[FFmpeg-devel] [PATCH] avio: add avio_get_str as a replacement for get_strz

[Reimar Döffinger]

On Tue, Mar 01, 2011 at 06:33:56PM +0100, Anton Khirnov wrote:
>  /**
> + * Read a UTF-8 string from pb. The reading will terminate when either
> + * a NULL character was encountered or maxlen bytes have been read.
> + *
> + * @return number of bytes read (is always <= maxlen).
> + */
> +int avio_get_str(AVIOContext *pb, int maxlen, char *buf, int buflen);

1) If you already say UTF-8 string you should definitely use uint8_t as type.
2) The mention of UTF-8 is quite questionable since the code does not care one
   bit about UTF-8 (e.g. it doesn't try to avoid storing partial encodings in the
   destination).

>  char *get_strz(AVIOContext *s, char *buf, int maxlen)
>  {
> -    int i = 0;
> -    char c;
> -
> -    while ((c = avio_r8(s))) {
> -        if (i < maxlen-1)
> -            buf[i++] = c;
> -    }
> -
> -    buf[i] = 0; /* Ensure null terminated, but may be truncated */
> -
> +    avio_get_str(s, INT_MAX, buf, maxlen);
>      return buf;
>  }

> +int avio_get_str(AVIOContext *s, int maxlen, char *buf, int buflen)
> +{
> +    int ret = 0;
> +
> +    while (ret < maxlen) {
> +        char c = avio_r8(s);
> +        ret++;
> +        if (!c)
> +            break;
> +        if (ret < buflen - 1)
> +            *buf++ = c;
> +    }
> +    *buf = 0;
> +    return ret;


How about something like this instead:

int i;
av_assert(buflen >= 0 && maxlen >= 0);
// reserve 1 byte for terminating 0
buflen = FFMIN(buflen - 1, maxlen);
for (i = 0; i < buflen; i++)
    if (!(buf[i] = avio_r8(s)))
        return i + 1;
// note: your code currently is wrong for that case
if (buflen)
    buf[i] = 0;
for (; i < maxlen; i++)
    if (!avio_r8(s))
        return i + 1;
return maxlen;