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lib/ngx_pagespeed/src/ngx_event_connection.h

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+/*
+ * Copyright 2014 Google 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.
+ */
+
+// Author: oschaaf@we-amp.com (Otto van der Schaaf)
+//
+// NgxEventConnection implements a means to send events from other threads to
+// nginx's event loop, and is implemented by a named pipe under the hood.
+// A single instance is used by NgxBaseFetch, and one instance is created per
+// NgxUrlAsyncFetcher when native fetching is on.
+
+#ifndef NGX_EVENT_CONNECTION_H_
+#define NGX_EVENT_CONNECTION_H_
+
+extern "C" {
+#include <ngx_http.h>
+}
+
+#include <pthread.h>
+
+#include "pagespeed/kernel/base/string.h"
+#include "pagespeed/kernel/http/headers.h"
+
+namespace net_instaweb {
+
+class NgxEventConnection;
+
+// Represents a single event that can be written to or read from the pipe.
+// Technically, sender is the only data we need to send. type and connection are
+// included to provide a means to trace the events along with some more
+// info.
+typedef struct {
+  char type;
+  void* sender;
+  NgxEventConnection* connection;
+} ps_event_data;
+
+// Handler signature for receiving events
+typedef void (*callbackPtr)(const ps_event_data&);
+
+// Abstracts a connection to nginx through which events can be written.
+class NgxEventConnection {
+ public:
+  explicit NgxEventConnection(callbackPtr handler);
+
+  // Creates the file descriptors and ngx_connection_t required for event
+  // messaging between pagespeed and nginx.
+  bool Init(ngx_cycle_t* cycle);
+  // Shuts down the underlying file descriptors and connection created in Init()
+  void Shutdown();
+  // Constructs a ps_event_data and writes it to the underlying named pipe.
+  bool WriteEvent(char type, void* sender);
+  // Convenience overload for clients that have a single event type.
+  bool WriteEvent(void* sender);
+  // Reads and processes what is available in the named pipe's buffer.
+  void Drain();
+ private:
+  static bool CreateNgxConnection(ngx_cycle_t* cycle, ngx_fd_t pipe_fd);
+  static void ReadEventHandler(ngx_event_t* e);
+  static bool ReadAndNotify(ngx_fd_t fd);
+
+  callbackPtr event_handler_;
+  // We own these file descriptors
+  ngx_fd_t pipe_write_fd_;
+  ngx_fd_t pipe_read_fd_;
+
+  DISALLOW_COPY_AND_ASSIGN(NgxEventConnection);
+};
+
+}  // namespace net_instaweb
+
+#endif  // NGX_EVENT_CONNECTION_H_