Re: [PATCH] hfsplus: fix the bug that cannot recognize files with hangul file name

["Ernesto A. Fernández" <ernesto.mnd.fernandez@gmail.com>]

On Thu, Nov 23, 2017 at 10:36:37AM -0800, Viacheslav Dubeyko wrote:
> On Thu, 2017-11-23 at 08:32 -0300, Ernesto A. Fernández wrote:
> > Hi:
> > 
> > your issue seems to be in the decomposition of hangul characters, not
> > in
> > the recomposition before printing. The hfsplus module on linux is
> > saving
> > the name of your actor as AC F5 C7 20, without performing any
> > decomposition at all.
> > 
> > The reason your patch hides the bug is because it causes linux to
> > present
> > filenames as decomposed utf8, so it is not necessary to decompose
> > again
> > before working with them. But the issue is still there, and you will
> > most
> > likely run into trouble if you make a hangul filename in linux and
> > try
> > to work with it in MacOS.
> > 
> > Reviewing the code it would seem that the developers completely
> > forgot
> > the hangul characters had their own rules for decomposition. It's
> > weird
> > because they did the composition part correctly.
> > 
> > I've made a quick draft of a patch, mostly by copying the code
> > provided
> > in the unicode web. I don't think we can actually use it on a 
> 
> 
> Could you please share the link for "the unicode web"?
> 
> Thanks,
> Vyacheslav Dubeyko.

I'm not asking for any reviews yet, just testing because I don't have
a Mac. As long as that's clear, this is the latest version of Unicode:

www.unicode.org/versions/Unicode10.0.0/

You want section 3.12.

> 
> 
> > release,
> > but it should be enough to check if I'm right. It works fine on
> > linux,
> > but I don't have a mac, so it would be great if you could test it for
> > me.
> > 
> > Thanks,
> > Ernest
> > 
> > (By the way, there is no reason you should have to use the
> > nodecompose
> > mount option, as the other reviewer suggested. Using that option will
> > have a similar effect to that of your patch. It will hide the
> > problem,
> > but if you create a hangul filename on linux with that option you
> > probably won't be able to use it on a mac.)
> > 
> > ---
> > diff --git a/fs/hfsplus/unicode.c b/fs/hfsplus/unicode.c
> > index dfa90c2..9006c61 100644
> > --- a/fs/hfsplus/unicode.c
> > +++ b/fs/hfsplus/unicode.c
> > @@ -272,7 +272,7 @@ static inline int asc2unichar(struct super_block
> > *sb, const char *astr, int len,
> >  	return size;
> >  }
> >  
> > -/* Decomposes a single unicode character. */
> > +/* Decomposes a single non-Hangul unicode character. */
> >  static inline u16 *decompose_unichar(wchar_t uc, int *size)
> >  {
> >  	int off;
> > @@ -296,6 +296,29 @@ static inline u16 *decompose_unichar(wchar_t uc,
> > int *size)
> >  	return hfsplus_decompose_table + (off / 4);
> >  }
> >  
> > +/* Decomposes a Hangul unicode character. */
> > +int decompose_hangul(wchar_t uc, u16 *result)
> > +{
> > +	int index;
> > +	int l, v, t;
> > +
> > +	index = uc - Hangul_SBase;
> > +	if (index < 0 || index >= Hangul_SCount)
> > +		return 0;
> > +
> > +	l = Hangul_LBase + index / Hangul_NCount;
> > +	v = Hangul_VBase + (index % Hangul_NCount) / Hangul_TCount;
> > +	t = Hangul_TBase + index % Hangul_TCount;
> > +
> > +	result[0] = l;
> > +	result[1] = v;
> > +	if (t != Hangul_TBase) {
> > +		result[2] = t;
> > +		return 3;
> > +	}
> > +	return 2;
> > +}
> > +
> >  int hfsplus_asc2uni(struct super_block *sb,
> >  		    struct hfsplus_unistr *ustr, int max_unistr_len,
> >  		    const char *astr, int len)
> > @@ -303,15 +326,23 @@ int hfsplus_asc2uni(struct super_block *sb,
> >  	int size, dsize, decompose;
> >  	u16 *dstr, outlen = 0;
> >  	wchar_t c;
> > +	u16 hangul_buf[3];
> >  
> >  	decompose = !test_bit(HFSPLUS_SB_NODECOMPOSE,
> > &HFSPLUS_SB(sb)->flags);
> >  	while (outlen < max_unistr_len && len > 0) {
> >  		size = asc2unichar(sb, astr, len, &c);
> >  
> > -		if (decompose)
> > -			dstr = decompose_unichar(c, &dsize);
> > -		else
> > +		if (decompose) {
> > +			/* Hangul is handled separately */
> > +			dstr = &hangul_buf[0];
> > +			dsize = decompose_hangul(c, dstr);
> > +			if (dsize == 0)
> > +				/* not Hangul */
> > +				dstr = decompose_unichar(c, &dsize);
> > +		} else {
> >  			dstr = NULL;
> > +		}
> > +
> >  		if (dstr) {
> >  			if (outlen + dsize > max_unistr_len)
> >  				break;