gistfile1.js

/* Super simple logging module */

var posix = require('posix');

/* Create a function for logging. This is asynchronous, and will queue up
 * pending log messages if log messages are submitted faster than they can be
 * written to disk. */
var log = function () {
	/* initialize logging (blocks) */
	var log_fd = posix.open('ss.log', process.O_WRONLY | process.O_APPEND | process.O_CREAT, process.S_IRUSR | process.S_IWUSR).wait();

	/* The queue of existing log messages. this chains requests in an mbuf-like
	 * manner, to avoid expensive memory allocations if the buffer gets
	 * large. */
	var log_queue = new Array();

	/* Write as much of the first log entry as possible, and try to requeue if
	 * there's more work to be done. */
	function write_log () {
		posix.write(log_fd, log_queue[0], null, "ascii").addCallback(function(bytes) {
				var remaining = log_queue[0].slice(bytes);
				if (remaining)
					log_queue[0] = remaining;
				else
					log_queue = log_queue.slice(1);
				if (log_queue.length)
					write_log();
			});
	}
	return function(msg) {
		var dispatch = (log_queue.length == 0);
		log_queue.push(msg + '\n');
		if (dispatch)
			write_log();
	};
}();

/* Test it out */
log('foo');
log('bar');