util/OptionParser: move to cmdline/

This library will depend on libfmt, and libutil shouldn't depend on
any library.

src/cmdline/OptionDef.hxx

@@ -0,0 +1,79 @@
+/*
+ * Copyright 2003-2022 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * 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 2 of the License, 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 MPD_UTIL_OPTIONDEF_HXX
+#define MPD_UTIL_OPTIONDEF_HXX
+
+#include <cassert>
+
+/**
+ * Command line option definition.
+ */
+class OptionDef
+{
+	const char *long_option;
+	char short_option;
+	bool has_value = false;
+	const char *desc;
+public:
+	constexpr OptionDef(const char *_long_option, const char *_desc)
+		: long_option(_long_option),
+		  short_option(0),
+		  desc(_desc) { }
+
+	constexpr OptionDef(const char *_long_option,
+			    char _short_option, const char *_desc)
+		: long_option(_long_option),
+		  short_option(_short_option),
+		  desc(_desc) { }
+
+	constexpr OptionDef(const char *_long_option,
+			    char _short_option, bool _has_value,
+			    const char *_desc) noexcept
+		:long_option(_long_option),
+		 short_option(_short_option),
+		 has_value(_has_value),
+		 desc(_desc) {}
+
+	constexpr bool HasLongOption() const { return long_option != nullptr; }
+	constexpr bool HasShortOption() const { return short_option != 0; }
+
+	constexpr bool HasValue() const noexcept {
+		return has_value;
+	}
+
+	constexpr bool HasDescription() const { return desc != nullptr; }
+
+	const char *GetLongOption() const {
+		assert(HasLongOption());
+		return long_option;
+	}
+
+	char GetShortOption() const {
+		assert(HasShortOption());
+		return short_option;
+	}
+
+	const char *GetDescription() const {
+		assert(HasDescription());
+		return desc;
+	}
+};
+
+#endif

src/cmdline/OptionParser.cxx

@@ -0,0 +1,96 @@
+/*
+ * Copyright 2003-2022 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * 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 2 of the License, 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.
+ */
+
+#include "OptionParser.hxx"
+#include "OptionDef.hxx"
+#include "util/RuntimeError.hxx"
+#include "util/StringCompare.hxx"
+
+static const char *
+Shift(std::span<const char *const> &s) noexcept
+{
+	const char *value = s.front();
+	s = s.subspan(1);
+	return value;
+}
+
+inline const char *
+OptionParser::CheckShiftValue(const char *s, const OptionDef &option)
+{
+	if (!option.HasValue())
+		return nullptr;
+
+	if (args.empty())
+		throw FormatRuntimeError("Value expected after %s", s);
+
+	return Shift(args);
+}
+
+inline OptionParser::Result
+OptionParser::IdentifyOption(const char *s)
+{
+	assert(s != nullptr);
+	assert(*s == '-');
+
+	if (s[1] == '-') {
+		for (const auto &i : options) {
+			if (!i.HasLongOption())
+				continue;
+
+			const char *t = StringAfterPrefix(s + 2, i.GetLongOption());
+			if (t == nullptr)
+				continue;
+
+			const char *value;
+
+			if (*t == 0)
+				value = CheckShiftValue(s, i);
+			else if (*t == '=')
+				value = t + 1;
+			else
+				continue;
+
+			return {int(&i - options.data()), value};
+		}
+	} else if (s[1] != 0 && s[2] == 0) {
+		const char ch = s[1];
+		for (const auto &i : options) {
+			if (i.HasShortOption() && ch == i.GetShortOption()) {
+				const char *value = CheckShiftValue(s, i);
+				return {int(&i - options.data()), value};
+			}
+		}
+	}
+
+	throw FormatRuntimeError("Unknown option: %s", s);
+}
+
+OptionParser::Result
+OptionParser::Next()
+{
+	while (!args.empty()) {
+		const char *arg = Shift(args);
+		if (arg[0] == '-')
+			return IdentifyOption(arg);
+
+		*remaining_tail++ = arg;
+	}
+
+	return {-1, nullptr};
+}

src/cmdline/OptionParser.hxx

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2003-2022 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * 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 2 of the License, 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 MPD_UTIL_OPTIONPARSER_HXX
+#define MPD_UTIL_OPTIONPARSER_HXX
+
+#include "OptionDef.hxx"
+
+#include <span>
+
+/**
+ * Command line option parser.
+ */
+class OptionParser
+{
+	std::span<const OptionDef> options;
+
+	std::span<const char *const> args;
+
+	const char **const remaining_head, **remaining_tail;
+
+public:
+	/**
+	 * Constructs #OptionParser.
+	 */
+	OptionParser(std::span<const OptionDef> _options,
+		     int _argc, char **_argv) noexcept
+		:options(_options), args(_argv + 1, _argc - 1),
+		 remaining_head(const_cast<const char **>(_argv + 1)),
+		 remaining_tail(remaining_head) {}
+
+	struct Result {
+		int index;
+		const char *value;
+
+		constexpr operator bool() const noexcept {
+			return index >= 0;
+		}
+	};
+
+	/**
+	 * Parses current command line entry.
+	 * Regardless of result, advances current position to the next
+	 * command line entry. 
+	 *
+	 * Throws on error.
+	 */
+	Result Next();
+
+	/**
+	 * Returns the remaining non-option arguments.
+	 */
+	std::span<const char *const> GetRemaining() const noexcept {
+		return {remaining_head, remaining_tail};
+	}
+
+private:
+	const char *CheckShiftValue(const char *s, const OptionDef &option);
+	Result IdentifyOption(const char *s);
+};
+
+#endif

src/cmdline/meson.build

@@ -0,0 +1,9 @@
+cmdline = static_library(
+  'cmdline',
+  'OptionParser.cxx',
+  include_directories: inc,
+)
+
+cmdline_dep = declare_dependency(
+  link_with: cmdline,
+)