On 9/18/2019 12:35 PM, René Scharfe wrote:
> Pass the target strbuf to the callback function grab_nth_branch_switch()
> by reference so that it can add the result string directly instead of
> having it put the string into a temporary strbuf first. This gets rid
> of an extra allocation and a string copy.
>
> Signed-off-by: René Scharfe <l.s.r@xxxxxx>
> ---
> Patch formatted with --function-context for easier reviewing.
I appreciate this. I needed to look through the whole method to see that
previously "buf" was used to take the resulting value on a successful
parse.
> sha1-name.c | 11 ++++-------
> 1 file changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/sha1-name.c b/sha1-name.c
> index c665e3f96d..85196929c7 100644
> --- a/sha1-name.c
> +++ b/sha1-name.c
> @@ -1286,70 +1286,67 @@ static int get_oid_oneline(struct repository *r,
>
> struct grab_nth_branch_switch_cbdata {
> int remaining;
> - struct strbuf buf;
> + struct strbuf *sb;
> };
>
> static int grab_nth_branch_switch(struct object_id *ooid, struct object_id *noid,
> const char *email, timestamp_t timestamp, int tz,
> const char *message, void *cb_data)
> {
> struct grab_nth_branch_switch_cbdata *cb = cb_data;
> const char *match = NULL, *target = NULL;
> size_t len;
>
> if (skip_prefix(message, "checkout: moving from ", &match))
> target = strstr(match, " to ");
>
> if (!match || !target)
> return 0;
> if (--(cb->remaining) == 0) {
> len = target - match;
> - strbuf_reset(&cb->buf);
> - strbuf_add(&cb->buf, match, len);
> + strbuf_reset(cb->sb);
> + strbuf_add(cb->sb, match, len);
> return 1; /* we are done */
It seems that now "buf" is still only being replaced on a successful parse, since
this strbuf_reset and strbuf_add is happening only on a return 1, which terminates
the refs_for_each... method.
> }
> return 0;
> }
>
> /*
> * Parse @{-N} syntax, return the number of characters parsed
> * if successful; otherwise signal an error with negative value.
> */
> static int interpret_nth_prior_checkout(struct repository *r,
> const char *name, int namelen,
> struct strbuf *buf)
> {
> long nth;
> int retval;
> struct grab_nth_branch_switch_cbdata cb;
> const char *brace;
> char *num_end;
>
> if (namelen < 4)
> return -1;
> if (name[0] != '@' || name[1] != '{' || name[2] != '-')
> return -1;
> brace = memchr(name, '}', namelen);
> if (!brace)
> return -1;
> nth = strtol(name + 3, &num_end, 10);
> if (num_end != brace)
> return -1;
> if (nth <= 0)
> return -1;
> cb.remaining = nth;
> - strbuf_init(&cb.buf, 20);
> + cb.sb = buf;
>
> retval = refs_for_each_reflog_ent_reverse(get_main_ref_store(r),
> "HEAD", grab_nth_branch_switch, &cb);
> if (0 < retval) {
> - strbuf_reset(buf);
> - strbuf_addbuf(buf, &cb.buf);
> retval = brace - name + 1;
> } else
> retval = 0;
>
> - strbuf_release(&cb.buf);
> return retval;
> }
>
The reaction in this method appears correct, too.
Thanks,
-Stolee
