AP_ROMFS: added directory listing interface

libraries/AP_ROMFS/AP_ROMFS.cpp

@@ -113,3 +113,21 @@ void AP_ROMFS::free(const uint8_t *data)
     ::free(const_cast<uint8_t *>(data));
 #endif
 }
+
+/*
+  directory listing interface. Start with ofs=0. Returns pathnames
+  that match dirname prefix. Ends with nullptr return when no more
+  files found
+*/
+const char *AP_ROMFS::dir_list(const char *dirname, uint16_t &ofs)
+{
+    const size_t dlen = strlen(dirname);
+    for ( ; ofs < ARRAY_SIZE(files); ofs++) {
+        if (strncmp(dirname, files[ofs].filename, dlen) == 0 &&
+            files[ofs].filename[dlen] == '/') {
+            // found one
+            return files[ofs++].filename;
+        }
+    }
+    return nullptr;
+}

libraries/AP_ROMFS/AP_ROMFS.h

@@ -16,6 +16,13 @@ public:
     // free returned data
     static void free(const uint8_t *data);
 
+    /*
+      directory listing interface. Start with ofs=0. Returns pathnames
+      that match dirname prefix. Ends with nullptr return when no more
+      files found
+    */
+    static const char *dir_list(const char *dirname, uint16_t &ofs);
+
 private:
     // find an embedded file
     static const uint8_t *find_file(const char *name, uint32_t &size);