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Implement generalized btree push, note the boundary conditions when id=weight

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This really just required care around calculating the expected B-tree id
and rbyd id (which are different!).

B-tree append, aka B-tree push with id=weight, is actually the outlier.
We need a B-tree id that can identify the rbyd we're appending to, but
this id itself doesn't exist in the tree yet, which can be a bit tricky.
This commit is contained in:
Christopher Haster
2023-03-07 13:04:57 -06:00
parent d6a2666614
commit 0a3c6b39c1
4 changed files with 276 additions and 36 deletions
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lfs.c
+37 -31
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@@ -1913,13 +1913,10 @@ static lfs_ssize_t lfsr_rbyd_bisect(lfs_t *lfs, const lfsr_rbyd_t *rbyd) {
bsize += LFSR_TAG_DSIZE + size;
if (bsize >= dsize/2) {
// well this shouldn't happen unless attr limits have gone wrong
LFS_ASSERT((lfs_size_t)id + 1 < rbyd->weight);
// round up so that we always include at least one id in the
// first rbyd
if ((lfs_size_t)id + 1 >= rbyd->weight) {
// well this shouldn't happen unless attr limits have gone wrong
return LFS_ERR_RANGE;
}
return id + 1;
}
}
@@ -2382,7 +2379,7 @@ static int lfsr_rbyd_append(lfs_t *lfs, lfsr_rbyd_t *rbyd,
lfs_swap32(&jump, &branch_);
lfs_swap16(&p_alts[0], &alt);
lfs_swaps32(&p_weights[0], &weight);
lfs_sswap32(&p_weights[0], &weight);
lfs_swap32(&p_jumps[0], &jump);
alt = lfsr_tag_mkblack(alt);
@@ -2447,7 +2444,7 @@ static int lfsr_rbyd_append(lfs_t *lfs, lfsr_rbyd_t *rbyd,
lower_id, upper_id,
tag_, id_)) {
lfs_swap16(&p_alts[0], &alt);
lfs_swaps32(&p_weights[0], &weight);
lfs_sswap32(&p_weights[0], &weight);
lfs_swap32(&p_jumps[0], &jump);
p_alts[0] = lfsr_tag_mkred(p_alts[0]);
alt = lfsr_tag_mkblack(alt);
@@ -2503,10 +2500,10 @@ static int lfsr_rbyd_append(lfs_t *lfs, lfsr_rbyd_t *rbyd,
if (diverged >= 4 || !lfsr_tag_isalt(alt)) {
diverged ^= 0x1;
lfs_swap16(&tag_, &other_tag_);
lfs_swaps32(&id_, &other_id_);
lfs_sswap32(&id_, &other_id_);
lfs_swap32(&branch, &other_branch);
lfs_swaps32(&lower_id, &other_lower_id);
lfs_swaps32(&upper_id, &other_upper_id);
lfs_sswap32(&lower_id, &other_lower_id);
lfs_sswap32(&upper_id, &other_upper_id);
lfs_swap16(&lower_tag, &other_lower_tag);
lfs_swap16(&upper_tag, &other_upper_tag);
}
@@ -3038,7 +3035,7 @@ static int lfsr_rbyd_commit(lfs_t *lfs, lfsr_rbyd_t *rbyd,
/// Rbyd b-tree operations ///
// TODO this is a weird null, move weight out of inlined?
#define LFSR_BTREE_NULL ((lfsr_btree_t){.tag=0x2, .u.inlined.weight=0})
#define LFSR_BTREE_NULL ((lfsr_btree_t){.weight=0})
// B-tree on-disk encoding
@@ -3099,16 +3096,16 @@ static lfs_ssize_t lfsr_btree_lookup(lfs_t *lfs,
lfsr_rbyd_t *rbyd_, lfs_ssize_t *rid_,
lfs_size_t *weight_,
void *buffer, lfs_size_t size) {
// in range?
if (id >= btree->weight) {
return LFS_ERR_NOENT;
}
// inlined?
if (btree->tag) {
// in range?
if (id >= btree->u.inlined.weight) {
return LFS_ERR_NOENT;
}
// TODO how many of these should be conditional?
