Added full dir list and rudimentary block allocator

In writing the initial allocator, I ran into the rather
difficult problem of trying to iterate through the entire
filesystem cheaply and with only constant memory consumption
(which prohibits recursive functions).

The solution was to simply thread all directory blocks onto a
massive linked-list that spans the entire filesystem.

With the linked-list it was easy to create a traverse function
for all blocks in use on the filesystem (which has potential
for other utility), and add the rudimentary block allocator
using a bit-vector.

While the linked-list may add complexity (especially where
needing to maintain atomic operations), the linked-list helps
simplify what is currently the most expensive operation in
the filesystem, with no cost to space (the linked-list can
reuse the pointers used for chained directory blocks).

1 files changed, 7 insertions, 0 deletions

diff --git a/lfs_config.h b/lfs_config.h
index fd1e6ad..e679409 100644
--- a/lfs_config.h
+++ b/lfs_config.h
@@ -19,7 +19,14 @@ typedef int32_t  lfs_soff_t;
 typedef uint32_t lfs_block_t;
 
 // Maximum length of file name
+#ifndef LFS_NAME_MAX
 #define LFS_NAME_MAX 255
+#endif
+
+// Lookahead distance
+#ifndef LFS_CFG_LOOKAHEAD
+#define LFS_CFG_LOOKAHEAD 128
+#endif
 
 // Logging operations
 #include <stdio.h>