libusb/os/poll_windows.c

   1 /*
   2  * poll_windows: poll compatibility wrapper for Windows
   3  * Copyright © 2012-2013 RealVNC Ltd.
   4  * Copyright © 2009-2010 Pete Batard <pete@akeo.ie>
   5  * With contributions from Michael Plante, Orin Eman et al.
   6  * Parts of poll implementation from libusb-win32, by Stephan Meyer et al.
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  *
  22  */
  23
  24 /*
  25  * poll() and pipe() Windows compatibility layer for libusbx 1.0
  26  *
  27  * The way this layer works is by using OVERLAPPED with async I/O transfers, as
  28  * OVERLAPPED have an associated event which is flagged for I/O completion.
  29  *
  30  * For USB pollable async I/O, you would typically:
  31  * - obtain a Windows HANDLE to a file or device that has been opened in
  32  *   OVERLAPPED mode
  33  * - call usbi_create_fd with this handle to obtain a custom fd.
  34  *   Note that if you need simultaneous R/W access, you need to call create_fd
  35  *   twice, once in RW_READ and once in RW_WRITE mode to obtain 2 separate
  36  *   pollable fds
  37  * - leave the core functions call the poll routine and flag POLLIN/POLLOUT
  38  *
  39  * The pipe pollable synchronous I/O works using the overlapped event associated
  40  * with a fake pipe. The read/write functions are only meant to be used in that
  41  * context.
  42  */
  43 #include <errno.h>
  44 #include <stdio.h>
  45 #include <stdlib.h>
  46
  47 #include "libusbi.h"
  48
  49 // Uncomment to debug the polling layer
  50 //#define DEBUG_POLL_WINDOWS
  51 #if defined(DEBUG_POLL_WINDOWS)
  52 #define poll_dbg usbi_dbg
  53 #else
  54 // MSVC++ < 2005 cannot use a variadic argument and non MSVC
  55 // compilers produce warnings if parenthesis are ommitted.
  56 #if defined(_MSC_VER) && (_MSC_VER < 1400)
  57 #define poll_dbg
  58 #else
  59 #define poll_dbg(...)
  60 #endif
  61 #endif
  62
  63 #if defined(_PREFAST_)
  64 #pragma warning(disable:28719)
  65 #endif
  66
  67 #define CHECK_INIT_POLLING do {if(!is_polling_set) init_polling();} while(0)
  68
  69 // public fd data
  70 const struct winfd INVALID_WINFD = {-1, INVALID_HANDLE_VALUE, NULL, NULL, NULL, RW_NONE};
  71 struct winfd poll_fd[MAX_FDS];
  72 // internal fd data
  73 struct {
  74         CRITICAL_SECTION mutex; // lock for fds
  75         // Additional variables for XP CancelIoEx partial emulation
  76         HANDLE original_handle;
  77         DWORD thread_id;
  78 } _poll_fd[MAX_FDS];
  79
  80 // globals
  81 BOOLEAN is_polling_set = FALSE;
  82 LONG pipe_number = 0;
  83 static volatile LONG compat_spinlock = 0;
  84
  85 #if !defined(_WIN32_WCE)
  86 // CancelIoEx, available on Vista and later only, provides the ability to cancel
  87 // a single transfer (OVERLAPPED) when used. As it may not be part of any of the
  88 // platform headers, we hook into the Kernel32 system DLL directly to seek it.
