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pma: rewrite _pending_nlist_merge

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This commit is contained in:
barter-simsum 2023-12-04 17:07:48 -05:00
parent bbc1c88120
commit 5beb2da584
1 changed files with 47 additions and 64 deletions
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111
rust/ares_pma/c-src/btree.c
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@ -820,21 +820,6 @@ _pending_nlist_insert(BT_state *state, pgno_t nodepg)
head->next = new;
}
static void
_pending_nlist_clear(BT_state *state)
{
/* there's no need for a pending freelist "pop" routine as we only clear nodes
from it after all have been merged with the real freelists */
BT_nlistnode *prev = state->pending_nlist;
BT_nlistnode *next = prev->next;
while (prev) {
free(prev);
prev = next;
next = next->next;
}
state->pending_nlist = 0;
}
static BT_nlistnode *
_nlist_find(BT_nlistnode *head, BT_page *va)
/* find a node */
@ -844,46 +829,59 @@ _nlist_find(BT_nlistnode *head, BT_page *va)
static void
_pending_nlist_merge(BT_state *state)
/* merge state->pending_nlist with state->nlist. To be called when syncing */
{
BT_nlistnode *src_head = state->pending_nlist;
BT_nlistnode *dst_head = state->nlist;
BT_nlistnode **src_head = &state->pending_nlist;
BT_nlistnode **dst_head = &state->nlist;
while (src_head) {
/* ;;: todo refactor */
while (dst_head) {
BT_page *dst_va = dst_head->va;
BT_page *src_va = src_head->va;
if (dst_head->va <= src_head->va
&& dst_head->va + dst_head->sz >= src_head->va) {
/* found node in nlist that fits node in pending nlist */
dst_head->sz += 1;
break;
}
else if (dst_head->va + dst_head->sz < src_head->va
&& dst_head->next->va > src_head->va) {
/* pending nlist node belongs between two nlist nodes */
BT_nlistnode *new = calloc(1, sizeof *new);
memcpy(new, src_head, sizeof *src_head);
new->sz = 1;
new->va = src_head->va;
/* insert */
new->next = dst_head->next;
dst_head->next = new;
break;
}
dst_head = dst_head->next;
}
if (src_head) {
/* need to track prev or use double indirection */
while (*dst_head) {
/* src cleared. done */
if (!*src_head) {
return;
}
/* check if src node should be merged with dst **************************/
BT_page *dst_va = (*dst_head)->va;
size_t dst_sz = (*dst_head)->sz;
BT_page *src_va = (*src_head)->va;
/* NB: while we don't currently coalesce the pending nlist, it's not that
hard to account for if we did, so might as well generalize the merge
algorithm */
size_t src_sz = (*src_head)->sz;
BT_page *dst_next_va = *dst_head ? (*dst_head)->next->va : 0;
src_head = src_head->next;
/* source node immediately follows dst node's termination */
if (dst_va + dst_sz == src_va) {
(*dst_head)->sz += src_sz; /* widen dst node */
/* advance src node and free previous */
BT_nlistnode *prev = *src_head;
src_head = &(*src_head)->next;
free(prev);
}
_pending_nlist_clear(state);
/* source node's termination immediately precedes dst node */
else if (dst_next_va == src_va + src_sz) {
(*dst_head)->va = src_va; /* pull va back */
(*dst_head)->sz += src_sz; /* widen node */
/* advance src node and free previous */
BT_nlistnode *prev = *src_head;
src_head = &(*src_head)->next;
free(prev);
}
/* src node lies between but isn't contiguous with dst */
else if (src_va > dst_va + dst_sz
&& src_va + src_sz < dst_next_va) {
/* link src node in */
(*src_head)->next = (*dst_head)->next;
(*dst_head)->next = *src_head;
/* and advance src node */
src_head = &(*src_head)->next;
}
/* otherwise, advance dst node */
else {
dst_head = &(*dst_head)->next;
}
}
/* merge what remains of src if anything */
*dst_head = *src_head;
}
static void
@ -928,21 +926,6 @@ _pending_flist_insert(BT_state *state, pgno_t pg, size_t sz)
head->next = new;
}
/* static void */
/* _pending_flist_clear(BT_state *state) */
/* { */
/* /\* as with _pending_flist_clear. We only remove nodes from this list if it's */
/* fully merged with state->flist *\/ */
/* BT_flistnode *prev = state->pending_flist; */
/* BT_flistnode *next = prev->next; */
/* while (prev) { */
/* free(prev); */
/* prev = next; */
/* next = next->next; */
/* } */
/* state->pending_flist = 0; */
/* } */
static void
_pending_flist_merge(BT_state *state)
{