1  /* Copyright (C) 1991-2023 Free Software Foundation, Inc.
       2     This file is part of the GNU C Library.
       3  
       4     The GNU C Library is free software; you can redistribute it and/or
       5     modify it under the terms of the GNU Lesser General Public
       6     License as published by the Free Software Foundation; either
       7     version 2.1 of the License, or (at your option) any later version.
       8  
       9     The GNU C Library 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 GNU
      12     Lesser General Public License for more details.
      13  
      14     You should have received a copy of the GNU Lesser General Public
      15     License along with the GNU C Library; if not, see
      16     <https://www.gnu.org/licenses/>.  */
      17  
      18  #include <errno.h>
      19  #include <grp.h>
      20  #include <libc-lock.h>
      21  #include <stdio.h>
      22  #include <stdlib.h>
      23  #include <set-freeres.h>
      24  
      25  
      26  /* We need to protect the dynamic buffer handling.  */
      27  __libc_lock_define_initialized (static, lock);
      28  
      29  static char *buffer;
      30  
      31  /* Read one entry from the given stream.  */
      32  struct group *
      33  fgetgrent (FILE *stream)
      34  {
      35    static size_t buffer_size;
      36    static struct group resbuf;
      37    fpos_t pos;
      38    struct group *result;
      39    int save;
      40  
      41    if (__builtin_expect (fgetpos (stream, &pos), 0) != 0)
      42      return NULL;
      43  
      44    /* Get lock.  */
      45    __libc_lock_lock (lock);
      46  
      47    /* Allocate buffer if not yet available.  */
      48    if (buffer == NULL)
      49      {
      50        buffer_size = NSS_BUFLEN_GROUP;
      51        buffer = malloc (buffer_size);
      52      }
      53  
      54    while (buffer != NULL
      55  	 && (__fgetgrent_r (stream, &resbuf, buffer, buffer_size, &result)
      56  	     == ERANGE))
      57      {
      58        char *new_buf;
      59        buffer_size += NSS_BUFLEN_GROUP;
      60        new_buf = realloc (buffer, buffer_size);
      61        if (__glibc_unlikely (new_buf == NULL))
      62  	{
      63  	  /* We are out of memory.  Free the current buffer so that the
      64  	     process gets a chance for a normal termination.  */
      65  	  save = errno;
      66  	  free (buffer);
      67  	  __set_errno (save);
      68  	}
      69        buffer = new_buf;
      70  
      71        /* Reset the stream.  */
      72        if (fsetpos (stream, &pos) != 0)
      73  	buffer = NULL;
      74      }
      75  
      76    if (buffer == NULL)
      77      result = NULL;
      78  
      79    /* Release lock.  Preserve error value.  */
      80    save = errno;
      81    __libc_lock_unlock (lock);
      82    __set_errno (save);
      83  
      84    return result;
      85  }
      86  
      87  weak_alias (buffer, __libc_fgetgrent_freemem_ptr)