  89 static BOOL (__stdcall *pCancelIoEx)(HANDLE, LPOVERLAPPED) = NULL;
  90 #define Use_Duplicate_Handles (pCancelIoEx == NULL)
  91
  92 static inline void setup_cancel_io(void)
  93 {
  94         HMODULE hKernel32 = GetModuleHandleA("KERNEL32");
  95         if (hKernel32 != NULL) {
  96                 pCancelIoEx = (BOOL (__stdcall *)(HANDLE,LPOVERLAPPED))
  97                         GetProcAddress(hKernel32, "CancelIoEx");
  98         }
  99         usbi_dbg("Will use CancelIo%s for I/O cancellation",
 100                 Use_Duplicate_Handles?"":"Ex");
 101 }
 102
 103 static inline BOOL cancel_io(int _index)
 104 {
 105         if ((_index < 0) || (_index >= MAX_FDS)) {
 106                 return FALSE;
 107         }
 108
 109         if ( (poll_fd[_index].fd < 0) || (poll_fd[_index].handle == INVALID_HANDLE_VALUE)
 110           || (poll_fd[_index].handle == 0) || (poll_fd[_index].overlapped == NULL) ) {
 111                 return TRUE;
 112         }
 113         if (poll_fd[_index].itransfer && poll_fd[_index].cancel_fn) {
 114                 // Cancel outstanding transfer via the specific callback
 115                 (*poll_fd[_index].cancel_fn)(poll_fd[_index].itransfer);
 116                 return TRUE;
 117         }
 118         if (pCancelIoEx != NULL) {
 119                 return (*pCancelIoEx)(poll_fd[_index].handle, poll_fd[_index].overlapped);
 120         }
 121         if (_poll_fd[_index].thread_id == GetCurrentThreadId()) {
 122                 return CancelIo(poll_fd[_index].handle);
 123         }
 124         usbi_warn(NULL, "Unable to cancel I/O that was started from another thread");
 125         return FALSE;
 126 }
 127 #else
 128 #define Use_Duplicate_Handles FALSE
 129
 130 static __inline void setup_cancel_io()
 131 {
 132         // No setup needed on WinCE
 133 }
 134
 135 static __inline BOOL cancel_io(int _index)
 136 {
 137         if ((_index < 0) || (_index >= MAX_FDS)) {
 138                 return FALSE;
 139         }
 140         if ( (poll_fd[_index].fd < 0) || (poll_fd[_index].handle == INVALID_HANDLE_VALUE)
 141           || (poll_fd[_index].handle == 0) || (poll_fd[_index].overlapped == NULL) ) {
 142                 return TRUE;
 143         }
 144         if (poll_fd[_index].itransfer && poll_fd[_index].cancel_fn) {
 145                 // Cancel outstanding transfer via the specific callback
 146                 (*poll_fd[_index].cancel_fn)(poll_fd[_index].itransfer);
 147         }
 148         return TRUE;
 149 }
 150 #endif
 151
 152 // Init
 153 void init_polling(void)
 154 {
 155         int i;
 156
 157         while (InterlockedExchange((LONG *)&compat_spinlock, 1) == 1) {
 158                 SleepEx(0, TRUE);
 159         }
 160         if (!is_polling_set) {
 161                 setup_cancel_io();
 162                 for (i=0; i<MAX_FDS; i++) {
 163                         poll_fd[i] = INVALID_WINFD;
 164                         _poll_fd[i].original_handle = INVALID_HANDLE_VALUE;
 165                         _poll_fd[i].thread_id = 0;
 166                         InitializeCriticalSection(&_poll_fd[i].mutex);
 167                 }
 168                 is_polling_set = TRUE;
 169         }
 170         InterlockedExchange((LONG *)&compat_spinlock, 0);
 171 }
 172
 173 // Internal function to retrieve the table index (and lock the fd mutex)
 174 static int _fd_to_index_and_lock(int fd)
 175 {
 176         int i;
 177
 178         if (fd < 0)
 179                 return -1;
 180
 181         for (i=0; i<MAX_FDS; i++) {
 182                 if (poll_fd[i].fd == fd) {
 183                         EnterCriticalSection(&_poll_fd[i].mutex);
 184                         // fd might have changed before we got to critical
 185                         if (poll_fd[i].fd != fd) {
 186                                 LeaveCriticalSection(&_poll_fd[i].mutex);
 187                                 continue;
 188                         }
 189                         return i;
 190                 }
 191         }
 192         return -1;
 193 }
 194
 195 static OVERLAPPED *create_overlapped(void)
 196 {
 197         OVERLAPPED *overlapped = (OVERLAPPED*) calloc(1, sizeof(OVERLAPPED));
 198         if (overlapped == NULL) {
 199                 return NULL;
 200         }
 201         overlapped->hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
 202         if(overlapped->hEvent == NULL) {
