/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*        All Rights Reserved   */

/*
 *  NAME
 *      xsetenv, xgetenv, Xgetenv - manage an alternate environment space
 *
 *  SYNOPSIS
 *      int ret = xsetenv(file)
 *      char *x = xgetenv("FOO");
 *      char *x = Xgetenv("FOO");
 *
 *  DESCRIPTION
 *      xsetenv() reads the given file into an internal buffer
 *      and sets up an alternate environment.
 *
 *      Return values:  1 - OKAY
 *                      0 - troubles reading the file
 *                      -1 - troubles opening the file
 *
 *      xgetenv() returns the environment value from the
 *      alternate environment.
 *
 *      Return values:  (char *)0 - no value for that variable
 *                      pointer  - the value
 *
 *      Xgetenv() returns the environment value from the
 *      alternate environment.
 *
 *      Return values:  "" - no value for that variable
 *                      pointer  - the value
 *
 *  LIMITATIONS
 *      Assumes the environment is < 5120 bytes, as in the UNIX
 *      System environment. Assumes < 512 lines in the file.
 *      These values may be adjusted below.
 */

#include <sys/types.h>
#include "libmail.h"
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <ctype.h>

#include <stdlib.h>
#include <unistd.h>

#define MAXVARS  512
#define MAXENV  5120

static char **xenv = 0;
static char *(xenvptrs[MAXVARS]);
static char xbuf[MAXENV];

static void reduce(char *);

/*
 *      set up an environment buffer
 *      and the pointers into it
 */
int
xsetenv(char *xfile)
{
        int envctr, infd;
        ssize_t i, nread;

        /* Open the file */
        infd = open(xfile, O_RDONLY);
        if (infd == -1) {
                return (-1);
        }

        /* Read in the entire file. */
        nread = read(infd, xbuf, sizeof (xbuf));
        if (nread < 0) {
                (void) close(infd);
                return (0);
        }

        /*
         * Set up pointers into the buffer.
         * Replace \n with \0.
         * Collapse white space around the = sign and at the
         * beginning and end of the line.
         */
        xenv = xenvptrs;
        xenv[0] = &xbuf[0];
        for (i = 0, envctr = 0; i < nread; i++) {
                if (xbuf[i] == '\n') {
                        xbuf[i] = '\0';
                        reduce(xenv[envctr]);
                        xenv[++envctr] = &xbuf[i+1];
                        if (envctr == MAXVARS) {
                                break;
                        }
                }
        }

        xenv[envctr] = 0;
        (void) close(infd);
        return (1);
}

/*
 *      Let getenv() do the dirty work
 *      of looking up the variable. We
 *      do this by temporarily resetting
 *      environ to point to the local area.
 */
char *
xgetenv(char *env)
{
        extern char **environ;
        char *ret, **svenviron = environ;

        environ = xenv;
        ret = getenv(env);
        environ = svenviron;
        return (ret);
}

/*
 *      Let xgetenv() do the dirty work
 *      of looking up the variable.
 */
char *
Xgetenv(char *env)
{
        char *ret = xgetenv(env);
        return (ret ? ret : "");
}

/*
 * Remove the spaces within the environment variable.
 * The variable can look like this:
 *
 * <sp1> variable <sp2> = <sp3> value <sp4> \0
 *
 * All spaces can be removed, except within
 * the variable name and the value.
 */

static void
reduce(char *from)
{
        char *to = from;
        char *svfrom = from;

        /* <sp1> */
        while (*from &&isspace((int)*from))
                from++;

        /* variable */
        while (*from && (*from != '=') && !isspace((int)*from))
                *to++ = *from++;

        /* <sp2> */
        while (*from && isspace((int)*from))
                from++;

        /* = */
        if (*from == '=')
                *to++ = *from++;

        /* <sp3> */
        while (*from && isspace((int)*from))
                from++;

        /* value */
        while (*from)
                *to++ = *from++;

        /* <sp4> */
        while ((to > svfrom) && isspace((int)to[-1]))
                to--;
        *to = '\0';
}