initial code repo

[stor4nfv.git] / src / ceph / src / msg / async / dpdk / stream.h

diff --git a/src/ceph/src/msg/async/dpdk/stream.h b/src/ceph/src/msg/async/dpdk/stream.h
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+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*- 
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  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.
+ */
+/*
+ * Copyright (C) 2014 Cloudius Systems, Ltd.
+ */
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2015 XSky <haomai@xsky.com>
+ *
+ * Author: Haomai Wang <haomaiwang@gmail.com>
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software
+ * Foundation.  See file COPYING.
+ *
+ */
+
+#ifndef CEPH_MSG_STREAM_H_
+#define CEPH_MSG_STREAM_H_
+
+#include <exception>
+#include <cassert>
+
+// A stream<> is the producer side.  It may call produce() as long
+// as the returned from the previous invocation is ready.
+// To signify no more data is available, call close().
+//
+// A subscription<> is the consumer side.  It is created by a call
+// to stream::listen().  Calling subscription::start(),
+// which registers the data processing callback, starts processing
+// events.  It may register for end-of-stream notifications by
+// return the when_done() future, which also delivers error
+// events (as exceptions).
+//
+// The consumer can pause generation of new data by returning
+// positive integer; when it becomes ready, the producer
+// will resume processing.
+
+template <typename... T>
+class subscription;
+
+template <typename... T>
+class stream {
+  subscription<T...>* _sub = nullptr;
+  int done;
+  bool ready;
+ public:
+  using next_fn = std::function<int (T...)>;
+  stream() = default;
+  stream(const stream&) = delete;
+  stream(stream&&) = delete;
+  ~stream() {
+    if (_sub) {
+      _sub->_stream = nullptr;
+    }
+  }
+
+  void operator=(const stream&) = delete;
+  void operator=(stream&&) = delete;
+
+  // Returns a subscription that reads value from this
+  // stream.
+  subscription<T...> listen() {
+    return subscription<T...>(this);
+  }
+
+  // Returns a subscription that reads value from this
+  // stream, and also sets up the listen function.
+  subscription<T...> listen(next_fn next) {
+    auto sub = subscription<T...>(this);
+    sub.start(std::move(next));
+    return sub;
+  }
+
+  // Becomes ready when the listener is ready to accept
+  // values.  Call only once, when beginning to produce
+  // values.
+  bool started() {
+    return ready;
+  }
+
+  // Produce a value.  Call only after started(), and after
+  // a previous produce() is ready.
+  int produce(T... data) {
+      return _sub->_next(std::move(data)...);
+  }
+
+  // End the stream.   Call only after started(), and after
+  // a previous produce() is ready.  No functions may be called
+  // after this.
+  void close() {
+    done = 1;
+  }
+
+  // Signal an error.   Call only after started(), and after
+  // a previous produce() is ready.  No functions may be called
+  // after this.
+  void set_exception(int error) {
+    done = error;
+  }
+ private:
+  void start();
+  friend class subscription<T...>;
+};
+
+template <typename... T>
+class subscription {
+ public:
+  using next_fn = typename stream<T...>::next_fn;
+ private:
+  stream<T...>* _stream;
+  next_fn _next;
+ private:
+  explicit subscription(stream<T...>* s): _stream(s) {
+    assert(!_stream->_sub);
+    _stream->_sub = this;
+  }
+
+ public:
+  subscription(subscription&& x)
+    : _stream(x._stream), _next(std::move(x._next)) {
+    x._stream = nullptr;
+    if (_stream) {
+      _stream->_sub = this;
+    }
+  }
+  ~subscription() {
+    if (_stream) {
+      _stream->_sub = nullptr;
+    }
+  }
+
+  /// \brief Start receiving events from the stream.
+  ///
+  /// \param next Callback to call for each event
+  void start(std::function<int (T...)> next) {
+    _next = std::move(next);
+    _stream->ready = true;
+  }
+
+  // Becomes ready when the stream is empty, or when an error
+  // happens (in that case, an exception is held).
+  int done() {
+    return _stream->done;
+  }
+
+  friend class stream<T...>;
+};
+
+#endif /* CEPH_MSG_STREAM_H_ */