/* Copyright (C) 1992,1995-2001,2004, 2008 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, see
   <https://www.gnu.org/licenses/>.  */

#if HAVE_CONFIG_H
# include <config.h>
#endif

#include <errno.h>
#if !_LIBC
# if !defined errno && !defined HAVE_ERRNO_DECL
extern int errno;
# endif
# define __set_errno(ev) ((errno) = (ev))
#endif

#if _LIBC || HAVE_STDLIB_H
# include <stdlib.h>
#endif
#if _LIBC || HAVE_STRING_H
# include <string.h>
#endif
#if _LIBC || HAVE_UNISTD_H
# include <unistd.h>
#endif

#define __environ	environ

#if _LIBC
# define LOCK
# define UNLOCK
#endif

/* In the GNU C library we must keep the namespace clean.  */
#ifdef _LIBC
__typeof__(setenv) __setenv;
__typeof__(unsetenv) __unsetenv;
__typeof__(clearenv) __clearenv;
# define setenv __setenv
# define unsetenv __unsetenv
# define clearenv __clearenv
#endif

#undef USE_TSEARCH
#define KNOWN_VALUE(Str) NULL
#define STORE_VALUE(Str) do { } while (0)

/* 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.  */
static 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;

  LOCK;

  /* 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 || __builtin_expect (*ep == NULL, 1))
    {
      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)
	{
	  UNLOCK;
	  return -1;
	}

      /* 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.  */
#ifdef USE_TSEARCH
# ifdef __GNUC__
	  char new_value[namelen + 1 + vallen];
# else
	  char *new_value = (char *) alloca (namelen + 1 + vallen);
# endif
# ifdef _LIBC
	  __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
		     value, vallen);
# else
	  memcpy (new_value, name, namelen);
	  new_value[namelen] = '=';
	  memcpy (&new_value[namelen + 1], value, vallen);
# endif

	  new_environ[size] = KNOWN_VALUE (new_value);
	  if (__builtin_expect (new_environ[size] == NULL, 1))
#endif
	    {
	      new_environ[size] = (char *) malloc (namelen + 1 + vallen);
	      if (__builtin_expect (new_environ[size] == NULL, 0))
		{
		  __set_errno (ENOMEM);
		  UNLOCK;
		  return -1;
		}

#ifdef USE_TSEARCH
	      memcpy (new_environ[size], new_value, namelen + 1 + vallen);
#else
	      memcpy (new_environ[size], name, namelen);
	      new_environ[size][namelen] = '=';
	      memcpy (&new_environ[size][namelen + 1], value, vallen);
#endif
	      /* And save the value now.  We cannot do this when we remove
		 the string since then we cannot decide whether it is a
		 user string or not.  */
	      STORE_VALUE (new_environ[size]);
	    }
	}

      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
	{
#ifdef USE_TSEARCH
# ifdef __GNUC__
	  char new_value[namelen + 1 + vallen];
# else
	  char *new_value = (char *) alloca (namelen + 1 + vallen);
# endif
# ifdef _LIBC
	  __mempcpy (__mempcpy (__mempcpy (new_value, name, namelen), "=", 1),
		     value, vallen);
# else
	  memcpy (new_value, name, namelen);
	  new_value[namelen] = '=';
	  memcpy (&new_value[namelen + 1], value, vallen);
# endif

	  np = KNOWN_VALUE (new_value);
	  if (__builtin_expect (np == NULL, 1))
#endif
	    {
	      np = malloc (namelen + 1 + vallen);
	      if (__builtin_expect (np == NULL, 0))
		{
		  UNLOCK;
		  return -1;
		}

#ifdef USE_TSEARCH
	      memcpy (np, new_value, namelen + 1 + vallen);
#else
	      memcpy (np, name, namelen);
	      np[namelen] = '=';
	      memcpy (&np[namelen + 1], value, vallen);
#endif
	      /* And remember the value.  */
	      STORE_VALUE (np);
	    }
	}

      *ep = np;
    }

  UNLOCK;

  return 0;
}


int
setenv (const char *name, const char *value, int replace)
{
  if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
    {
      __set_errno (EINVAL);
      return -1;
    }

  return __add_to_environ (name, value, NULL, replace);
}

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);

  LOCK;

  ep = __environ;
  if (ep != NULL)
  {
    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;
  }
  
  UNLOCK;

  return 0;
}

/* 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)
{
  LOCK;

  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;

  UNLOCK;

  return 0;
}
#ifdef _LIBC
# ifdef HAVE_WEAK_SYMBOLS
#  undef setenv
#  undef unsetenv
#  undef clearenv
weak_alias (__setenv, setenv)
weak_alias (__unsetenv, unsetenv)
weak_alias (__clearenv, clearenv)
# endif
#endif
