Merge pull request #976 from ethcore/rpc-logs

Exposing application logs via RPC.

util/src/log.rs

@@ -19,6 +19,8 @@
 use std::env;
 use rlog::{LogLevelFilter};
 use env_logger::LogBuilder;
+use std::sync::{RwLock, RwLockReadGuard};
+use arrayvec::ArrayVec;
 
 lazy_static! {
 	static ref LOG_DUMMY: bool = {
@@ -40,3 +42,79 @@ lazy_static! {
 pub fn init_log() {
 	let _ = *LOG_DUMMY;
 }
+
+const LOG_SIZE : usize = 128;
+
+/// Logger implementation that keeps up to `LOG_SIZE` log elements.
+pub struct RotatingLogger {
+	/// Defined logger levels
+	levels: String,
+	/// Logs array. Latest log is always at index 0
+	logs: RwLock<ArrayVec<[String; LOG_SIZE]>>,
+}
+
+impl RotatingLogger {
+
+	/// Creates new `RotatingLogger` with given levels.
+	/// It does not enforce levels - it's just read only.
+	pub fn new(levels: String) -> Self {
+		RotatingLogger {
+			levels: levels,
+			logs: RwLock::new(ArrayVec::<[_; LOG_SIZE]>::new()),
+		}
+	}
+
+	/// Append new log entry
+	pub fn append(&self, log: String) {
+		self.logs.write().unwrap().insert(0, log);
+	}
+
+	/// Return levels
+	pub fn levels(&self) -> &str {
+		&self.levels
+	}
+
+	/// Return logs
+	pub fn logs(&self) -> RwLockReadGuard<ArrayVec<[String; LOG_SIZE]>> {
+		self.logs.read().unwrap()
+	}
+
+}
+
+#[cfg(test)]
+mod test {
+	use super::RotatingLogger;
+
+	fn logger() -> RotatingLogger {
+		RotatingLogger::new("test".to_owned())
+	}
+
+	#[test]
+	fn should_return_log_levels() {
+		// given
+		let logger = logger();
+
+		// when
+		let levels = logger.levels();
+
+		// then
+		assert_eq!(levels, "test");
+	}
+
+	#[test]
+	fn should_return_latest_logs() {
+		// given
+		let logger = logger();
+
+		// when
+		logger.append("a".to_owned());
+		logger.append("b".to_owned());
+
+		// then
+		let logs = logger.logs();
+		assert_eq!(logs[0], "b".to_owned());
+		assert_eq!(logs[1], "a".to_owned());
+		assert_eq!(logs.len(), 2);
+	}
+}
+