Initial checkin of gRPC to third_party/

third_party/grpc/src/core/iomgr/wakeup_fd_posix.h

Index: third_party/grpc/src/core/iomgr/wakeup_fd_posix.h
diff --git a/third_party/grpc/src/core/iomgr/wakeup_fd_posix.h b/third_party/grpc/src/core/iomgr/wakeup_fd_posix.h
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+/*
+ *
+ * Copyright 2015, Google Inc.
+ * 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.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * 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.
+ *
+ */
+
+/*
+ * wakeup_fd abstracts the concept of a file descriptor for the purpose of
+ * waking up a thread in select()/poll()/epoll_wait()/etc.
+
+ * The poll() family of system calls provide a way for a thread to block until
+ * there is activity on one (or more) of a set of file descriptors. An
+ * application may wish to wake up this thread to do non file related work. The
+ * typical way to do this is to add a pipe to the set of file descriptors, then
+ * write to the pipe to wake up the thread in poll().
+ *
+ * Linux has a lighter weight eventfd specifically designed for this purpose.
+ * wakeup_fd abstracts the difference between the two.
+ *
+ * Setup:
+ * 1. Before calling anything, call global_init() at least once.
+ * 1. Call grpc_wakeup_fd_create() to get a wakeup_fd.
+ * 2. Add the result of GRPC_WAKEUP_FD_FD to the set of monitored file
+ *    descriptors for the poll() style API you are using. Monitor the file
+ *    descriptor for readability.
+ * 3. To tear down, call grpc_wakeup_fd_destroy(). This closes the underlying
+ *    file descriptor.
+ *
+ * Usage:
+ * 1. To wake up a polling thread, call grpc_wakeup_fd_wakeup() on a wakeup_fd
+ *    it is monitoring.
+ * 2. If the polling thread was awakened by a wakeup_fd event, call
+ *    grpc_wakeup_fd_consume_wakeup() on it.
+ */
+#ifndef GRPC_INTERNAL_CORE_IOMGR_WAKEUP_FD_POSIX_H
+#define GRPC_INTERNAL_CORE_IOMGR_WAKEUP_FD_POSIX_H
+
+void grpc_wakeup_fd_global_init(void);
+void grpc_wakeup_fd_global_destroy(void);
+
+/* Force using the fallback implementation. This is intended for testing
+ * purposes only.*/
+void grpc_wakeup_fd_global_init_force_fallback(void);
+
+typedef struct grpc_wakeup_fd grpc_wakeup_fd;
+
+typedef struct grpc_wakeup_fd_vtable {
+  void (*init)(grpc_wakeup_fd* fd_info);
+  void (*consume)(grpc_wakeup_fd* fd_info);
+  void (*wakeup)(grpc_wakeup_fd* fd_info);
+  void (*destroy)(grpc_wakeup_fd* fd_info);
+  /* Must be called before calling any other functions */
+  int (*check_availability)(void);
+} grpc_wakeup_fd_vtable;
+
+struct grpc_wakeup_fd {
+  int read_fd;
+  int write_fd;
+};
+
+extern int grpc_allow_specialized_wakeup_fd;
+
+#define GRPC_WAKEUP_FD_GET_READ_FD(fd_info) ((fd_info)->read_fd)
+
+void grpc_wakeup_fd_init(grpc_wakeup_fd* fd_info);
+void grpc_wakeup_fd_consume_wakeup(grpc_wakeup_fd* fd_info);
+void grpc_wakeup_fd_wakeup(grpc_wakeup_fd* fd_info);
+void grpc_wakeup_fd_destroy(grpc_wakeup_fd* fd_info);
+
+/* Defined in some specialized implementation's .c file, or by
+ * wakeup_fd_nospecial.c if no such implementation exists. */
+extern const grpc_wakeup_fd_vtable grpc_specialized_wakeup_fd_vtable;
+
+#endif /* GRPC_INTERNAL_CORE_IOMGR_WAKEUP_FD_POSIX_H */