1/* Copyright (C) 1992,1995-1999,2000-2003,2005 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 Library General Public License as
6   published by the Free Software Foundation; either version 2 of the
7   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   Library General Public License for more details.
13
14   You should have received a copy of the GNU Library General Public
15   License along with the GNU C Library; see the file COPYING.LIB.  If not,
16   write to the Free Software Foundation, Inc., 51 Franklin Street,
17   Fifth Floor, Boston, MA 02110-1301, USA.  */
18
19#ifdef HAVE_CONFIG_H
20# include <config.h>
21#endif
22#include <alloca.h>
23
24#include <errno.h>
25#ifndef __set_errno
26# define __set_errno(ev) ((errno) = (ev))
27#endif
28
29#include <stdlib.h>
30#include <string.h>
31#if _LIBC || HAVE_UNISTD_H
32# include <unistd.h>
33#endif
34
35#if !_LIBC
36# include "allocsa.h"
37#endif
38
39#if !_LIBC
40# define __environ	environ
41# ifndef HAVE_ENVIRON_DECL
42extern char **environ;
43# endif
44#endif
45
46#if _LIBC
47/* This lock protects against simultaneous modifications of `environ'.  */
48# include <bits/libc-lock.h>
49__libc_lock_define_initialized (static, envlock)
50# define LOCK	__libc_lock_lock (envlock)
51# define UNLOCK	__libc_lock_unlock (envlock)
52#else
53# define LOCK
54# define UNLOCK
55#endif
56
57/* In the GNU C library we must keep the namespace clean.  */
58#ifdef _LIBC
59# define setenv __setenv
60# define clearenv __clearenv
61# define tfind __tfind
62# define tsearch __tsearch
63#endif
64
65/* In the GNU C library implementation we try to be more clever and
66   allow arbitrarily many changes of the environment given that the used
67   values are from a small set.  Outside glibc this will eat up all
68   memory after a while.  */
69#if defined _LIBC || (defined HAVE_SEARCH_H && defined HAVE_TSEARCH \
70		      && defined __GNUC__)
71# define USE_TSEARCH	1
72# include <search.h>
73typedef int (*compar_fn_t) (const void *, const void *);
74
75/* This is a pointer to the root of the search tree with the known
76   values.  */
77static void *known_values;
78
79# define KNOWN_VALUE(Str) \
80  ({									      \
81    void *value = tfind (Str, &known_values, (compar_fn_t) strcmp);	      \
82    value != NULL ? *(char **) value : NULL;				      \
83  })
84# define STORE_VALUE(Str) \
85  tsearch (Str, &known_values, (compar_fn_t) strcmp)
86
87#else
88# undef USE_TSEARCH
89
90# define KNOWN_VALUE(Str) NULL
91# define STORE_VALUE(Str) do { } while (0)
92
93#endif
94
95
96/* If this variable is not a null pointer we allocated the current
97   environment.  */
98static char **last_environ;
99
100
101/* This function is used by `setenv' and `putenv'.  The difference between
102   the two functions is that for the former must create a new string which
103   is then placed in the environment, while the argument of `putenv'
104   must be used directly.  This is all complicated by the fact that we try
105   to reuse values once generated for a `setenv' call since we can never
106   free the strings.  */
107int
108__add_to_environ (const char *name, const char *value, const char *combined,
109		  int replace)
110{
111  register char **ep;
112  register size_t size;
113  const size_t namelen = strlen (name);
114  const size_t vallen = value != NULL ? strlen (value) + 1 : 0;
115
116  LOCK;
117
118  /* We have to get the pointer now that we have the lock and not earlier
119     since another thread might have created a new environment.  */
120  ep = __environ;
121
122  size = 0;
123  if (ep != NULL)
124    {
125      for (; *ep != NULL; ++ep)
126	if (!strncmp (*ep, name, namelen) && (*ep)[namelen] == '=')
127	  break;
128	else
129	  ++size;
130    }
131
132  if (ep == NULL || *ep == NULL)
133    {
134      char **new_environ;
135#ifdef USE_TSEARCH
136      char *new_value;
137#endif
138
139      /* We allocated this space; we can extend it.  */
140      new_environ =
141	(char **) (last_environ == NULL
142		   ? malloc ((size + 2) * sizeof (char *))
143		   : realloc (last_environ, (size + 2) * sizeof (char *)));
144      if (new_environ == NULL)
145	{
146	  UNLOCK;
147	  return -1;
148	}
149
150      /* If the whole entry is given add it.  */
151      if (combined != NULL)
152	/* We must not add the string to the search tree since it belongs
153	   to the user.  */
