Quint Guvernator <quintus.pub...@gmail.com> writes:

> memcmp() is replaced with negated starts_with() when comparing strings
> from the beginning and when it is logical to do so. starts_with() looks
> nicer and it saves the extra argument of the length of the comparing
> string.
>
> Signed-off-by: Quint Guvernator <quintus.pub...@gmail.com>
> ---

Thanks.  This probably needs retitled, though (hint: "replaces"?
who does so?) and the message rewritten (see numerous reviews on
other GSoC micros from Eric).

> diff --git a/builtin/apply.c b/builtin/apply.c
> index 0189523..de84dce 100644
> --- a/builtin/apply.c
> +++ b/builtin/apply.c
> @@ -1631,7 +1631,7 @@ static int parse_fragment(const char *line, unsigned 
> long size,
>                * l10n of "\ No newline..." is at least that long.
>                */
>               case '\\':
> -                     if (len < 12 || memcmp(line, "\\ ", 2))
> +                     if (len < 12 || !starts_with(line, "\\ "))
>                               return -1;
>                       break;
>               }
> @@ -1646,7 +1646,7 @@ static int parse_fragment(const char *line, unsigned 
> long size,
>        * it in the above loop because we hit oldlines == newlines == 0
>        * before seeing it.
>        */
> -     if (12 < size && !memcmp(line, "\\ ", 2))
> +     if (12 < size && starts_with(line, "\\ "))
>               offset += linelen(line, size);
>  
>       patch->lines_added += added;

The above two looks sensible.

I sense that there is a bonus point for an independent follow-up
patch to unify the conflicting definitions of what an incomplete
line should look like.  Hint, hint...

> @@ -1673,7 +1673,7 @@ static int parse_single_patch(const char *line, 
> unsigned long size, struct patch
>       unsigned long oldlines = 0, newlines = 0, context = 0;
>       struct fragment **fragp = &patch->fragments;
>  
> -     while (size > 4 && !memcmp(line, "@@ -", 4)) {
> +     while (size > 4 && starts_with(line, "@@ -")) {

If there were a variant of starts_with() that works on a counted
string, and rewriting this using it to

        while (starts_with_counted(line, size, "@@ -")) {

would make perfect sense, but as written above, I do not think it is
an improvement.

> diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
> index 3e1d5c3..4135980 100644
> --- a/builtin/for-each-ref.c
> +++ b/builtin/for-each-ref.c
> @@ -193,7 +193,7 @@ static int verify_format(const char *format)
>               at = parse_atom(sp + 2, ep);
>               cp = ep + 1;
>  
> -             if (!memcmp(used_atom[at], "color:", 6))
> +             if (starts_with(used_atom[at], "color:"))
>                       need_color_reset_at_eol = !!strcmp(used_atom[at], 
> color_reset);
>       }
>       return 0;

Good.

> diff --git a/builtin/mktag.c b/builtin/mktag.c
> index 640ab64..640c28f 100644
> --- a/builtin/mktag.c
> +++ b/builtin/mktag.c
> @@ -57,7 +57,7 @@ static int verify_tag(char *buffer, unsigned long size)
>  
>       /* Verify type line */
>       type_line = object + 48;
> -     if (memcmp(type_line - 1, "\ntype ", 6))
> +     if (!starts_with(type_line - 1, "\ntype "))
>               return error("char%d: could not find \"\\ntype \"", 47);
>  
>       /* Verify tag-line */

Good.

> @@ -66,7 +66,7 @@ static int verify_tag(char *buffer, unsigned long size)
>               return error("char%"PRIuMAX": could not find next \"\\n\"",
>                               (uintmax_t) (type_line - buffer));
>       tag_line++;
> -     if (memcmp(tag_line, "tag ", 4) || tag_line[4] == '\n')
> +     if (!starts_with(tag_line, "tag ") || tag_line[4] == '\n')
>               return error("char%"PRIuMAX": no \"tag \" found",
>                               (uintmax_t) (tag_line - buffer));

Not quite.  I suspect that what actually makes this strange and
tricky is that this "no tag found" check is misplaced.  It found the
type line, expects that the next line is a tag line, and instead of
validating the remainder of type line, it does this thing, and then
verifies the actual type string, and for that, it needs tag_line
variable to stay where it is.

If we flipped the order of things around the codepath a bit, then we
should be able to first validate the type line, and then use
skip-prefix to skip the "tag " part (while validating that that line
actually begins with "tag ") and check the tag name is a non-empty
string that consists of a good character.  All of that is a topic
for a separate patch.

> diff --git a/builtin/patch-id.c b/builtin/patch-id.c
> index 3cfe02d..23ef424 100644
> --- a/builtin/patch-id.c
> +++ b/builtin/patch-id.c
> @@ -81,14 +81,14 @@ static int get_one_patchid(unsigned char *next_sha1, 
> git_SHA_CTX *ctx, struct st
>               }
>  
>               /* Ignore commit comments */
> -             if (!patchlen && memcmp(line, "diff ", 5))
> +             if (!patchlen && !starts_with(line, "diff "))
>                       continue;
>               /* Parsing diff header?  */
>               if (before == -1) {
> -                     if (!memcmp(line, "index ", 6))
> +                     if (starts_with(line, "index "))
>                               continue;
> -                     else if (!memcmp(line, "--- ", 4))
> +                     else if (starts_with(line, "--- "))
>                               before = after = 1;
>                       else if (!isalpha(line[0]))
>                               break;

Looks good.

