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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-04 17:44:55 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-04 17:44:55 +0000
commit5068d34c08f951a7ea6257d305a1627b09a95817 (patch)
tree08213e2be853396a3b07ce15dbe222644dcd9a89 /src/base/future_util.hh
parentInitial commit. (diff)
downloadlnav-5068d34c08f951a7ea6257d305a1627b09a95817.tar.xz
lnav-5068d34c08f951a7ea6257d305a1627b09a95817.zip
Adding upstream version 0.11.1.upstream/0.11.1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/base/future_util.hh')
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1 files changed, 111 insertions, 0 deletions
diff --git a/src/base/future_util.hh b/src/base/future_util.hh
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+/**
+ * Copyright (c) 2020, Timothy Stack
+ *
+ * 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 Timothy Stack 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 REGENTS 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 REGENTS 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.
+ */
+
+#ifndef lnav_future_util_hh
+#define lnav_future_util_hh
+
+#include <deque>
+#include <future>
+
+namespace lnav {
+namespace futures {
+
+/**
+ * Create a future that is ready to immediately return a result.
+ *
+ * @tparam T The result type of the future.
+ * @param t The value the future should return.
+ * @return The new future.
+ */
+template<class T>
+std::future<std::decay_t<T>>
+make_ready_future(T&& t)
+{
+ std::promise<std::decay_t<T>> pr;
+ auto r = pr.get_future();
+ pr.set_value(std::forward<T>(t));
+ return r;
+}
+
+/**
+ * A queue used to limit the number of futures that are running concurrently.
+ *
+ * @tparam T The result of the futures.
+ * @tparam MAX_QUEUE_SIZE The maximum number of futures that can be in flight.
+ */
+template<typename T, int MAX_QUEUE_SIZE = 8>
+class future_queue {
+public:
+ /**
+ * @param processor The function to execute with the result of a future.
+ */
+ explicit future_queue(std::function<void(T&)> processor)
+ : fq_processor(processor){};
+
+ ~future_queue()
+ {
+ this->pop_to();
+ }
+
+ /**
+ * Add a future to the queue. If the size of the queue is greater than the
+ * MAX_QUEUE_SIZE, this call will block waiting for the first queued
+ * future to return a result.
+ *
+ * @param f The future to add to the queue.
+ */
+ void push_back(std::future<T>&& f)
+ {
+ this->fq_deque.emplace_back(std::move(f));
+ this->pop_to(MAX_QUEUE_SIZE);
+ }
+
+ /**
+ * Removes the next future from the queue, waits for the result, and then
+ * repeats until the queue reaches the given size.
+ *
+ * @param size The new desired size of the queue.
+ */
+ void pop_to(size_t size = 0)
+ {
+ while (this->fq_deque.size() > size) {
+ auto v = this->fq_deque.front().get();
+ this->fq_processor(v);
+ this->fq_deque.pop_front();
+ }
+ }
+
+ std::function<void(T&)> fq_processor;
+ std::deque<std::future<T>> fq_deque;
+};
+
+} // namespace futures
+} // namespace lnav
+
+#endif