Pull from FB rev 63ce89e2f2301e6bba44a111cc7d4218022156f6

[folly.git] / folly / eventfd.h

diff --git a/folly/eventfd.h b/folly/eventfd.h
new file mode 100644 (file)
index 0000000..fdd895d
--- /dev/null
+++ b/folly/eventfd.h
@@ -0,0 +1,79 @@
+/*
+ * Copyright 2012 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Wrapper around the eventfd system call, as defined in <sys/eventfd.h>
+ * in glibc 2.9+.
+ *
+ * @author Tudor Bosman (tudorb@fb.com)
+ */
+
+#ifndef FOLLY_BASE_EVENTFD_H_
+#define FOLLY_BASE_EVENTFD_H_
+
+#ifndef __linux__
+#error This file may be compiled on Linux only.
+#endif
+
+#include <sys/syscall.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+// Use existing __NR_eventfd2 if already defined
+// Values from the Linux kernel source:
+// arch/x86/include/asm/unistd_{32,64}.h
+#ifndef __NR_eventfd2
+#if defined(__x86_64__)
+#define __NR_eventfd2  290
+#elif defined(__i386__)
+#define __NR_eventfd2  328
+#else
+#error "Can't define __NR_eventfd2 for your architecture."
+#endif
+#endif
+
+#ifndef EFD_SEMAPHORE
+#define EFD_SEMAPHORE 1
+#endif
+
+/* from linux/fcntl.h - this conflicts with fcntl.h so include just the #define
+ * we need
+ */
+#ifndef O_CLOEXEC
+#define O_CLOEXEC 02000000 /* set close_on_exec */
+#endif
+
+#ifndef EFD_CLOEXEC
+#define EFD_CLOEXEC O_CLOEXEC
+#endif
+
+#ifndef EFD_NONBLOCK
+#define EFD_NONBLOCK O_NONBLOCK
+#endif
+
+namespace folly {
+
+// http://www.kernel.org/doc/man-pages/online/pages/man2/eventfd.2.html
+inline int eventfd(unsigned int initval, int flags) {
+  // Use the eventfd2 system call, as in glibc 2.9+
+  // (requires kernel 2.6.30+)
+  return syscall(__NR_eventfd2, initval, flags);
+}
+
+}  // namespace folly
+
+#endif /* FOLLY_BASE_EVENTFD_H_ */
+