InfoMagic Source Code 1993 July/THE_SOURCE_CODE_CD_ROM.iso/gnu/screen-3.2b/putenv.c

C/C++ Source or Header | 1992-02-02 | 5.5 KB | 203 lines

/* Copyright (c) 1991
 *      Juergen Weigert ([e-mail])
 *      Michael Schroeder ([e-mail])
 * Copyright (c) 1987 Oliver Laumann
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 1, or (at your option)
 * any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program (see the file COPYING); if not, write to the
 * Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * Noteworthy contributors to screen's design and implementation:
 *    Wayne Davison ([e-mail])
 *    Patrick Wolfe ([e-mail], kailand!pat)
 *    Bart Schaefer ([e-mail])
 *    Nathan Glasser ([e-mail])
 *    Larry W. Virden ([e-mail])
 *    Howard Chu ([e-mail])
 *    Tim MacKenzie ([e-mail])
 *    Markku Jarvinen (mta@{cc,cs,ee}.tut.fi)
 *    Marc Boucher ([e-mail])
 *
 ****************************************************************
 */

/*
 *  putenv  --  put value into environment
 *
 *  Usage:  i = putenv (string)
 *    int i;
 *    char  *string;
 *
 *  where string is of the form <name>=<value>.
 *  If "value" is 0, then "name" will be deleted from the environment.
 *  Putenv returns 0 normally, -1 on error (not enough core for malloc).
 *
 *  Putenv may need to add a new name into the environment, or to
 *  associate a value longer than the current value with a particular
 *  name.  So, to make life simpler, putenv() copies your entire
 *  environment into the heap (i.e. malloc()) from the stack
 *  (i.e. where it resides when your process is initiated) the first
 *  time you call it.
 *
 *  HISTORY
 *  3-Sep-91 Michael Schroeder (mlschroe). Modified to behave as
 *    as putenv.
 * 16-Aug-91 Tim MacKenzie (tym) at Monash University. Modified for
 *    use in screen (iScreen) (ignores final int parameter)
 * 14-Oct-85 Michael Mauldin (mlm) at Carnegie-Mellon University
 *      Ripped out of CMU lib for Rob-O-Matic portability
 * 20-Nov-79  Steven Shafer (sas) at Carnegie-Mellon University
 *    Created for VAX.  Too bad Bell Labs didn't provide this.  It's
 *    unfortunate that you have to copy the whole environment onto the
 *    heap, but the bookkeeping-and-not-so-much-copying approach turns
 *    out to be much hairier.  So, I decided to do the simple thing,
 *    copying the entire environment onto the heap the first time you
 *    call putenv(), then doing realloc() uniformly later on.
 */
#include "config.h"

#if defined(NEEDSETENV)

#define EXTRASIZE 5        /* increment to add to env. size */

char *index(), *malloc(), *realloc();
int   strlen();

static int  envsize = -1;    /* current size of environment */
extern char **environ;        /* the global which is your env. */

static int  findenv();        /* look for a name in the env. */
static int  newenv();        /* copy env. from stack to heap */
static int  moreenv();        /* incr. size of env. */

int unsetenv(name)
char *name;
{
  register int i;

  i = findenv(name);
  if (i<0)
    return;            /* Already here */

  free(environ[i]);
  if (envsize > 0)
    envsize--;
  for (; environ[i]; i++)
    environ[i] = environ[i+1];
}

int putenv(string)
char *string;
{
  register int  i, j;
  register char *p;

  if (envsize < 0)
    {                /* first time putenv called */
      if (newenv() < 0)        /* copy env. to heap */
    return (-1);
    }

  i = findenv(string);        /* look for name in environment */

  if (i < 0)
    {            /* name must be added */
      for (i = 0; environ[i]; i++);
      if (i >= (envsize - 1))
    {            /* need new slot */
      if (moreenv() < 0)
        return (-1);
    }
      p = malloc(strlen(string) + 1);
      if (p == 0)        /* not enough core */
    return (-1);
      environ[i + 1] = 0;    /* new end of env. */
    }
  else
    {            /* name already in env. */
      p = realloc(environ[i], strlen(string) + 1);
      if (p == 0)
    return (-1);
    }
  sprintf(p, "%s", string); /* copy into env. */
  environ[i] = p;

  return (0);
}

static int  findenv(name)
char *name;
{
  register char *namechar, *envchar;
  register int  i, found;

  found = 0;
  for (i = 0; environ[i] && !found; i++)
    {
      envchar = environ[i];
      namechar = name;
      while (*namechar && *namechar != '=' && (*namechar == *envchar))
        {
      namechar++;
      envchar++;
        }
      found = ((*namechar == '\0' || *namechar == '=') && *envchar == '=');
    }
  return (found ? i - 1 : -1);
}

static int newenv()
{
  register char **env, *elem;
  register int i, esize;

  for (i = 0; environ[i]; i++)
    ;
  esize = i + EXTRASIZE + 1;
  env = (char **)malloc(esize * sizeof (elem));
  if (env == 0)
    return (-1);

  for (i = 0; environ[i]; i++)
    {
      elem = malloc(strlen(environ[i]) + 1);
      if (elem == 0)
    return (-1);
      env[i] = elem;
      strcpy(elem, environ[i]);
    }

  env[i] = 0;
  environ = env;
  envsize = esize;
  return (0);
}

static int moreenv()
{
  register int  esize;
  register char **env;

  esize = envsize + EXTRASIZE;
  env = (char **)realloc(environ, esize * sizeof (*env));
  if (env == 0)
    return (-1);
  environ = env;
  envsize = esize;
  return (0);
}

#endif /* NEEDSETENV */