read resource files safely

put a limit on the amount of data read

app/coffee/SafeReader.coffee

@@ -0,0 +1,24 @@
+fs = require "fs"
+
+module.exports = SafeReader =
+
+	# safely read up to size bytes from a file and return result as a
+	# string
+
+	readFile: (file, size, encoding, callback = (error, result) ->) ->
+		fs.open file, 'r', (err, fd) ->
+			return callback() if err? and  err.code is 'ENOENT'
+			return callback(err) if err?
+
+			# safely return always closing the file
+			callbackWithClose = (err, result) ->
+				fs.close fd, (err1) ->
+					return callback(err) if err?
+					return callback(err1) if err1?
+					callback(null, result)
+
+			buff = new Buffer(size, 0) # fill with zeros
+			fs.read fd, buff, 0, buff.length, 0, (err, bytesRead, buffer) ->
+				return callbackWithClose(err) if err?
+				result = buffer.toString(encoding, 0, bytesRead)
+				callbackWithClose(null, result)