev_to_main) |
| 252 | return +1; |
| 253 | else |
| 254 | return 0; |
| 255 | } |
| 256 | |
| 257 | static int handle_find_evtomain(void *av, void *bv) |
| 258 | { |
| 259 | HANDLE *a = (HANDLE *)av; |
| 260 | struct handle *b = (struct handle *)bv; |
| 261 | |
| 262 | if ((unsigned)*a < (unsigned)b->u.g.ev_to_main) |
| 263 | return -1; |
| 264 | else if ((unsigned)*a > (unsigned)b->u.g.ev_to_main) |
| 265 | return +1; |
| 266 | else |
| 267 | return 0; |
| 268 | } |
| 269 | |
| 270 | struct handle *handle_input_new(HANDLE handle, handle_inputfn_t gotdata) |
| 271 | { |
| 272 | struct handle *h = snew(struct handle); |
| 273 | |
| 274 | h->output = FALSE; |
| 275 | h->u.i.h = 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; |
| 279 | h->u.i.busy = FALSE; |
| 280 | h->u.i.defunct = FALSE; |
| 281 | h->u.i.moribund = FALSE; |
| 282 | h->u.i.done = FALSE; |
| 283 | |
| 284 | if (!handles_by_evtomain) |
| 285 | handles_by_evtomain = newtree234(handle_cmp_evtomain); |
| 286 | add234(handles_by_evtomain, h); |
| 287 | |
| 288 | CreateThread(NULL, 0, handle_input_threadfunc, |
| 289 | &h->u.i, 0, NULL); |
| 290 | |
| 291 | handle_throttle(&h->u.i, 0); /* start first read operation */ |
| 292 | |
| 293 | return h; |
| 294 | } |
| 295 | |
| 296 | struct handle *handle_output_new(HANDLE handle, handle_outputfn_t sentdata) |
| 297 | { |
| 298 | struct handle *h = snew(struct handle); |
| 299 | |
| 300 | h->output = TRUE; |
| 301 | h->u.o.h = 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); |
| 304 | h->u.o.busy = FALSE; |
| 305 | h->u.o.defunct = FALSE; |
| 306 | h->u.o.moribund = FALSE; |
| 307 | h->u.o.done = FALSE; |
| 308 | bufchain_init(&h->u.o.queued_data); |
| 309 | h->u.o.sentdata = sentdata; |
| 310 | |
| 311 | if (!handles_by_evtomain) |
| 312 | handles_by_evtomain = newtree234(handle_cmp_evtomain); |
| 313 | add234(handles_by_evtomain, h); |
| 314 | |
| 315 | CreateThread(NULL, 0, handle_output_threadfunc, |
| 316 | &h->u.i, 0, NULL); |
| 317 | |
| 318 | return h; |
| 319 | } |
| 320 | |
| 321 | int handle_write(struct handle *h, const void *data, int len) |
| 322 | { |
| 323 | assert(h->output); |
| 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); |
| 327 | } |
| 328 | |
| 329 | HANDLE *handle_get_events(int *nevents) |
| 330 | { |
| 331 | HANDLE *ret; |
| 332 | struct handle *h; |
| 333 | int i, n, size; |
| 334 | |
| 335 | /* |
| 336 | * Go through our tree counting the handle objects currently |
| 337 | * engaged in useful activity. |
| 338 | */ |
| 339 | ret = NULL; |
| 340 | n = size = 0; |
| 341 | if (handles_by_evtomain) { |
| 342 | for (i = 0; (h = index234(handles_by_evtomain, i)) != NULL; i++) { |
| 343 | if (h->u.g.busy) { |
| 344 | if (n >= size) { |
| 345 | size += 32; |
| 346 | ret = sresize(ret, size, HANDLE); |
| 347 | } |
| 348 | ret[n++] = h->u.g.ev_to_main; |
| 349 | } |
| 350 | } |
| 351 | } |
| 352 | |
| 353 | *nevents = n; |
| 354 | return ret; |
| 355 | } |
| 356 | |
