When over the SD limit, continue from the last sorted file

This gives a significant speed boost when just above the sorting limit, while only costing 2 bytes of ram

Firmware/cardreader.cpp

@@ -779,7 +779,15 @@ void CardReader::getfilename_sorted(const uint16_t nr, uint8_t sdSort) {
     if (nr < sort_count)
         getfilename_simple(sort_entries[(sdSort == SD_SORT_ALPHA) ? (sort_count - nr - 1) : nr]);
     else
-        getfilename(nr);
+        getfilename_afterMaxSorting(nr);
+}
+
+void CardReader::getfilename_afterMaxSorting(uint16_t entry, const char * const match/*=NULL*/)
+{
+	curDir = &workDir;
+	nrFiles = entry - sort_count + 1;
+	curDir->seekSet(lastSortedFilePosition << 5);
+	lsDive("", *curDir, match, LS_GetFilename);
 }
 
 /**
@@ -830,6 +838,7 @@ void CardReader::presort() {
 			LongTimer sortingSpeedtestTimer;
 			sortingSpeedtestTimer.start();
 #endif //SORTING_SPEEDTEST
+			lastSortedFilePosition = position >> 5;
 
 			// By default re-read the names from SD for every compare
 			// retaining only two filenames at a time. This is very
@@ -989,6 +998,7 @@ void CardReader::presort() {
 
 void CardReader::flush_presort() {
 	sort_count = 0;
+	lastSortedFilePosition = 0;
 }
 
 #endif // SDCARD_SORT_ALPHA

Firmware/cardreader.h

@@ -64,6 +64,7 @@ public:
   #ifdef SDCARD_SORT_ALPHA
      void presort();
      void getfilename_sorted(const uint16_t nr, uint8_t sdSort);
+     void getfilename_afterMaxSorting(uint16_t entry, const char * const match = NULL);
   #endif
 
   FORCE_INLINE bool isFileOpen() { return file.isOpen(); }
@@ -98,8 +99,8 @@ public:
   int lastnr; //last number of the autostart;
 #ifdef SDCARD_SORT_ALPHA
   bool presort_flag;
-  char dir_names[MAX_DIR_DEPTH][9];
 #endif // SDCARD_SORT_ALPHA
+  char dir_names[MAX_DIR_DEPTH][9];
 private:
   SdFile root,*curDir,workDir,workDirParents[MAX_DIR_DEPTH];
   uint16_t workDirDepth;
@@ -108,6 +109,7 @@ private:
 #ifdef SDCARD_SORT_ALPHA
   uint16_t sort_count;        // Count of sorted items in the current directory
   uint16_t sort_entries[SDSORT_LIMIT];
+  uint16_t lastSortedFilePosition;
 
 #endif // SDCARD_SORT_ALPHA