Import libusb 1.0.9-rc3 into third_party

third_party/libusb/libusb/os/poll_windows.c

+/*
+ * poll_windows: poll compatibility wrapper for Windows
+ * Copyright (C) 2009-2010 Pete Batard <pbatard@gmail.com>
+ * With contributions from Michael Plante, Orin Eman et al.
+ * Parts of poll implementation from libusb-win32, by Stephan Meyer et al.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ */
+
+/*
+ * poll() and pipe() Windows compatibility layer for libusb 1.0
+ *
+ * The way this layer works is by using OVERLAPPED with async I/O transfers, as
+ * OVERLAPPED have an associated event which is flagged for I/O completion.
+ *
+ * For USB pollable async I/O, you would typically:
+ * - obtain a Windows HANDLE to a file or device that has been opened in
+ *   OVERLAPPED mode
+ * - call usbi_create_fd with this handle to obtain a custom fd.
+ *   Note that if you need simultaneous R/W access, you need to call create_fd
+ *   twice, once in _O_RDONLY and once in _O_WRONLY mode to obtain 2 separate
+ *   pollable fds
+ * - leave the core functions call the poll routine and flag POLLIN/POLLOUT
+ *
+ * The pipe pollable synchronous I/O works using the overlapped event associated
+ * with a fake pipe. The read/write functions are only meant to be used in that
+ * context.
+ */
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <io.h>
+
+#include <libusbi.h>
+
+// Uncomment to debug the polling layer
+//#define DEBUG_POLL_WINDOWS
+#if defined(DEBUG_POLL_WINDOWS)
+#define poll_dbg usbi_dbg
+#else
+// MSVC6 cannot use a variadic argument and non MSVC
+// compilers produce warnings if parenthesis are ommitted.
+#if defined(_MSC_VER)
+#define poll_dbg
+#else
+#define poll_dbg(...)
+#endif
+#endif
+
+#if defined(_PREFAST_)
+#pragma warning(disable:28719)
+#endif
+
+#if defined(__CYGWIN__)
+// cygwin produces a warning unless these prototypes are defined
+extern int _open(char* name, int flags);
+extern int _close(int fd);
+extern int _snprintf(char *buffer, size_t count, const char *format, ...);
+#define NUL_DEVICE "/dev/null"
+#else
+#define NUL_DEVICE "NUL"
+#endif
+
+#define CHECK_INIT_POLLING do {if(!is_polling_set) init_polling();} while(0)
+
+// public fd data
+const struct winfd INVALID_WINFD = {-1, INVALID_HANDLE_VALUE, NULL, RW_NONE};
+struct winfd poll_fd[MAX_FDS];
+// internal fd data
+struct {
+        CRITICAL_SECTION mutex; // lock for fds
+        // Additional variables for XP CancelIoEx partial emulation
+        HANDLE original_handle;
+        DWORD thread_id;
+} _poll_fd[MAX_FDS];
+
+// globals
+BOOLEAN is_polling_set = FALSE;
+#if defined(DYNAMIC_FDS)
+HANDLE fd_update = INVALID_HANDLE_VALUE;        // event to notify poll of fd update
+HANDLE new_fd[MAX_FDS];         // overlapped event handles for fds created since last poll
+unsigned nb_new_fds = 0;        // nb new fds created since last poll
+usbi_mutex_t new_fd_mutex;      // mutex required for the above
+#endif
+LONG pipe_number = 0;
+static volatile LONG compat_spinlock = 0;
+
+// CancelIoEx, available on Vista and later only, provides the ability to cancel
+// a single transfer (OVERLAPPED) when used. As it may not be part of any of the
+// platform headers, we hook into the Kernel32 system DLL directly to seek it.
