From addecbfdefe9f00214db9af438b0fe255e92a16a Mon Sep 17 00:00:00 2001
From: Alexander Karatarakis <alkarata@microsoft.com>
Date: Thu, 22 Sep 2016 23:28:14 -0700
Subject: Introduce vcpkg_Maps utility namespace

---
 toolsrc/include/vcpkg_Maps.h                    | 18 ++++++++++++++++++
 toolsrc/vcpkgcommon/vcpkgcommon.vcxproj         |  1 +
 toolsrc/vcpkgcommon/vcpkgcommon.vcxproj.filters |  3 +++
 3 files changed, 22 insertions(+)
 create mode 100644 toolsrc/include/vcpkg_Maps.h

diff --git a/toolsrc/include/vcpkg_Maps.h b/toolsrc/include/vcpkg_Maps.h
new file mode 100644
index 000000000..5b7b8ed46
--- /dev/null
+++ b/toolsrc/include/vcpkg_Maps.h
@@ -0,0 +1,18 @@
+#pragma once
+
+#include <unordered_map>
+#include <unordered_set>
+
+namespace vcpkg { namespace Maps
+{
+    template <typename K, typename V>
+    std::unordered_set<K> extract_key_set(const std::unordered_map<K, V>& input_map)
+    {
+        std::unordered_set<K> key_set;
+        for (auto const& element : input_map)
+        {
+            key_set.insert(element.first);
+        }
+        return key_set;
+    }
+}}
diff --git a/toolsrc/vcpkgcommon/vcpkgcommon.vcxproj b/toolsrc/vcpkgcommon/vcpkgcommon.vcxproj
index e91cf2cf8..d5e68fde3 100644
--- a/toolsrc/vcpkgcommon/vcpkgcommon.vcxproj
+++ b/toolsrc/vcpkgcommon/vcpkgcommon.vcxproj
@@ -131,6 +131,7 @@
     <ClInclude Include="..\include\vcpkg_Checks.h" />
     <ClInclude Include="..\include\vcpkg_Files.h" />
     <ClInclude Include="..\include\vcpkg_Graphs.h" />
+    <ClInclude Include="..\include\vcpkg_Maps.h" />
     <ClInclude Include="..\include\vcpkg_Sets.h" />
     <ClInclude Include="..\include\vcpkg_Strings.h" />
     <ClInclude Include="..\include\vcpkg_System.h" />
diff --git a/toolsrc/vcpkgcommon/vcpkgcommon.vcxproj.filters b/toolsrc/vcpkgcommon/vcpkgcommon.vcxproj.filters
index 969cf58b4..ae747d687 100644
--- a/toolsrc/vcpkgcommon/vcpkgcommon.vcxproj.filters
+++ b/toolsrc/vcpkgcommon/vcpkgcommon.vcxproj.filters
@@ -50,6 +50,9 @@
     <ClInclude Include="..\include\opt_bool.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="..\include\vcpkg_Maps.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
     <ClInclude Include="..\include\vcpkg_Sets.h">
       <Filter>Header Files</Filter>
     </ClInclude>
-- 
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