nss/fgetsgent.c

   1 /* Copyright (C) 2009-2023 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 <libc-lock.h>
  20 #include <gshadow.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <set-freeres.h>
  24
  25
  26 /* A reasonable size for a buffer to start with.  */
  27 #define BUFLEN_SPWD 1024
  28
  29 /* We need to protect the dynamic buffer handling.  */
  30 __libc_lock_define_initialized (static, lock);
  31
  32 static char *buffer;
  33
  34 /* Read one shadow entry from the given stream.  */
  35 struct sgrp *
  36 fgetsgent (FILE *stream)
  37 {
  38   static size_t buffer_size;
  39   static struct sgrp resbuf;
  40   fpos_t pos;
  41   struct sgrp *result;
  42   int save;
  43
  44   if (fgetpos (stream, &pos) != 0)
  45     return NULL;
  46
  47   /* Get lock.  */
  48   __libc_lock_lock (lock);
  49
  50   /* Allocate buffer if not yet available.  */
  51   if (buffer == NULL)
  52     {
  53       buffer_size = BUFLEN_SPWD;
  54       buffer = malloc (buffer_size);
  55     }
  56
  57   while (buffer != NULL
  58          && (__fgetsgent_r (stream, &resbuf, buffer, buffer_size, &result)
  59              == ERANGE))
  60     {
  61       char *new_buf;
  62       buffer_size += BUFLEN_SPWD;
  63       new_buf = realloc (buffer, buffer_size);
  64       if (new_buf == NULL)
  65         {
  66           /* We are out of memory.  Free the current buffer so that the
  67              process gets a chance for a normal termination.  */
  68           save = errno;
  69           free (buffer);
  70           __set_errno (save);
  71         }
  72       buffer = new_buf;
  73
  74       /* Reset the stream.  */
  75       if (fsetpos (stream, &pos) != 0)
  76         buffer = NULL;
  77     }
  78
  79   if (buffer == NULL)
  80     result = NULL;
  81
  82   /* Release lock.  Preserve error value.  */
  83   save = errno;
  84   __libc_lock_unlock (lock);
  85   __set_errno (save);
  86
  87   return result;
  88 }
  89
  90 weak_alias (buffer, __libc_fgetsgent_freeres_ptr);