utils/mu-regex: add PCRE Regex wrapper

Add a thin c++ wrapper for GLib's GRegex (which is a PCRE wrapper
itself). PCRE is much faster than C++ std::regex, it may even matter in
some use-cases.

lib/utils/mu-regex.hh

@@ -0,0 +1,133 @@
+/*
+** Copyright (C) 2022 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
+**
+** This program is free software; you can redistribute it and/or modify it
+** under the terms of the GNU General Public License as published by the
+** Free Software Foundation; either version 3, or (at your option) any
+** later version.
+**
+** This program is distributed in the hope that it will be useful,
+** but WITHOUT ANY WARRANTY; without even the implied warranty of
+** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+** GNU General Public License for more details.
+**
+** You should have received a copy of the GNU General Public License
+** along with this program; if not, write to the Free Software Foundation,
+** Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+**
+*/
+#ifndef MU_REGEX_HH__
+#define MU_REGEX_HH__
+
+#include <glib.h>
+#include <utils/mu-result.hh>
+
+namespace Mu {
+/**
+ * RAII wrapper around a GRegex which in itself is a wrapper around PCRE. We use
+ * PCRE rather than std::regex because it is much faster.
+ */
+struct Regex {
+	/**
+	 * Trivial constructor
+	 *
+	 * @return
+	 */
+	Regex() noexcept: rx_{}  {}
+
+
+	/**
+	 * Construct a new Regex object
+	 *
+	 * @param ptrn PRRE regular expression pattern
+	 * @param cflags compile flags
+	 * @param mflags match flags
+	 *
+	 * @return a Regex object or an error.
+	 */
+	static Result<Regex> make(const std::string& ptrn,
+				  GRegexCompileFlags cflags = G_REGEX_DEFAULT,
+				   GRegexMatchFlags mflags = G_REGEX_MATCH_DEFAULT) noexcept try {
+		return Regex(ptrn.c_str(), cflags, mflags);
+	} catch (const Error& err) {
+		return Err(err);
+	}
+
+	/**
+	 * DTOR
+	 */
+	~Regex() {
+		if (rx_)
+			g_regex_unref(rx_);
+	}
+
+	/**
+	 * Cast to the the underlying GRegex*
+	 *
+	 * @return a GRegex*
+	 */
+	operator const GRegex*() const noexcept { return rx_; }
+
+	/**
+	 * Doe this object contain a valid GRegex*?
+	 *
+	 * @return true or false
+	 */
+	operator bool() const noexcept { return !!rx_; }
+
+
+	// No need for a move CTOR, copying is cheap (GRegex is refcounted)
+
+	/**
+	 * Copy CTOR
+	 *
+	 * @param other some other Regex
+	 */
+	Regex(const Regex& other) noexcept { *this = other; }
+
+	/**
+	 * operator=
+	 *
+	 * @param other copy some other object to this one
+	 *
+	 * @return *this
+	 */
+	Regex& operator=(const Regex& other) noexcept {
+		if (this != &other) {
+			auto oldrx = rx_;
+			rx_ = other.rx_ ? g_regex_ref(other.rx_): nullptr;
+			if (oldrx)
+				g_regex_unref(oldrx);
+		}
+		return *this;
+	}
+
+	/**
+	 * Does this regexp match the given string? An unset Regex matches
+	 * nothing.
+	 *
+	 * @param str
+	 * @param mflags
+	 *
+	 * @return true or false
+	 */
+	bool matches(const std::string& str,
+		     GRegexMatchFlags mflags=G_REGEX_MATCH_DEFAULT) const noexcept {
+		return rx_ ? g_regex_match(rx_, str.c_str(), mflags, {}) : false;
+	}
+
+private:
+	Regex(const char *ptrn, GRegexCompileFlags cflags, GRegexMatchFlags mflags) {
+		GError *err{};
+		rx_ = g_regex_new(ptrn, cflags, mflags, &err);
+		if (!rx_)
+			throw Err(Error::Code::InvalidArgument,
+				  "invalid regexp: '%s'", ptrn);
+	}
+	GRegex *rx_{};
+};
+
+} // namespace Mu
+
+
+#endif /* MU_REGEX_HH__ */