/**
* Returns the current file cache.
*
* @param root root directory
* @return id, or {@code null} if newer file cache exists
* @throws InterruptedException interruption
*/
ProjectCache cache(final IOFile root) throws InterruptedException {
final ProjectCache pc = cache;
if (pc == null) {
// no file cache available: create and return new one
cache = new ProjectCache();
add(root, cache);
cache.finish();
} else {
// wait until file cache is initialized
while (!pc.valid()) {
Thread.yield();
// file cache was replaced with newer version
if (pc != cache) throw new InterruptedException();
}
}
// return existing file cache
return cache;
}
