X-Git-Url: http://47.100.26.94:8080/?a=blobdiff_plain;f=app%2Fsrc%2Fmain%2Fjni%2Flibusb-1.0.22%2Flibusb%2Fos%2Fwindows_nt_common.c;fp=app%2Fsrc%2Fmain%2Fjni%2Flibusb-1.0.22%2Flibusb%2Fos%2Fwindows_nt_common.c;h=92dbde5a8445669463bca2330cfe4e46c62f508a;hb=577426ccc66649228285c4a0b6ba8752836059c6;hp=0000000000000000000000000000000000000000;hpb=b7202442677d0cf41e6e59870cd6c34e5619b8b9;p=rtmpclient.git

diff --git a/app/src/main/jni/libusb-1.0.22/libusb/os/windows_nt_common.c b/app/src/main/jni/libusb-1.0.22/libusb/os/windows_nt_common.c
new file mode 100644
index 0000000..92dbde5
--- /dev/null
+++ b/app/src/main/jni/libusb-1.0.22/libusb/os/windows_nt_common.c
@@ -0,0 +1,1008 @@
+/*
+ * windows backend for libusb 1.0
+ * Copyright © 2009-2012 Pete Batard <pete@akeo.ie>
+ * With contributions from Michael Plante, Orin Eman et al.
+ * Parts of this code adapted from libusb-win32-v1 by Stephan Meyer
+ * HID Reports IOCTLs inspired from HIDAPI by Alan Ott, Signal 11 Software
+ * Hash table functions adapted from glibc, by Ulrich Drepper et al.
+ * Major code testing contribution by Xiaofan Chen
+ *
+ * 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
+ */
+
+#include <config.h>
+
+#include <inttypes.h>
+#include <process.h>
+#include <stdio.h>
+
+#include "libusbi.h"
+#include "windows_common.h"
+#include "windows_nt_common.h"
+
+// Public
+BOOL (WINAPI *pCancelIoEx)(HANDLE, LPOVERLAPPED);
+enum windows_version windows_version = WINDOWS_UNDEFINED;
+
+ // Global variables for init/exit
+static unsigned int init_count = 0;
+static bool usbdk_available = false;
+
+// Global variables for clock_gettime mechanism
+static uint64_t hires_ticks_to_ps;
+static uint64_t hires_frequency;
+
+#define TIMER_REQUEST_RETRY_MS	100
+#define WM_TIMER_REQUEST	(WM_USER + 1)
+#define WM_TIMER_EXIT		(WM_USER + 2)
+
+// used for monotonic clock_gettime()
+struct timer_request {
+	struct timespec *tp;
+	HANDLE event;
+};
+
+// Timer thread
+static HANDLE timer_thread = NULL;
+static DWORD timer_thread_id = 0;
+
+/* Kernel32 dependencies */
+DLL_DECLARE_HANDLE(Kernel32);
+/* This call is only available from XP SP2 */
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, IsWow64Process, (HANDLE, PBOOL));
+
+/* User32 dependencies */
+DLL_DECLARE_HANDLE(User32);
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, GetMessageA, (LPMSG, HWND, UINT, UINT));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, PeekMessageA, (LPMSG, HWND, UINT, UINT, UINT));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, PostThreadMessageA, (DWORD, UINT, WPARAM, LPARAM));
+
+static unsigned __stdcall windows_clock_gettime_threaded(void *param);
+
+/*
+* Converts a windows error to human readable string
+* uses retval as errorcode, or, if 0, use GetLastError()
+*/
+#if defined(ENABLE_LOGGING)
+const char *windows_error_str(DWORD error_code)
+{
+	static char err_string[ERR_BUFFER_SIZE];
+
+	DWORD size;
+	int len;
+
+	if (error_code == 0)
+		error_code = GetLastError();
+
+	len = sprintf(err_string, "[%u] ", (unsigned int)error_code);
+
+	// Translate codes returned by SetupAPI. The ones we are dealing with are either
+	// in 0x0000xxxx or 0xE000xxxx and can be distinguished from standard error codes.
+	// See http://msdn.microsoft.com/en-us/library/windows/hardware/ff545011.aspx
+	switch (error_code & 0xE0000000) {
+	case 0:
+		error_code = HRESULT_FROM_WIN32(error_code); // Still leaves ERROR_SUCCESS unmodified
+		break;
+	case 0xE0000000:
+		error_code = 0x80000000 | (FACILITY_SETUPAPI << 16) | (error_code & 0x0000FFFF);
+		break;
+	default:
+		break;
+	}
+
+	size = FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM|FORMAT_MESSAGE_IGNORE_INSERTS,
+			NULL, error_code, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+			&err_string[len], ERR_BUFFER_SIZE - len, NULL);
+	if (size == 0) {
+		DWORD format_error = GetLastError();
+		if (format_error)
+			snprintf(err_string, ERR_BUFFER_SIZE,
+				"Windows error code %u (FormatMessage error code %u)",
+				(unsigned int)error_code, (unsigned int)format_error);
+		else
+			snprintf(err_string, ERR_BUFFER_SIZE, "Unknown error code %u", (unsigned int)error_code);
+	} else {
+		// Remove CRLF from end of message, if present
+		size_t pos = len + size - 2;
+		if (err_string[pos] == '\r')
+			err_string[pos] = '\0';
+	}
+
+	return err_string;
+}
+#endif
+
+static inline struct windows_context_priv *_context_priv(struct libusb_context *ctx)
+{
+	return (struct windows_context_priv *)ctx->os_priv;
+}
+
+/* Hash table functions - modified From glibc 2.3.2:
+   [Aho,Sethi,Ullman] Compilers: Principles, Techniques and Tools, 1986
+   [Knuth]            The Art of Computer Programming, part 3 (6.4)  */
+
+#define HTAB_SIZE 1021UL	// *MUST* be a prime number!!
