[lib/LinuxVersion] add linux kernel version comparison macros

emper/lib/LinuxVersion.cpp

+// SPDX-License-Identifier: LGPL-3.0-or-later
+// Copyright © 2021 Florian Fischer
+#include "lib/LinuxVersion.hpp"
+
+#include <cassert>
+#include <cerrno>
+#include <cstdlib>
+
+#include "Common.hpp"
+#include "Debug.hpp"
+
+static auto checked_strtol(const std::string& s) -> long {
+	static const int DECIMAL = 10;
+	char* endptr;
+	const char* startptr = s.c_str();
+	errno = 0;
+
+	long res = strtol(startptr, &endptr, DECIMAL);
+	if (errno != 0) {
+		DIE_MSG_ERRNO("strtol failed");
+	}
+
+	if (endptr == startptr) {
+		DIE_MSG("strtol found no digits in " << s);
+	}
+
+	if (endptr != startptr + s.size()) {
+		LOGW("LinuxVersion compare ignored non digits in " << s)
+	}
+
+	return res;
+}
+
+namespace emper::lib {
+
+LinuxVersion LinuxVersion::linuxVersion;
+
+// Returns 1 if s is smaller, -1 if this is smaller, 0 if equal
+auto LinuxVersion::compare(const std::string& s) -> int {
+	size_t last_dot_pos = 0, last_dot_pos2 = 0;
+
+	for (;;) {
+		size_t dot_pos = this->version.find('.', last_dot_pos);
+		// We run out of parts to compare the versions must be equal
+		if (dot_pos == std::string::npos) return 0;
+
+		size_t dot_pos2 = s.find('.', last_dot_pos2);
+		assert(dot_pos2 != std::string::npos);
+
+		long n1 = checked_strtol(this->version.substr(last_dot_pos, dot_pos - last_dot_pos));
+		long n2 = checked_strtol(s.substr(last_dot_pos2, dot_pos2 - last_dot_pos2));
+
+		if (n1 > n2) return 1;
+
+		if (n1 < n2) return -1;
+
+		last_dot_pos = dot_pos + 1;
+		last_dot_pos2 = dot_pos2 + 1;
+	}
+}
+
+}	 // namespace emper::lib

emper/lib/LinuxVersion.hpp

+// SPDX-License-Identifier: LGPL-3.0-or-later
+// Copyright © 2021 Florian Fischer
+#pragma once
+
+#include <sys/utsname.h>
+
+#include <string>
+
+namespace emper::lib {
+class LinuxVersion {
+	std::string version;
+
+	auto compare(const std::string& s) -> int;
+
+ public:
+	static LinuxVersion linuxVersion;
+
+	LinuxVersion() {
+		struct utsname buf;
+		uname(&buf);
+		this->version = std::string(buf.release);
+	}
+
+	auto operator>(const std::string& s) -> bool { return compare(s) > 0; }
+
+	auto operator<(const std::string& s) -> bool { return compare(s) < 0; }
+
+	auto operator==(const std::string& s) -> bool { return compare(s) == 0; }
+
+	auto operator>=(const std::string& s) -> bool { return *this > s || *this == s; }
+
+	auto operator<=(const std::string& s) -> bool { return *this < s || *this == s; }
+};
+}	 // namespace emper::lib
+
+#define EMPER_LINUX_EQ(version) \
+	([]() -> bool { return empere::lib::LinuxVersion::linuxVersion == version; }())
+#define EMPER_LINUX_GT(version) \
+	([]() -> bool { return emper::lib::LinuxVersion::linuxVersion > version; }())
+#define EMPER_LINUX_GE(version) \
+	([]() -> bool { return emper::lib::LinuxVersion::linuxVersion >= version; }())
+#define EMPER_LINUX_LT(version) \
+	([]() -> bool { return emper::lib::LinuxVersion::linuxVersion < version; }())
+#define EMPER_LINUX_LE(version) \
+	([]() -> bool { return emper::lib::LinuxVersion::linuxVersion <= version; }())

emper/lib/meson.build

 emper_cpp_sources += files(
   'DebugUtil.cpp',
+  'LinuxVersion.cpp',
 )