 203                 free (overlapped);
 204                 return NULL;
 205         }
 206         return overlapped;
 207 }
 208
 209 static void free_overlapped(OVERLAPPED *overlapped)
 210 {
 211         if (overlapped == NULL)
 212                 return;
 213
 214         if ( (overlapped->hEvent != 0)
 215           && (overlapped->hEvent != INVALID_HANDLE_VALUE) ) {
 216                 CloseHandle(overlapped->hEvent);
 217         }
 218         free(overlapped);
 219 }
 220
 221 void exit_polling(void)
 222 {
 223         int i;
 224
 225         while (InterlockedExchange((LONG *)&compat_spinlock, 1) == 1) {
 226                 SleepEx(0, TRUE);
 227         }
 228         if (is_polling_set) {
 229                 is_polling_set = FALSE;
 230
 231                 for (i=0; i<MAX_FDS; i++) {
 232                         // Cancel any async I/O (handle can be invalid)
 233                         cancel_io(i);
 234                         // If anything was pending on that I/O, it should be
 235                         // terminating, and we should be able to access the fd
 236                         // mutex lock before too long
 237                         EnterCriticalSection(&_poll_fd[i].mutex);
 238                         free_overlapped(poll_fd[i].overlapped);
 239                         if (Use_Duplicate_Handles) {
 240                                 // Close duplicate handle
 241                                 if (_poll_fd[i].original_handle != INVALID_HANDLE_VALUE) {
 242                                         CloseHandle(poll_fd[i].handle);
 243                                 }
 244                         }
 245                         poll_fd[i] = INVALID_WINFD;
 246                         LeaveCriticalSection(&_poll_fd[i].mutex);
 247                         DeleteCriticalSection(&_poll_fd[i].mutex);
 248                 }
 249         }
 250         InterlockedExchange((LONG *)&compat_spinlock, 0);
 251 }
 252
 253 /*
 254  * Create a fake pipe.
 255  * As libusbx only uses pipes for signaling, all we need from a pipe is an
 256  * event. To that extent, we create a single wfd and overlapped as a means
 257  * to access that event.
 258  */
 259 int usbi_pipe(int filedes[2])
 260 {
 261         int i;
 262         OVERLAPPED* overlapped;
 263
 264         CHECK_INIT_POLLING;
 265
 266         overlapped = create_overlapped();
 267
 268         if (overlapped == NULL) {
 269                 return -1;
 270         }
 271         // The overlapped must have status pending for signaling to work in poll
 272         overlapped->Internal = STATUS_PENDING;
 273         overlapped->InternalHigh = 0;
 274
 275         for (i=0; i<MAX_FDS; i++) {
 276                 if (poll_fd[i].fd < 0) {
 277                         EnterCriticalSection(&_poll_fd[i].mutex);
 278                         // fd might have been allocated before we got to critical
 279                         if (poll_fd[i].fd >= 0) {
 280                                 LeaveCriticalSection(&_poll_fd[i].mutex);
 281                                 continue;
 282                         }
 283
 284                         // Use index as the unique fd number
 285                         poll_fd[i].fd = i;
 286                         // Read end of the "pipe"
 287                         filedes[0] = poll_fd[i].fd;
 288                         // We can use the same handle for both ends
 289                         filedes[1] = filedes[0];
 290
 291                         poll_fd[i].handle = DUMMY_HANDLE;
 292                         poll_fd[i].overlapped = overlapped;
 293                         // There's no polling on the write end, so we just use READ for our needs
 294                         poll_fd[i].rw = RW_READ;
 295                         _poll_fd[i].original_handle = INVALID_HANDLE_VALUE;
 296                         LeaveCriticalSection(&_poll_fd[i].mutex);
 297                         return 0;
 298                 }
 299         }
 300         free_overlapped(overlapped);
 301         return -1;
 302 }
 303
 304 /*
 305  * Create both an fd and an OVERLAPPED from an open Windows handle, so that
 306  * it can be used with our polling function
 307  * The handle MUST support overlapped transfers (usually requires CreateFile
 308  * with FILE_FLAG_OVERLAPPED)
 309  * Return a pollable file descriptor struct, or INVALID_WINFD on error
 310  *
