FTL: Add variadic concatenation
For now, the arguments can only be integers, string literals, and
truncated string views, as this will mainly be used for tracing.
Bug: 185536303
Test: ftl_test
Change-Id: I3141992c6c9438710f04b056e67a5e8811d39f78
diff --git a/include/ftl/details/concat.h b/include/ftl/details/concat.h
new file mode 100644
index 0000000..8ce949e
--- /dev/null
+++ b/include/ftl/details/concat.h
@@ -0,0 +1,62 @@
+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#pragma once
+
+#include <functional>
+#include <string_view>
+
+#include <ftl/string.h>
+
+namespace android::ftl::details {
+
+template <typename T, typename = void>
+struct StaticString;
+
+template <typename T>
+struct StaticString<T, std::enable_if_t<std::is_integral_v<T>>> {
+ static constexpr std::size_t N = to_chars_length_v<T>;
+
+ explicit StaticString(T v) : view(to_chars(buffer, v)) {}
+
+ to_chars_buffer_t<T> buffer;
+ const std::string_view view;
+};
+
+template <std::size_t M>
+struct StaticString<const char (&)[M], void> {
+ static constexpr std::size_t N = M - 1;
+
+ explicit constexpr StaticString(const char (&str)[M]) : view(str, N) {}
+
+ const std::string_view view;
+};
+
+template <std::size_t N>
+struct Truncated {
+ std::string_view view;
+};
+
+template <std::size_t M>
+struct StaticString<Truncated<M>, void> {
+ static constexpr std::size_t N = M;
+
+ explicit constexpr StaticString(Truncated<M> str) : view(str.view.substr(0, N)) {}
+
+ const std::string_view view;
+};
+
+} // namespace android::ftl::details