+static BOOL (__stdcall *pCancelIoEx)(HANDLE, LPOVERLAPPED) = NULL;
+#define CancelIoEx_Available (pCancelIoEx != NULL)
+static __inline BOOL cancel_io(int _index)
+{
+        if ((_index < 0) || (_index >= MAX_FDS)) {
+                return FALSE;
+        }
+
+        if ( (poll_fd[_index].fd < 0) || (poll_fd[_index].handle == INVALID_HANDLE_VALUE)
+          || (poll_fd[_index].handle == 0) || (poll_fd[_index].overlapped == NULL) ) {
+                return TRUE;
+        }
+        if (CancelIoEx_Available) {
+                return (*pCancelIoEx)(poll_fd[_index].handle, poll_fd[_index].overlapped);
+        }
+        if (_poll_fd[_index].thread_id == GetCurrentThreadId()) {
+                return CancelIo(poll_fd[_index].handle);
+        }
+        usbi_warn(NULL, "Unable to cancel I/O that was started from another thread");
+        return FALSE;
+}
+
+// Init
+void init_polling(void)
+{
+        int i;
+
+        while (InterlockedExchange((LONG *)&compat_spinlock, 1) == 1) {
+                SleepEx(0, TRUE);
+        }
+        if (!is_polling_set) {
+                pCancelIoEx = (BOOL (__stdcall *)(HANDLE,LPOVERLAPPED))
+                        GetProcAddress(GetModuleHandleA("KERNEL32"), "CancelIoEx");
+                usbi_dbg("Will use CancelIo%s for I/O cancellation",
+                        CancelIoEx_Available?"Ex":"");
+                for (i=0; i<MAX_FDS; i++) {
+                        poll_fd[i] = INVALID_WINFD;
+                        _poll_fd[i].original_handle = INVALID_HANDLE_VALUE;
+                        _poll_fd[i].thread_id = 0;
+                        InitializeCriticalSection(&_poll_fd[i].mutex);
+                }
+#if defined(DYNAMIC_FDS)
+                // We need to create an update event so that poll is warned when there
+                // are new/deleted fds during a timeout wait operation
+                fd_update = CreateEvent(NULL, TRUE, FALSE, NULL);
+                if (fd_update == NULL) {
+                        usbi_err(NULL, "unable to create update event");
+                }
+                usbi_mutex_init(&new_fd_mutex, NULL);
+                nb_new_fds = 0;
+#endif
+                is_polling_set = TRUE;
+        }
+        compat_spinlock = 0;
+}
+
+// Internal function to retrieve the table index (and lock the fd mutex)
+int _fd_to_index_and_lock(int fd)
+{
+        int i;
+
+        if (fd <= 0)
+                return -1;
+
+        for (i=0; i<MAX_FDS; i++) {
+                if (poll_fd[i].fd == fd) {
+                        EnterCriticalSection(&_poll_fd[i].mutex);
+                        // fd might have changed before we got to critical
+                        if (poll_fd[i].fd != fd) {
+                                LeaveCriticalSection(&_poll_fd[i].mutex);
+                                continue;
+                        }
+                        return i;
+                }
+        }
+        return -1;
+}
+
+OVERLAPPED *create_overlapped(void)
+{
+        OVERLAPPED *overlapped = calloc(1, sizeof(OVERLAPPED));
+        if (overlapped == NULL) {
+                return NULL;
+        }
+        overlapped->hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
+        if(overlapped->hEvent == NULL) {
+                free (overlapped);
+                return NULL;
+        }
+        return overlapped;
+}
+
+void free_overlapped(OVERLAPPED *overlapped)
+{
+        if (overlapped == NULL)
+                return;
+
+        if ( (overlapped->hEvent != 0)
+          && (overlapped->hEvent != INVALID_HANDLE_VALUE) ) {
+                CloseHandle(overlapped->hEvent);
+        }
+        free(overlapped);
+}
+
+void reset_overlapped(OVERLAPPED *overlapped)
+{
+        HANDLE event_handle;
+        if (overlapped == NULL)
+                return;
+
+        event_handle = overlapped->hEvent;
+        if (event_handle != NULL) {
+                ResetEvent(event_handle);
+        }
+        memset(overlapped, 0, sizeof(OVERLAPPED));
+        overlapped->hEvent = event_handle;
+}
+
+void exit_polling(void)
+{
+        int i;
+
+        while (InterlockedExchange((LONG *)&compat_spinlock, 1) == 1) {
+                SleepEx(0, TRUE);
+        }
+        if (is_polling_set) {
+                is_polling_set = FALSE;
+
+                for (i=0; i<MAX_FDS; i++) {
+                        // Cancel any async I/O (handle can be invalid)
+                        cancel_io(i);
