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Reworked lfsr_bshrub_t, renamed file.o -> file.b

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This moves all of the shrub tracking logic from lfsr_obshrub_t into
lfsr_bshrub_t, completely drops the lfsr_obshrub_t type, and changes all
lfsr_bshrub_* functions to take lfsr_bshrub_t instead of the mdir+shrub
pair.

This makes the lfsr_bshrub_* functions <-> lfsr_bshrub_t relationship
more consistent with other APIs, such as lfsr_btree_t:

  - lfsr_bshrub_lookupnext(lfs, &file->o.o.mdir, &file->o.bshrub, ...)
  + lfsr_bshrub_lookupnext(lfs, &file->b, ...)

I think the reason why this design wasn't obvious before is because, at
least conceptually, having the lfsr_mdir_t live inside the lfsr_bshrub_t
is a bit weird. It's only thanks to lfsr_file_t invasively using the
internal lfsr_mdir_t that we can avoid duplicate lfsr_mdir_t objects.

This also reorganizes the structs in lfs.h a bit, and renames the
related file.o -> file.b fields (much needed because lfs->gc.t.o.o.mdir.
rbyd.blocks was starting to get _real_ confusing).

---

Unfortunately, reducing the number of arguments to lfsr_bshrub_*
functions did not save nearly as much code as I thought it would. It
even ended up with a net _increase_ of code, apparently due to needing
to recalculate the bshrub->shrub offset more often:

           code          stack          ctx
  before: 36476           2608          640
  after:  36484 (+0.0%)   2608 (+0.0%)  640 (+0.0%)

Strange, but this rework is still worthwhile if only for the code
readability.
This commit is contained in:
Christopher Haster
2025-02-03 03:07:30 -06:00
parent fd62ef9674
commit bc639b03f2
7 changed files with 487 additions and 506 deletions
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tests/test_mount.toml
+2 -2
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@@ -188,7 +188,7 @@ code = '''
// hack, don't use the internals like this
uint8_t wbuf[SIZE];
while ((file.o.o.mdir.rbyd.eoff & 0x7fffffff) <= GC_COMPACT_THRESH) {
while ((file.b.o.mdir.rbyd.eoff & 0x7fffffff) <= GC_COMPACT_THRESH) {
lfsr_file_rewind(&lfs, &file) => 0;
for (lfs_size_t j = 0; j < SIZE; j++) {
wbuf[j] = 'a' + (TEST_PRNG(&prng) % 26);
@@ -230,7 +230,7 @@ code = '''
// mdir should have been compacted
lfsr_file_open(&lfs, &file, "jellyfish", LFS_O_RDONLY) => 0;
assert((file.o.o.mdir.rbyd.eoff & 0x7fffffff) <= GC_COMPACT_THRESH);
assert((file.b.o.mdir.rbyd.eoff & 0x7fffffff) <= GC_COMPACT_THRESH);
// check we can still read the file
uint8_t rbuf[SIZE];