uclibc-ng/libc/stdlib/setenv.c

/* Copyright (C) 1992,95,96,97,98,99,2000,2001 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.

   modified for uClibc by Erik Andersen <andersen@codepoet.org>
*/

#include <features.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

libc_hidden_proto(memcpy)
libc_hidden_proto(strchr)
libc_hidden_proto(strlen)
libc_hidden_proto(strncmp)
libc_hidden_proto(strndup)
libc_hidden_proto(unsetenv)

#include <bits/uClibc_mutex.h>
__UCLIBC_MUTEX_STATIC(mylock, PTHREAD_MUTEX_INITIALIZER);


/* If this variable is not a null pointer we allocated the current
   environment.  */
static char **last_environ;


/* This function is used by `setenv' and `putenv'.  The difference between
   the two functions is that for the former must create a new string which
   is then placed in the environment, while the argument of `putenv'
   must be used directly.  This is all complicated by the fact that we try
   to reuse values once generated for a `setenv' call since we can never
   free the strings.  */
int __add_to_environ (const char *name, const char *value,
	const char *combined, int replace) attribute_hidden;
int __add_to_environ (const char *name, const char *value,
					  const char *combined, int replace)
{
    register char **ep;
    register size_t size;
    const size_t namelen = strlen (name);
    const size_t vallen = value != NULL ? strlen (value) + 1 : 0;
    int rv = -1;

    __UCLIBC_MUTEX_LOCK(mylock);

    /* We have to get the pointer now that we have the lock and not earlier
       since another thread might have created a new environment.  */
    ep = __environ;

    size = 0;
    if (ep != NULL) {
		for (; *ep != NULL; ++ep) {
			if (!strncmp (*ep, name, namelen) && (*ep)[namelen] == '=')
				break;
			else
				++size;
		}
    }

    if (ep == NULL || *ep == NULL) {
		char **new_environ;

		/* We allocated this space; we can extend it.  */
		new_environ = (char **) realloc (last_environ, (size + 2) * sizeof (char *));
		if (new_environ == NULL) {
			goto DONE;
		}

		/* If the whole entry is given add it.  */
		if (combined != NULL) {
			/* We must not add the string to the search tree since it belongs
			   to the user.  */
			new_environ[size] = (char *) combined;
		} else {
			/* See whether the value is already known.  */
			new_environ[size] = (char *) malloc (namelen + 1 + vallen);
			if (new_environ[size] == NULL) {
				__set_errno (ENOMEM);
				goto DONE;
			}

			memcpy (new_environ[size], name, namelen);
			new_environ[size][namelen] = '=';
			memcpy (&new_environ[size][namelen + 1], value, vallen);
		}

		if (__environ != last_environ) {
			memcpy ((char *) new_environ, (char *) __environ,
					size * sizeof (char *));
		}

		new_environ[size + 1] = NULL;
		last_environ = __environ = new_environ;
    } else if (replace) {
		char *np;

		/* Use the user string if given.  */
		if (combined != NULL) {
			np = (char *) combined;
		} else {
			np = malloc (namelen + 1 + vallen);
			if (np == NULL) {
				goto DONE;
			}
			memcpy (np, name, namelen);
			np[namelen] = '=';
			memcpy (&np[namelen + 1], value, vallen);
		}
		*ep = np;
    }

    rv = 0;

 DONE:
    __UCLIBC_MUTEX_UNLOCK(mylock);
    return rv;
}

libc_hidden_proto(setenv)
int setenv (const char *name, const char *value, int replace)
{
    return __add_to_environ (name, value, NULL, replace);
}
libc_hidden_def(setenv)

libc_hidden_proto(unsetenv)
int unsetenv (const char *name)
{
    size_t len;
    char **ep;

    if (name == NULL || *name == '\0' || strchr (name, '=') != NULL) {
		__set_errno (EINVAL);
		return -1;
    }

    len = strlen (name);
    __UCLIBC_MUTEX_LOCK(mylock);
    ep = __environ;
    while (*ep != NULL) {
		if (!strncmp (*ep, name, len) && (*ep)[len] == '=') {
			/* Found it.  Remove this pointer by moving later ones back.  */
			char **dp = ep;
			do {
				dp[0] = dp[1];
			} while (*dp++);
			/* Continue the loop in case NAME appears again.  */
		} else {
			++ep;
		}
    }
    __UCLIBC_MUTEX_UNLOCK(mylock);
    return 0;
}
libc_hidden_def(unsetenv)

/* The `clearenv' was planned to be added to POSIX.1 but probably
   never made it.  Nevertheless the POSIX.9 standard (POSIX bindings
   for Fortran 77) requires this function.  */
int clearenv (void)
{
    __UCLIBC_MUTEX_LOCK(mylock);
    if (__environ == last_environ && __environ != NULL) {
		/* We allocated this environment so we can free it.  */
		free (__environ);
		last_environ = NULL;
    }
    /* Clear the environment pointer removes the whole environment.  */
    __environ = NULL;
    __UCLIBC_MUTEX_UNLOCK(mylock);
    return 0;
}

/* Put STRING, which is of the form "NAME=VALUE", in the environment.  */
int putenv (char *string)
{
    int result;
    const char *const name_end = strchr (string, '=');

    if (name_end != NULL) {
		char *name = strndup(string, name_end - string);
		result = __add_to_environ (name, NULL, string, 1);
		free(name);
		return(result);
    }
    unsetenv (string);
    return 0;
}