+                        // If anything was pending on that I/O, it should be
+                        // terminating, and we should be able to access the fd
+                        // mutex lock before too long
+                        EnterCriticalSection(&_poll_fd[i].mutex);
+                        if ( (poll_fd[i].fd > 0) && (poll_fd[i].handle != INVALID_HANDLE_VALUE) && (poll_fd[i].handle != 0)
+                          && (GetFileType(poll_fd[i].handle) == FILE_TYPE_UNKNOWN) ) {
+                                _close(poll_fd[i].fd);
+                        }
+                        free_overlapped(poll_fd[i].overlapped);
+                        if (!CancelIoEx_Available) {
+                                // Close duplicate handle
+                                if (_poll_fd[i].original_handle != INVALID_HANDLE_VALUE) {
+                                        CloseHandle(poll_fd[i].handle);
+                                }
+                        }
+                        poll_fd[i] = INVALID_WINFD;
+#if defined(DYNAMIC_FDS)
+                        usbi_mutex_destroy(&new_fd_mutex);
+                        CloseHandle(fd_update);
+                        fd_update = INVALID_HANDLE_VALUE;
+#endif
+                        LeaveCriticalSection(&_poll_fd[i].mutex);
+                        DeleteCriticalSection(&_poll_fd[i].mutex);
+                }
+        }
+        compat_spinlock = 0;
+}
+
+/*
+ * Create a fake pipe.
+ * As libusb only uses pipes for signaling, all we need from a pipe is an
+ * event. To that extent, we create a single wfd and overlapped as a means
+ * to access that event.
+ */
+int usbi_pipe(int filedes[2])
+{
+        int i;
+        OVERLAPPED* overlapped;
+
+        CHECK_INIT_POLLING;
+
+        overlapped = calloc(1, sizeof(OVERLAPPED));
+        if (overlapped == NULL) {
+                return -1;
+        }
+        // The overlapped must have status pending for signaling to work in poll
+        overlapped->Internal = STATUS_PENDING;
+        overlapped->InternalHigh = 0;
+
+        // Read end of the "pipe"
+        filedes[0] = _open(NUL_DEVICE, _O_WRONLY);
+        if (filedes[0] < 0) {
+                usbi_err(NULL, "could not create pipe: errno %d", errno);
+                goto out1;
+        }
+        // We can use the same handle for both ends
+        filedes[1] = filedes[0];
+        poll_dbg("pipe filedes = %d", filedes[0]);
+
+        // Note: manual reset must be true (second param) as the reset occurs in read
+        overlapped->hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
+        if(!overlapped->hEvent) {
+                goto out2;
+        }
+
+        for (i=0; i<MAX_FDS; i++) {
+                if (poll_fd[i].fd < 0) {
+                        EnterCriticalSection(&_poll_fd[i].mutex);
+                        // fd might have been allocated before we got to critical
+                        if (poll_fd[i].fd >= 0) {
+                                LeaveCriticalSection(&_poll_fd[i].mutex);
+                                continue;
+                        }
+
+                        poll_fd[i].fd = filedes[0];
+                        poll_fd[i].handle = DUMMY_HANDLE;
+                        poll_fd[i].overlapped = overlapped;
+                        // There's no polling on the write end, so we just use READ for our needs
+                        poll_fd[i].rw = RW_READ;
+                        _poll_fd[i].original_handle = INVALID_HANDLE_VALUE;
+                        LeaveCriticalSection(&_poll_fd[i].mutex);
+                        return 0;
+                }
+        }
+
+        CloseHandle(overlapped->hEvent);
+out2:
+        _close(filedes[0]);
+out1:
+        free(overlapped);
+        return -1;
+}
+
+/*
+ * Create both an fd and an OVERLAPPED from an open Windows handle, so that
+ * it can be used with our polling function
+ * The handle MUST support overlapped transfers (usually requires CreateFile
+ * with FILE_FLAG_OVERLAPPED)
+ * Return a pollable file descriptor struct, or INVALID_WINFD on error
+ *
+ * Note that the fd returned by this function is a per-transfer fd, rather
+ * than a per-session fd and cannot be used for anything else but our
+ * custom functions (the fd itself points to the NUL: device)
+ * if you plan to do R/W on the same handle, you MUST create 2 fds: one for
+ * read and one for write. Using a single R/W fd is unsupported and will
+ * produce unexpected results
