gshadow/sgetsgent.c

   1 /* Copyright (C) 2009-2021 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 <stdlib.h>
  22
  23
  24 /* A reasonable size for a buffer to start with.  */
  25 #define BUFLEN_SPWD 1024
  26
  27 /* We need to protect the dynamic buffer handling.  */
  28 __libc_lock_define_initialized (static, lock);
  29
  30 /* Read one shadow entry from the given stream.  */
  31 struct sgrp *
  32 sgetsgent (const char *string)
  33 {
  34   static char *buffer;
  35   static size_t buffer_size;
  36   static struct sgrp resbuf;
  37   struct sgrp *result;
  38   int save;
  39
  40   /* Get lock.  */
  41   __libc_lock_lock (lock);
  42
  43   /* Allocate buffer if not yet available.  */
  44   if (buffer == NULL)
  45     {
  46       buffer_size = BUFLEN_SPWD;
  47       buffer = malloc (buffer_size);
  48     }
  49
  50   while (buffer != NULL
  51          && __sgetsgent_r (string, &resbuf, buffer, buffer_size, &result) != 0
  52          && errno == ERANGE)
  53     {
  54       char *new_buf;
  55       buffer_size += BUFLEN_SPWD;
  56       new_buf = realloc (buffer, buffer_size);
  57       if (new_buf == NULL)
  58         {
  59           /* We are out of memory.  Free the current buffer so that the
  60              process gets a chance for a normal termination.  */
  61           save = errno;
  62           free (buffer);
  63           __set_errno (save);
  64         }
  65       buffer = new_buf;
  66     }
  67
  68   if (buffer == NULL)
  69     result = NULL;
  70
  71   /* Release lock.  Preserve error value.  */
  72   save = errno;
  73   __libc_lock_unlock (lock);
  74   __set_errno (save);
  75
  76   return result;
  77 }