util/GenerateArray: new utility library

src/util/GenerateArray.hxx

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2020 Max Kellermann <max.kellermann@gmail.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef GENERATE_ARRAY_HXX
+#define GENERATE_ARRAY_HXX
+
+#include <array>
+#include <utility>
+
+template<std::size_t N, typename F, std::size_t... I>
+constexpr auto
+_GenerateArray(F &&f, std::index_sequence<I...>) noexcept
+{
+	using T = decltype(f(0));
+
+	return std::array<T, N>{f(I)...};
+}
+
+/**
+ * Generate a `constexpr` std::array at compile time by calling the
+ * given function for each index.
+ *
+ * @param N the number of elements in the array
+ * @param F the function (called N times with the index as only parameter)
+ */
+template<std::size_t N, typename F>
+constexpr auto
+GenerateArray(F &&f) noexcept
+{
+	return _GenerateArray<N>(std::forward<F>(f),
+				 std::make_index_sequence<N>());
+}
+
+#endif
+