+ */
+struct winfd usbi_create_fd(HANDLE handle, int access_mode)
+{
+        int i, fd;
+        struct winfd wfd = INVALID_WINFD;
+        OVERLAPPED* overlapped = NULL;
+
+        CHECK_INIT_POLLING;
+
+        if ((handle == 0) || (handle == INVALID_HANDLE_VALUE)) {
+                return INVALID_WINFD;
+        }
+
+        if ((access_mode != _O_RDONLY) && (access_mode != _O_WRONLY)) {
+                usbi_warn(NULL, "only one of _O_RDONLY or _O_WRONLY are supported.\n"
+                        "If you want to poll for R/W simultaneously, create multiple fds from the same handle.");
+                return INVALID_WINFD;
+        }
+        if (access_mode == _O_RDONLY) {
+                wfd.rw = RW_READ;
+        } else {
+                wfd.rw = RW_WRITE;
+        }
+
+        // Ensure that we get a non system conflicting unique fd, using
+        // the same fd attribution system as the pipe ends
+        fd = _open(NUL_DEVICE, _O_WRONLY);
+        if (fd < 0) {
+                return INVALID_WINFD;
+        }
+
+        overlapped = create_overlapped();
+        if(overlapped == NULL) {
+                _close(fd);
+                return INVALID_WINFD;
+        }
+
+        for (i=0; i<MAX_FDS; i++) {
+                if (poll_fd[i].fd < 0) {
+                        EnterCriticalSection(&_poll_fd[i].mutex);
+                        // fd might have been removed before we got to critical
+                        if (poll_fd[i].fd >= 0) {
+                                LeaveCriticalSection(&_poll_fd[i].mutex);
+                                continue;
+                        }
+                        wfd.fd = fd;
+                        // Attempt to emulate some of the CancelIoEx behaviour on platforms
+                        // that don't have it
+                        if (!CancelIoEx_Available) {
+                                _poll_fd[i].thread_id = GetCurrentThreadId();
+                                if (!DuplicateHandle(GetCurrentProcess(), handle, GetCurrentProcess(),
+                                        &wfd.handle, 0, TRUE, DUPLICATE_SAME_ACCESS)) {
+                                        usbi_dbg("could not duplicate handle for CancelIo - using original one");
+                                        wfd.handle = handle;
+                                        // Make sure we won't close the original handle on fd deletion then
+                                        _poll_fd[i].original_handle = INVALID_HANDLE_VALUE;
+                                } else {
+                                        _poll_fd[i].original_handle = handle;
+                                }
+                        } else {
+                                wfd.handle = handle;
+                        }
+                        wfd.overlapped = overlapped;
+                        memcpy(&poll_fd[i], &wfd, sizeof(struct winfd));
+                        LeaveCriticalSection(&_poll_fd[i].mutex);
+#if defined(DYNAMIC_FDS)
+                        usbi_mutex_lock(&new_fd_mutex);
+                        new_fd[nb_new_fds++] = overlapped->hEvent;
+                        usbi_mutex_unlock(&new_fd_mutex);
+                        // Notify poll that fds have been updated
+                        SetEvent(fd_update);
+#endif
+                        return wfd;
+                }
+        }
+        free_overlapped(overlapped);
+        _close(fd);
+        return INVALID_WINFD;
+}
+
+void _free_index(int _index)
+{
+        // Cancel any async IO (Don't care about the validity of our handles for this)
+        cancel_io(_index);
+        // close fake handle for devices
+        if ( (poll_fd[_index].handle != INVALID_HANDLE_VALUE) && (poll_fd[_index].handle != 0)
+          && (GetFileType(poll_fd[_index].handle) == FILE_TYPE_UNKNOWN) ) {
+                _close(poll_fd[_index].fd);
+        }
+        // close the duplicate handle (if we have an actual duplicate)
+        if (!CancelIoEx_Available) {
+                if (_poll_fd[_index].original_handle != INVALID_HANDLE_VALUE) {
+                        CloseHandle(poll_fd[_index].handle);
+                }
+                _poll_fd[_index].original_handle = INVALID_HANDLE_VALUE;
+                _poll_fd[_index].thread_id = 0;
+        }
+        free_overlapped(poll_fd[_index].overlapped);
+        poll_fd[_index] = INVALID_WINFD;
+}
+
+/*
+ * Release a pollable file descriptor.
