libmail/common/xgetenv.c

	xgetenv.c revision 7257d1b4d25bfac0c802847390e98a464fd787ac
/*
 * 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   */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*
 *  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';
}