1/* Copyright (C) 1992,1995-1999,2000-2003,2005,2006 Free Software Foundation, Inc.
2   This file is part of the GNU C Library.
3
4   This program is free software; you can redistribute it and/or modify
5   it under the terms of the GNU General Public License as published by
6   the Free Software Foundation; either version 2, or (at your option)
7   any later version.
8
9   This program 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
12   GNU General Public License for more details.
13
14   You should have received a copy of the GNU General Public License along
15   with this program; if not, write to the Free Software Foundation,
16   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
17
18#if !_LIBC
19# include <config.h>
20#endif
21#include <alloca.h>
22
23#include <errno.h>
24#ifndef __set_errno
25# define __set_errno(ev) ((errno) = (ev))
26#endif
27
28#include <stdlib.h>
29#include <string.h>
30#if _LIBC || HAVE_UNISTD_H
31# include <unistd.h>
32#endif
33
34#if !_LIBC
35# include "allocsa.h"
36#endif
37
38#if !_LIBC
39# define __environ	environ
40# ifndef HAVE_ENVIRON_DECL
41extern char **environ;
42# endif
43#endif
44
45#if _LIBC
46/* This lock protects against simultaneous modifications of `environ'.  */
47# include <bits/libc-lock.h>
48__libc_lock_define_initialized (static, envlock)
49# define LOCK	__libc_lock_lock (envlock)
50# define UNLOCK	__libc_lock_unlock (envlock)
51#else
52# define LOCK
53# define UNLOCK
54#endif
55
56/* In the GNU C library we must keep the namespace clean.  */
57#ifdef _LIBC
58# define setenv __setenv
59# define clearenv __clearenv
60# define tfind __tfind
61# define tsearch __tsearch
62#endif
63
64/* In the GNU C library implementation we try to be more clever and
65   allow arbitrarily many changes of the environment given that the used
66   values are from a small set.  Outside glibc this will eat up all
67   memory after a while.  */
68#if defined _LIBC || (defined HAVE_SEARCH_H && defined HAVE_TSEARCH \
69		      && defined __GNUC__)
70# define USE_TSEARCH	1
71# include <search.h>
72typedef int (*compar_fn_t) (const void *, const void *);
73
74/* This is a pointer to the root of the search tree with the known
75   values.  */
76static void *known_values;
77
78# define KNOWN_VALUE(Str) \
79  ({									      \
80    void *value = tfind (Str, &known_values, (compar_fn_t) strcmp);	      \
81    value != NULL ? *(char **) value : NULL;				      \
82  })
83# define STORE_VALUE(Str) \
84  tsearch (Str, &known_values, (compar_fn_t) strcmp)
85
86#else
87# undef USE_TSEARCH
88
89# define KNOWN_VALUE(Str) NULL
90# define STORE_VALUE(Str) do { } while (0)
91
92#endif
93
94
95/* If this variable is not a null pointer we allocated the current
96   environment.  */
97static char **last_environ;
98
99
100/* This function is used by `setenv' and `putenv'.  The difference between
101   the two functions is that for the former must create a new string which
102   is then placed in the environment, while the argument of `putenv'
103   must be used directly.  This is all complicated by the fact that we try
104   to reuse values once generated for a `setenv' call since we can never
105   free the strings.  */
106int
107__add_to_environ (const char *name, const char *value, const char *combined,
108		  int replace)
109{
110  register char **ep;
111  register size_t size;
112  const size_t namelen = strlen (name);
113  const size_t vallen = value != NULL ? strlen (value) + 1 : 0;
114
115  LOCK;
116
117  /* We have to get the pointer now that we have the lock and not earlier
118     since another thread might have created a new environment.  */
119  ep = __environ;
120
121  size = 0;
122  if (ep != NULL)
123    {
124      for (; *ep != NULL; ++ep)
125	if (!strncmp (*ep, name, namelen) && (*ep)[namelen] == '=')
126	  break;
127	else
128	  ++size;
129    }
130
131  if (ep == NULL || *ep == NULL)
132    {
133      char **new_environ;
134#ifdef USE_TSEARCH
135      char *new_value;
136#endif
137
138      /* We allocated this space; we can extend it.  */
139      new_environ =
140	(char **) (last_environ == NULL
141		   ? malloc ((size + 2) * sizeof (char *))
142		   : realloc (last_environ, (size + 2) * sizeof (char *)));
143      if (new_environ == NULL)
144	{
145	  UNLOCK;
146	  return -1;
147	}
148
149      /* If the whole entry is given add it.  */
150      if (combined != NULL)
151	/* We must not add the string to the search tree since it belongs
