On Wed, Oct 26, 2022 at 08:42:02AM +0200, Ahmad Fatoum wrote:
> The implementation of strjoin is a bit suboptimal. The destination
> string is traversed from the beginning due to strcat and we have a
> left-over separator at the end, while it should only be in-between.
>
> Fix this.
Rather than fixing a just introduced function I would expect a patch
introducing strjoin() and then another one converting the time command
over to use it.
> +void *mempcpy(void *dest, const void *src, size_t count)
> +{
> + return memcpy(dest, src, count) + count;
> +}
> +EXPORT_SYMBOL(mempcpy);
>
> #ifndef __HAVE_ARCH_MEMMOVE
> /**
> @@ -943,7 +948,7 @@ char *strjoin(const char *separator, char **arr, size_t arrlen)
> {
> size_t separatorlen;
> int len = 1; /* '\0' */
> - char *buf;
> + char *buf, *p;
> int i;
>
> separatorlen = strlen(separator);
> @@ -951,12 +956,14 @@ char *strjoin(const char *separator, char **arr, size_t arrlen)
> for (i = 0; i < arrlen; i++)
> len += strlen(arr[i]) + separatorlen;
>
> - buf = xzalloc(len);
> + p = buf = xmalloc(len);
>
> for (i = 0; i < arrlen; i++) {
> - strcat(buf, arr[i]);
> - strcat(buf, separator);
> + p = stpcpy(p, arr[i]);
> + p = mempcpy(p, separator, separatorlen);
> }
>
> + p[-separatorlen] = '\0';
That's a bit hard to read. How about:
for (i = 0; i < arrlen; i++) {
p = stpcpy(p, arr[i]);
if (i < arrlen - 1)
p = stpcpy(p, separator);
}
That would also allow you to optimize the allocated buffer size above.
Sascha
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