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Swap memory allocation strategy for lists of lines for diffs

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Now we use a single allocation block for all the lines, rather than
calling strdup on them one at a time.  This should help performance
a tiny bit.
This commit is contained in:
Nick Mathewson 2017-03-07 18:43:49 -05:00
parent b36e311eab
commit 52fa6bb947
1 changed files with 21 additions and 13 deletions
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34
src/or/consdiff.c
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@ -1046,24 +1046,28 @@ consdiff_apply_diff(const smartlist_t *cons1,
}
/**
* Helper: For every NL-terminated line in <b>s</b>, add a copy of that line
* Helper: For every NL-terminated line in <b>s</b>, add that line
* (without trailing newline) to <b>out</b>. Return -1 if there are any
* non-NL terminated lines; 0 otherwise.
*
* Unlike smartlist_split_string, this function avoids ambiguity on its
* Modifies <b>s</b> in place: don't do anything with <b>s</b> after you're
* done here, besides freeing it.
*
* Unlike tor_split_lines, this function avoids ambiguity on its
* handling of a final line that isn't NL-terminated.
*/
static int
consensus_split_lines(smartlist_t *out, const char *s)
consensus_split_lines(smartlist_t *out, char *s)
{
/* XXXX If we used string slices, we could avoid a bunch of copies here. */
while (*s) {
const char *eol = strchr(s, '\n');
char *eol = strchr(s, '\n');
if (!eol) {
/* File doesn't end with newline. */
return -1;
}
smartlist_add(out, tor_strndup(s, eol-s));
*eol = 0;
smartlist_add(out, s);
s = eol+1;
}
return 0;
@ -1110,20 +1114,22 @@ consensus_diff_generate(const char *cons1,
if (BUG(r1 < 0 || r2 < 0))
return NULL; // LCOV_EXCL_LINE
char *cons1_copy = tor_strdup(cons1);
char *cons2_copy = tor_strdup(cons2);
lines1 = smartlist_new();
lines2 = smartlist_new();
if (consensus_split_lines(lines1, cons1) < 0)
if (consensus_split_lines(lines1, cons1_copy) < 0)
goto done;
if (consensus_split_lines(lines2, cons2) < 0)
if (consensus_split_lines(lines2, cons2_copy) < 0)
goto done;
result_lines = consdiff_gen_diff(lines1, lines2, &d1, &d2);
done:
SMARTLIST_FOREACH(lines1, char *, cp, tor_free(cp));
smartlist_free(lines1);
SMARTLIST_FOREACH(lines2, char *, cp, tor_free(cp));
smartlist_free(lines2);
tor_free(cons1_copy);
tor_free(cons2_copy);
if (result_lines) {
result = consensus_join_lines(result_lines);
@ -1149,20 +1155,22 @@ consensus_diff_apply(const char *consensus,
if (BUG(r1 < 0))
return NULL; // LCOV_EXCL_LINE
char *cons_copy = tor_strdup(consensus);
char *diff_copy = tor_strdup(diff);
lines1 = smartlist_new();
lines2 = smartlist_new();
if (consensus_split_lines(lines1, consensus) < 0)
if (consensus_split_lines(lines1, cons_copy) < 0)
goto done;
if (consensus_split_lines(lines2, diff) < 0)
if (consensus_split_lines(lines2, diff_copy) < 0)
goto done;
result = consdiff_apply_diff(lines1, lines2, &d1);
done:
SMARTLIST_FOREACH(lines1, char *, cp, tor_free(cp));
smartlist_free(lines1);
SMARTLIST_FOREACH(lines2, char *, cp, tor_free(cp));
smartlist_free(lines2);
tor_free(cons_copy);
tor_free(diff_copy);
return result;
}