3 files changed, 147 insertions, 0 deletions
diff --git a/build/config/utility b/build/config/utility
new file mode 100644
index 0000000..2973516
--- /dev/null
+++ b/build/config/utility
@@ -0,0 +1,45 @@
+// file      : build/config/utility -*- C++ -*-
+// copyright : Copyright (c) 2014-2015 Code Synthesis Tools CC
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef BUILD_CONFIG_UTILITY
+#define BUILD_CONFIG_UTILITY
+
+#include <string>
+#include <utility> // pair
+
+namespace build
+{
+  class scope;
+  class list_value;
+
+  namespace config
+  {
+    // Set, if necessary, a required config.* variable.
+    //
+    // Return the reference to the value as well as the indication of
+    // whether the variable has actually been set.
+    //
+    template <typename T>
+    std::pair<const T&, bool>
+    required (scope& root, const char* name, const T& default_value);
+
+    std::pair<const std::string&, bool>
+    required (scope& root, const char* name, const char* default_value);
+
+    // Set, if necessary, an optional config.* variable. In particular,
+    // an unspecified variable is set to NULL which is used to to
+    // distinguish between the "configured as unspecified" and "not
+    // yet configured" cases.
+    //
+    // Return the pointer to the value, which can be NULL.
+    //
+    template <typename T>
+    const T*
+    optional (scope& root, const char* name);
+  }
+}
+
+#include <build/config/utility.txx>
+
+#endif // BUILD_CONFIG_UTILITY
diff --git a/build/config/utility.cxx b/build/config/utility.cxx
new file mode 100644
index 0000000..8b26239
--- /dev/null
+++ b/build/config/utility.cxx
@@ -0,0 +1,41 @@
+// file      : build/config/utility.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2015 Code Synthesis Tools CC
+// license   : MIT; see accompanying LICENSE file
+
+#include <build/config/utility>
+
+using namespace std;
+
+namespace build
+{
+  namespace config
+  {
+    // The same as the template except it is a bit more efficient
+    // when it comes to not creating the default value string
+    // unnecessarily.
+    //
+    pair<const string&, bool>
+    required (scope& root, const char* name, const char* def_value)
+    {
+      string r;
+      const variable& var (variable_pool.find (name));
+
+      if (auto v = root[var])
+      {
+        const string& s (v.as<const string&> ());
+
+        if (!v.belongs (*global_scope)) // A value from (some) config.build.
+          return pair<const string&, bool> (s, false);
+
+        r = s;
+      }
+      else
+        r = def_value;
+
+      auto v (root.assign (var));
+      v = move (r);
+
+      return pair<const string&, bool> (v.as<const string&> (), true);
+    }
+  }
+}
diff --git a/build/config/utility.txx b/build/config/utility.txx
new file mode 100644
index 0000000..e37c2b5
--- /dev/null
+++ b/build/config/utility.txx
@@ -0,0 +1,61 @@
+// file      : build/config/utility.txx -*- C++ -*-
+// copyright : Copyright (c) 2014-2015 Code Synthesis Tools CC
+// license   : MIT; see accompanying LICENSE file
+
+#include <utility> // move()
+
+#include <build/scope>
+#include <build/variable>
+
+namespace build
+{
+  namespace config
+  {
+    template <typename T>
+    std::pair<const T&, bool>
+    required (scope& root, const char* name, const T& def_value)
+    {
+      T r;
+      const variable& var (variable_pool.find (name));
+
+      if (auto v = root[var])
+      {
+        const T& s (v.as<const T&> ());
+
+        if (!v.belongs (*global_scope)) // A value from (some) config.build.
+          return std::pair<const T&, bool> (s, false);
+
+        r = s;
+      }
+      else
+        r = def_value;
+
+      auto v (root.assign (var));
+      v = std::move (r);
+
+      return std::pair<const T&, bool> (v.as<const T&> (), true);
+    }
+
+    template <typename T>
+    const T*
+    optional (scope& root, const char* name)
+    {
+      const T* r (nullptr);
+      const variable& var (variable_pool.find (name));
+
+      auto v (root[var]);
+
+      if (v.defined ())
+      {
+        if (v.belongs (*global_scope))
+          root.assign (var) = v;
+
+        r =  v.null () ? nullptr : &v.as<const T&> ();
+      }
+      else
+        root.assign (var) = nullptr;
+
+      return r;
+    }
+  }
+}