Github/littlefs
1
Fork 0
Code Actions Activity

Dropped separate BTREE/BRANCH encodings

Browse Source 
There is a bit of redundancy here, as we already know the weights of
btree's inner-branches from their parents. But in theory sharing the
same encoding for both the top level btree reference and inner-branches
should offer more chance for deduplication and hopefully less code.

This also moves some members around in the btree encoding so that the
redund blocks are at the beginning. This _might_ simplify decoding of
the variable-length redund blocks at some point.

Current btree encoding:

  .----+----+----+----.
  |       blocks    ...  redund leb128s (1-20 bytes)
  :                   :
  |----+----+----+----|
  |       trunk     ...  1 leb128 (1-5 bytes)
  |----+----+----+----|
  |       weight    ...  1 leb128 (1-5 bytes)
  |----+----+----+----|
  |       cksum       |  1 le32 (4 bytes)
  '----+----+----+----'

This also partially reverts some tag name changes:

- BNAME -> BRANCH
- DMARK -> BOOKMARK
This commit is contained in:
Christopher Haster
2023-08-22 13:20:37 -05:00
parent f70e7fe709
commit 256430213d
6 changed files with 114 additions and 178 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lfs.c
+60 -106
View File
@@ -589,8 +589,8 @@ enum lfsr_tag_type {
LFSR_TAG_GRM = 0x0100,
LFSR_TAG_NAME = 0x0200,
LFSR_TAG_BNAME = 0x0200,
LFSR_TAG_DMARK = 0x0201,
LFSR_TAG_BRANCH = 0x0200,
LFSR_TAG_BOOKMARK = 0x0201,
LFSR_TAG_REG = 0x0202,
LFSR_TAG_DIR = 0x0203,
@@ -601,8 +601,7 @@ enum lfsr_tag_type {
LFSR_TAG_MDIR = 0x0311,
LFSR_TAG_MTREE = 0x0314,
LFSR_TAG_MROOT = 0x0318,
LFSR_TAG_BRANCH = 0x031c,
LFSR_TAG_DID = 0x0320,
LFSR_TAG_DID = 0x031c,
LFSR_TAG_UATTR = 0x0400,
LFSR_TAG_SATTR = 0x0500,
@@ -3380,7 +3379,7 @@ static int lfsr_rbyd_namelookup(lfs_t *lfs, const lfsr_rbyd_t *rbyd,
// if we have no name or a vestigial name, treat this rid as always lt
lfs_scmp_t cmp;
if ((tag__ == LFSR_TAG_BNAME && rid__-(weight__-1) == 0)
if ((tag__ == LFSR_TAG_BRANCH && rid__-(weight__-1) == 0)
|| lfsr_tag_suptype(tag__) != LFSR_TAG_NAME) {
cmp = LFS_CMP_LT;
@@ -3463,60 +3462,8 @@ static inline lfs_size_t lfsr_btree_setinlined(lfs_size_t weight) {
// btree on-disk encoding
// 2 leb128 + 1 crc32c => 14 bytes (worst case)
#define LFSR_BRANCH_DSIZE (5+5+4)
static lfs_ssize_t lfsr_branch_todisk(lfs_t *lfs, const lfsr_rbyd_t *branch,
uint8_t buffer[static LFSR_BRANCH_DSIZE]) {
(void)lfs;
lfs_ssize_t d = 0;
lfs_ssize_t d_ = lfs_toleb128(branch->block, &buffer[d], 5);
if (d_ < 0) {
return d_;
}
d += d_;
d_ = lfs_toleb128(branch->trunk, &buffer[d], 5);
if (d_ < 0) {
return d_;
}
d += d_;
lfs_tole32_(branch->cksum, &buffer[d]);
d += 4;
return d;
}
static int lfsr_data_readbranch(lfs_t *lfs, lfsr_data_t *data,
lfs_size_t weight,
lfsr_rbyd_t *branch) {
// setting off to 0 here will trigger asserts if we try to append
// without fetching first
branch->eoff = 0;
branch->weight = weight;
int err = lfsr_data_readleb128(lfs, data, (int32_t*)&branch->block);
if (err) {
return err;
}
err = lfsr_data_readleb128(lfs, data, (int32_t*)&branch->trunk);
if (err) {
return err;
}
err = lfsr_data_readle32(lfs, data, &branch->cksum);
if (err) {
