[FFmpeg-devel] [PATCH] lavu/error: add av_make_strerr() and av_err2str() convenience utilities

[Nicolas George]

Le tridi 23 prairial, an CCXX, Stefano Sabatini a écrit :
> These functions are modeled after the corresponding utilities in
> libavutil/timestamp.h.
> ---
>  libavutil/error.c |    7 ++-----
>  libavutil/error.h |   22 ++++++++++++++++++++++
>  2 files changed, 24 insertions(+), 5 deletions(-)
> 
> diff --git a/libavutil/error.c b/libavutil/error.c
> index 16c2587..7f08314 100644
> --- a/libavutil/error.c
> +++ b/libavutil/error.c
> @@ -78,17 +78,14 @@ int av_strerror(int errnum, char *errbuf, size_t errbuf_size)
>  int main(void)
>  {
>      int i;
> -    char errbuf[256];
>  
>      for (i = 0; i < FF_ARRAY_ELEMS(error_entries); i++) {
>          struct error_entry *entry = &error_entries[i];
> -        av_strerror(entry->num, errbuf, sizeof(errbuf));
> -        printf("%d: %s [%s]\n", entry->num, errbuf, entry->tag);
> +        printf("%d: %s [%s]\n", entry->num, av_err2str(entry->num), entry->tag);
>      }
>  
>      for (i = 0; i < 256; i++) {
> -        av_strerror(-i, errbuf, sizeof(errbuf));
> -        printf("%d: %s\n", -i, errbuf);
> +        printf("%d: %s\n", -i, av_err2str(-i));
>      }
>  
>      return 0;
> diff --git a/libavutil/error.h b/libavutil/error.h
> index 316734f..0f3945e 100644
> --- a/libavutil/error.h
> +++ b/libavutil/error.h
> @@ -82,6 +82,28 @@
>   */
>  int av_strerror(int errnum, char *errbuf, size_t errbuf_size);
>  
> +#define AV_ERROR_MAX_STRING_SIZE 64
> +
> +/**
> + * Fill the provided buffer with a string containing an error string
> + * representation.
> + *
> + * @param buf         a buffer with size in bytes of at least AV_ERROR_MAX_STRING_SIZE
> + * @param errnum      error code to describe
> + * @return the buffer in input, filled with the error description
> + */
> +static inline char *av_make_strerr(char *errbuf, int errnum)

I would be somewhat happier if there was a size argument, and the
MAX_STRING_SIZE was only for the macro with the automatic buffer.

> +{
> +    av_strerror(errnum, errbuf, AV_ERROR_MAX_STRING_SIZE);
> +    return errbuf;

If the error code is one of our internal ones, the function could return
directly the pointer to the static string and avoid a string copy. I do not
know if it really matters, though, as errors should be rare.

> +}
> +
> +/**
> + * Convenience macro, the return value should be used only directly in
> + * function arguments but never stand-alone.
> + */
> +#define av_err2str(errnum) av_make_strerr((char[AV_ERROR_MAX_STRING_SIZE]){0}, errnum)

This part LGTM.

Regards,

-- 
  Nicolas George
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