1 files changed, 49 insertions, 0 deletions
diff --git a/configutil/src/lib/hostfilter.h b/configutil/src/lib/hostfilter.h
new file mode 100644
index 00000000000..8c255c930cc
--- /dev/null
+++ b/configutil/src/lib/hostfilter.h
@@ -0,0 +1,49 @@
+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+#pragma once
+
+#include <unordered_set>
+#include <string>
+
+/**
+ * Simple host filter which in its default empty state implicitly includes all
+ * hosts, or only an explicit subset iff at least one host has been provided
+ * to the filter as part of construction.
+ */
+class HostFilter {
+public:
+    using HostSet = std::unordered_set<std::string>;
+private:
+    HostSet _hosts;
+public:
+    /**
+     * Empty host filter; all hosts are implicitly included.
+     */
+    HostFilter() : _hosts() {}
+
+    /**
+     * Explicitly given host set; only the hosts whose name exactly match
+     * one of the provided names will pass the includes(name) check.
+     */
+    explicit HostFilter(const std::unordered_set<std::string>& hosts)
+        : _hosts(hosts)
+    {
+    }
+
+    explicit HostFilter(std::unordered_set<std::string>&& hosts)
+        : _hosts(std::move(hosts))
+    {
+    }
+
+    HostFilter(HostFilter&&) = default;
+    HostFilter& operator=(HostFilter&&) = default;
+
+    HostFilter(const HostFilter&) = default;
+    HostFilter& operator=(const HostFilter&) = default;
+
+    bool includes(const std::string& candidate) const {
+        if (_hosts.empty()) {
+            return true;
+        }
+        return (_hosts.find(candidate) != _hosts.end());
+    }
+};