source/texk/kpathsea/find-suffix.c

   1 /* find-suffix.c: return the stuff after a dot.
   2
   3    Copyright 1992, 1993, 1995, 2008, 2011 Karl Berry.
   4
   5    This library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    This library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this library; if not, see <http://www.gnu.org/licenses/>.  */
  17
  18 #include <kpathsea/config.h>
  19
  20 #include <kpathsea/c-pathch.h>
  21
  22
  23 /* Return pointer to first character after `.' in last directory element
  24    of NAME.  If the name is `foo' or `/foo.bar/baz', we have no extension.  */
  25
  26 /* The the result of strrchr(NAME, '.'), when not NULL, is a non-const
  27    pointer into the string NAME.  However, this is cheating (motivated
  28    by limitations of the C language) when the argument NAME is a
  29    const string, because in that case the (technically non-const) result
  30    from strrchr() is certainly not modifiable.
  31
  32    We do not want to repeat this kind of cheating for find_suffix() and
  33    therefore declare find_suffix(NAME) as const.  When find_suffix(NAME)
  34    is non-NULL and the argument NAME is modifiable (i.e., non-const)
  35    then NAME+(find_suffix(NAME)-NAME) is an equivalent modifiable string
  36    and the pointer arithmetic is optimized away by modern compilers.  */
  37
  38 const_string
  39 find_suffix (const_string name)
  40 {
  41   const_string dot_pos = strrchr (name, '.');
  42   const_string p;
  43
  44   if (dot_pos == NULL)
  45     return NULL;
  46
  47   for (p = dot_pos + 1; *p; p++) {
  48     if (IS_DIR_SEP (*p))
  49       return NULL;
  50 #if defined(WIN32)
  51     else if (IS_KANJI(p))
  52       p++;
  53 #endif
  54   }
  55
  56   return dot_pos + 1;
  57 }