+
+typedef struct htab_entry {
+	unsigned long used;
+	char *str;
+} htab_entry;
+
+static htab_entry *htab_table = NULL;
+static usbi_mutex_t htab_mutex;
+static unsigned long htab_filled;
+
+/* Before using the hash table we must allocate memory for it.
+   We allocate one element more as the found prime number says.
+   This is done for more effective indexing as explained in the
+   comment for the hash function.  */
+static bool htab_create(struct libusb_context *ctx)
+{
+	if (htab_table != NULL) {
+		usbi_err(ctx, "hash table already allocated");
+		return true;
+	}
+
+	// Create a mutex
+	usbi_mutex_init(&htab_mutex);
+
+	usbi_dbg("using %lu entries hash table", HTAB_SIZE);
+	htab_filled = 0;
+
+	// allocate memory and zero out.
+	htab_table = calloc(HTAB_SIZE + 1, sizeof(htab_entry));
+	if (htab_table == NULL) {
+		usbi_err(ctx, "could not allocate space for hash table");
+		return false;
+	}
+
+	return true;
+}
+
+/* After using the hash table it has to be destroyed.  */
+static void htab_destroy(void)
+{
+	unsigned long i;
+
+	if (htab_table == NULL)
+		return;
+
+	for (i = 0; i < HTAB_SIZE; i++)
+		free(htab_table[i].str);
+
+	safe_free(htab_table);
+
+	usbi_mutex_destroy(&htab_mutex);
+}
+
+/* This is the search function. It uses double hashing with open addressing.
+   We use a trick to speed up the lookup. The table is created with one
+   more element available. This enables us to use the index zero special.
+   This index will never be used because we store the first hash index in
+   the field used where zero means not used. Every other value means used.
+   The used field can be used as a first fast comparison for equality of
+   the stored and the parameter value. This helps to prevent unnecessary
+   expensive calls of strcmp.  */
+unsigned long htab_hash(const char *str)
+{
+	unsigned long hval, hval2;
+	unsigned long idx;
+	unsigned long r = 5381;
+	int c;
+	const char *sz = str;
+
+	if (str == NULL)
+		return 0;
+
+	// Compute main hash value (algorithm suggested by Nokia)
+	while ((c = *sz++) != 0)
+		r = ((r << 5) + r) + c;
+	if (r == 0)
+		++r;
+
+	// compute table hash: simply take the modulus
+	hval = r % HTAB_SIZE;
+	if (hval == 0)
+		++hval;
+
+	// Try the first index
+	idx = hval;
+
+	// Mutually exclusive access (R/W lock would be better)
+	usbi_mutex_lock(&htab_mutex);
+
+	if (htab_table[idx].used) {
+		if ((htab_table[idx].used == hval) && (strcmp(str, htab_table[idx].str) == 0))
+			goto out_unlock; // existing hash
+
+		usbi_dbg("hash collision ('%s' vs '%s')", str, htab_table[idx].str);
+
+		// Second hash function, as suggested in [Knuth]
+		hval2 = 1 + hval % (HTAB_SIZE - 2);
+
+		do {
+			// Because size is prime this guarantees to step through all available indexes
+			if (idx <= hval2)
+				idx = HTAB_SIZE + idx - hval2;
+			else
+				idx -= hval2;
+
+			// If we visited all entries leave the loop unsuccessfully
+			if (idx == hval)
+				break;
+
+			// If entry is found use it.
