Add lazy.h

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;
+    };
+}

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" />

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>