Hi guys,
here is the second part of nice talloc features.
talloc_*_append(dest, src) works in O(n^2) complexity as it needs to do
strlen(dest) and strlen(src). Talloc also provides an alternative
talloc_*_append_buffer(dest, src) which uses size of the dest context
to determine the length of the string. Its complexity is O(n) as it
runs only strlen(src).
Let me show it on an example. One part of the sysdb filter creation for
sudo contains:
for (i=0; groupnames[i] != NULL; i++) {
filter = talloc_asprintf_append(filter, "(%s=%%%s)",
SYSDB_SUDO_CACHE_AT_USER,
groupnames[i]);
NULL_CHECK(specific_filter, ret, done);
}
groupnames contains all groups that a user is member of.
Let's say he's a member of 100 groups where each group name consist of
10 characters. We will run strlen(filter) 100 times with total of
sum[i=1..100](10*i) = 50 500 iterations but we can simply make it 0 if
we replace talloc_*_append with talloc_*_append_buffer.
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