+			if ((htab_table[idx].used == hval) && (strcmp(str, htab_table[idx].str) == 0))
+				goto out_unlock;
+		} while (htab_table[idx].used);
+	}
+
+	// Not found => New entry
+
+	// If the table is full return an error
+	if (htab_filled >= HTAB_SIZE) {
+		usbi_err(NULL, "hash table is full (%lu entries)", HTAB_SIZE);
+		idx = 0;
+		goto out_unlock;
+	}
+
+	htab_table[idx].str = _strdup(str);
+	if (htab_table[idx].str == NULL) {
+		usbi_err(NULL, "could not duplicate string for hash table");
+		idx = 0;
+		goto out_unlock;
+	}
+
+	htab_table[idx].used = hval;
+	++htab_filled;
+
+out_unlock:
+	usbi_mutex_unlock(&htab_mutex);
+
+	return idx;
+}
+
+/*
+* Make a transfer complete synchronously
+*/
+void windows_force_sync_completion(OVERLAPPED *overlapped, ULONG size)
+{
+	overlapped->Internal = STATUS_COMPLETED_SYNCHRONOUSLY;
+	overlapped->InternalHigh = size;
+	SetEvent(overlapped->hEvent);
+}
+
+static BOOL windows_init_dlls(void)
+{
+	DLL_GET_HANDLE(Kernel32);
+	DLL_LOAD_FUNC_PREFIXED(Kernel32, p, IsWow64Process, FALSE);
+	pCancelIoEx = (BOOL (WINAPI *)(HANDLE, LPOVERLAPPED))
+		GetProcAddress(DLL_HANDLE_NAME(Kernel32), "CancelIoEx");
+	usbi_dbg("Will use CancelIo%s for I/O cancellation", pCancelIoEx ? "Ex" : "");
+
+	DLL_GET_HANDLE(User32);
+	DLL_LOAD_FUNC_PREFIXED(User32, p, GetMessageA, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(User32, p, PeekMessageA, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(User32, p, PostThreadMessageA, TRUE);
+
+	return TRUE;
+}
+
+static void windows_exit_dlls(void)
+{
+	DLL_FREE_HANDLE(Kernel32);
+	DLL_FREE_HANDLE(User32);
+}
+
+static bool windows_init_clock(struct libusb_context *ctx)
+{
+	DWORD_PTR affinity, dummy;
+	HANDLE event;
+	LARGE_INTEGER li_frequency;
+	int i;
+
+	if (QueryPerformanceFrequency(&li_frequency)) {
+		// The hires frequency can go as high as 4 GHz, so we'll use a conversion
+		// to picoseconds to compute the tv_nsecs part in clock_gettime
+		hires_frequency = li_frequency.QuadPart;
+		hires_ticks_to_ps = UINT64_C(1000000000000) / hires_frequency;
+		usbi_dbg("hires timer available (Frequency: %"PRIu64" Hz)", hires_frequency);
+
+		// Because QueryPerformanceCounter might report different values when
+		// running on different cores, we create a separate thread for the timer
+		// calls, which we glue to the first available core always to prevent timing discrepancies.
+		if (!GetProcessAffinityMask(GetCurrentProcess(), &affinity, &dummy) || (affinity == 0)) {
+			usbi_err(ctx, "could not get process affinity: %s", windows_error_str(0));
+			return false;
+		}
+
+		// The process affinity mask is a bitmask where each set bit represents a core on
+		// which this process is allowed to run, so we find the first set bit
+		for (i = 0; !(affinity & (DWORD_PTR)(1 << i)); i++);
+		affinity = (DWORD_PTR)(1 << i);
+
+		usbi_dbg("timer thread will run on core #%d", i);
+
+		event = CreateEvent(NULL, FALSE, FALSE, NULL);
+		if (event == NULL) {
+			usbi_err(ctx, "could not create event: %s", windows_error_str(0));
+			return false;
+		}
+
+		timer_thread = (HANDLE)_beginthreadex(NULL, 0, windows_clock_gettime_threaded, (void *)event,
+				0, (unsigned int *)&timer_thread_id);
+		if (timer_thread == NULL) {
+			usbi_err(ctx, "unable to create timer thread - aborting");
+			CloseHandle(event);
+			return false;
+		}
+
+		if (!SetThreadAffinityMask(timer_thread, affinity))
+			usbi_warn(ctx, "unable to set timer thread affinity, timer discrepancies may arise");
+
+		// Wait for timer thread to init before continuing.
+		if (WaitForSingleObject(event, INFINITE) != WAIT_OBJECT_0) {
+			usbi_err(ctx, "failed to wait for timer thread to become ready - aborting");
+			CloseHandle(event);
+			return false;
+		}
+
+		CloseHandle(event);
+	} else {
+		usbi_dbg("no hires timer available on this platform");
+		hires_frequency = 0;
+		hires_ticks_to_ps = UINT64_C(0);
+	}
+
+	return true;
+}
+
+static void windows_destroy_clock(void)
+{
+	if (timer_thread) {
+		// actually the signal to quit the thread.
+		if (!pPostThreadMessageA(timer_thread_id, WM_TIMER_EXIT, 0, 0)
+				|| (WaitForSingleObject(timer_thread, INFINITE) != WAIT_OBJECT_0)) {
+			usbi_dbg("could not wait for timer thread to quit");
+			TerminateThread(timer_thread, 1);
+			// shouldn't happen, but we're destroying
+			// all objects it might have held anyway.