return err;
}
return 0;
}
// 3 leb128 + 1 crc32c => 19 bytes (worst case)
#define LFSR_BTREE_DSIZE (5+LFSR_BRANCH_DSIZE)
#define LFSR_BTREE_DSIZE (5+5+5+4)
static lfs_ssize_t lfsr_btree_todisk(lfs_t *lfs, const lfsr_rbyd_t *btree,
uint8_t buffer[static LFSR_BTREE_DSIZE]) {
@@ -3525,18 +3472,27 @@ static lfs_ssize_t lfsr_btree_todisk(lfs_t *lfs, const lfsr_rbyd_t *btree,
LFS_ASSERT(!lfsr_btree_isinlined((const lfsr_btree_t*)btree));
lfs_ssize_t d = 0;
lfs_ssize_t d_ = lfs_toleb128(btree->weight, &buffer[d], 5);
lfs_ssize_t d_ = lfs_toleb128(btree->block, &buffer[d], 5);
if (d_ < 0) {
return d_;
}
d += d_;
d_ = lfsr_branch_todisk(lfs, btree, &buffer[d]);
d_ = lfs_toleb128(btree->trunk, &buffer[d], 5);
if (d_ < 0) {
return d_;
}
d += d_;
d_ = lfs_toleb128(btree->weight, &buffer[d], 5);
if (d_ < 0) {
return d_;
}
d += d_;
lfs_tole32_(btree->cksum, &buffer[d]);
d += 4;
return d;
}
@@ -3562,13 +3518,22 @@ static int lfsr_data_readbtree(lfs_t *lfs, lfsr_data_t *data,
// without fetching first
btree->eoff = 0;
lfs_size_t weight;
int err = lfsr_data_readleb128(lfs, data, (int32_t*)&weight);
int err = lfsr_data_readleb128(lfs, data, (int32_t*)&btree->block);
if (err) {
return err;
}
err = lfsr_data_readbranch(lfs, data, weight, btree);
err = lfsr_data_readleb128(lfs, data, (int32_t*)&btree->trunk);
if (err) {
return err;
}
err = lfsr_data_readleb128(lfs, data, (int32_t*)&btree->weight);
if (err) {
return err;
}
err = lfsr_data_readle32(lfs, data, &btree->cksum);
if (err) {
return err;
}
@@ -3635,12 +3600,12 @@ static int lfsr_btree_lookupnext_(lfs_t *lfs,
}
// found another branch
if (tag__ == LFSR_TAG_BRANCH) {
if (tag__ == LFSR_TAG_BTREE) {
// adjust rid with subtree's weight
rid -= (rid__ - (weight__-1));
// fetch the next branch
err = lfsr_data_readbranch(lfs, &data__, weight__, &branch);
err = lfsr_data_readbtree(lfs, &data__, &branch);
if (err) {
return err;
}
@@ -3739,7 +3704,7 @@ static int lfsr_btree_parent(lfs_t *lfs,
}
// didn't find our child?
if (tag__ != LFSR_TAG_BRANCH) {
if (tag__ != LFSR_TAG_BTREE) {
return LFS_ERR_NOENT;
}
@@ -3748,7 +3713,7 @@ static int lfsr_btree_parent(lfs_t *lfs,
// fetch the next branch
lfsr_rbyd_t branch_;
err = lfsr_data_readbranch(lfs, &data__, weight__, &branch_);
err = lfsr_data_readbtree(lfs, &data__, &branch_);
if (err) {
return err;
}
@@ -3877,7 +3842,7 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
// we need some scratch space for tail-recursive attrs here
lfsr_attr_t scratch_attrs[4];
uint8_t scratch_buf[2*LFSR_BRANCH_DSIZE];
uint8_t scratch_buf[2*LFSR_BTREE_DSIZE];
// tail-recursively commit to btree
while (true) {
@@ -3955,16 +3920,12 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
// try the right sibling
if (rid+1 < (lfs_ssize_t)parent.weight) {
// try looking up the sibling
// TODO do we really need to fetch sibling_weight if we get
// it in our btree struct?
lfs_ssize_t sibling_rid;
lfsr_tag_t sibling_tag;
lfs_size_t sibling_weight;
lfsr_data_t sibling_data;
err = lfsr_rbyd_lookupnext(lfs, &parent,
rid+1, LFSR_TAG_NAME,
&sibling_rid, &sibling_tag, &sibling_weight,
&sibling_data);
&sibling_rid, &sibling_tag, NULL, &sibling_data);
if (err) {