+ *
+ * Note that the associated Windows handle is not closed by this call
+ */
+void usbi_free_fd(int fd)
+{
+        int _index;
+
+        CHECK_INIT_POLLING;
+
+        _index = _fd_to_index_and_lock(fd);
+        if (_index < 0) {
+                return;
+        }
+        _free_index(_index);
+        LeaveCriticalSection(&_poll_fd[_index].mutex);
+}
+
+/*
+ * The functions below perform various conversions between fd, handle and OVERLAPPED
+ */
+struct winfd fd_to_winfd(int fd)
+{
+        int i;
+        struct winfd wfd;
+
+        CHECK_INIT_POLLING;
+
+        if (fd <= 0)
+                return INVALID_WINFD;
+
+        for (i=0; i<MAX_FDS; i++) {
+                if (poll_fd[i].fd == fd) {
+                        EnterCriticalSection(&_poll_fd[i].mutex);
+                        // fd might have been deleted before we got to critical
+                        if (poll_fd[i].fd != fd) {
+                                LeaveCriticalSection(&_poll_fd[i].mutex);
+                                continue;
+                        }
+                        memcpy(&wfd, &poll_fd[i], sizeof(struct winfd));
+                        LeaveCriticalSection(&_poll_fd[i].mutex);
+                        return wfd;
+                }
+        }
+        return INVALID_WINFD;
+}
+
+struct winfd handle_to_winfd(HANDLE handle)
+{
+        int i;
+        struct winfd wfd;
+
+        CHECK_INIT_POLLING;
+
+        if ((handle == 0) || (handle == INVALID_HANDLE_VALUE))
+                return INVALID_WINFD;
+
+        for (i=0; i<MAX_FDS; i++) {
+                if (poll_fd[i].handle == handle) {
+                        EnterCriticalSection(&_poll_fd[i].mutex);
+                        // fd might have been deleted before we got to critical
+                        if (poll_fd[i].handle != handle) {
+                                LeaveCriticalSection(&_poll_fd[i].mutex);
+                                continue;
+                        }
+                        memcpy(&wfd, &poll_fd[i], sizeof(struct winfd));
+                        LeaveCriticalSection(&_poll_fd[i].mutex);
+                        return wfd;
+                }
+        }
+        return INVALID_WINFD;
+}
+
+struct winfd overlapped_to_winfd(OVERLAPPED* overlapped)
+{
+        int i;
+        struct winfd wfd;
+
+        CHECK_INIT_POLLING;
+
+        if (overlapped == NULL)
+                return INVALID_WINFD;
+
+        for (i=0; i<MAX_FDS; i++) {
+                if (poll_fd[i].overlapped == overlapped) {
+                        EnterCriticalSection(&_poll_fd[i].mutex);
+                        // fd might have been deleted before we got to critical
+                        if (poll_fd[i].overlapped != overlapped) {
+                                LeaveCriticalSection(&_poll_fd[i].mutex);
+                                continue;
+                        }
+                        memcpy(&wfd, &poll_fd[i], sizeof(struct winfd));
+                        LeaveCriticalSection(&_poll_fd[i].mutex);
+                        return wfd;
+                }
+        }
+        return INVALID_WINFD;
+}
+
+/*
+ * POSIX poll equivalent, using Windows OVERLAPPED
+ * Currently, this function only accepts one of POLLIN or POLLOUT per fd
+ * (but you can create multiple fds from the same handle for read and write)
+ */
+int usbi_poll(struct pollfd *fds, unsigned int nfds, int timeout)
+{
+        unsigned i;
+        int _index, object_index, triggered;
+        HANDLE *handles_to_wait_on;
+        int *handle_to_index;
+        DWORD nb_handles_to_wait_on = 0;
+        DWORD ret;
+
+#if defined(DYNAMIC_FDS)
+        DWORD nb_extra_handles = 0;
+        unsigned j;
+
+        // To address the possibility of missing new fds between the time the new
+        // pollable fd set is assembled, and the ResetEvent() call below, an
+        // additional new_fd[] HANDLE table is used for any new fd that was created
+        // since the last call to poll (see below)
+        ResetEvent(fd_update);
+
+        // At this stage, any new fd creation will be detected through the fd_update
+        // event notification, and any previous creation that we may have missed
+        // will be picked up through the existing new_fd[] table.