+		}
+		CloseHandle(timer_thread);
+		timer_thread = NULL;
+		timer_thread_id = 0;
+	}
+}
+
+/* Windows version detection */
+static BOOL is_x64(void)
+{
+	BOOL ret = FALSE;
+
+	// Detect if we're running a 32 or 64 bit system
+	if (sizeof(uintptr_t) < 8) {
+		if (pIsWow64Process != NULL)
+			pIsWow64Process(GetCurrentProcess(), &ret);
+	} else {
+		ret = TRUE;
+	}
+
+	return ret;
+}
+
+static void get_windows_version(void)
+{
+	OSVERSIONINFOEXA vi, vi2;
+	const char *arch, *w = NULL;
+	unsigned major, minor, version;
+	ULONGLONG major_equal, minor_equal;
+	BOOL ws;
+
+	windows_version = WINDOWS_UNDEFINED;
+
+	memset(&vi, 0, sizeof(vi));
+	vi.dwOSVersionInfoSize = sizeof(vi);
+	if (!GetVersionExA((OSVERSIONINFOA *)&vi)) {
+		memset(&vi, 0, sizeof(vi));
+		vi.dwOSVersionInfoSize = sizeof(OSVERSIONINFOA);
+		if (!GetVersionExA((OSVERSIONINFOA *)&vi))
+			return;
+	}
+
+	if (vi.dwPlatformId != VER_PLATFORM_WIN32_NT)
+		return;
+
+	if ((vi.dwMajorVersion > 6) || ((vi.dwMajorVersion == 6) && (vi.dwMinorVersion >= 2))) {
+		// Starting with Windows 8.1 Preview, GetVersionEx() does no longer report the actual OS version
+		// See: http://msdn.microsoft.com/en-us/library/windows/desktop/dn302074.aspx
+
+		major_equal = VerSetConditionMask(0, VER_MAJORVERSION, VER_EQUAL);
+		for (major = vi.dwMajorVersion; major <= 9; major++) {
+			memset(&vi2, 0, sizeof(vi2));
+			vi2.dwOSVersionInfoSize = sizeof(vi2);
+			vi2.dwMajorVersion = major;
+			if (!VerifyVersionInfoA(&vi2, VER_MAJORVERSION, major_equal))
+				continue;
+
+			if (vi.dwMajorVersion < major) {
+				vi.dwMajorVersion = major;
+				vi.dwMinorVersion = 0;
+			}
+
+			minor_equal = VerSetConditionMask(0, VER_MINORVERSION, VER_EQUAL);
+			for (minor = vi.dwMinorVersion; minor <= 9; minor++) {
+				memset(&vi2, 0, sizeof(vi2));
+				vi2.dwOSVersionInfoSize = sizeof(vi2);
+				vi2.dwMinorVersion = minor;
+				if (!VerifyVersionInfoA(&vi2, VER_MINORVERSION, minor_equal))
+					continue;
+
+				vi.dwMinorVersion = minor;
+				break;
+			}
+
+			break;
+		}
+	}
+
+	if ((vi.dwMajorVersion > 0xf) || (vi.dwMinorVersion > 0xf))
+		return;
+
+	ws = (vi.wProductType <= VER_NT_WORKSTATION);
+	version = vi.dwMajorVersion << 4 | vi.dwMinorVersion;
+	switch (version) {
+	case 0x50: windows_version = WINDOWS_2000;  w = "2000";	break;
+	case 0x51: windows_version = WINDOWS_XP;    w = "XP";	break;
+	case 0x52: windows_version = WINDOWS_2003;  w = "2003";	break;
+	case 0x60: windows_version = WINDOWS_VISTA; w = (ws ? "Vista" : "2008");  break;
+	case 0x61: windows_version = WINDOWS_7;	    w = (ws ? "7" : "2008_R2");	  break;
+	case 0x62: windows_version = WINDOWS_8;	    w = (ws ? "8" : "2012");	  break;
+	case 0x63: windows_version = WINDOWS_8_1;   w = (ws ? "8.1" : "2012_R2"); break;
+	case 0x64: windows_version = WINDOWS_10;    w = (ws ? "10" : "2016");	  break;
+	default:
+		if (version < 0x50) {
+			return;
+		} else {
+			windows_version = WINDOWS_11_OR_LATER;
+			w = "11 or later";
+		}
+	}
+
+	arch = is_x64() ? "64-bit" : "32-bit";
+
+	if (vi.wServicePackMinor)
+		usbi_dbg("Windows %s SP%u.%u %s", w, vi.wServicePackMajor, vi.wServicePackMinor, arch);
+	else if (vi.wServicePackMajor)
+		usbi_dbg("Windows %s SP%u %s", w, vi.wServicePackMajor, arch);
+	else
+		usbi_dbg("Windows %s %s", w, arch);
+}
+
+/*
+* Monotonic and real time functions
+*/
+static unsigned __stdcall windows_clock_gettime_threaded(void *param)
+{
+	struct timer_request *request;
+	LARGE_INTEGER hires_counter;
+	MSG msg;
+
+	// The following call will create this thread's message queue
+	// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms644946.aspx
+	pPeekMessageA(&msg, NULL, WM_USER, WM_USER, PM_NOREMOVE);
+
+	// Signal windows_init_clock() that we're ready to service requests
+	if (!SetEvent((HANDLE)param))
+		usbi_dbg("SetEvent failed for timer init event: %s", windows_error_str(0));
+	param = NULL;
+
+	// Main loop - wait for requests
+	while (1) {
+		if (pGetMessageA(&msg, NULL, WM_TIMER_REQUEST, WM_TIMER_EXIT) == -1) {
+			usbi_err(NULL, "GetMessage failed for timer thread: %s", windows_error_str(0));
+			return 1;
