/* environ.c -- library for manipulating environments for GNU.
   Copyright (C) 1986 Free Software Foundation, Inc.

		       NO WARRANTY

  BECAUSE THIS PROGRAM IS LICENSED FREE OF CHARGE, WE PROVIDE ABSOLUTELY
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  4. You may not copy, sublicense, distribute or transfer this program
except as expressly provided under this License Agreement.  Any attempt
otherwise to copy, sublicense, distribute or transfer this program is void and
your rights to use the program under this License agreement shall be
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  5. If you wish to incorporate parts of this program into other free
programs whose distribution conditions are different, write to the Free
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In other words, feel free to share this program, but don't try to
stop anyone else from sharing it.  */

#define min(a, b) ((a) < (b) ? (a) : (b))
#define max(a, b) ((a) > (b) ? (a) : (b))

#include "environ.h"

/* Return a new environment object.  */

struct environ *
make_environ ()
{
  register struct environ *e;

  e = (struct environ *) xmalloc (sizeof (struct environ));

  e->allocated = 10;
  e->vector = (char **) xmalloc ((e->allocated + 1) * sizeof (char *));
  e->vector[0] = 0;
  return e;
}

/* Free an environment and all the strings in it.  */

void
free_environ (e)
     register struct environ *e;
{
  register char **vector = e->vector;

  while (*vector)
    free (*vector++);

  free (e);
}

/* Copy the environment given to this process into E.
   Also copies all the strings in it, so we can be sure
   that all strings in these environments are safe to free.  */

void
init_environ (e)
     register struct environ *e;
{
  extern char **environ;
  register int i;

  for (i = 0; environ[i]; i++);

  if (e->allocated < i)
    {
      e->allocated = max (i, e->allocated + 10);
      e->vector = (char **) xrealloc (e->vector,
				      (e->allocated + 1) * sizeof (char *));
    }

  bcopy (environ, e->vector, (i + 1) * sizeof (char *));

  while (--i >= 0)
    {
      register int len = strlen (e->vector[i]);
      register char *new = (char *) xmalloc (len + 1);
      bcopy (e->vector[i], new, len);
      e->vector[i] = new;
    }
}

/* Return the vector of environment E.
   This is used to get something to pass to execve.  */

char **
environ_vector (e)
     struct environ *e;
{
  return e->vector;
}

/* Return the value in environment E of variable VAR.  */

char *
get_in_environ (e, var)
     struct environ *e;
     char *var;
{
  register int len = strlen (var);
  register char **vector = e->vector;
  register char *s;

  for (; s = *vector; vector++)
    if (!strncmp (s, var, len)
	&& s[len] == '=')
      return &s[len + 1];

  return 0;
}

/* Store the value in E of VAR as VALUE.  */

void
set_in_environ (e, var, value)
     struct environ *e;
     char *var;
     char *value;
{
  register int i;
  register int len = strlen (var);
  register char **vector = e->vector;
  register char *s;

  for (i = 0; s = vector[i]; i++)
    if (!strncmp (s, var, len)
	&& s[len] == '=')
      break;

  if (s == 0)
    {
      if (i == e->allocated)
	{
	  e->allocated += 10;
	  vector = (char **) xrealloc (vector,
				       (e->allocated + 1) * sizeof (char *));
	  e->vector = vector;
	}
      vector[i + 1] = 0;
    }
  else
    free (s);

  s = (char *) xmalloc (len + strlen (value) + 2);
  strcpy (s, var);
  strcat (s, "=");
  strcat (s, value);
  vector[i] = s;
  return;
}

/* Remove the setting for variable VAR from environment E.  */

void
unset_in_environ (e, var)
     struct environ *e;
     char *var;
{
  register int len = strlen (var);
  register char **vector = e->vector;
  register char *s;

  for (; s = *vector; vector++)
    if (!strncmp (s, var, len)
	&& s[len] == '=')
      {
	free (s);
	bcopy (vector + 1, vector,
	       (e->allocated - (vector - e->vector)) * sizeof (char *));
	e->vector[e->allocated - 1] = 0;
	return;
      }
}