Adding upstream version 18.2.2.upstream/18.2.2

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

1 files changed, 25 insertions, 0 deletions

diff --git a/src/common/weighted_shuffle.h b/src/common/weighted_shuffle.h
new file mode 100644
index 000000000..10def0a01
--- /dev/null
+++ b/src/common/weighted_shuffle.h
@@ -0,0 +1,25 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#pragma once
+
+#include <algorithm>
+#include <iterator>
+#include <random>
+
+template <class RandomIt, class DistIt, class URBG>
+void weighted_shuffle(RandomIt first, RandomIt last,
+		      DistIt weight_first, DistIt weight_last,
+		      URBG &&g)
+{
+  if (first == last) {
+    return;
+  } else {
+    std::discrete_distribution d{weight_first, weight_last};
+    if (auto n = d(g); n > 0) {
+      std::iter_swap(first, std::next(first, n));
+      std::iter_swap(weight_first, std::next(weight_first, n));
+    }
+    weighted_shuffle(++first, last, ++weight_first, weight_last, std::move(g));
+  }
+}