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authorAaron Griffin <aaronmgriffin@gmail.com>2007-11-06 00:55:45 -0600
committerAaron Griffin <aaronmgriffin@gmail.com>2007-11-06 22:47:10 -0600
commit2ee90ddae23dd86c68223c0d6c49f0b92d62429d (patch)
tree050a4d45e7e56c5a860df533cf4557f34de8416d /lib/libalpm/alpm_list.c
parentbdab234d977dd2e9417a39f5191e495d5c460ee7 (diff)
Maintain list tail pointers in the head node
List head nodes contain null 'prev' pointer, which we can (ab)use to maintain a back reference to the tail pointer of the list. While list additions are not _significantly_ improved, they are still sped up. Original $ time pacman -Qo /usr/bin/wtpt /usr/bin/wtpt is owned by lcms 1.17-2 real 0m3.623s user 0m1.883s sys 0m1.473s New $ time pacman -Qo /usr/bin/wtpt /usr/bin/wtpt is owned by lcms 1.17-2 real 0m2.006s user 0m0.263s sys 0m1.627s Signed-off-by: Aaron Griffin <aaronmgriffin@gmail.com>
Diffstat (limited to 'lib/libalpm/alpm_list.c')
-rw-r--r--lib/libalpm/alpm_list.c59
1 files changed, 44 insertions, 15 deletions
diff --git a/lib/libalpm/alpm_list.c b/lib/libalpm/alpm_list.c
index faeecc0a..6f6ee8f0 100644
--- a/lib/libalpm/alpm_list.c
+++ b/lib/libalpm/alpm_list.c
@@ -53,7 +53,7 @@ alpm_list_t SYMEXPORT *alpm_list_new()
list = malloc(sizeof(alpm_list_t));
if(list) {
list->data = NULL;
- list->prev = NULL;
+ list->prev = list; /* maintain a back reference to the tail pointer */
list->next = NULL;
}
@@ -127,6 +127,7 @@ alpm_list_t SYMEXPORT *alpm_list_add(alpm_list_t *list, void *data)
}
lp->next->prev = lp;
lp = lp->next;
+ list->prev = lp;
}
lp->data = data;
@@ -173,6 +174,11 @@ alpm_list_t SYMEXPORT *alpm_list_add_sorted(alpm_list_t *list, void *data, alpm_
} else {
list = add; /* At beginning, or new list */
}
+
+ if(next == NULL) {
+ /* At end, adjust tail pointer on head node */
+ list->prev = add;
+ }
return(list);
}
@@ -230,6 +236,15 @@ alpm_list_t SYMEXPORT *alpm_list_mmerge(alpm_list_t *left, alpm_list_t *right, a
lp->next = right;
right->prev = lp;
}
+
+ /* Find our tail pointer
+ * TODO maintain this in the algorithm itself */
+ lp = newlist;
+ while(lp && lp->next) {
+ lp = lp->next;
+ }
+ newlist->prev = lp;
+
return(newlist);
}
@@ -269,7 +284,7 @@ alpm_list_t SYMEXPORT *alpm_list_msort(alpm_list_t *list, int n, alpm_list_fn_cm
* @return the resultant list
*/
alpm_list_t SYMEXPORT *alpm_list_remove(alpm_list_t *haystack, const void *needle, alpm_list_fn_cmp fn, void **data)
-{ /* TODO I modified this to remove ALL matching items. Do we need a remove_first? */
+{
alpm_list_t *i = haystack, *tmp = NULL;
if(data) {
@@ -283,16 +298,23 @@ alpm_list_t SYMEXPORT *alpm_list_remove(alpm_list_t *haystack, const void *needl
tmp = i->next;
if(fn(needle, i->data) == 0) {
/* we found a matching item */
- if(i->next) {
- i->next->prev = i->prev;
- }
- if(i->prev) {
- i->prev->next = i->next;
- }
-
if(i == haystack) {
+ /* Special case: removing the head node which has a back reference to
+ * the tail node */
/* The item found is the first in the chain */
- haystack = haystack->next;
+ haystack = i->next;
+ if(haystack) {
+ haystack->prev = i->prev;
+ }
+ i->prev = NULL;
+ } else {
+ /* Normal case, non-head node */
+ if(i->next) {
+ i->next->prev = i->prev;
+ }
+ if(i->prev) {
+ i->prev->next = i->next;
+ }
}
if(data) {
@@ -300,8 +322,10 @@ alpm_list_t SYMEXPORT *alpm_list_remove(alpm_list_t *haystack, const void *needl
}
i->data = NULL;
free(i);
+ i = NULL;
+ } else {
+ i = tmp;
}
- i = tmp;
}
return(haystack);
@@ -431,6 +455,11 @@ alpm_list_t SYMEXPORT *alpm_list_reverse(alpm_list_t *list)
alpm_list_t *newlist = NULL;
lp = alpm_list_last(list);
+ if(list) {
+ /* break our reverse circular list */
+ list->prev = NULL;
+ }
+
while(lp) {
newlist = alpm_list_add(newlist, lp->data);
lp = lp->prev;
@@ -490,11 +519,11 @@ inline alpm_list_t SYMEXPORT *alpm_list_next(const alpm_list_t *node)
*/
alpm_list_t SYMEXPORT *alpm_list_last(const alpm_list_t *list)
{
- const alpm_list_t *i = list;
- while(i && i->next) {
- i = i->next;
+ if(list) {
+ return(list->prev);
+ } else {
+ return(NULL);
}
- return((alpm_list_t*)i);
}
/**