Adding upstream version 18.2.2.upstream/18.2.2

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 69 insertions, 0 deletions

diff --git a/src/rocksdb/util/channel.h b/src/rocksdb/util/channel.h
new file mode 100644
index 000000000..19b956297
--- /dev/null
+++ b/src/rocksdb/util/channel.h
@@ -0,0 +1,69 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#include <condition_variable>
+#include <mutex>
+#include <queue>
+#include <utility>
+
+#include "rocksdb/rocksdb_namespace.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+template <class T>
+class channel {
+ public:
+  explicit channel() : eof_(false) {}
+
+  channel(const channel&) = delete;
+  void operator=(const channel&) = delete;
+
+  void sendEof() {
+    std::lock_guard<std::mutex> lk(lock_);
+    eof_ = true;
+    cv_.notify_all();
+  }
+
+  bool eof() {
+    std::lock_guard<std::mutex> lk(lock_);
+    return buffer_.empty() && eof_;
+  }
+
+  size_t size() const {
+    std::lock_guard<std::mutex> lk(lock_);
+    return buffer_.size();
+  }
+
+  // writes elem to the queue
+  void write(T&& elem) {
+    std::unique_lock<std::mutex> lk(lock_);
+    buffer_.emplace(std::forward<T>(elem));
+    cv_.notify_one();
+  }
+
+  /// Moves a dequeued element onto elem, blocking until an element
+  /// is available.
+  // returns false if EOF
+  bool read(T& elem) {
+    std::unique_lock<std::mutex> lk(lock_);
+    cv_.wait(lk, [&] { return eof_ || !buffer_.empty(); });
+    if (eof_ && buffer_.empty()) {
+      return false;
+    }
+    elem = std::move(buffer_.front());
+    buffer_.pop();
+    cv_.notify_one();
+    return true;
+  }
+
+ private:
+  std::condition_variable cv_;
+  mutable std::mutex lock_;
+  std::queue<T> buffer_;
+  bool eof_;
+};
+}  // namespace ROCKSDB_NAMESPACE