+		}
+
+		switch (msg.message) {
+		case WM_TIMER_REQUEST:
+			// Requests to this thread are for hires always
+			// Microsoft says that this function always succeeds on XP and later
+			// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms644904.aspx
+			request = (struct timer_request *)msg.lParam;
+			QueryPerformanceCounter(&hires_counter);
+			request->tp->tv_sec = (long)(hires_counter.QuadPart / hires_frequency);
+			request->tp->tv_nsec = (long)(((hires_counter.QuadPart % hires_frequency) / 1000) * hires_ticks_to_ps);
+			if (!SetEvent(request->event))
+				usbi_err(NULL, "SetEvent failed for timer request: %s", windows_error_str(0));
+			break;
+		case WM_TIMER_EXIT:
+			usbi_dbg("timer thread quitting");
+			return 0;
+		}
+	}
+}
+
+static void windows_transfer_callback(const struct windows_backend *backend,
+	struct usbi_transfer *itransfer, DWORD io_result, DWORD io_size)
+{
+	int status, istatus;
+
+	usbi_dbg("handling I/O completion with errcode %u, size %u", (unsigned int)io_result, (unsigned int)io_size);
+
+	switch (io_result) {
+	case NO_ERROR:
+		status = backend->copy_transfer_data(itransfer, (uint32_t)io_size);
+		break;
+	case ERROR_GEN_FAILURE:
+		usbi_dbg("detected endpoint stall");
+		status = LIBUSB_TRANSFER_STALL;
+		break;
+	case ERROR_SEM_TIMEOUT:
+		usbi_dbg("detected semaphore timeout");
+		status = LIBUSB_TRANSFER_TIMED_OUT;
+		break;
+	case ERROR_OPERATION_ABORTED:
+		istatus = backend->copy_transfer_data(itransfer, (uint32_t)io_size);
+		if (istatus != LIBUSB_TRANSFER_COMPLETED)
+			usbi_dbg("Failed to copy partial data in aborted operation: %d", istatus);
+
+		usbi_dbg("detected operation aborted");
+		status = LIBUSB_TRANSFER_CANCELLED;
+		break;
+	case ERROR_FILE_NOT_FOUND:
+		usbi_dbg("detected device removed");
+		status = LIBUSB_TRANSFER_NO_DEVICE;
+		break;
+	default:
+		usbi_err(ITRANSFER_CTX(itransfer), "detected I/O error %u: %s", (unsigned int)io_result, windows_error_str(io_result));
+		status = LIBUSB_TRANSFER_ERROR;
+		break;
+	}
+	backend->clear_transfer_priv(itransfer);	// Cancel polling
+	if (status == LIBUSB_TRANSFER_CANCELLED)
+		usbi_handle_transfer_cancellation(itransfer);
+	else
+		usbi_handle_transfer_completion(itransfer, (enum libusb_transfer_status)status);
+}
+
+static void windows_handle_callback(const struct windows_backend *backend,
+	struct usbi_transfer *itransfer, DWORD io_result, DWORD io_size)
+{
+	struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
+
+	switch (transfer->type) {
+	case LIBUSB_TRANSFER_TYPE_CONTROL:
+	case LIBUSB_TRANSFER_TYPE_BULK:
+	case LIBUSB_TRANSFER_TYPE_INTERRUPT:
+	case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
+		windows_transfer_callback(backend, itransfer, io_result, io_size);
+		break;
+	case LIBUSB_TRANSFER_TYPE_BULK_STREAM:
+		usbi_warn(ITRANSFER_CTX(itransfer), "bulk stream transfers are not yet supported on this platform");
+		break;
+	default:
+		usbi_err(ITRANSFER_CTX(itransfer), "unknown endpoint type %d", transfer->type);
+	}
+}
+
+static int windows_init(struct libusb_context *ctx)
+{
+	struct windows_context_priv *priv = _context_priv(ctx);
+	HANDLE semaphore;
+	char sem_name[11 + 8 + 1]; // strlen("libusb_init") + (32-bit hex PID) + '\0'
+	int r = LIBUSB_ERROR_OTHER;
+	bool winusb_backend_init = false;
+
+	sprintf(sem_name, "libusb_init%08X", (unsigned int)(GetCurrentProcessId() & 0xFFFFFFFF));
+	semaphore = CreateSemaphoreA(NULL, 1, 1, sem_name);
+	if (semaphore == NULL) {
+		usbi_err(ctx, "could not create semaphore: %s", windows_error_str(0));
+		return LIBUSB_ERROR_NO_MEM;
+	}
+
+	// A successful wait brings our semaphore count to 0 (unsignaled)
+	// => any concurent wait stalls until the semaphore's release
+	if (WaitForSingleObject(semaphore, INFINITE) != WAIT_OBJECT_0) {
+		usbi_err(ctx, "failure to access semaphore: %s", windows_error_str(0));
+		CloseHandle(semaphore);
+		return LIBUSB_ERROR_NO_MEM;
+	}
+
+	// NB: concurrent usage supposes that init calls are equally balanced with
+	// exit calls. If init is called more than exit, we will not exit properly
+	if (++init_count == 1) { // First init?