+#endif
+
+        CHECK_INIT_POLLING;
+
+        triggered = 0;
+        handles_to_wait_on = malloc((nfds+1)*sizeof(HANDLE));   // +1 for fd_update
+        handle_to_index = malloc(nfds*sizeof(int));
+        if ((handles_to_wait_on == NULL) || (handle_to_index == NULL)) {
+                errno = ENOMEM;
+                triggered = -1;
+                goto poll_exit;
+        }
+
+        for (i = 0; i < nfds; ++i) {
+                fds[i].revents = 0;
+
+                // Only one of POLLIN or POLLOUT can be selected with this version of poll (not both)
+                if ((fds[i].events & ~POLLIN) && (!(fds[i].events & POLLOUT))) {
+                        fds[i].revents |= POLLERR;
+                        errno = EACCES;
+                        usbi_warn(NULL, "unsupported set of events");
+                        triggered = -1;
+                        goto poll_exit;
+                }
+
+                _index = _fd_to_index_and_lock(fds[i].fd);
+                poll_dbg("fd[%d]=%d: (overlapped=%p) got events %04X", i, poll_fd[_index].fd, poll_fd[_index].overlapped, fds[i].events);
+
+                if ( (_index < 0) || (poll_fd[_index].handle == INVALID_HANDLE_VALUE)
+                  || (poll_fd[_index].handle == 0) || (poll_fd[_index].overlapped == NULL)) {
+                        fds[i].revents |= POLLNVAL | POLLERR;
+                        errno = EBADF;
+                        if (_index >= 0) {
+                                LeaveCriticalSection(&_poll_fd[_index].mutex);
+                        }
+                        usbi_warn(NULL, "invalid fd");
+                        triggered = -1;
+                        goto poll_exit;
+                }
+
+                // IN or OUT must match our fd direction
+                if ((fds[i].events & POLLIN) && (poll_fd[_index].rw != RW_READ)) {
+                        fds[i].revents |= POLLNVAL | POLLERR;
+                        errno = EBADF;
+                        usbi_warn(NULL, "attempted POLLIN on fd without READ access");
+                        LeaveCriticalSection(&_poll_fd[_index].mutex);
+                        triggered = -1;
+                        goto poll_exit;
+                }
+
+                if ((fds[i].events & POLLOUT) && (poll_fd[_index].rw != RW_WRITE)) {
+                        fds[i].revents |= POLLNVAL | POLLERR;
+                        errno = EBADF;
+                        usbi_warn(NULL, "attempted POLLOUT on fd without WRITE access");
+                        LeaveCriticalSection(&_poll_fd[_index].mutex);
+                        triggered = -1;
+                        goto poll_exit;
+                }
+
+                // The following macro only works if overlapped I/O was reported pending
+                if ( (HasOverlappedIoCompleted(poll_fd[_index].overlapped))
+                  || (HasOverlappedIoCompletedSync(poll_fd[_index].overlapped)) ) {
+                        poll_dbg("  completed");
+                        // checks above should ensure this works:
+                        fds[i].revents = fds[i].events;
+                        triggered++;
+                } else {
+                        handles_to_wait_on[nb_handles_to_wait_on] = poll_fd[_index].overlapped->hEvent;
+                        handle_to_index[nb_handles_to_wait_on] = i;
+#if defined(DYNAMIC_FDS)
+                        // If this fd from the poll set is also part of the new_fd event handle table, remove it
+                        usbi_mutex_lock(&new_fd_mutex);
+                        for (j=0; j<nb_new_fds; j++) {
+                                if (handles_to_wait_on[nb_handles_to_wait_on] == new_fd[j]) {
