inet/inet_ntoa.c

   1 /* Convert Inet number to ASCII representation.
   2    Copyright (C) 1997, 1998, 2000, 2001 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <arpa/inet.h>
  24 #include <bits/libc-lock.h>
  25
  26 /* The interface of this function is completely stupid, it requires a
  27    static buffer.  We relax this a bit in that we allow at least one
  28    buffer for each thread.  */
  29
  30 /* This is the key for the thread specific memory.  */
  31 static __libc_key_t key;
  32
  33 /* If nonzero the key allocation failed and we should better use a
  34    static buffer than fail.  */
  35 static char local_buf[18];
  36 static char *static_buf;
  37
  38 /* Destructor for the thread-specific data.  */
  39 static void init (void);
  40 static void free_key_mem (void *mem);
  41
  42
  43 char *
  44 inet_ntoa (struct in_addr in)
  45 {
  46   __libc_once_define (static, once);
  47   char *buffer;
  48   unsigned char *bytes;
  49
  50   /* If we have not yet initialized the buffer do it now.  */
  51   __libc_once (once, init);
  52
  53   if (static_buf != NULL)
  54     buffer = static_buf;
  55   else
  56     {
  57       /* We don't use the static buffer and so we have a key.  Use it
  58          to get the thread-specific buffer.  */
  59       buffer = __libc_getspecific (key);
  60       if (buffer == NULL)
  61         {
  62           /* No buffer allocated so far.  */
  63           buffer = malloc (18);
  64           if (buffer == NULL)
  65             /* No more memory available.  We use the static buffer.  */
  66             buffer = local_buf;
  67           else
  68             __libc_setspecific (key, buffer);
  69         }
  70     }
  71
  72   bytes = (unsigned char *) &in;
  73   __snprintf (buffer, 18, "%d.%d.%d.%d",
  74               bytes[0], bytes[1], bytes[2], bytes[3]);
  75
  76   return buffer;
  77 }
  78
  79
  80 /* Initialize buffer.  */
  81 static void
  82 init (void)
  83 {
  84   if (__libc_key_create (&key, free_key_mem))
  85     /* Creating the key failed.  This means something really went
  86        wrong.  In any case use a static buffer which is better than
  87        nothing.  */
  88     static_buf = local_buf;
  89 }
  90
  91
  92 /* Free the thread specific data, this is done if a thread terminates.  */
  93 static void
  94 free_key_mem (void *mem)
  95 {
  96   free (mem);
  97   __libc_setspecific (key, NULL);
  98 }