nl_tokens: ReadFileCache is an EventEmitter subclass that caches file contents in memory so that subsequent calls to readFileP return the same contents regardless of any changes in the underlying file .
pl_tokens: function ReadFileCache ( sourceDir , charset ) { assert . ok ( this instanceof ReadFileCache ) ; assert . strictEqual ( typeof sourceDir , "string" ) ; this . charset = charset ; EventEmitter . call ( this ) ; Object . defineProperties ( this , { sourceDir : { value : sourceDir } , sourceCache : { <mask> : { } } } ) ; }