/**
* Stats the given file. If <tt>throttleRate</tt> seconds have passed since
* the last time stat() was called on this file, then the file will be
* re-stat()ted, otherwise the cached stat information will be returned.
*
* @param filename The file to stat.
* @param stat A pointer to a stat struct; the retrieved stat information
* will be stored here.
* @param throttleRate Tells this CachedFileStat that the file may only
* be statted at most every <tt>throttleRate</tt> seconds.
* @return 0 if the stat() call succeeded or if the cached stat information was used;
* -1 if something went wrong while statting the file. In the latter
* case, <tt>errno</tt> will be populated with an appropriate error code.
* @throws SystemException Something went wrong while retrieving the
* system time. stat() errors will <em>not</em> result in
* SystemException being thrown.
* @throws boost::thread_interrupted
*/
int stat(const string &filename, struct stat *buf, unsigned int throttleRate = 0) {
boost::unique_lock<boost::mutex> l(lock);
EntryMap::iterator it(cache.find(filename));
EntryPtr entry;
int ret;
if (it == cache.end()) {
// Filename not in cache.
// If cache is full, remove the least recently used
// cache entry.
if (maxSize != 0 && cache.size() == maxSize) {
EntryList::iterator listEnd(entries.end());
listEnd--;
string filename((*listEnd)->filename);
entries.pop_back();
cache.erase(filename);
}
// Add to cache as most recently used.
entry = EntryPtr(new Entry(filename));
entries.push_front(entry);
cache[filename] = entries.begin();
} else {
// Cache hit.
entry = *it->second;
// Mark this cache item as most recently used.
entries.erase(it->second);
entries.push_front(entry);
cache[filename] = entries.begin();
}
ret = entry->refresh(throttleRate);
*buf = entry->info;
return ret;
}
/**
* Change the maximum size of the cache. If the new size is larger
* than the old size, then the oldest entries in the cache are
* removed.
*
* A size of 0 means unlimited.
*/
void setMaxSize(unsigned int maxSize) {
boost::unique_lock<boost::mutex> l(lock);
if (maxSize != 0) {
int toRemove = cache.size() - maxSize;
for (int i = 0; i < toRemove; i++) {
string filename(entries.back()->filename);
entries.pop_back();
cache.erase(filename);
}
}
this->maxSize = maxSize;
}