if (id_) {
*id_ = btree->u.inlined.weight-1;
*id_ = btree->weight-1;
}
if (tag_) {
*tag_ = btree->tag;
@@ -3118,7 +3115,7 @@ static lfs_ssize_t lfsr_btree_lookup(lfs_t *lfs,
*rid_ = -1;
}
if (weight_) {
*weight_ = btree->u.inlined.weight;
*weight_ = btree->weight;
}
memcpy(buffer, btree->u.inlined.buf,
@@ -3215,9 +3212,10 @@ static int lfsr_btree_parent(lfs_t *lfs,
const lfsr_btree_t *btree, lfs_size_t id, const lfsr_rbyd_t *child,
lfsr_rbyd_t *rbyd_, lfs_ssize_t *rid_) {
// inlined? root?
if (btree->tag || (
btree->u.trunk.block == child->block
&& btree->u.trunk.limit == child->off)) {
if (id >= btree->weight
|| btree->tag
|| (btree->u.trunk.block == child->block
&& btree->u.trunk.limit == child->off)) {
return LFS_ERR_NOENT;
}
@@ -3919,6 +3917,7 @@ static int lfsr_btree_commit(lfs_t *lfs,
}
// at this point rbyd should be the trunk of our tree
btree->weight = rbyd->weight;
btree->u.trunk.block = rbyd->block;
btree->u.trunk.limit = rbyd->off;
return 0;
@@ -3928,13 +3927,15 @@ static int lfsr_btree_push(lfs_t *lfs,
lfsr_btree_t *btree,
lfs_size_t id, lfsr_tag_t tag, lfs_size_t weight,
const void *buffer, lfs_size_t size) {
LFS_ASSERT(id <= btree->weight);
// printf("- push(%d, %x, w%d) -\n", id, tag, weight);
// null btree?
if (btree->tag && btree->u.inlined.weight == 0) {
if (btree->weight == 0) {
LFS_ASSERT(id == 0);
btree->tag = tag;
btree->u.inlined.weight = weight;
btree->weight = weight;
LFS_ASSERT(size <= LFSR_BTREE_INLINE_SIZE);
memcpy(btree->u.inlined.buf, buffer, size);
@@ -3943,8 +3944,6 @@ static int lfsr_btree_push(lfs_t *lfs,
// inlined btree, need to expand into an rbyd
} else if (btree->tag) {
LFS_ASSERT(id == btree->u.inlined.weight);
lfsr_rbyd_t rbyd;
int err = lfsr_rbyd_alloc(lfs, &rbyd, 1);
if (err) {
@@ -3953,9 +3952,9 @@ static int lfsr_btree_push(lfs_t *lfs,
// commit our entries
err = lfsr_rbyd_commit(lfs, &rbyd,
LFSR_ATTR(GROW, 0, NULL, btree->u.inlined.weight,
LFSR_ATTR(MKBRANCH, 0+btree->u.inlined.weight-1, NULL, 0,
LFSR_ATTR_(btree->tag, 0+btree->u.inlined.weight-1,
LFSR_ATTR(GROW, 0, NULL, btree->weight,
LFSR_ATTR(MKBRANCH, 0+btree->weight-1, NULL, 0,
LFSR_ATTR_(btree->tag, 0+btree->weight-1,
btree->u.inlined.buf, btree->u.inlined.size,
LFSR_ATTR(GROW, id, NULL, weight,
LFSR_ATTR(MKBRANCH, id+weight-1, NULL, 0,
@@ -3967,6 +3966,7 @@ static int lfsr_btree_push(lfs_t *lfs,
}
btree->tag = 0;
btree->weight = rbyd.weight;
btree->u.trunk.block = rbyd.block;
btree->u.trunk.limit = rbyd.off;
return 0;
@@ -3978,16 +3978,22 @@ static int lfsr_btree_push(lfs_t *lfs,
// return ENOENT, is this ok?
lfsr_rbyd_t rbyd;
lfs_ssize_t rid;
lfs_ssize_t size = lfsr_btree_lookup(lfs, btree, id-weight,
lfs_ssize_t size = lfsr_btree_lookup(lfs, btree,
lfs_min32(id, btree->weight-1),
NULL, NULL, &rbyd, &rid, NULL, NULL, 0);
if (size < 0) {
return size;
}
rid += 1;
// adjust rid if we're appending
if (id >= btree->weight) {
rid += 1;
}
// commit our id into the tree, letting lfsr_btree_commit take care
// of the rest
return lfsr_btree_commit(lfs, btree, id-weight, &rbyd,
return lfsr_btree_commit(lfs, btree,
lfs_min32(id, btree->weight-1), &rbyd,
LFSR_ATTR(GROW, rid, NULL, weight,
LFSR_ATTR(MKBRANCH, rid+weight-1, NULL, 0,
LFSR_ATTR_(tag, rid+weight-1, buffer, size,