152	   to the user.  */
153	new_environ[size] = (char *) combined;
154      else
155	{
156	  /* See whether the value is already known.  */
157#ifdef USE_TSEARCH
158# ifdef _LIBC
159	  new_value = (char *) alloca (namelen + 1 + vallen);
160	  __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
161		     value, vallen);
162# else
163	  new_value = (char *) allocsa (namelen + 1 + vallen);
164	  if (new_value == NULL)
165	    {
166	      __set_errno (ENOMEM);
167	      UNLOCK;
168	      return -1;
169	    }
170	  memcpy (new_value, name, namelen);
171	  new_value[namelen] = '=';
172	  memcpy (&new_value[namelen + 1], value, vallen);
173# endif
174
175	  new_environ[size] = KNOWN_VALUE (new_value);
176	  if (new_environ[size] == NULL)
177#endif
178	    {
179	      new_environ[size] = (char *) malloc (namelen + 1 + vallen);
180	      if (new_environ[size] == NULL)
181		{
182#if defined USE_TSEARCH && !defined _LIBC
183		  freesa (new_value);
184#endif
185		  __set_errno (ENOMEM);
186		  UNLOCK;
187		  return -1;
188		}
189
190#ifdef USE_TSEARCH
191	      memcpy (new_environ[size], new_value, namelen + 1 + vallen);
192#else
193	      memcpy (new_environ[size], name, namelen);
194	      new_environ[size][namelen] = '=';
195	      memcpy (&new_environ[size][namelen + 1], value, vallen);
196#endif
197	      /* And save the value now.  We cannot do this when we remove
198		 the string since then we cannot decide whether it is a
199		 user string or not.  */
200	      STORE_VALUE (new_environ[size]);
201	    }
202#if defined USE_TSEARCH && !defined _LIBC
203	  freesa (new_value);
204#endif
205	}
206
207      if (__environ != last_environ)
208	memcpy ((char *) new_environ, (char *) __environ,
209		size * sizeof (char *));
210
211      new_environ[size + 1] = NULL;
212
213      last_environ = __environ = new_environ;
214    }
215  else if (replace)
216    {
217      char *np;
218
219      /* Use the user string if given.  */
220      if (combined != NULL)
221	np = (char *) combined;
222      else
223	{
224#ifdef USE_TSEARCH
225	  char *new_value;
226# ifdef _LIBC
227	  new_value = alloca (namelen + 1 + vallen);
228	  __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
229		     value, vallen);
230# else
231	  new_value = allocsa (namelen + 1 + vallen);
232	  if (new_value == NULL)
233	    {
234	      __set_errno (ENOMEM);
235	      UNLOCK;
236	      return -1;
237	    }
238	  memcpy (new_value, name, namelen);
239	  new_value[namelen] = '=';
240	  memcpy (&new_value[namelen + 1], value, vallen);
241# endif
242
243	  np = KNOWN_VALUE (new_value);
244	  if (np == NULL)
245#endif
246	    {
247	      np = malloc (namelen + 1 + vallen);
248	      if (np == NULL)
249		{
250#if defined USE_TSEARCH && !defined _LIBC
251		  freesa (new_value);
252#endif
253		  __set_errno (ENOMEM);
254		  UNLOCK;
255		  return -1;
256		}
257
258#ifdef USE_TSEARCH
259	      memcpy (np, new_value, namelen + 1 + vallen);
260#else
261	      memcpy (np, name, namelen);
262	      np[namelen] = '=';
263	      memcpy (&np[namelen + 1], value, vallen);
264#endif
265	      /* And remember the value.  */
266	      STORE_VALUE (np);
267	    }
268#if defined USE_TSEARCH && !defined _LIBC
269	  freesa (new_value);
270#endif
271	}
272
273      *ep = np;
274    }
275
276  UNLOCK;
277
278  return 0;
279}
280
281int
282setenv (const char *name, const char *value, int replace)
283{
284  return __add_to_environ (name, value, NULL, replace);
285}
286
287/* The `clearenv' was planned to be added to POSIX.1 but probably
288   never made it.  Nevertheless the POSIX.9 standard (POSIX bindings
289   for Fortran 77) requires this function.  */
290int
291clearenv (void)
292{
293  LOCK;
294
295  if (__environ == last_environ && __environ != NULL)
296    {
297      /* We allocated this environment so we can free it.  */
298      free (__environ);
299      last_environ = NULL;
300    }
301
302  /* Clear the environment pointer removes the whole environment.  */
303  __environ = NULL;
304
305  UNLOCK;
306
307  return 0;
308}
309
310#ifdef _LIBC
311static void
312free_mem (void)
313{
314  /* Remove all traces.  */
315  clearenv ();
316
317  /* Now remove the search tree.  */
318  __tdestroy (known_values, free);
319  known_values = NULL;
320}
321text_set_element (__libc_subfreeres, free_mem);
322
323
324# undef setenv
325# undef clearenv
326weak_alias (__setenv, setenv)
327weak_alias (__clearenv, clearenv)
328#endif
329