> @@ -96,14 +96,14 @@ static int get_one_patchid(unsigned char *next_sha1, 
> git_SHA_CTX *ctx, struct st
>  
>               /* Looking for a valid hunk header?  */
>               if (before == 0 && after == 0) {
> -                     if (!memcmp(line, "@@ -", 4)) {
> +                     if (starts_with(line, "@@ -")) {
>                               /* Parse next hunk, but ignore line numbers.  */
>                               scan_hunk_header(line, &before, &after);
>                               continue;
>                       }
>  
>                       /* Split at the end of the patch.  */
> -                     if (memcmp(line, "diff ", 5))
> +                     if (!starts_with(line, "diff "))
>                               break;
>  
>                       /* Else we're parsing another header.  */

Looks good.

> diff --git a/connect.c b/connect.c
> index 4150412..5ae2aaa 100644
> --- a/connect.c
> +++ b/connect.c
> @@ -30,11 +30,11 @@ static int check_ref(const char *name, int len, unsigned 
> int flags)
>               return 0;
>  
>       /* REF_HEADS means that we want regular branch heads */
> -     if ((flags & REF_HEADS) && !memcmp(name, "heads/", 6))
> +     if ((flags & REF_HEADS) && starts_with(name, "heads/"))
>               return 1;
>  
>       /* REF_TAGS means that we want tags */
> -     if ((flags & REF_TAGS) && !memcmp(name, "tags/", 5))
> +     if ((flags & REF_TAGS) && starts_with(name, "tags/"))
>               return 1;
>  
>       /* All type bits clear means that we are ok with anything */

Looks good.

> diff --git a/imap-send.c b/imap-send.c
> index 0bc6f7f..019de18 100644
> --- a/imap-send.c
> +++ b/imap-send.c
> @@ -524,7 +524,7 @@ static struct imap_cmd *v_issue_imap_cmd(struct 
> imap_store *ctx,
>       if (Verbose) {
>               if (imap->num_in_progress)
>                       printf("(%d in progress) ", imap->num_in_progress);
> -             if (memcmp(cmd->cmd, "LOGIN", 5))
> +             if (!starts_with(cmd->cmd, "LOGIN"))
>                       printf(">>> %s", buf);
>               else
>                       printf(">>> %d LOGIN <user> <pass>\n", cmd->tag);

Looks good.

> @@ -802,7 +802,7 @@ static int get_cmd_result(struct imap_store *ctx, struct 
> imap_cmd *tcmd)
>                               resp = DRV_OK;
>                       else {
>                               if (!strcmp("NO", arg)) {
> -                                     if (cmdp->cb.create && cmd && 
> (cmdp->cb.trycreate || !memcmp(cmd, "[TRYCREATE]", 11))) { /* SELECT, APPEND 
> or UID COPY */
> +                                     if (cmdp->cb.create && cmd && 
> (cmdp->cb.trycreate || starts_with(cmd, "[TRYCREATE]"))) { /* SELECT, APPEND 
> or UID COPY */
>                                               p = strchr(cmdp->cmd, '"');
>                                               if (!issue_imap_cmd(ctx, NULL, 
> "CREATE \"%.*s\"", (int)(strchr(p + 1, '"') - p + 1), p)) {
>                                                       resp = RESP_BAD;
> @@ -827,7 +827,7 @@ static int get_cmd_result(struct imap_store *ctx, struct 
> imap_cmd *tcmd)
>                               } else /*if (!strcmp("BAD", arg))*/
>                                       resp = RESP_BAD;
>                               fprintf(stderr, "IMAP command '%s' returned 
> response (%s) - %s\n",
> -                                      memcmp(cmdp->cmd, "LOGIN", 5) ?
> +                                      !starts_with(cmdp->cmd, "LOGIN") ?
>                                                       cmdp->cmd : "LOGIN 
> <user> <pass>",
>                                                       arg, cmd ? cmd : "");
>                       }

Looks good.

> diff --git a/remote.c b/remote.c
> index 5f63d55..bd02b0e 100644
> --- a/remote.c
> +++ b/remote.c
> @@ -1149,7 +1149,7 @@ static int match_explicit(struct ref *src, struct ref 
> *dst,
>       case 1:
>               break;
>       case 0:
> -             if (!memcmp(dst_value, "refs/", 5))
> +             if (starts_with(dst_value, "refs/"))
>                       matched_dst = make_linked_ref(dst_value, dst_tail);
>               else if (is_null_sha1(matched_src->new_sha1))
>                       error("unable to delete '%s': remote ref does not 
> exist",

Looks good.
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