environ.c

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

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  5. If you wish to incorporate parts of this program into other free
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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;
      }
}