+		// Load DLL imports
+		if (!windows_init_dlls()) {
+			usbi_err(ctx, "could not resolve DLL functions");
+			goto init_exit;
+		}
+
+		get_windows_version();
+
+		if (windows_version == WINDOWS_UNDEFINED) {
+			usbi_err(ctx, "failed to detect Windows version");
+			r = LIBUSB_ERROR_NOT_SUPPORTED;
+			goto init_exit;
+		}
+
+		if (!windows_init_clock(ctx))
+			goto init_exit;
+
+		if (!htab_create(ctx))
+			goto init_exit;
+
+		r = winusb_backend.init(ctx);
+		if (r != LIBUSB_SUCCESS)
+			goto init_exit;
+		winusb_backend_init = true;
+
+		r = usbdk_backend.init(ctx);
+		if (r == LIBUSB_SUCCESS) {
+			usbi_dbg("UsbDk backend is available");
+			usbdk_available = true;
+		} else {
+			usbi_info(ctx, "UsbDk backend is not available");
+			// Do not report this as an error
+			r = LIBUSB_SUCCESS;
+		}
+	}
+
+	// By default, new contexts will use the WinUSB backend
+	priv->backend = &winusb_backend;
+
+	r = LIBUSB_SUCCESS;
+
+init_exit: // Holds semaphore here
+	if ((init_count == 1) && (r != LIBUSB_SUCCESS)) { // First init failed?
+		if (winusb_backend_init)
+			winusb_backend.exit(ctx);
+		htab_destroy();
+		windows_destroy_clock();
+		windows_exit_dlls();
+		--init_count;
+	}
+
+	ReleaseSemaphore(semaphore, 1, NULL); // increase count back to 1
+	CloseHandle(semaphore);
+	return r;
+}
+
+static void windows_exit(struct libusb_context *ctx)
+{
+	HANDLE semaphore;
+	char sem_name[11 + 8 + 1]; // strlen("libusb_init") + (32-bit hex PID) + '\0'
+	UNUSED(ctx);
+
+	sprintf(sem_name, "libusb_init%08X", (unsigned int)(GetCurrentProcessId() & 0xFFFFFFFF));
+	semaphore = CreateSemaphoreA(NULL, 1, 1, sem_name);
+	if (semaphore == NULL)
+		return;
+
+	// A successful wait brings our semaphore count to 0 (unsignaled)
+	// => any concurent wait stalls until the semaphore release
+	if (WaitForSingleObject(semaphore, INFINITE) != WAIT_OBJECT_0) {
+		CloseHandle(semaphore);
+		return;
+	}
+
+	// Only works if exits and inits are balanced exactly
+	if (--init_count == 0) { // Last exit
+		if (usbdk_available) {
+			usbdk_backend.exit(ctx);
+			usbdk_available = false;
+		}
+		winusb_backend.exit(ctx);
+		htab_destroy();
+		windows_destroy_clock();
+		windows_exit_dlls();
+	}
+
+	ReleaseSemaphore(semaphore, 1, NULL); // increase count back to 1
+	CloseHandle(semaphore);
+}
+
+static int windows_set_option(struct libusb_context *ctx, enum libusb_option option, va_list ap)
+{
+	struct windows_context_priv *priv = _context_priv(ctx);
+
+	UNUSED(ap);
+
+	switch (option) {
+	case LIBUSB_OPTION_USE_USBDK:
+		if (usbdk_available) {
+			usbi_dbg("switching context %p to use UsbDk backend", ctx);
+			priv->backend = &usbdk_backend;
+		} else {
+			usbi_err(ctx, "UsbDk backend not available");
+			return LIBUSB_ERROR_NOT_FOUND;
+		}
+		return LIBUSB_SUCCESS;
+	default:
+		return LIBUSB_ERROR_NOT_SUPPORTED;
+	}
+
+}
+
+static int windows_get_device_list(struct libusb_context *ctx, struct discovered_devs **discdevs)
+{
+	struct windows_context_priv *priv = _context_priv(ctx);
+	return priv->backend->get_device_list(ctx, discdevs);
+}
+
+static int windows_open(struct libusb_device_handle *dev_handle)
+{
+	struct windows_context_priv *priv = _context_priv(HANDLE_CTX(dev_handle));
+	return priv->backend->open(dev_handle);
+}
+
+static void windows_close(struct libusb_device_handle *dev_handle)
+{
+	struct windows_context_priv *priv = _context_priv(HANDLE_CTX(dev_handle));
+	priv->backend->close(dev_handle);
+}
+
+static int windows_get_device_descriptor(struct libusb_device *dev,
+	unsigned char *buffer, int *host_endian)
+{
+	struct windows_context_priv *priv = _context_priv(DEVICE_CTX(dev));
+	*host_endian = 0;
+	return priv->backend->get_device_descriptor(dev, buffer);
+}
+
+static int windows_get_active_config_descriptor(struct libusb_device *dev,
+	unsigned char *buffer, size_t len, int *host_endian)
+{
+	struct windows_context_priv *priv = _context_priv(DEVICE_CTX(dev));
+	*host_endian = 0;
+	return priv->backend->get_active_config_descriptor(dev, buffer, len);
+}
+
+static int windows_get_config_descriptor(struct libusb_device *dev,
+	uint8_t config_index, unsigned char *buffer, size_t len, int *host_endian)
+{
+	struct windows_context_priv *priv = _context_priv(DEVICE_CTX(dev));
+	*host_endian = 0;
+	return priv->backend->get_config_descriptor(dev, config_index, buffer, len);