154	new_environ[size] = (char *) combined;
155      else
156	{
157	  /* See whether the value is already known.  */
158#ifdef USE_TSEARCH
159# ifdef _LIBC
160	  new_value = (char *) alloca (namelen + 1 + vallen);
161	  __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
162		     value, vallen);
163# else
164	  new_value = (char *) allocsa (namelen + 1 + vallen);
165	  if (new_value == NULL)
166	    {
167	      __set_errno (ENOMEM);
168	      UNLOCK;
169	      return -1;
170	    }
171	  memcpy (new_value, name, namelen);
172	  new_value[namelen] = '=';
173	  memcpy (&new_value[namelen + 1], value, vallen);
174# endif
175
176	  new_environ[size] = KNOWN_VALUE (new_value);
177	  if (new_environ[size] == NULL)
178#endif
179	    {
180	      new_environ[size] = (char *) malloc (namelen + 1 + vallen);
181	      if (new_environ[size] == NULL)
182		{
183#if defined USE_TSEARCH && !defined _LIBC
184		  freesa (new_value);
185#endif
186		  __set_errno (ENOMEM);
187		  UNLOCK;
188		  return -1;
189		}
190
191#ifdef USE_TSEARCH
192	      memcpy (new_environ[size], new_value, namelen + 1 + vallen);
193#else
194	      memcpy (new_environ[size], name, namelen);
195	      new_environ[size][namelen] = '=';
196	      memcpy (&new_environ[size][namelen + 1], value, vallen);
197#endif
198	      /* And save the value now.  We cannot do this when we remove
199		 the string since then we cannot decide whether it is a
200		 user string or not.  */
201	      STORE_VALUE (new_environ[size]);
202	    }
203#if defined USE_TSEARCH && !defined _LIBC
204	  freesa (new_value);
205#endif
206	}
207
208      if (__environ != last_environ)
209	memcpy ((char *) new_environ, (char *) __environ,
210		size * sizeof (char *));
211
212      new_environ[size + 1] = NULL;
213
214      last_environ = __environ = new_environ;
215    }
216  else if (replace)
217    {
218      char *np;
219
220      /* Use the user string if given.  */
221      if (combined != NULL)
222	np = (char *) combined;
223      else
224	{
225#ifdef USE_TSEARCH
226	  char *new_value;
227# ifdef _LIBC
228	  new_value = alloca (namelen + 1 + vallen);
229	  __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
230		     value, vallen);
231# else
232	  new_value = allocsa (namelen + 1 + vallen);
233	  if (new_value == NULL)
234	    {
235	      __set_errno (ENOMEM);
236	      UNLOCK;
237	      return -1;
238	    }
239	  memcpy (new_value, name, namelen);
240	  new_value[namelen] = '=';
241	  memcpy (&new_value[namelen + 1], value, vallen);
242# endif
243
244	  np = KNOWN_VALUE (new_value);
245	  if (np == NULL)
246#endif
247	    {
248	      np = malloc (namelen + 1 + vallen);
249	      if (np == NULL)
250		{
251#if defined USE_TSEARCH && !defined _LIBC
252		  freesa (new_value);
253#endif
254		  __set_errno (ENOMEM);
255		  UNLOCK;
256		  return -1;
257		}
258
259#ifdef USE_TSEARCH
260	      memcpy (np, new_value, namelen + 1 + vallen);
261#else
262	      memcpy (np, name, namelen);
263	      np[namelen] = '=';
264	      memcpy (&np[namelen + 1], value, vallen);
265#endif
266	      /* And remember the value.  */
267	      STORE_VALUE (np);
268	    }
269#if defined USE_TSEARCH && !defined _LIBC
270	  freesa (new_value);
271#endif
272	}
273
274      *ep = np;
275    }
276
277  UNLOCK;
278
279  return 0;
280}
281
282int
283setenv (const char *name, const char *value, int replace)
284{
285  return __add_to_environ (name, value, NULL, replace);
286}
287
288/* The `clearenv' was planned to be added to POSIX.1 but probably
289   never made it.  Nevertheless the POSIX.9 standard (POSIX bindings
290   for Fortran 77) requires this function.  */
291int
292clearenv (void)
293{
294  LOCK;
295
296  if (__environ == last_environ && __environ != NULL)
297    {
298      /* We allocated this environment so we can free it.  */
299      free (__environ);
300      last_environ = NULL;
301    }
302
303  /* Clear the environment pointer removes the whole environment.  */
304  __environ = NULL;
305
306  UNLOCK;
307
308  return 0;
309}
310
311#ifdef _LIBC
312static void
313free_mem (void)
314{
315  /* Remove all traces.  */
316  clearenv ();
317
318  /* Now remove the search tree.  */
319  __tdestroy (known_values, free);
320  known_values = NULL;
321}
322text_set_element (__libc_subfreeres, free_mem);
323
324
325# undef setenv
326# undef clearenv
327weak_alias (__setenv, setenv)
328weak_alias (__clearenv, clearenv)
329#endif
330