| 357 | static void handle_destroy(struct handle *h) |
| 358 | { |
| 359 | if (h->output) |
| 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); |
| 364 | sfree(h); |
| 365 | } |
| 366 | |
| 367 | void handle_free(struct handle *h) |
| 368 | { |
| 369 | /* |
| 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. |
| 374 | */ |
| 375 | assert(h && !h->u.g.moribund); |
| 376 | if (h->u.g.busy) { |
| 377 | /* |
| 378 | * Just set the moribund flag, which will be noticed next |
| 379 | * time an operation completes. |
| 380 | */ |
| 381 | h->u.g.moribund = TRUE; |
| 382 | } else if (h->u.g.defunct) { |
| 383 | /* |
| 384 | * There isn't even a subthread; we can go straight to |
| 385 | * handle_destroy. |
| 386 | */ |
| 387 | handle_destroy(h); |
| 388 | } else { |
| 389 | /* |
| 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. |
| 393 | */ |
| 394 | h->u.g.moribund = TRUE; |
| 395 | h->u.g.done = TRUE; |
| 396 | SetEvent(h->u.g.ev_from_main); |
| 397 | } |
| 398 | } |
| 399 | |
| 400 | void handle_got_event(HANDLE event) |
| 401 | { |
| 402 | struct handle *h; |
| 403 | |
| 404 | assert(handles_by_evtomain); |
| 405 | h = find234(handles_by_evtomain, &event, handle_find_evtomain); |
| 406 | if (!h) { |
| 407 | /* |
| 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. |
| 414 | */ |
| 415 | return; |
| 416 | } |
| 417 | |
| 418 | if (h->u.g.moribund) { |
| 419 | /* |
| 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. |
| 424 | */ |
| 425 | if (h->u.g.done) { |
| 426 | handle_destroy(h); |
| 427 | } else { |
| 428 | h->u.g.done = TRUE; |
| 429 | SetEvent(h->u.g.ev_from_main); |
| 430 | } |
| 431 | return; |
| 432 | } |
| 433 | |
| 434 | if (!h->output) { |
| 435 | int backlog; |
| 436 | |
| 437 | h->u.i.busy = FALSE; |
| 438 | |
| 439 | /* |
| 440 | * A signal on an input handle means data has arrived. |
| 441 | */ |
| 442 | if (h->u.i.len == 0) { |
| 443 | /* |
| 444 | * EOF, or (nearly equivalently) read error. |
| 445 | */ |
| 446 | h->u.i.gotdata(h, NULL, (h->u.i.readret ? 0 : -1)); |
| 447 | h->u.i.defunct = TRUE; |
| 448 | } else { |
| 449 | backlog = h->u.i.gotdata(h, h->u.i.buffer, h->u.i.len); |
| 450 | handle_throttle(&h->u.i, backlog); |
| 451 | } |
| 452 | } else { |
| 453 | h->u.o.busy = FALSE; |
| 454 | |
| 455 | /* |
| 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. |
| 459 | */ |
| 460 | if (!h->u.o.writeret) { |
| 461 | /* |
| 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). |
| 465 | */ |
| 466 | h->u.o.sentdata(h, -1); |
| 467 | h->u.o.defunct = TRUE; |
| 468 | } else { |
| 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); |
| 472 | } |
| 473 | } |
| 474 | } |
| 475 | |
| 476 | void handle_unthrottle(struct handle *h, int backlog) |
| 477 | { |
| 478 | assert(!h->output); |
| 479 | handle_throttle(&h->u.i, backlog); |
| 480 | } |
| 481 | |
| 482 | int handle_backlog(struct handle *h) |
| 483 | { |
| 484 | assert(h->output); |
| 485 | return bufchain_size(&h->u.o.queued_data); |
| 486 | } |