config: abstract fs utils to fix esp32 builds

src/FsUtils.cpp

@@ -0,0 +1,57 @@
+#include "FsUtils.h"
+
+filename_iterator::filename_iterator()
+  : suffix(NULL),
+    valid(false)
+{}
+
+filename_iterator::filename_iterator(const char* path, const char* suffix)
+#ifdef BOARD_ESP8266
+  : dir(LittleFS.openDir(path)),
+#endif
+#ifdef BOARD_ESP32
+  : dir(LittleFS.open(path)),
+#endif
+    valid(true),
+    suffix(suffix)
+{
+  next();
+}
+
+void
+filename_iterator::next()
+{
+  if (!valid) {
+    return;
+  }
+  int extPos = -1;
+  do {
+#ifdef BOARD_ESP8266
+    valid = dir.next();
+    if (valid) {
+      String fname = dir.fileName();
+      extPos = fname.lastIndexOf(suffix);
+      if (extPos != -1) {
+        ret = fname.substring(0, extPos);
+      }
+    }
+#endif
+#ifdef BOARD_ESP32
+    File next = dir.openNextFile();
+    valid = (bool)next;
+    if (valid && !next.isDirectory()) {
+      String fname = next.name();
+      extPos = fname.lastIndexOf(suffix);
+      if (extPos != -1) {
+        ret = fname.substring(0, extPos);
+      }
+    }
+#endif
+  } while (valid && extPos == -1);
+}
+
+filename_iterator& filename_iterator::operator++()
+{
+  next();
+  return *this;
+}