job/dispatch: add chunked image job queueing

CMakeLists.txt

@@ -277,6 +277,7 @@ list (
     io.hpp
     iterator.hpp
     job/fwd.hpp
+    job/dispatch.hpp
     job/queue.cpp
     job/queue.hpp
     json/fwd.hpp

job/dispatch.hpp

@@ -0,0 +1,81 @@
+/*
+ * 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 2018 Danny Robson <danny@nerdcruft.net>
+ */
+
+#ifndef CRUFT_UTIL_JOB_DISPATCH_HPP
+#define CRUFT_UTIL_JOB_DISPATCH_HPP
+
+#include "queue.hpp"
+
+#include "../extent.hpp"
+#include "../region.hpp"
+
+#include <vector>
+
+namespace util::job {
+    // call a function across all elements of a container using the supplied
+    // job queue.
+    //
+    // threads will have work sizes dictated by a supplied extent.
+    //
+    // returns a cookie, or container of cookies, to wait on.
+    //
+    // TODO: extend to 1d and 3d
+    template <
+        typename ContainerT,
+        typename FunctionT,
+        typename ...Args,
+        size_t DimensionV
+    >
+    std::vector<queue::cookie>
+    dispatch (
+        util::job::queue &q,
+        ContainerT &data,
+        util::extent<DimensionV,int> chunk,
+        FunctionT &func,
+        Args ...args)
+    {
+        auto chunked_func = [&func] (ContainerT &inner_data,
+                                     auto param,
+                                     Args... inner_args)
+        {
+            for (auto p: param) {
+                if (!inner_data.extent ().exclusive (p))
+                    continue;
+                inner_data[p][0] = std::invoke (func, p.template cast<float> (), inner_args...);
+            }
+        };
+
+        std::vector<queue::cookie> cookies;
+
+        const extent2i count = (data.extent () + chunk - 1) / chunk;
+
+        for (auto index: count.step ()) {
+            util::point<DimensionV,int> base = index * chunk;
+            cookies.push_back (
+                q.submit (
+                    chunked_func,
+                    std::ref (data),
+                    util::region<DimensionV,int> {base, chunk}.step (),
+                    args...
+                )
+            );
+        }
+
+        return cookies;
+    }
+}
+
+#endif