szaszm commented on code in PR #1584: URL: https://github.com/apache/nifi-minifi-cpp/pull/1584#discussion_r1229570316
########## libminifi/include/utils/gsl.h: ########## @@ -17,6 +17,7 @@ #pragma once +#include <span> Review Comment: Now that the utils were moved, do we need this include? ########## libminifi/include/utils/span.h: ########## @@ -0,0 +1,47 @@ +/** + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You 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 <span> + +namespace org::apache::nifi::minifi::utils { + +namespace detail { +template<typename T> +using remove_cvref_t = typename std::remove_cv<typename std::remove_reference<T>::type>::type; +} // namespace detail + +template<typename Container, typename T> +Container span_to(std::span<T> span) { + static_assert(std::is_constructible<Container, typename std::span<T>::iterator, typename std::span<T>::iterator>::value, + "The destination container must have an iterator (pointer) range constructor"); + return Container(std::begin(span), std::end(span)); +} +template<template<typename...> class Container, typename T> +Container<detail::remove_cvref_t<T>> span_to(std::span<T> span) { + static_assert(std::is_constructible<Container<detail::remove_cvref_t<T>>, typename std::span<T>::iterator, typename std::span<T>::iterator>::value, + "The destination container must have an iterator (pointer) range constructor"); + return span_to<Container<detail::remove_cvref_t<T>>>(span); +} + +template<typename T, typename U> +std::span<T> as_span(std::span<U> value) { + return std::span{reinterpret_cast<T*>(value.data()), value.size_bytes() / sizeof(T)}; +} Review Comment: I believe it's undefined behavior to access the result of this unless it's the same (without cv-qual.) as the original contained type, `unsigned char` or `std::byte` (for which we use `std::as_bytes`/`std::as_writable_bytes`), or another trivial layout-compatible type. I don't know a better solution for now: `memcpy`/`std::bit_cast` everywhere seems a bit excessive, will cause ownership problems, and the current non-standard approach still works, and will most likely keep working with at least GCC. (They generally don't like to break such things, even if non-standard.) Can we add a comment about this? Feel free to simplify the language or omit some details, as you see fit. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: issues-unsubscr...@nifi.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