 311  * Note that the fd returned by this function is a per-transfer fd, rather
 312  * than a per-session fd and cannot be used for anything else but our
 313  * custom functions (the fd itself points to the NUL: device)
 314  * if you plan to do R/W on the same handle, you MUST create 2 fds: one for
 315  * read and one for write. Using a single R/W fd is unsupported and will
 316  * produce unexpected results
 317  */
 318 struct winfd usbi_create_fd(HANDLE handle, int access_mode, struct usbi_transfer *itransfer, cancel_transfer *cancel_fn)
 319 {
 320         int i;
 321         struct winfd wfd = INVALID_WINFD;
 322         OVERLAPPED* overlapped = NULL;
 323
 324         CHECK_INIT_POLLING;
 325
 326         if ((handle == 0) || (handle == INVALID_HANDLE_VALUE)) {
 327                 return INVALID_WINFD;
 328         }
 329
 330         wfd.itransfer = itransfer;
 331         wfd.cancel_fn = cancel_fn;
 332
 333         if ((access_mode != RW_READ) && (access_mode != RW_WRITE)) {
 334                 usbi_warn(NULL, "only one of RW_READ or RW_WRITE are supported.\n"
 335                         "If you want to poll for R/W simultaneously, create multiple fds from the same handle.");
 336                 return INVALID_WINFD;
 337         }
 338         if (access_mode == RW_READ) {
 339                 wfd.rw = RW_READ;
 340         } else {
 341                 wfd.rw = RW_WRITE;
 342         }
 343
 344         overlapped = create_overlapped();
 345         if(overlapped == NULL) {
 346                 return INVALID_WINFD;
 347         }
 348
 349         for (i=0; i<MAX_FDS; i++) {
 350                 if (poll_fd[i].fd < 0) {
 351                         EnterCriticalSection(&_poll_fd[i].mutex);
 352                         // fd might have been removed before we got to critical
 353                         if (poll_fd[i].fd >= 0) {
 354                                 LeaveCriticalSection(&_poll_fd[i].mutex);
 355                                 continue;
 356                         }
 357                         // Use index as the unique fd number
 358                         wfd.fd = i;
 359                         // Attempt to emulate some of the CancelIoEx behaviour on platforms
 360                         // that don't have it
 361                         if (Use_Duplicate_Handles) {
 362                                 _poll_fd[i].thread_id = GetCurrentThreadId();
 363                                 if (!DuplicateHandle(GetCurrentProcess(), handle, GetCurrentProcess(),
 364                                         &wfd.handle, 0, TRUE, DUPLICATE_SAME_ACCESS)) {
 365                                         usbi_dbg("could not duplicate handle for CancelIo - using original one");
 366                                         wfd.handle = handle;
 367                                         // Make sure we won't close the original handle on fd deletion then
 368                                         _poll_fd[i].original_handle = INVALID_HANDLE_VALUE;
 369                                 } else {
 370                                         _poll_fd[i].original_handle = handle;
 371                                 }
 372                         } else {
 373                                 wfd.handle = handle;
 374                         }
 375                         wfd.overlapped = overlapped;
 376                         memcpy(&poll_fd[i], &wfd, sizeof(struct winfd));
 377                         LeaveCriticalSection(&_poll_fd[i].mutex);
 378                         return wfd;
 379                 }
 380         }
 381         free_overlapped(overlapped);
 382         return INVALID_WINFD;
 383 }
 384
 385 static void _free_index(int _index)
 386 {
 387         // Cancel any async IO (Don't care about the validity of our handles for this)
 388         cancel_io(_index);
 389         // close the duplicate handle (if we have an actual duplicate)
 390         if (Use_Duplicate_Handles) {
 391                 if (_poll_fd[_index].original_handle != INVALID_HANDLE_VALUE) {
 392                         CloseHandle(poll_fd[_index].handle);
 393                 }
 394                 _poll_fd[_index].original_handle = INVALID_HANDLE_VALUE;
 395                 _poll_fd[_index].thread_id = 0;
 396         }
 397         free_overlapped(poll_fd[_index].overlapped);
 398         poll_fd[_index] = INVALID_WINFD;
 399 }
 400
 401 /*
 402  * Release a pollable file descriptor.
