add os[1-8]-ref for os refereces, add guide, add README

os8-ref/src/logging.rs

@@ -0,0 +1,45 @@
+//! Global logger
+
+use log::{self, Level, LevelFilter, Log, Metadata, Record};
+
+/// a simple logger
+struct SimpleLogger;
+
+impl Log for SimpleLogger {
+    fn enabled(&self, _metadata: &Metadata) -> bool {
+        true
+    }
+    fn log(&self, record: &Record) {
+        if !self.enabled(record.metadata()) {
+            return;
+        }
+        let color = match record.level() {
+            Level::Error => 31, // Red
+            Level::Warn => 93,  // BrightYellow
+            Level::Info => 34,  // Blue
+            Level::Debug => 32, // Green
+            Level::Trace => 90, // BrightBlack
+        };
+        println!(
+            "\u{1B}[{}m[{:>5}] {}\u{1B}[0m",
+            color,
+            record.level(),
+            record.args(),
+        );
+    }
+    fn flush(&self) {}
+}
+
+/// initiate logger
+pub fn init() {
+    static LOGGER: SimpleLogger = SimpleLogger;
+    log::set_logger(&LOGGER).unwrap();
+    log::set_max_level(match option_env!("LOG") {
+        Some("ERROR") => LevelFilter::Error,
+        Some("WARN") => LevelFilter::Warn,
+        Some("INFO") => LevelFilter::Info,
+        Some("DEBUG") => LevelFilter::Debug,
+        Some("TRACE") => LevelFilter::Trace,
+        _ => LevelFilter::Off,
+    });
+}