commit 52fa6bb9475251179430c43d3342279b08f7619d Author: Nick Mathewson nickm@torproject.org Date: Tue Mar 7 18:43:49 2017 -0500

Swap memory allocation strategy for lists of lines for diffs

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. --- src/or/consdiff.c | 34 +++++++++++++++++++++------------- 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/src/or/consdiff.c b/src/or/consdiff.c index ea1613d..dfb97d4 100644 --- a/src/or/consdiff.c +++ b/src/or/consdiff.c @@ -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; }