 403  *
 404  * Note that the associated Windows handle is not closed by this call
 405  */
 406 void usbi_free_fd(int fd)
 407 {
 408         int _index;
 409
 410         CHECK_INIT_POLLING;
 411
 412         _index = _fd_to_index_and_lock(fd);
 413         if (_index < 0) {
 414                 return;
 415         }
 416         _free_index(_index);
 417         LeaveCriticalSection(&_poll_fd[_index].mutex);
 418 }
 419
 420 /*
 421  * The functions below perform various conversions between fd, handle and OVERLAPPED
 422  */
 423 struct winfd fd_to_winfd(int fd)
 424 {
 425         int i;
 426         struct winfd wfd;
 427
 428         CHECK_INIT_POLLING;
 429
 430         if (fd <= 0)
 431                 return INVALID_WINFD;
 432
 433         for (i=0; i<MAX_FDS; i++) {
 434                 if (poll_fd[i].fd == fd) {
 435                         EnterCriticalSection(&_poll_fd[i].mutex);
 436                         // fd might have been deleted before we got to critical
 437                         if (poll_fd[i].fd != fd) {
 438                                 LeaveCriticalSection(&_poll_fd[i].mutex);
 439                                 continue;
 440                         }
 441                         memcpy(&wfd, &poll_fd[i], sizeof(struct winfd));
 442                         LeaveCriticalSection(&_poll_fd[i].mutex);
 443                         return wfd;
 444                 }
 445         }
 446         return INVALID_WINFD;
 447 }
 448
 449 struct winfd handle_to_winfd(HANDLE handle)
 450 {
 451         int i;
 452         struct winfd wfd;
 453
 454         CHECK_INIT_POLLING;
 455
 456         if ((handle == 0) || (handle == INVALID_HANDLE_VALUE))
 457                 return INVALID_WINFD;
 458
 459         for (i=0; i<MAX_FDS; i++) {
 460                 if (poll_fd[i].handle == handle) {
 461                         EnterCriticalSection(&_poll_fd[i].mutex);
 462                         // fd might have been deleted before we got to critical
 463                         if (poll_fd[i].handle != handle) {
 464                                 LeaveCriticalSection(&_poll_fd[i].mutex);
 465                                 continue;
 466                         }
 467                         memcpy(&wfd, &poll_fd[i], sizeof(struct winfd));
 468                         LeaveCriticalSection(&_poll_fd[i].mutex);
 469                         return wfd;
 470                 }
 471         }
 472         return INVALID_WINFD;
 473 }
 474
 475 struct winfd overlapped_to_winfd(OVERLAPPED* overlapped)
 476 {
 477         int i;
 478         struct winfd wfd;
 479
 480         CHECK_INIT_POLLING;
 481
 482         if (overlapped == NULL)
 483                 return INVALID_WINFD;
 484
 485         for (i=0; i<MAX_FDS; i++) {
 486                 if (poll_fd[i].overlapped == overlapped) {
 487                         EnterCriticalSection(&_poll_fd[i].mutex);
 488                         // fd might have been deleted before we got to critical
 489                         if (poll_fd[i].overlapped != overlapped) {
 490                                 LeaveCriticalSection(&_poll_fd[i].mutex);
 491                                 continue;
 492                         }
 493                         memcpy(&wfd, &poll_fd[i], sizeof(struct winfd));
 494                         LeaveCriticalSection(&_poll_fd[i].mutex);
 495                         return wfd;
 496                 }
 497         }
 498         return INVALID_WINFD;
 499 }
 500
 501 /*
 502  * POSIX poll equivalent, using Windows OVERLAPPED
 503  * Currently, this function only accepts one of POLLIN or POLLOUT per fd
 504  * (but you can create multiple fds from the same handle for read and write)
 505  */
 506 int usbi_poll(struct pollfd *fds, unsigned int nfds, int timeout)
 507 {
 508         unsigned i;
 509         int _index, object_index, triggered;
 510         HANDLE *handles_to_wait_on;
 511         int *handle_to_index;
 512         DWORD nb_handles_to_wait_on = 0;
 513         DWORD ret;
 514
 515         CHECK_INIT_POLLING;
 516
 517         triggered = 0;
 518         handles_to_wait_on = (HANDLE*) calloc(nfds+1, sizeof(HANDLE));  // +1 for fd_update
 519         handle_to_index = (int*) calloc(nfds, sizeof(int));
 520         if ((handles_to_wait_on == NULL) || (handle_to_index == NULL)) {
