Add Windows support

Via Cygwin/MinGW, libusb now has windows support.
Thanks to contributors: Michael Plante, Orin Eman, Peter Stuge,
Stephan Meyer, Xiaofan Chen.

1 files changed, 860 insertions, 0 deletions

diff --git a/libusb/os/poll_windows.c b/libusb/os/poll_windows.c
new file mode 100644
index 0000000..59c3b07
--- /dev/null
+++ b/libusb/os/poll_windows.c
@@ -0,0 +1,860 @@
+/*
+ * 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 _close(int fd);
+extern int _snprintf(char *buffer, size_t count, const char *format, ...);
+extern int cygwin_attach_handle_to_fd(char *name, int fd, HANDLE handle, int bin, int access_mode);
+// _open_osfhandle() is not available on cygwin, but we can emulate
+// it for our needs with cygwin_attach_handle_to_fd()
+static inline int _open_osfhandle(intptr_t osfhandle, int flags)
+{
+	int access_mode;
+	switch (flags) {
+	case _O_RDONLY:
+		access_mode = GENERIC_READ;
+		break;
+	case _O_WRONLY:
+		access_mode = GENERIC_WRITE;
+		break;
+	case _O_RDWR:
+		access_mode = GENERIC_READ|GENERIC_WRITE;
+		break;
+	default:
+		usbi_err(NULL, "unsupported access mode");
+		return -1;
+	}
+	return cygwin_attach_handle_to_fd("/dev/null", -1, (HANDLE)osfhandle, -1, access_mode);
+}
+#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)
+__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(GetModuleHandle("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;
+	HANDLE handle;
+	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"
+	handle = CreateFileA("NUL", 0, 0, NULL, OPEN_EXISTING, 0, NULL);
+	if (handle == INVALID_HANDLE_VALUE) {
+		usbi_err(NULL, "could not create pipe: errcode %d", (int)GetLastError());
+		goto out1;
+	}
+	filedes[0] = _open_osfhandle((intptr_t)handle, _O_RDONLY);
+	// 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 = 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:
+	CloseHandle(handle);
+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
+	fd = _open_osfhandle((intptr_t)CreateFileA("NUL", 0, 0,
+		NULL, OPEN_EXISTING, 0, NULL), _O_RDWR);
+	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_warn(NULL, "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);
+		}
+		if (CloseHandle(poll_fd[index].handle) == 0) {
+			errno = EIO;
+		} else {
+			r = 0;
+		}
+		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;
+}