n/basis: add runtime switchable basis function

Makefile.am

@@ -146,10 +146,12 @@ UTIL_FILES   =			\
     noise/basis/constant.cpp	\
     noise/basis/constant.hpp	\
     noise/basis/constant.ipp	\
-    noise/basis/value.hpp	\
-    noise/basis/value.ipp	\
     noise/basis/perlin.hpp	\
     noise/basis/perlin.ipp	\
+    noise/basis/runtime.cpp	\
+    noise/basis/runtime.hpp	\
+    noise/basis/value.hpp	\
+    noise/basis/value.ipp	\
     noise/basis/worley.hpp	\
     noise/basis/worley.ipp	\
     noise/fractal/base.hpp	\

noise/basis/runtime.cpp

@@ -0,0 +1,20 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Copyright 2012-2015 Danny Robson <danny@nerdcruft.net>
+ */
+
+#include "runtime.hpp"
+
+
+template struct util::noise::basis::runtime<float>;

noise/basis/runtime.hpp

@@ -0,0 +1,80 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Copyright 2012-2015 Danny Robson <danny@nerdcruft.net>
+ */
+
+
+#ifndef __UTIL_NOISE_BASIS_RUNTIME_HPP
+#define __UTIL_NOISE_BASIS_RUNTIME_HPP
+
+#include "../basis.hpp"
+#include "../../point.hpp"
+#include "../../range.hpp"
+
+#include <memory>
+
+namespace util { namespace noise { namespace basis {
+    template <typename T>
+    struct runtime {
+    public:
+        runtime (seed_t) {}
+        runtime (runtime&&) = default;
+        runtime (const runtime&) = delete;
+        runtime& operator= (const runtime&) = delete;
+
+        // basis functions
+        T operator () (util::point<2,T> p) const { return (*m_child) (p); }
+        range<T> bounds (void) const { return m_child->bounds (); }
+
+        seed_t seed (void) const { return m_child->seed (); }
+        seed_t seed (seed_t) { return m_child->seed (); }
+
+    private:
+        struct base {
+            virtual ~base () = default;
+            virtual T operator() (util::point<2,T>) const = 0;
+            virtual range<T> bounds (void) const = 0;
+            virtual seed_t seed (void) const = 0;
+            virtual seed_t seed (seed_t) = 0;
+        };
+
+        template <typename B>
+        struct child : public base {
+            child (seed_t _seed): data (_seed) { }
+            virtual T operator() (util::point<2,T> p) const override { return data (p); }
+            virtual range<T> bounds (void) const override { return data.bounds (); }
+            virtual seed_t seed (void) const override { return data.seed (); }
+            virtual seed_t seed (seed_t _seed) override { return data.seed (_seed); }
+
+        private:
+            B data;
+        };
+
+        std::unique_ptr<base> m_child;
+
+    public:
+        template <typename B>
+        void
+        reset (seed_t _seed)
+        {
+            using basis_t = B;
+            using child_t = child<basis_t>;
+
+            m_child.reset (new child_t (_seed));
+        }
+    };
+} } }
+
+#endif
+