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Diffstat (limited to '')
-rw-r--r-- | src/base/opt_util.hh | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/src/base/opt_util.hh b/src/base/opt_util.hh new file mode 100644 index 0000000..aea038e --- /dev/null +++ b/src/base/opt_util.hh @@ -0,0 +1,105 @@ +/** + * Copyright (c) 2019, Timothy Stack + * + * All rights reserved. + * + * 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. + * * Neither the name of Timothy Stack nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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 lnav_opt_util_hh +#define lnav_opt_util_hh + +#include <stdlib.h> + +#include "optional.hpp" + +namespace detail { + +template<class T> +typename std::enable_if<std::is_void<T>::value, T>::type +void_or_nullopt() +{ + return; +} + +template<class T> +typename std::enable_if<not std::is_void<T>::value, T>::type +void_or_nullopt() +{ + return nonstd::nullopt; +} + +template<class T> +struct is_optional : std::false_type { +}; + +template<class T> +struct is_optional<nonstd::optional<T>> : std::true_type { +}; +} // namespace detail + +template<class T, + class F, + std::enable_if_t<detail::is_optional<std::decay_t<T>>::value, int> = 0> +auto +operator|(T&& t, F f) + -> decltype(detail::void_or_nullopt<decltype(f(std::forward<T>(t). + operator*()))>()) +{ + using return_type = decltype(f(std::forward<T>(t).operator*())); + if (t) + return f(std::forward<T>(t).operator*()); + else + return detail::void_or_nullopt<return_type>(); +} + +template<class T> +optional_constexpr nonstd::optional<typename std::decay<T>::type> +make_optional_from_nullable(T&& v) +{ + if (v != nullptr) { + return nonstd::optional<typename std::decay<T>::type>( + std::forward<T>(v)); + } + return nonstd::nullopt; +} + +template<template<typename, typename...> class C, typename T> +nonstd::optional<T> +cget(const C<T>& container, size_t index) +{ + if (index < container.size()) { + return container[index]; + } + + return nonstd::nullopt; +} + +inline nonstd::optional<const char*> +getenv_opt(const char* name) +{ + return make_optional_from_nullable(getenv(name)); +} + +#endif |