huge work on FAT32, initial support for writing

ext/sd/fat32/DirIterator.h

@@ -20,8 +20,73 @@ public:
 
 	}
 
+	DirEntryAt cur() {
+		AbsPos pos = fs.clusterToAbsPos(curCluster) + (curSectorInCluster * fs.desc.bytesPerSector) + (curEntryInSector * sizeof(DirEntry));
+		DirEntry* dirEntry = reinterpret_cast<DirEntry*>(buf + (curEntryInSector * sizeof(DirEntry)));
+		return DirEntryAt(pos, dirEntry);
+	}
 
-	DirEntry* next() {
+	/** get the next usable entry within the current directory */
+	DirEntryAt nextUsable() {
+
+		while(true) {
+
+			DirEntryAt dea = next(false);
+
+			// check it
+			if (!dea.isValid())			{return DirEntryAt::invalid();}
+			if (dea.isLongFileName())	{continue;}
+			if (dea.isUnused())			{continue;}
+			if (dea.isEndOfDirectory())	{return DirEntryAt::invalid();}
+
+			// usable!
+			return dea;
+
+		}
+
+	}
+
+	/** get (or create) a free entry within the current directory */
+	DirEntryAt nextFree() {
+
+		while(true) {
+
+			DirEntryAt dea = next(true);
+
+			// check it
+			if (!dea.isValid())					{return DirEntryAt::invalid();}
+
+			if (dea.isUnused()) {
+
+				// switch from "unused" to something usable
+				//dea.setName("NEW.ONE");
+				//dea.entry.attr.raw = 0;
+				//return dea;
+
+			}
+
+			if (dea.isEndOfDirectory()) {
+
+				// add a new EndOfDirectory entry afterwards
+				DirEntryAt dea2 = next(true);
+				dea2.setEndOfDirectory();
+				fs.write(dea2);
+
+				// switch from "end of directory" to something usable
+				dea.setName("NEW.ONE");
+				dea.entry.attr.raw = 0;
+				return dea;
+
+			}
+
+
+		}
+
+	}
+
+private:
+
+	DirEntryAt next(bool allocIfNeeded) {
 
 		while(true) {
 
@@ -35,8 +100,23 @@ public:
 				// end of cluster reached?
 				if (curSectorInCluster >= fs.desc.sectorsPerCluster) {
 
-					// find next cluster
-					curCluster = fs.getNextCluster(curCluster);			// number of the next cluster (if any)
+					// find next cluster (if any)
+					const ClusterNr nextCluster = fs.getNextCluster(curCluster);
+
+					// reached end of clusters?
+					if (nextCluster.isEndOfClusters()) {
+
+						// do not alloc new entries? -> done here
+						if (!allocIfNeeded) {
+							return DirEntryAt::invalid();
+						} else {
+							curCluster = fs.allocFreeCluster(curCluster);
+						}
+
+					} else {
+						curCluster = nextCluster;
+					}
+
 					curSectorInCluster = 0;
 
 				}
@@ -47,18 +127,10 @@ public:
 			}
 
 			// the current entry
-			DirEntry* dirEntry = reinterpret_cast<DirEntry*>(buf + (sizeof(DirEntry) * curEntryInSector));
+			DirEntryAt dea = cur();
 			++curEntryInSector;
 
-			// check it
-			if (dirEntry->isLongFileName())		{continue;}
-			if (dirEntry->isUnused())			{continue;}
-			if (dirEntry->isEndOfDirectory())	{
-				return nullptr;
-			}
-
-			// usable!
-			return dirEntry;
+			return dea;
 
 		}