Re: has_prefix and has_suffix proposal for glib 2.2

[Alex Larsson <alexl redhat com>]

On Sun, 5 May 2002, Evan Martin wrote:

> On Fri, May 03, 2002 at 05:15:40PM -0400, Alex Larsson wrote:
> > +  str_len = strlen (str);
> > +  suffix_len = strlen (suffix);
> > +
> > +  if (str_len < suffix_len)
> > +    return FALSE;
> > +
> > +  return strcmp (str + str_len - suffix_len, suffix) == 0;
> 
> Isn't this sort of arithmetic not UTF-8 safe?
> Or are of none the GTK functions of this nature intended to be?

It is safe if both of the strings are valid UTF-8. In fact it is correct 
for all sane encodings if the strings passed are valid strings of the 
same encoding.
 
> > +gboolean
> > +g_str_has_prefix (const gchar  *str,
> > +		  const gchar  *prefix)
> > +{
> > +  int str_len;
> > +  int prefix_len;
> > +  
> > +  g_return_val_if_fail (str != NULL, FALSE);
> > +  g_return_val_if_fail (prefix != NULL, FALSE);
> > +
> > +  str_len = strlen (str);
> > +  prefix_len = strlen (prefix);
> > +
> > +  if (str_len < prefix_len)
> > +    return FALSE;
> > +  
> > +  return strncmp (str, prefix, prefix_len) == 0;
> 
> Wouldn't it be faster to not calculate the lengths?  That requires
> iterating through both of the strings once before even comparing them.
> I guess if you're worried about speed you wouldn't use strncmp because
> you're only concerned with whether they match...
> 
> Well, I stand by my first comment, at least. ;)

Perhaps we should not calculate the length of the first string. That's not 
strictly necessary, and it may be long. But I doubt it will matter much 
for real life usage of this function.

-- 
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 Alexander Larsson                                            Red Hat, Inc 
                   alexl redhat com    alla lysator liu se 
He's an all-American Amish messiah on the run. She's a strong-willed impetuous 
research scientist from aristocratic European stock. They fight crime!