LFS_ASSERT(err != LFS_ERR_NOENT);
return err;
@@ -3980,9 +3941,8 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
}
}
LFS_ASSERT(sibling_tag == LFSR_TAG_BRANCH);
err = lfsr_data_readbranch(lfs, &sibling_data, sibling_weight,
&sibling);
LFS_ASSERT(sibling_tag == LFSR_TAG_BTREE);
err = lfsr_data_readbtree(lfs, &sibling_data, &sibling);
if (err) {
return err;
}
@@ -4005,16 +3965,12 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
// try the left sibling
if (rid-(lfs_ssize_t)rbyd.weight >= 0) {
// try looking up the sibling
// TODO do we really need to fetch sibling_weight if we get
// it in our btree struct?
lfs_ssize_t sibling_rid;
lfsr_tag_t sibling_tag;
lfs_size_t sibling_weight;
lfsr_data_t sibling_data;
err = lfsr_rbyd_lookupnext(lfs, &parent,
rid-rbyd.weight, LFSR_TAG_NAME,
&sibling_rid, &sibling_tag, &sibling_weight,
&sibling_data);
&sibling_rid, &sibling_tag, NULL, &sibling_data);
if (err) {
LFS_ASSERT(err != LFS_ERR_NOENT);
return err;
@@ -4030,9 +3986,8 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
}
}
LFS_ASSERT(sibling_tag == LFSR_TAG_BRANCH);
err = lfsr_data_readbranch(lfs, &sibling_data, sibling_weight,
&sibling);
LFS_ASSERT(sibling_tag == LFSR_TAG_BTREE);
err = lfsr_data_readbtree(lfs, &sibling_data, &sibling);
if (err) {
return err;
}
@@ -4108,7 +4063,7 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
return 0;
}
lfs_ssize_t scratch_dsize = lfsr_branch_todisk(lfs, &rbyd_,
lfs_ssize_t scratch_dsize = lfsr_btree_todisk(lfs, &rbyd_,
scratch_buf);
if (scratch_dsize < 0) {
return scratch_dsize;
@@ -4126,7 +4081,7 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
attr_count = 1;
} else {
scratch_attrs[0] = LFSR_ATTR(
bid+rid, BRANCH, 0,
bid+rid, BTREE, 0,
BUF(scratch_buf, scratch_dsize));
scratch_attrs[1] = LFSR_ATTR(
bid+rid, GROW, -rbyd.weight + rbyd_.weight,
@@ -4241,13 +4196,13 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
}
uint8_t *scratch1_buf = scratch_buf;
uint8_t *scratch2_buf = scratch_buf + LFSR_BRANCH_DSIZE;
lfs_ssize_t scratch1_dsize = lfsr_branch_todisk(lfs, &rbyd_,
uint8_t *scratch2_buf = scratch_buf + LFSR_BTREE_DSIZE;
lfs_ssize_t scratch1_dsize = lfsr_btree_todisk(lfs, &rbyd_,
scratch1_buf);
if (scratch1_dsize < 0) {
return scratch1_dsize;
}
lfs_ssize_t scratch2_dsize = lfsr_branch_todisk(lfs, &sibling,
lfs_ssize_t scratch2_dsize = lfsr_btree_todisk(lfs, &sibling,
scratch2_buf);
if (scratch2_dsize < 0) {
return scratch2_dsize;
@@ -4259,12 +4214,12 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
LFS_ASSERT(sibling.weight > 0);
if (rbyd.weight == 0) {
scratch_attrs[0] = LFSR_ATTR(
bid, BRANCH, +rbyd_.weight,
bid, BTREE, +rbyd_.weight,
BUF(scratch1_buf, scratch1_dsize));
scratch_attrs[1] = LFSR_ATTR_NOOP;
} else {
scratch_attrs[0] = LFSR_ATTR(
bid+rid, BRANCH, 0,
bid+rid, BTREE, 0,
BUF(scratch1_buf, scratch1_dsize));
scratch_attrs[1] = LFSR_ATTR(
bid+rid, GROW, -rbyd.weight + rbyd_.weight,
@@ -4272,13 +4227,13 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
}
scratch_attrs[2] = LFSR_ATTR(
bid+rid - rbyd.weight + rbyd_.weight + 1,
BRANCH,
BTREE,
+sibling.weight,
BUF(scratch2_buf, scratch2_dsize));
if (lfsr_tag_suptype(split_tag) == LFSR_TAG_NAME) {
