From 47b53b9015deaa2f569d788447254c8bc3de96a9 Mon Sep 17 00:00:00 2001
From: Alexander Karatarakis <alkarata@microsoft.com>
Date: Thu, 9 Mar 2017 18:24:04 -0800
Subject: Add lazy.h

---
 toolsrc/include/lazy.h                    | 26 ++++++++++++++++++++++++++
 toolsrc/vcpkglib/vcpkglib.vcxproj         |  1 +
 toolsrc/vcpkglib/vcpkglib.vcxproj.filters |  3 +++
 3 files changed, 30 insertions(+)
 create mode 100644 toolsrc/include/lazy.h

diff --git a/toolsrc/include/lazy.h b/toolsrc/include/lazy.h
new file mode 100644
index 000000000..f9dbd8dc7
--- /dev/null
+++ b/toolsrc/include/lazy.h
@@ -0,0 +1,26 @@
+#pragma once
+
+namespace vcpkg
+{
+    template <typename T>
+    class lazy
+    {
+    public:
+        lazy() : value(T()), initialized(false) {}
+
+        template <class F>
+        T const& get_lazy(F& f) const
+        {
+            if (!initialized)
+            {
+                value = f();
+                initialized = true;
+            }
+            return value;
+        }
+
+    private:
+        mutable T value;
+        mutable bool initialized;
+    };
+}
diff --git a/toolsrc/vcpkglib/vcpkglib.vcxproj b/toolsrc/vcpkglib/vcpkglib.vcxproj
index b96dd1050..dd5dd124a 100644
--- a/toolsrc/vcpkglib/vcpkglib.vcxproj
+++ b/toolsrc/vcpkglib/vcpkglib.vcxproj
@@ -137,6 +137,7 @@
   </ItemDefinitionGroup>
   <ItemGroup>
     <ClInclude Include="..\include\BinaryParagraph.h" />
+    <ClInclude Include="..\include\lazy.h" />
     <ClInclude Include="..\include\PostBuildLint_BuildInfo.h" />
     <ClInclude Include="..\include\PostBuildLint_BuildPolicies.h" />
     <ClInclude Include="..\include\coff_file_reader.h" />
diff --git a/toolsrc/vcpkglib/vcpkglib.vcxproj.filters b/toolsrc/vcpkglib/vcpkglib.vcxproj.filters
index aefba7a49..d701321be 100644
--- a/toolsrc/vcpkglib/vcpkglib.vcxproj.filters
+++ b/toolsrc/vcpkglib/vcpkglib.vcxproj.filters
@@ -293,5 +293,8 @@
     <ClInclude Include="..\include\vcpkg_Chrono.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="..\include\lazy.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>
\ No newline at end of file
-- 
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