+}
+
+static int windows_get_config_descriptor_by_value(struct libusb_device *dev,
+	uint8_t bConfigurationValue, unsigned char **buffer, int *host_endian)
+{
+	struct windows_context_priv *priv = _context_priv(DEVICE_CTX(dev));
+	*host_endian = 0;
+	return priv->backend->get_config_descriptor_by_value(dev, bConfigurationValue, buffer);
+}
+
+static int windows_get_configuration(struct libusb_device_handle *dev_handle, int *config)
+{
+	struct windows_context_priv *priv = _context_priv(HANDLE_CTX(dev_handle));
+	return priv->backend->get_configuration(dev_handle, config);
+}
+
+static int windows_set_configuration(struct libusb_device_handle *dev_handle, int config)
+{
+	struct windows_context_priv *priv = _context_priv(HANDLE_CTX(dev_handle));
+	return priv->backend->set_configuration(dev_handle, config);
+}
+
+static int windows_claim_interface(struct libusb_device_handle *dev_handle, int interface_number)
+{
+	struct windows_context_priv *priv = _context_priv(HANDLE_CTX(dev_handle));
+	return priv->backend->claim_interface(dev_handle, interface_number);
+}
+
+static int windows_release_interface(struct libusb_device_handle *dev_handle, int interface_number)
+{
+	struct windows_context_priv *priv = _context_priv(HANDLE_CTX(dev_handle));
+	return priv->backend->release_interface(dev_handle, interface_number);
+}
+
+static int windows_set_interface_altsetting(struct libusb_device_handle *dev_handle,
+	int interface_number, int altsetting)
+{
+	struct windows_context_priv *priv = _context_priv(HANDLE_CTX(dev_handle));
+	return priv->backend->set_interface_altsetting(dev_handle, interface_number, altsetting);
+}
+
+static int windows_clear_halt(struct libusb_device_handle *dev_handle, unsigned char endpoint)
+{
+	struct windows_context_priv *priv = _context_priv(HANDLE_CTX(dev_handle));
+	return priv->backend->clear_halt(dev_handle, endpoint);
+}
+
+static int windows_reset_device(struct libusb_device_handle *dev_handle)
+{
+	struct windows_context_priv *priv = _context_priv(HANDLE_CTX(dev_handle));
+	return priv->backend->reset_device(dev_handle);
+}
+
+static void windows_destroy_device(struct libusb_device *dev)
+{
+	struct windows_context_priv *priv = _context_priv(DEVICE_CTX(dev));
+	priv->backend->destroy_device(dev);
+}
+
+static int windows_submit_transfer(struct usbi_transfer *itransfer)
+{
+	struct windows_context_priv *priv = _context_priv(ITRANSFER_CTX(itransfer));
+	return priv->backend->submit_transfer(itransfer);
+}
+
+static int windows_cancel_transfer(struct usbi_transfer *itransfer)
+{
+	struct windows_context_priv *priv = _context_priv(ITRANSFER_CTX(itransfer));
+	return priv->backend->cancel_transfer(itransfer);
+}
+
+static void windows_clear_transfer_priv(struct usbi_transfer *itransfer)
+{
+	struct windows_context_priv *priv = _context_priv(ITRANSFER_CTX(itransfer));
+	priv->backend->clear_transfer_priv(itransfer);
+}
+
+static int windows_handle_events(struct libusb_context *ctx, struct pollfd *fds, POLL_NFDS_TYPE nfds, int num_ready)
+{
+	struct windows_context_priv *priv = _context_priv(ctx);
+	struct usbi_transfer *itransfer;
+	DWORD io_size, io_result;
+	POLL_NFDS_TYPE i;
+	bool found;
+	int transfer_fd;
+	int r = LIBUSB_SUCCESS;
+
+	usbi_mutex_lock(&ctx->open_devs_lock);
+	for (i = 0; i < nfds && num_ready > 0; i++) {
+
+		usbi_dbg("checking fd %d with revents = %04x", fds[i].fd, fds[i].revents);
+
+		if (!fds[i].revents)
+			continue;
+
+		num_ready--;
+
+		// Because a Windows OVERLAPPED is used for poll emulation,
+		// a pollable fd is created and stored with each transfer
+		found = false;
+		transfer_fd = -1;
+		usbi_mutex_lock(&ctx->flying_transfers_lock);
+		list_for_each_entry(itransfer, &ctx->flying_transfers, list, struct usbi_transfer) {
+			transfer_fd = priv->backend->get_transfer_fd(itransfer);
+			if (transfer_fd == fds[i].fd) {
+				found = true;
+				break;
+			}
+		}
+		usbi_mutex_unlock(&ctx->flying_transfers_lock);
+
+		if (found) {
+			priv->backend->get_overlapped_result(itransfer, &io_result, &io_size);
+
+			usbi_remove_pollfd(ctx, transfer_fd);
+
+			// let handle_callback free the event using the transfer wfd
+			// If you don't use the transfer wfd, you run a risk of trying to free a
+			// newly allocated wfd that took the place of the one from the transfer.
