added partial CancelIoEx emulation for XP and earlierr207

also added warning when CancelIo tries to cancel I/O started
from another thread

1 files changed, 30 insertions, 3 deletions

diff --git a/libusb/os/poll_windows.c b/libusb/os/poll_windows.c
index 0fa2dce..0d8d487 100644
--- a/libusb/os/poll_windows.c
+++ b/libusb/os/poll_windows.c
@@ -123,7 +123,9 @@ struct winfd poll_fd[MAX_FDS];
 struct {
 	CRITICAL_SECTION mutex; // lock for fds
 	BYTE marker;            // 1st byte of a usbi_read operation gets stored here
-
+	// Additional variables for XP CancelIoEx partial emulation
+	HANDLE original_handle;
+	DWORD thread_id;
 } _poll_fd[MAX_FDS];
 
 // globals
@@ -146,11 +148,19 @@ __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 (pCancelIoEx != NULL) {
 		return (*pCancelIoEx)(poll_fd[index].handle, poll_fd[index].overlapped);
-	} else {
+	}
+	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
@@ -169,6 +179,8 @@ void init_polling(void)
 		for (i=0; i<MAX_FDS; i++) {
 			poll_fd[i] = INVALID_WINFD;
 			_poll_fd[i].marker = 0;
+			_poll_fd[i].original_handle = INVALID_HANDLE_VALUE;
+			_poll_fd[i].thread_id = 0;
 			InitializeCriticalSection(&_poll_fd[i].mutex);
 		}
 #if defined(DYNAMIC_FDS)
@@ -470,7 +482,19 @@ struct winfd usbi_create_fd(HANDLE handle, int access_mode)
 				continue;
 			}
 			wfd.fd = fd;
-			wfd.handle = handle;
+			// Attempt to emulate some of the CancelIoEx behaviour on platforms
+			// that don't have it
+			if (pCancelIoEx == NULL) {
+				_poll_fd[i].thread_id = GetCurrentThreadId();
+				_poll_fd[i].original_handle = handle;
+				if (!DuplicateHandle(GetCurrentProcess(), handle, GetCurrentProcess(),
+					&wfd.handle, 0, TRUE, DUPLICATE_SAME_ACCESS)) {
+					usbi_warn(NULL, "could not duplicate handle for CancelIo - using orignal one");
+					wfd.handle = handle;
+				}
+			} else {
+				wfd.handle = handle;
+			}
 			wfd.overlapped = overlapped;
 			memcpy(&poll_fd[i], &wfd, sizeof(struct winfd));
 			LeaveCriticalSection(&_poll_fd[i].mutex);
@@ -499,6 +523,9 @@ void _free_index(int index)
 		_close(poll_fd[index].fd);
 	}
 	free_overlapped(poll_fd[index].overlapped);
+	CloseHandle(_poll_fd[index].original_handle);
+	_poll_fd[index].original_handle = INVALID_HANDLE_VALUE;
+	_poll_fd[index].thread_id = 0;
 	poll_fd[index] = INVALID_WINFD;
 }