[v4,04/10] kunit: string-stream: Add option to make all lines end with newline

Add an optional feature to string_stream that will append a newline to
any added string that does not already end with a newline. The purpose
of this is so that string_stream can be used to collect log lines.

This is enabled/disabled by calling string_stream_set_append_newlines().

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
---
 lib/kunit/string-stream.c | 28 +++++++++++++++++++++-------
 lib/kunit/string-stream.h |  7 +++++++
 2 files changed, 28 insertions(+), 7 deletions(-)

On Mon, Aug 14, 2023 at 9:23 AM Richard Fitzgerald
<rf@opensource.cirrus.com> wrote:
>
> Add an optional feature to string_stream that will append a newline to
> any added string that does not already end with a newline. The purpose
> of this is so that string_stream can be used to collect log lines.
>
> This is enabled/disabled by calling string_stream_set_append_newlines().
>
> Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>

Hello!

I just wanted to look over handling the newline and this looks good to
me. I agree with David that I don't mind one extra allocated byte.

Reviewed-by: Rae Moar <rmoar@google.com>

Thanks!
-Rae

> ---
>  lib/kunit/string-stream.c | 28 +++++++++++++++++++++-------
>  lib/kunit/string-stream.h |  7 +++++++
>  2 files changed, 28 insertions(+), 7 deletions(-)
>
> diff --git a/lib/kunit/string-stream.c b/lib/kunit/string-stream.c
> index ed24d86af9f5..1dcf6513b692 100644
> --- a/lib/kunit/string-stream.c
> +++ b/lib/kunit/string-stream.c
> @@ -44,32 +44,46 @@ int string_stream_vadd(struct string_stream *stream,
>                        va_list args)
>  {
>         struct string_stream_fragment *frag_container;
> -       int len;
> +       int buf_len, result_len;
>         va_list args_for_counting;
>
>         /* Make a copy because `vsnprintf` could change it */
>         va_copy(args_for_counting, args);
>
>         /* Evaluate length of formatted string */
> -       len = vsnprintf(NULL, 0, fmt, args_for_counting);
> +       buf_len = vsnprintf(NULL, 0, fmt, args_for_counting);
>
>         va_end(args_for_counting);
>
> -       if (len == 0)
> +       if (buf_len == 0)
>                 return 0;
>
> +       /* Reserve one extra for possible appended newline. */
> +       if (stream->append_newlines)
> +               buf_len++;
> +
>         /* Need space for null byte. */
> -       len++;
> +       buf_len++;
>
>         frag_container = alloc_string_stream_fragment(stream->test,
> -                                                     len,
> +                                                     buf_len,
>                                                       stream->gfp);
>         if (IS_ERR(frag_container))
>                 return PTR_ERR(frag_container);
>
> -       len = vsnprintf(frag_container->fragment, len, fmt, args);
> +       if (stream->append_newlines) {
> +               /* Don't include reserved newline byte in writeable length. */
> +               result_len = vsnprintf(frag_container->fragment, buf_len - 1, fmt, args);
> +
> +               /* Append newline if necessary. */
> +               if (frag_container->fragment[result_len - 1] != '\n')
> +                       result_len = strlcat(frag_container->fragment, "\n", buf_len);
> +       } else {
> +               result_len = vsnprintf(frag_container->fragment, buf_len, fmt, args);
> +       }
> +
>         spin_lock(&stream->lock);
> -       stream->length += len;
> +       stream->length += result_len;
>         list_add_tail(&frag_container->node, &stream->fragments);
>         spin_unlock(&stream->lock);
>
> diff --git a/lib/kunit/string-stream.h b/lib/kunit/string-stream.h
> index b669f9a75a94..048930bf97f0 100644
> --- a/lib/kunit/string-stream.h
> +++ b/lib/kunit/string-stream.h
> @@ -25,6 +25,7 @@ struct string_stream {
>         spinlock_t lock;
>         struct kunit *test;
>         gfp_t gfp;
> +       bool append_newlines;
>  };
>
>  struct kunit;
> @@ -47,4 +48,10 @@ bool string_stream_is_empty(struct string_stream *stream);
>
>  void string_stream_destroy(struct string_stream *stream);
>
> +static inline void string_stream_set_append_newlines(struct string_stream *stream,
> +                                                    bool append_newlines)
> +{
> +       stream->append_newlines = append_newlines;
> +}
> +
>  #endif /* _KUNIT_STRING_STREAM_H */
> --
> 2.30.2
>