Re: [PATCH] Fix Q-encoded multi-octet-char split in email.

[Jeff King <peff@peff.net>]

On Wed, Jul 04, 2012 at 03:19:31PM +0900, Katsuyama Takeharu wrote:

> diff --git a/pretty.c b/pretty.c
> --- a/pretty.c
> +++ b/pretty.c
> @@ -272,6 +272,13 @@ static void add_rfc2047(struct strbuf *sb, const char
> *line, int len,
>      static const int max_length = 78; /* per rfc2822 */
>      int i;
>      int line_len;
> +    int utf8_ctr, use_utf8;
> +    const char *utf8_start;
> +
> +    if (is_encoding_utf8(encoding) && encoding != NULL)
> +        use_utf8 = 1;
> +    else
> +        use_utf8 = 0;

I think you can drop the "encoding != NULL" here. If we don't have an
explicit encoding, git always assumes utf8 (also, as it happens we never
hit this point with a NULL encoding in the current code anyway, though
that could in theory change in the future).

> > Can we re-use utf8_width here instead of rewriting these rules?
> 
> Yes you can. But there are an issue which utf8_width seems not to return
> correct value.  It returns 3  even if  a provided code has 3 octet utf-8
> char(e.g. 0xE38292).
> I expect it returns 2.

Hmm. I think I may have led you astray. It seems that the return value
of utf8_width is not about the byte-width of the character
representation, but rather about the intended character-width of the
glyph. But since we are encoding the bytes, we care about the former.

So I think you would really want to use pick_one_utf8_char and see how
many characters it consumed, like this:

  const char *p = &line[i];
  pick_one_utf8_char(&p, NULL);
  if (!p) /* not valid utf8, just assume single byte */
          utf8_ctr = 1;
  else
          utf8_ctr = p - &line[i];

-Peff