+                                        new_fd[j] = INVALID_HANDLE_VALUE;
+                                        break;
+                                }
+                        }
+                        usbi_mutex_unlock(&new_fd_mutex);
+#endif
+                        nb_handles_to_wait_on++;
+                }
+                LeaveCriticalSection(&_poll_fd[_index].mutex);
+        }
+#if defined(DYNAMIC_FDS)
+        // At this stage, new_fd[] should only contain events from fds that
+        // have been added since the last call to poll, but are not (yet) part
+        // of the pollable fd set. Typically, these would be from fds that have
+        // been created between the construction of the fd set and the calling
+        // of poll.
+        // Event if we won't be able to return usable poll data on these events,
+        // make sure we monitor them to return an EINTR code
+        usbi_mutex_lock(&new_fd_mutex); // We could probably do without
+        for (i=0; i<nb_new_fds; i++) {
+                if (new_fd[i] != INVALID_HANDLE_VALUE) {
+                        handles_to_wait_on[nb_handles_to_wait_on++] = new_fd[i];
+                        nb_extra_handles++;
+                }
+        }
+        usbi_mutex_unlock(&new_fd_mutex);
+        poll_dbg("dynamic_fds: added %d extra handles", nb_extra_handles);
+#endif
+
+        // If nothing was triggered, wait on all fds that require it
+        if ((timeout != 0) && (triggered == 0) && (nb_handles_to_wait_on != 0)) {
+#if defined(DYNAMIC_FDS)
+                // Register for fd update notifications
+                handles_to_wait_on[nb_handles_to_wait_on++] = fd_update;
+                nb_extra_handles++;
+#endif
+                if (timeout < 0) {
+                        poll_dbg("starting infinite wait for %d handles...", (int)nb_handles_to_wait_on);
+                } else {
+                        poll_dbg("starting %d ms wait for %d handles...", timeout, (int)nb_handles_to_wait_on);
+                }
+                ret = WaitForMultipleObjects(nb_handles_to_wait_on, handles_to_wait_on,
+                        FALSE, (timeout<0)?INFINITE:(DWORD)timeout);
+                object_index = ret-WAIT_OBJECT_0;
+                if ((object_index >= 0) && ((DWORD)object_index < nb_handles_to_wait_on)) {
+#if defined(DYNAMIC_FDS)
+                        if ((DWORD)object_index >= (nb_handles_to_wait_on-nb_extra_handles)) {
+                                // Detected fd update => flag a poll interruption
+                                if ((DWORD)object_index == (nb_handles_to_wait_on-1))
+                                        poll_dbg("  dynamic_fds: fd_update event");
+                                else
+                                        poll_dbg("  dynamic_fds: new fd I/O event");
+                                errno = EINTR;
+                                triggered = -1;
+                                goto poll_exit;
+                        }
+#endif
+                        poll_dbg("  completed after wait");
+                        i = handle_to_index[object_index];
+                        _index = _fd_to_index_and_lock(fds[i].fd);
+                        fds[i].revents = fds[i].events;
+                        triggered++;
+                        if (_index >= 0) {
+                                LeaveCriticalSection(&_poll_fd[_index].mutex);
+                        }
+                } else if (ret == WAIT_TIMEOUT) {
+                        poll_dbg("  timed out");
+                        triggered = 0;  // 0 = timeout
+                } else {
+                        errno = EIO;
+                        triggered = -1; // error
+                }
