class DirIterator {

	static constexpr const char* NAME = "FAT32_DirI";

	FS& fs;
	ClusterNr curCluster;
	uint8_t curEntryInSector;	// current DirEntry within the current sector
	uint8_t curSectorInCluster;	// current Sector within the current cluster

	uint8_t buf[512];

public:

	DirIterator(FS& fs, ClusterNr clusterNr) : fs(fs), curCluster(clusterNr), curEntryInSector(0), curSectorInCluster(0) {

		Log::addInfo(NAME, "init @ Cluster %d", curCluster);

		// read the first sector in the first cluster
		read(curCluster, 0);

	}


	DirEntry* next() {

		while(true) {

			// end of sector reached?
			if (curEntryInSector >= fs.tmp.dirEntriesPerSector) {

				// next sector
				++curSectorInCluster;
				curEntryInSector = 0;

				// end of cluster reached?
				if (curSectorInCluster >= fs.desc.sectorsPerCluster) {

					// find next cluster
					curCluster = fs.getNextCluster(curCluster);			// number of the next cluster (if any)
					curSectorInCluster = 0;

				}

				// fetch from disk
				read(curCluster, curSectorInCluster);

			}

			// the current entry
			DirEntry* dirEntry = reinterpret_cast<DirEntry*>(buf + (sizeof(DirEntry) * curEntryInSector));
			++curEntryInSector;

			// check it
			if (dirEntry->isLongFileName())		{continue;}
			if (dirEntry->isUnused())			{continue;}
			if (dirEntry->isEndOfDirectory())	{
				return nullptr;
			}

			// usable!
			return dirEntry;

		}

	}

private:

	/** fetch one sector within a cluster */
	void read(ClusterNr clusterNr, uint8_t sectorInCluster) {
		Log::addInfo(NAME, "fetching sector %d in clusterNr %d", sectorInCluster, clusterNr) ;
		const AbsPos pos = fs.clusterToAbsPos(clusterNr) + (curSectorInCluster * fs.desc.bytesPerSector);
		fs.dev.read(pos, fs.desc.bytesPerSector, buf);
	}



};