Discussion
Looking at some of LittleFS's support underlying the routines for writing directories to a microcontroller's harddrive...
There's several for extracting certain bits from an attributes "tag", or handling endianness.
There's a couple more helpers for (recursively or not) gathering all entries in a directory, which invokes a further surprisingly simple helper for detect cycles via Brent's Algorithm. In turn invoking an equality helper. The recursive variant uses an explicit stack.
1/?
There's a helpers for bitwise-manipulating "g-states", & a getter routine for (via a complex suite of other helpers) reading the g-state for a directory entry.
There's a `lfs_dir_commitcrc()` helper which repeatedly (via other helpers) reads data from the harddrive to compute a CRC from while occasionally committing it to disk as an attribute. Then computes the CRC from that.
There's a helper to flag the cache as dropped.
And there's a helper to split/compact the commit.
3/4!
That split/compact helper starts which repeatedly sums (via the directory-traverse routine with a callback) the directory-size in some sort of aligned binary size & invokes another helper to apply found split if any. Afterwords it carefully considers applying another split, & unconditionally compacts the result.
The split routine allocates a directory, defers to the compaction routine, & updates some linkedlists.
As for the compaction routine...
4/5!!
The compaction routine checks (via another routine) some cycles properties, compares a pair, & repeatedly serializes data to the microcontroller's harddrive. Returning whether anything was relocated.
Each iteration of this loop prepares a commit, invokes (via a light wrapper) the harddrive's erase method propagating any errors, writes an endianness-corrected header, traverses directory to write attributes, writes another attributes for nil-terminators, ...
5/6 Definitely!
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Furthermore the recursive variant invokes a callback for each entry, & invokes the cached-wrapper around the harddrive-read method itself. In this case its callback lightly wraps `lfs_dir_commitattr()` (also called directly from the relocating-commit routine) which reformats a tag & defers on to `lfs_dir_commitprog()` at least twice, or follows up the first call with repeated reads of data to commit. Then adds a CRC.
This carefully & repeatedly writes data into the Program-cache flushing it.
2