Partially revert "win,code: remove GetQueuedCompletionStatus-based poller"

This reverts commit fd8d212a80,
and thereby restores partial support for using libuv under Wine
(which does not implement GetQueuedCompletionStatusEx).

PR-URL: https://github.com/libuv/libuv/pull/1963
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Bert Belder <bertbelder@gmail.com>

src/win/core.c

@@ -381,6 +381,57 @@ int uv_backend_timeout(const uv_loop_t* loop) {
 }
 
 
+static void uv__poll_wine(uv_loop_t* loop, DWORD timeout) {
+  DWORD bytes;
+  ULONG_PTR key;
+  OVERLAPPED* overlapped;
+  uv_req_t* req;
+  int repeat;
+  uint64_t timeout_time;
+
+  timeout_time = loop->time + timeout;
+
+  for (repeat = 0; ; repeat++) {
+    GetQueuedCompletionStatus(loop->iocp,
+                              &bytes,
+                              &key,
+                              &overlapped,
+                              timeout);
+
+    if (overlapped) {
+      /* Package was dequeued */
+      req = uv_overlapped_to_req(overlapped);
+      uv_insert_pending_req(loop, req);
+
+      /* Some time might have passed waiting for I/O,
+       * so update the loop time here.
+       */
+      uv_update_time(loop);
+    } else if (GetLastError() != WAIT_TIMEOUT) {
+      /* Serious error */
+      uv_fatal_error(GetLastError(), "GetQueuedCompletionStatus");
+    } else if (timeout > 0) {
+      /* GetQueuedCompletionStatus can occasionally return a little early.
+       * Make sure that the desired timeout target time is reached.
+       */
+      uv_update_time(loop);
+      if (timeout_time > loop->time) {
+        timeout = (DWORD)(timeout_time - loop->time);
+        /* The first call to GetQueuedCompletionStatus should return very
+         * close to the target time and the second should reach it, but
+         * this is not stated in the documentation. To make sure a busy
+         * loop cannot happen, the timeout is increased exponentially
+         * starting on the third round.
+         */
+        timeout += repeat ? (1 << (repeat - 1)) : 0;
+        continue;
+      }
+    }
+    break;
+  }
+}
+
+
 static void uv__poll(uv_loop_t* loop, DWORD timeout) {
   BOOL success;
   uv_req_t* req;
@@ -473,7 +524,11 @@ int uv_run(uv_loop_t *loop, uv_run_mode mode) {
     if ((mode == UV_RUN_ONCE && !ran_pending) || mode == UV_RUN_DEFAULT)
       timeout = uv_backend_timeout(loop);
 
+    if (pGetQueuedCompletionStatusEx)
       uv__poll(loop, timeout);
+    else
+      uv__poll_wine(loop, timeout);
+
 
     uv_check_invoke(loop);
     uv_process_endgames(loop);

src/win/winapi.c

@@ -34,6 +34,9 @@ sNtQueryVolumeInformationFile pNtQueryVolumeInformationFile;
 sNtQueryDirectoryFile pNtQueryDirectoryFile;
 sNtQuerySystemInformation pNtQuerySystemInformation;
 
+/* Kernel32 function pointers */
+sGetQueuedCompletionStatusEx pGetQueuedCompletionStatusEx;
+
 /* Powrprof.dll function pointer */
 sPowerRegisterSuspendResumeNotification pPowerRegisterSuspendResumeNotification;
 
@@ -45,6 +48,7 @@ void uv_winapi_init(void) {
   HMODULE ntdll_module;
   HMODULE powrprof_module;
   HMODULE user32_module;
+  HMODULE kernel32_module;
 
   ntdll_module = GetModuleHandleA("ntdll.dll");
   if (ntdll_module == NULL) {
@@ -98,6 +102,15 @@ void uv_winapi_init(void) {
     uv_fatal_error(GetLastError(), "GetProcAddress");
   }
 
+  kernel32_module = GetModuleHandleA("kernel32.dll");
+  if (kernel32_module == NULL) {
+    uv_fatal_error(GetLastError(), "GetModuleHandleA");
+  }
+
+  pGetQueuedCompletionStatusEx = (sGetQueuedCompletionStatusEx) GetProcAddress(
+      kernel32_module,
+      "GetQueuedCompletionStatusEx");
+
   powrprof_module = LoadLibraryA("powrprof.dll");
   if (powrprof_module != NULL) {
     pPowerRegisterSuspendResumeNotification = (sPowerRegisterSuspendResumeNotification)

src/win/winapi.h

@@ -4642,6 +4642,14 @@ typedef NTSTATUS (NTAPI *sNtQueryDirectoryFile)
 # define ERROR_MUI_FILE_NOT_LOADED 15105
 #endif
 
+typedef BOOL (WINAPI *sGetQueuedCompletionStatusEx)
+             (HANDLE CompletionPort,
+              LPOVERLAPPED_ENTRY lpCompletionPortEntries,
+              ULONG ulCount,
+              PULONG ulNumEntriesRemoved,
+              DWORD dwMilliseconds,
+              BOOL fAlertable);
+
 /* from powerbase.h */
 #ifndef DEVICE_NOTIFY_CALLBACK
 # define DEVICE_NOTIFY_CALLBACK 2
@@ -4704,6 +4712,9 @@ extern sNtQueryVolumeInformationFile pNtQueryVolumeInformationFile;
 extern sNtQueryDirectoryFile pNtQueryDirectoryFile;
 extern sNtQuerySystemInformation pNtQuerySystemInformation;
 
+/* Kernel32 function pointers */
+extern sGetQueuedCompletionStatusEx pGetQueuedCompletionStatusEx;
+
 /* Powrprof.dll function pointer */
 extern sPowerRegisterSuspendResumeNotification pPowerRegisterSuspendResumeNotification;