+        }
+
+poll_exit:
+        if (handles_to_wait_on != NULL) {
+                free(handles_to_wait_on);
+        }
+        if (handle_to_index != NULL) {
+                free(handle_to_index);
+        }
+#if defined(DYNAMIC_FDS)
+        usbi_mutex_lock(&new_fd_mutex);
+        nb_new_fds = 0;
+        usbi_mutex_unlock(&new_fd_mutex);
+#endif
+        return triggered;
+}
+
+/*
+ * close a fake pipe fd
+ */
+int usbi_close(int fd)
+{
+        int _index;
+        int r = -1;
+
+        CHECK_INIT_POLLING;
+
+        _index = _fd_to_index_and_lock(fd);
+
+        if (_index < 0) {
+                errno = EBADF;
+        } else {
+                if (poll_fd[_index].overlapped != NULL) {
+                        // Must be a different event for each end of the pipe
+                        CloseHandle(poll_fd[_index].overlapped->hEvent);
+                        free(poll_fd[_index].overlapped);
+                }
+                r = _close(poll_fd[_index].fd);
+                if (r != 0) {
+                        errno = EIO;
+                }
+                poll_fd[_index] = INVALID_WINFD;
+                LeaveCriticalSection(&_poll_fd[_index].mutex);
+        }
+        return r;
+}
+
+/*
+ * synchronous write for fake "pipe" signaling
+ */
+ssize_t usbi_write(int fd, const void *buf, size_t count)
+{
+        int _index;
+
+        CHECK_INIT_POLLING;
+
+        if (count != sizeof(unsigned char)) {
+                usbi_err(NULL, "this function should only used for signaling");
+                return -1;
+        }
+
+        _index = _fd_to_index_and_lock(fd);
+
+        if ( (_index < 0) || (poll_fd[_index].overlapped == NULL) ) {
+                errno = EBADF;
+                if (_index >= 0) {
+                        LeaveCriticalSection(&_poll_fd[_index].mutex);
+                }
+                return -1;
+        }
+
+        poll_dbg("set pipe event (fd = %d, thread = %08X)", _index, GetCurrentThreadId());
+        SetEvent(poll_fd[_index].overlapped->hEvent);
+        poll_fd[_index].overlapped->Internal = STATUS_WAIT_0;
+        // If two threads write on the pipe at the same time, we need to
+        // process two separate reads => use the overlapped as a counter
+        poll_fd[_index].overlapped->InternalHigh++;
+
+        LeaveCriticalSection(&_poll_fd[_index].mutex);
+        return sizeof(unsigned char);
+}
+
+/*
+ * synchronous read for fake "pipe" signaling
+ */
+ssize_t usbi_read(int fd, void *buf, size_t count)
+{
+        int _index;
+        ssize_t r = -1;
+
+        CHECK_INIT_POLLING;
+
+        if (count != sizeof(unsigned char)) {
+                usbi_err(NULL, "this function should only used for signaling");
+                return -1;
+        }
+
+        _index = _fd_to_index_and_lock(fd);
+
+        if (_index < 0) {
+                errno = EBADF;
+                return -1;
+        }
+
+        if (WaitForSingleObject(poll_fd[_index].overlapped->hEvent, INFINITE) != WAIT_OBJECT_0) {
+                usbi_warn(NULL, "waiting for event failed: %d", (int)GetLastError());
+                errno = EIO;
+                goto out;
+        }
+
+        poll_dbg("clr pipe event (fd = %d, thread = %08X)", _index, GetCurrentThreadId());
+        poll_fd[_index].overlapped->InternalHigh--;
+        // Don't reset unless we don't have any more events to process
+        if (poll_fd[_index].overlapped->InternalHigh <= 0) {
+                ResetEvent(poll_fd[_index].overlapped->hEvent);
+                poll_fd[_index].overlapped->Internal = STATUS_PENDING;
+        }
+
+        r = sizeof(unsigned char);
+
+out:
+        LeaveCriticalSection(&_poll_fd[_index].mutex);
+        return r;
+}