lib/string-desc-contains.c

   1 /* String descriptors.
   2    Copyright (C) 2023-2024 Free Software Foundation, Inc.
   3
   4    This file is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU Lesser General Public License as
   6    published by the Free Software Foundation, either version 3 of the
   7    License, or (at your option) any later version.
   8
   9    This file is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Bruno Haible <bruno@clisp.org>, 2023.  */
  18
  19 #ifdef HAVE_CONFIG_H
  20 # include "config.h"
  21 #endif
  22
  23 /* Specification.  */
  24 #include "string-desc.h"
  25
  26 #include <string.h>
  27
  28
  29 /* This function is in a separate compilation unit, because not all users
  30    of the 'string-desc' module need this function and it depends on 'memmem'
  31    which — depending on platforms — costs up to 2 KB of binary code.  */
  32
  33 ptrdiff_t
  34 string_desc_contains (string_desc_t haystack, string_desc_t needle)
  35 {
  36   if (needle._nbytes == 0)
  37     return 0;
  38   if (haystack._nbytes == 0)
  39     return -1;
  40   void *found =
  41     memmem (haystack._data, haystack._nbytes, needle._data, needle._nbytes);
  42   if (found != NULL)
  43     return (char *) found - haystack._data;
  44   else
  45     return -1;
  46 }