 521                 errno = ENOMEM;
 522                 triggered = -1;
 523                 goto poll_exit;
 524         }
 525
 526         for (i = 0; i < nfds; ++i) {
 527                 fds[i].revents = 0;
 528
 529                 // Only one of POLLIN or POLLOUT can be selected with this version of poll (not both)
 530                 if ((fds[i].events & ~POLLIN) && (!(fds[i].events & POLLOUT))) {
 531                         fds[i].revents |= POLLERR;
 532                         errno = EACCES;
 533                         usbi_warn(NULL, "unsupported set of events");
 534                         triggered = -1;
 535                         goto poll_exit;
 536                 }
 537
 538                 _index = _fd_to_index_and_lock(fds[i].fd);
 539                 poll_dbg("fd[%d]=%d: (overlapped=%p) got events %04X", i, poll_fd[_index].fd, poll_fd[_index].overlapped, fds[i].events);
 540
 541                 if ( (_index < 0) || (poll_fd[_index].handle == INVALID_HANDLE_VALUE)
 542                   || (poll_fd[_index].handle == 0) || (poll_fd[_index].overlapped == NULL)) {
 543                         fds[i].revents |= POLLNVAL | POLLERR;
 544                         errno = EBADF;
 545                         if (_index >= 0) {
 546                                 LeaveCriticalSection(&_poll_fd[_index].mutex);
 547                         }
 548                         usbi_warn(NULL, "invalid fd");
 549                         triggered = -1;
 550                         goto poll_exit;
 551                 }
 552
 553                 // IN or OUT must match our fd direction
 554                 if ((fds[i].events & POLLIN) && (poll_fd[_index].rw != RW_READ)) {
 555                         fds[i].revents |= POLLNVAL | POLLERR;
 556                         errno = EBADF;
 557                         usbi_warn(NULL, "attempted POLLIN on fd without READ access");
 558                         LeaveCriticalSection(&_poll_fd[_index].mutex);
 559                         triggered = -1;
 560                         goto poll_exit;
 561                 }
 562
 563                 if ((fds[i].events & POLLOUT) && (poll_fd[_index].rw != RW_WRITE)) {
 564                         fds[i].revents |= POLLNVAL | POLLERR;
 565                         errno = EBADF;
 566                         usbi_warn(NULL, "attempted POLLOUT on fd without WRITE access");
 567                         LeaveCriticalSection(&_poll_fd[_index].mutex);
 568                         triggered = -1;
 569                         goto poll_exit;
 570                 }
 571
 572                 // The following macro only works if overlapped I/O was reported pending
 573                 if ( (HasOverlappedIoCompleted(poll_fd[_index].overlapped))
 574                   || (HasOverlappedIoCompletedSync(poll_fd[_index].overlapped)) ) {
 575                         poll_dbg("  completed");
 576                         // checks above should ensure this works:
 577                         fds[i].revents = fds[i].events;
 578                         triggered++;
 579                 } else {
 580                         handles_to_wait_on[nb_handles_to_wait_on] = poll_fd[_index].overlapped->hEvent;
 581                         handle_to_index[nb_handles_to_wait_on] = i;
 582                         nb_handles_to_wait_on++;
 583                 }
 584                 LeaveCriticalSection(&_poll_fd[_index].mutex);
 585         }
 586
 587         // If nothing was triggered, wait on all fds that require it
 588         if ((timeout != 0) && (triggered == 0) && (nb_handles_to_wait_on != 0)) {
 589                 if (timeout < 0) {
 590                         poll_dbg("starting infinite wait for %d handles...", (int)nb_handles_to_wait_on);
 591                 } else {
 592                         poll_dbg("starting %d ms wait for %d handles...", timeout, (int)nb_handles_to_wait_on);
 593                 }
 594                 ret = WaitForMultipleObjects(nb_handles_to_wait_on, handles_to_wait_on,
 595                         FALSE, (timeout<0)?INFINITE:(DWORD)timeout);
 596                 object_index = ret-WAIT_OBJECT_0;
 597                 if ((object_index >= 0) && ((DWORD)object_index < nb_handles_to_wait_on)) {
 598                         poll_dbg("  completed after wait");
 599                         i = handle_to_index[object_index];
