Add wepoll support to light up the epoll backend on Windows

libevent is lacking a scalable backend on Windows. Let's leverage the wepoll
library until Windows comes up with an epoll/kqueue compete user mode API.

- All regress tests pass for standard wepoll
- These 2 tests fail intermittently for changelist wepoll, so disabling
  changelist wepoll for now
     http/cancel_inactive_server
     http/stream_in
- verify target on Windows runs tests for both wepoll and win32 backends
- wepoll backend preferred over win32 backend
- wepoll version 1.5.6

v2: cleaner backend abstraction. Disallow wepoll on MinGW/Cygwin.
v3: Add wepoll.h to dist
v4: Make sure wepoll source files are excluded from cygwin/mingw builds
v5: Keep win32 as default backend on windows.
v6: Include wepoll in mingw builds. Verified that regress tests pass w/ WEPOLL backend.
v7: Enable wepoll on mingw when building with cmake
v8: Add wepoll testrunner for autotools test target

1 files changed, 111 insertions, 0 deletions

diff --git a/wepoll.h b/wepoll.h
new file mode 100644
index 00000000..e9f4a5d2
--- /dev/null
+++ b/wepoll.h
@@ -0,0 +1,111 @@
+/*
+ * wepoll - epoll for Windows
+ * https://github.com/piscisaureus/wepoll
+ *
+ * Copyright 2012-2020, Bert Belder <bertbelder@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *   * Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *
+ *   * Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef WEPOLL_H_
+#define WEPOLL_H_
+
+#define WEPOLL_EXPORT
+
+#include <stdint.h>
+
+enum EPOLL_EVENTS {
+  EPOLLIN      = (int) (1U <<  0),
+  EPOLLPRI     = (int) (1U <<  1),
+  EPOLLOUT     = (int) (1U <<  2),
+  EPOLLERR     = (int) (1U <<  3),
+  EPOLLHUP     = (int) (1U <<  4),
+  EPOLLRDNORM  = (int) (1U <<  6),
+  EPOLLRDBAND  = (int) (1U <<  7),
+  EPOLLWRNORM  = (int) (1U <<  8),
+  EPOLLWRBAND  = (int) (1U <<  9),
+  EPOLLMSG     = (int) (1U << 10), /* Never reported. */
+  EPOLLRDHUP   = (int) (1U << 13),
+  EPOLLONESHOT = (int) (1U << 31)
+};
+
+#define EPOLLIN      (1U <<  0)
+#define EPOLLPRI     (1U <<  1)
+#define EPOLLOUT     (1U <<  2)
+#define EPOLLERR     (1U <<  3)
+#define EPOLLHUP     (1U <<  4)
+#define EPOLLRDNORM  (1U <<  6)
+#define EPOLLRDBAND  (1U <<  7)
+#define EPOLLWRNORM  (1U <<  8)
+#define EPOLLWRBAND  (1U <<  9)
+#define EPOLLMSG     (1U << 10)
+#define EPOLLRDHUP   (1U << 13)
+#define EPOLLONESHOT (1U << 31)
+
+#define EPOLL_CTL_ADD 1
+#define EPOLL_CTL_MOD 2
+#define EPOLL_CTL_DEL 3
+
+typedef void* HANDLE;
+typedef uintptr_t SOCKET;
+
+typedef union epoll_data {
+  void* ptr;
+  int fd;
+  uint32_t u32;
+  uint64_t u64;
+  SOCKET sock; /* Windows specific */
+  HANDLE hnd;  /* Windows specific */
+} epoll_data_t;
+
+struct epoll_event {
+  uint32_t events;   /* Epoll events and flags */
+  epoll_data_t data; /* User data variable */
+};
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+WEPOLL_EXPORT HANDLE epoll_create(int size);
+WEPOLL_EXPORT HANDLE epoll_create1(int flags);
+
+WEPOLL_EXPORT int epoll_close(HANDLE ephnd);
+
+WEPOLL_EXPORT int epoll_ctl(HANDLE ephnd,
+                            int op,
+                            SOCKET sock,
+                            struct epoll_event* event);
+
+WEPOLL_EXPORT int epoll_wait(HANDLE ephnd,
+                             struct epoll_event* events,
+                             int maxevents,
+                             int timeout);
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif /* WEPOLL_H_ */