+			windows_handle_callback(priv->backend, itransfer, io_result, io_size);
+		} else {
+			usbi_err(ctx, "could not find a matching transfer for fd %d", fds[i].fd);
+			r = LIBUSB_ERROR_NOT_FOUND;
+			break;
+		}
+	}
+	usbi_mutex_unlock(&ctx->open_devs_lock);
+
+	return r;
+}
+
+static int windows_clock_gettime(int clk_id, struct timespec *tp)
+{
+	struct timer_request request;
+#if !defined(_MSC_VER) || (_MSC_VER < 1900)
+	FILETIME filetime;
+	ULARGE_INTEGER rtime;
+#endif
+	DWORD r;
+
+	switch (clk_id) {
+	case USBI_CLOCK_MONOTONIC:
+		if (timer_thread) {
+			request.tp = tp;
+			request.event = CreateEvent(NULL, FALSE, FALSE, NULL);
+			if (request.event == NULL)
+				return LIBUSB_ERROR_NO_MEM;
+
+			if (!pPostThreadMessageA(timer_thread_id, WM_TIMER_REQUEST, 0, (LPARAM)&request)) {
+				usbi_err(NULL, "PostThreadMessage failed for timer thread: %s", windows_error_str(0));
+				CloseHandle(request.event);
+				return LIBUSB_ERROR_OTHER;
+			}
+
+			do {
+				r = WaitForSingleObject(request.event, TIMER_REQUEST_RETRY_MS);
+				if (r == WAIT_TIMEOUT)
+					usbi_dbg("could not obtain a timer value within reasonable timeframe - too much load?");
+				else if (r == WAIT_FAILED)
+					usbi_err(NULL, "WaitForSingleObject failed: %s", windows_error_str(0));
+			} while (r == WAIT_TIMEOUT);
+			CloseHandle(request.event);
+
+			if (r == WAIT_OBJECT_0)
+				return LIBUSB_SUCCESS;
+			else
+				return LIBUSB_ERROR_OTHER;
+		}
+		// Fall through and return real-time if monotonic was not detected @ timer init
+	case USBI_CLOCK_REALTIME:
+#if defined(_MSC_VER) && (_MSC_VER >= 1900)
+		timespec_get(tp, TIME_UTC);
+#else
+		// We follow http://msdn.microsoft.com/en-us/library/ms724928%28VS.85%29.aspx
+		// with a predef epoch time to have an epoch that starts at 1970.01.01 00:00
+		// Note however that our resolution is bounded by the Windows system time
+		// functions and is at best of the order of 1 ms (or, usually, worse)
+		GetSystemTimeAsFileTime(&filetime);
+		rtime.LowPart = filetime.dwLowDateTime;
+		rtime.HighPart = filetime.dwHighDateTime;
+		rtime.QuadPart -= EPOCH_TIME;
+		tp->tv_sec = (long)(rtime.QuadPart / 10000000);
+		tp->tv_nsec = (long)((rtime.QuadPart % 10000000) * 100);
+#endif
+		return LIBUSB_SUCCESS;
+	default:
+		return LIBUSB_ERROR_INVALID_PARAM;
+	}
+}
+
+// NB: MSVC6 does not support named initializers.
+const struct usbi_os_backend usbi_backend = {
+	"Windows",
+	USBI_CAP_HAS_HID_ACCESS,
+	windows_init,
+	windows_exit,
+	windows_set_option,
+	windows_get_device_list,
+	NULL,	/* hotplug_poll */
+	windows_open,
+	windows_close,
+	windows_get_device_descriptor,
+	windows_get_active_config_descriptor,
+	windows_get_config_descriptor,
+	windows_get_config_descriptor_by_value,
+	windows_get_configuration,
+	windows_set_configuration,
+	windows_claim_interface,
+	windows_release_interface,
+	windows_set_interface_altsetting,
+	windows_clear_halt,
+	windows_reset_device,
+	NULL,	/* alloc_streams */
+	NULL,	/* free_streams */
+	NULL,	/* dev_mem_alloc */
+	NULL,	/* dev_mem_free */
+	NULL,	/* kernel_driver_active */
+	NULL,	/* detach_kernel_driver */
+	NULL,	/* attach_kernel_driver */
+	windows_destroy_device,
+	windows_submit_transfer,
+	windows_cancel_transfer,
+	windows_clear_transfer_priv,
+	windows_handle_events,
+	NULL,	/* handle_transfer_completion */
+	windows_clock_gettime,
+	sizeof(struct windows_context_priv),
+	sizeof(union windows_device_priv),
+	sizeof(union windows_device_handle_priv),
+	sizeof(union windows_transfer_priv),
+};