 600                         _index = _fd_to_index_and_lock(fds[i].fd);
 601                         fds[i].revents = fds[i].events;
 602                         triggered++;
 603                         if (_index >= 0) {
 604                                 LeaveCriticalSection(&_poll_fd[_index].mutex);
 605                         }
 606                 } else if (ret == WAIT_TIMEOUT) {
 607                         poll_dbg("  timed out");
 608                         triggered = 0;  // 0 = timeout
 609                 } else {
 610                         errno = EIO;
 611                         triggered = -1; // error
 612                 }
 613         }
 614
 615 poll_exit:
 616         if (handles_to_wait_on != NULL) {
 617                 free(handles_to_wait_on);
 618         }
 619         if (handle_to_index != NULL) {
 620                 free(handle_to_index);
 621         }
 622         return triggered;
 623 }
 624
 625 /*
 626  * close a fake pipe fd
 627  */
 628 int usbi_close(int fd)
 629 {
 630         int _index;
 631         int r = -1;
 632
 633         CHECK_INIT_POLLING;
 634
 635         _index = _fd_to_index_and_lock(fd);
 636
 637         if (_index < 0) {
 638                 errno = EBADF;
 639         } else {
 640                 free_overlapped(poll_fd[_index].overlapped);
 641                 poll_fd[_index] = INVALID_WINFD;
 642                 LeaveCriticalSection(&_poll_fd[_index].mutex);
 643         }
 644         return r;
 645 }
 646
 647 /*
 648  * synchronous write for fake "pipe" signaling
 649  */
 650 ssize_t usbi_write(int fd, const void *buf, size_t count)
 651 {
 652         int _index;
 653         UNUSED(buf);
 654
 655         CHECK_INIT_POLLING;
 656
 657         if (count != sizeof(unsigned char)) {
 658                 usbi_err(NULL, "this function should only used for signaling");
 659                 return -1;
 660         }
 661
 662         _index = _fd_to_index_and_lock(fd);
 663
 664         if ( (_index < 0) || (poll_fd[_index].overlapped == NULL) ) {
 665                 errno = EBADF;
 666                 if (_index >= 0) {
 667                         LeaveCriticalSection(&_poll_fd[_index].mutex);
 668                 }
 669                 return -1;
 670         }
 671
 672         poll_dbg("set pipe event (fd = %d, thread = %08X)", _index, GetCurrentThreadId());
 673         SetEvent(poll_fd[_index].overlapped->hEvent);
 674         poll_fd[_index].overlapped->Internal = STATUS_WAIT_0;
 675         // If two threads write on the pipe at the same time, we need to
 676         // process two separate reads => use the overlapped as a counter
 677         poll_fd[_index].overlapped->InternalHigh++;
 678
 679         LeaveCriticalSection(&_poll_fd[_index].mutex);
 680         return sizeof(unsigned char);
 681 }
 682
 683 /*
 684  * synchronous read for fake "pipe" signaling
 685  */
 686 ssize_t usbi_read(int fd, void *buf, size_t count)
 687 {
 688         int _index;
 689         ssize_t r = -1;
 690         UNUSED(buf);
 691
 692         CHECK_INIT_POLLING;
 693
 694         if (count != sizeof(unsigned char)) {
 695                 usbi_err(NULL, "this function should only used for signaling");
 696                 return -1;
 697         }
 698
 699         _index = _fd_to_index_and_lock(fd);
 700
 701         if (_index < 0) {
 702                 errno = EBADF;
 703                 return -1;
 704         }
 705
 706         if (WaitForSingleObject(poll_fd[_index].overlapped->hEvent, INFINITE) != WAIT_OBJECT_0) {
 707                 usbi_warn(NULL, "waiting for event failed: %d", (int)GetLastError());
 708                 errno = EIO;
 709                 goto out;
 710         }
 711
 712         poll_dbg("clr pipe event (fd = %d, thread = %08X)", _index, GetCurrentThreadId());
 713         poll_fd[_index].overlapped->InternalHigh--;
 714         // Don't reset unless we don't have any more events to process
 715         if (poll_fd[_index].overlapped->InternalHigh <= 0) {
 716                 ResetEvent(poll_fd[_index].overlapped->hEvent);
 717                 poll_fd[_index].overlapped->Internal = STATUS_PENDING;
 718         }
 719
 720         r = sizeof(unsigned char);
 721
 722 out:
 723         LeaveCriticalSection(&_poll_fd[_index].mutex);
 724         return r;
 725 }