1  /* String descriptors.
       2     Copyright (C) 2023 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    void *found =
      39      memmem (haystack._data, haystack._nbytes, needle._data, needle._nbytes);
      40    if (found != NULL)
      41      return (char *) found - haystack._data;
      42    else
      43      return -1;
      44  }