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alpm_list : add new alpm_list_diff_sorted function

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This is more efficient than alpm_list_diff since it assumes the two lists
are sorted. And also we get the two sides of the diff.

Even sorting should more efficient than the current list_diff. Sorting the
two lists should be O(n*log(n)+m*log(m)) while the current list_diff is
O(n*m). So I also reimplemented list_diff using list_diff_sorted.

Signed-off-by: Xavier Chantry <shiningxc@gmail.com>
Signed-off-by: Dan McGee <dan@archlinux.org>
This commit is contained in:
Xavier Chantry 2009-10-11 02:38:33 +02:00 committed by Dan McGee
parent 14ab02e289
commit 3dc87851cc
2 changed files with 70 additions and 17 deletions
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85
lib/libalpm/alpm_list.c
View File

@ -644,11 +644,65 @@ char SYMEXPORT *alpm_list_find_str(const alpm_list_t *haystack,
}
/**
* @brief Find the items in list `lhs` that are not present in list `rhs`.
* @brief Find the differences between list `left` and list `right`
*
* Entries are not duplicated. Operation is O(m*n). The first list is stepped
* through one node at a time, and for each node in the first list, each node
* in the second list is compared to it.
* The two lists must be sorted. Items only in list `left` are added to the
* `onlyleft` list. Items only in list `right` are added to the `onlyright`
* list.
*
* @param left the first list
* @param right the second list
* @param fn the comparison function
* @param onlyleft pointer to the first result list
* @param onlyright pointer to the second result list
*
*/
void SYMEXPORT alpm_list_diff_sorted(alpm_list_t *left,
alpm_list_t *right, alpm_list_fn_cmp fn,
alpm_list_t **onlyleft, alpm_list_t **onlyright)
{
alpm_list_t *l = left;
alpm_list_t *r = right;
if(!onlyleft && !onlyright) {
return;
}
while (l != NULL && r != NULL) {
int cmp = fn(l->data, r->data);
if(cmp < 0) {
if(onlyleft) {
*onlyleft = alpm_list_add(*onlyleft, l->data);
}
l = l->next;
}
else if(cmp > 0) {
if(onlyright) {
*onlyright = alpm_list_add(*onlyright, r->data);
}
r = r->next;
} else {
l = l->next;
r = r->next;
}
}
while (l != NULL) {
if(onlyleft) {
*onlyleft = alpm_list_add(*onlyleft, l->data);
}
l = l->next;
}
while (r != NULL) {
if(onlyright) {
*onlyright = alpm_list_add(*onlyright, r->data);
}
r = r->next;
}
}
/**
* @brief Find the items in list `lhs` that are not present in list `rhs`.
*
* @param lhs the first list
* @param rhs the second list
@ -659,21 +713,18 @@ char SYMEXPORT *alpm_list_find_str(const alpm_list_t *haystack,
alpm_list_t SYMEXPORT *alpm_list_diff(const alpm_list_t *lhs,
const alpm_list_t *rhs, alpm_list_fn_cmp fn)
{
const alpm_list_t *i, *j;
alpm_list_t *left, *right;
alpm_list_t *ret = NULL;
for(i = lhs; i; i = i->next) {
int found = 0;
for(j = rhs; j; j = j->next) {
if(fn(i->data, j->data) == 0) {
found = 1;
break;
}
}
if(!found) {
ret = alpm_list_add(ret, i->data);
}
}
left = alpm_list_copy(lhs);
left = alpm_list_msort(left, alpm_list_count(left), fn);
right = alpm_list_copy(rhs);
right = alpm_list_msort(right, alpm_list_count(right), fn);
alpm_list_diff_sorted(left, right, fn, &ret, NULL);
alpm_list_free(left);
alpm_list_free(right);
return(ret);
}

2
lib/libalpm/alpm_list.h
View File

@ -78,6 +78,8 @@ void *alpm_list_find(const alpm_list_t *haystack, const void *needle, alpm_list_
void *alpm_list_find_ptr(const alpm_list_t *haystack, const void *needle);
char *alpm_list_find_str(const alpm_list_t *haystack, const char *needle);
alpm_list_t *alpm_list_diff(const alpm_list_t *lhs, const alpm_list_t *rhs, alpm_list_fn_cmp fn);
void alpm_list_diff_sorted(alpm_list_t *left, alpm_list_t *right,
alpm_list_fn_cmp fn, alpm_list_t **onlyleft, alpm_list_t **onlyright);
#ifdef __cplusplus
}