move utilities to liblfjail

1 files changed, 136 insertions, 0 deletions

diff --git a/liblfjail/string_utils.hh b/liblfjail/string_utils.hh
new file mode 100644
index 0000000..f0ec5c1
--- /dev/null
+++ b/liblfjail/string_utils.hh
@@ -0,0 +1,136 @@
+/*
+ * This source code is released into the public domain.
+ */
+
+#ifndef	LFJAIL_STRING_UTILS_HH
+#define	LFJAIL_STRING_UTILS_HH
+
+#include <locale>
+#include <ranges>
+
+namespace lfjail {
+
+/*
+ * ctype_is: wrap std::ctype<T>::is() in a form suitable for use as an algorithm
+ * predicate, i.e., ctype_is(m) will return a functor object that takes any char
+ * type as an argument and returns bool.
+ *
+ * If the locale is not specified, the C locale is used by default.
+ */
+struct ctype_is_fn {
+private:
+	/*
+	 * This functor is what ctype_is() returns to the caller, and
+	 * implements the actual operation based on the provided mask
+	 * and locale.  Do it this way so that the functor can be a
+	 * template function itself, rather than requiring the caller
+	 * to provide a template argument for ctype_is.
+	 */
+	struct impl {
+		impl(std::ctype_base::mask mask, const std::locale &locale)
+		    : _mask(mask)
+		    , _locale(locale)
+		{}
+
+		template<std::integral CharT>
+		bool operator()(CharT c) const {
+			return (_get_ctype<CharT>().is(_mask, c));
+		}
+
+	private:
+		std::ctype_base::mask _mask;
+		const std::locale &_locale;
+
+		template<std::integral CharT>
+		const std::ctype<CharT> &_get_ctype() const {
+			return (std::use_facet<std::ctype<CharT>>(_locale));
+		}
+	};
+
+public:
+	/*
+	 * Create an instance of the functor and return it.
+	 */
+	impl operator()(std::ctype_base::mask mask,
+	    const std::locale &locale = std::locale::classic()) const
+	{
+		return (impl(mask, locale));
+	}
+
+};
+inline constexpr auto ctype_is = ctype_is_fn{};
+
+/*
+ * Remove leading whitespace from the given string_view.
+ */
+
+template<typename Char>
+std::basic_string_view<Char>
+skipws(std::basic_string_view<Char> text) {
+	auto isspace = ctype_is(std::ctype_base::space);
+	auto first_nonws = std::ranges::find_if_not(text, isspace);
+	return {first_nonws, end(text)};
+}
+
+template<typename Char>
+void skipws(std::basic_string_view<Char> *text) {
+	auto ret = skipws(*text);
+	*text = ret;
+}
+
+/*
+ * Split a string on a predicate.  Specifically, divide the string into two
+ * strings at the first character where the predicate matches, and return
+ * both strings.  If the predicate matched, the matching character will be
+ * discarded.
+ */
+
+template<typename Char,
+	 std::indirect_unary_predicate<
+	 	typename std::basic_string_view<Char>::iterator> Pred>
+std::pair<std::basic_string_view<Char>, std::basic_string_view<Char>>
+split(std::basic_string_view<Char> text, Pred pred)
+{
+	auto split_point = std::ranges::find_if(text, pred);
+
+	if (split_point == end(text))
+		return {text, {}};
+	else
+		return {{begin(text), split_point},
+			{std::next(split_point), end(text)}};
+}
+
+template<typename Char,
+	 std::indirect_unary_predicate<
+	 	typename std::basic_string_view<Char>::iterator> Pred>
+std::basic_string_view<Char>
+split(std::basic_string_view<Char> *text, Pred pred)
+{
+	auto [str, rest] = split(*text, pred);
+	*text = rest;
+	return str;
+}
+
+/*
+ * Return the next word from a string_view.  The by-value version returns
+ * a pair<next-word, remainder>, while the pointer version returns next-word
+ * and sets the input string to remainder.
+ */
+
+template<typename Char>
+std::pair<std::basic_string_view<Char>, std::basic_string_view<Char>>
+next_word(std::basic_string_view<Char> text)
+{
+	return (split(skipws(text), ctype_is(std::ctype_base::space)));
+}
+
+template<typename Char>
+std::basic_string_view<Char>
+next_word(std::basic_string_view<Char> *text) {
+	skipws(text);
+	return (split(text, ctype_is(std::ctype_base::space)));
+}
+
+} // namespace lfjail
+
+#endif	// LFJAIL_STRING_UTILS_HH