New API function lfs_find_free_blocks. It performs free block search …

…which later will not slow down a write operation.

lfs.c

@@ -576,6 +576,25 @@ static int lfs_alloc(lfs_t *lfs, lfs_block_t *block) {
         }
     }
 }
+
+int lfs_find_free_blocks(lfs_t *lfs){
+  // check if we have looked at all blocks since last ack
+  if (lfs->free.ack == 0) {
+    LFS_ERROR("No more free space %"PRIu32,
+      lfs->free.i + lfs->free.off);
+    return LFS_ERR_NOSPC;
+  }
+
+  lfs->free.off = (lfs->free.off + lfs->free.size)
+    % lfs->cfg->block_count;
+  lfs->free.size = lfs_min(8*lfs->cfg->lookahead_size, lfs->free.ack);
+  lfs->free.i = 0;
+
+  // find mask of free blocks from tree
+  memset(lfs->free.buffer, 0, lfs->cfg->lookahead_size);
+  int err = lfs_fs_traverse(lfs, lfs_alloc_lookahead, lfs);
+  return err;
+}
 #endif
 
 /// Metadata pair and directory operations ///

lfs.h

@@ -670,6 +670,10 @@ lfs_ssize_t lfs_fs_size(lfs_t *lfs);
 // Returns a negative error code on failure.
 int lfs_fs_traverse(lfs_t *lfs, int (*cb)(void*, lfs_block_t), void *data);
 
+// Use Traverse function and try to find free blocks. LittleFS free blocks search is unpredictable.
+// Search is costly operation which may delay write. In realtime write scenarios can be better to find them before a write.
+int lfs_find_free_blocks(lfs_t *lfs);
+
 #ifndef LFS_READONLY
 #ifdef LFS_MIGRATE
 // Attempts to migrate a previous version of littlefs