scratch_attrs[3] = LFSR_ATTR(
bid+rid - rbyd.weight + rbyd_.weight + sibling.weight,
BNAME,
BRANCH,
0,
DATA(split_data));
} else {
@@ -4324,7 +4279,7 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
}
err = lfsr_rbyd_append(lfs, &rbyd_,
split_rid, LFSR_TAG_BNAME, 0, split_data);
split_rid, LFSR_TAG_BRANCH, 0, split_data);
if (err) {
LFS_ASSERT(err != LFS_ERR_RANGE);
return err;
@@ -4356,7 +4311,7 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
return 0;
}
scratch_dsize = lfsr_branch_todisk(lfs, &rbyd_,
scratch_dsize = lfsr_btree_todisk(lfs, &rbyd_,
scratch_buf);
if (scratch_dsize < 0) {
return scratch_dsize;
@@ -4369,7 +4324,7 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
bid+rid+sibling.weight, RM, -sibling.weight,
NULL);
scratch_attrs[1] = LFSR_ATTR(
bid+rid, BRANCH, 0,
bid+rid, BTREE, 0,
BUF(scratch_buf, scratch_dsize));
scratch_attrs[2] = LFSR_ATTR(
bid+rid, GROW, -rbyd.weight + rbyd_.weight,
@@ -4434,12 +4389,12 @@ static int lfsr_btree_namelookup(lfs_t *lfs, const lfsr_btree_t *btree,
}
// found another branch
if (tag__ == LFSR_TAG_BRANCH) {
if (tag__ == LFSR_TAG_BTREE) {
// update our bid
bid += rid__ - (weight__-1);
// fetch the next branch
err = lfsr_data_readbranch(lfs, &data__, weight__, &branch);
err = lfsr_data_readbtree(lfs, &data__, &branch);
if (err) {
return err;
}
@@ -4565,13 +4520,12 @@ static int lfsr_btree_traversal_next(lfs_t *lfs,
}
// found another branch
if (tag__ == LFSR_TAG_BRANCH) {
if (tag__ == LFSR_TAG_BTREE) {
// adjust rid with subtree's weight
traversal->rid -= (rid__ - (weight__-1));
// fetch the next branch
err = lfsr_data_readbranch(lfs, &data__, weight__,
&traversal->branch);
err = lfsr_data_readbtree(lfs, &data__, &traversal->branch);
if (err) {
return err;
}
@@ -5382,7 +5336,7 @@ static int lfsr_mdir_commit(lfs_t *lfs, lfsr_mdir_t *mdir,
err = lfsr_btree_commit(lfs, &mtree_, LFSR_ATTRS(
LFSR_ATTR(mbid, MDIR, 0,
BUF(mdir_buf, mdir_dsize)),
LFSR_ATTR(mbid+1, BNAME, +1, DATA(split_data)),
LFSR_ATTR(mbid+1, BRANCH, +1, DATA(split_data)),
LFSR_ATTR(mbid+1, MDIR, 0,
BUF(msibling_buf, msibling_dsize))));
if (err) {
@@ -6625,7 +6579,7 @@ static int lfsr_formatinited(lfs_t *lfs) {
LFSR_ATTR(-1, SUPERMAGIC, 0, BUF("littlefs", 8)),
LFSR_ATTR(-1, SUPERCONFIG, 0,
BUF(superconfig_buf, superconfig_dsize)),
LFSR_ATTR(0, DMARK, +1, NAME(0, NULL, 0))));
LFSR_ATTR(0, BOOKMARK, +1, NAME(0, NULL, 0))));
if (err) {
return err;
}
@@ -6895,7 +6849,7 @@ int lfsr_mkdir(lfs_t *lfs, const char *path) {
// lose power before writing the entry in our parent
//
err = lfsr_mdir_commit(lfs, &mdir, LFSR_ATTRS(
LFSR_ATTR(mdir.mid.rid, DMARK, +1, NAME(did, NULL, 0)),
LFSR_ATTR(mdir.mid.rid, BOOKMARK, +1, NAME(did, NULL, 0)),
LFSR_ATTR(-1, GRM, 0, GRM(&((lfsr_grm_t){{
mdir.mid,
LFSR_MID(-1, -1)}})))));
@@ -6988,7 +6942,7 @@ int lfsr_remove(lfs_t *lfs, const char *path) {
return err;
}
if (tag_ != LFSR_TAG_DMARK) {
if (tag_ != LFSR_TAG_BOOKMARK) {
return LFS_ERR_NOTEMPTY;
}
}
@@ -7120,7 +7074,7 @@ int lfsr_rename(lfs_t *lfs, const char *old_path, const char *new_path) {
return err;
}
if (tag_ != LFSR_TAG_DMARK) {
if (tag_ != LFSR_TAG_BOOKMARK) {
return LFS_ERR_NOTEMPTY;
}
}