Usenet 1994 January/usenetsourcesnewsgroupsinfomagicjanuary1994.iso/sources/unix/volume21/coda/part01.Z/part01.bin/hostdb.c

C/C++ Source or Header | 1990-04-08 | 4.2 KB | 219 lines

/*
**  Copyright 1989 BBN Systems and Technologies Corporation.
**  All Rights Reserved.
**  This is free software, and may be distributed under the terms of the
**  GNU Public License; see the file COPYING for more details.
**
**  An implementation of the 4.2BSD hostname lookup routines.
**  Not based on licensed code.
*/
#include <stdio.h>
#include <ctype.h>
#ifdef    XENIX
#include <netdb.h>
#define HAVE_HOSTENT
/* Stupid, just plain stupid... */
#undef NULL
#define NULL        0
#endif    /* XENIX */
#ifdef    RCSID
static char RCS[] =
    "$Header: hostdb.c,v 2.0 90/03/23 14:41:30 rsalz Exp $";
#endif    /* RCSID */

/* Constants and shorthands. */
#define TRUE        1
#define FALSE        0
#define MAXALIASES    10
#define HOSTFILENAME    "/etc/hosts"
#define ADDRLEN        4

#define WHITE(c)    ((c) == ' ' || (c) == '\t')

#ifndef    AF_INET
#define AF_INET        2
#endif    /* AF_INET */


#ifndef    HAVE_HOSTENT
struct hostent {
    char    *h_name;        /* The host's official name    */
    char    **h_aliases;        /* A/K/A list            */
    int        h_addrtype;        /* Address type            */
    int        h_length;        /* Size of the address        */
    char    *h_addr;        /* Pointer to the address    */
};
#endif    /* HAVE_HOSTENT */


static FILE    *HostFile = NULL;    /* The open /etc/hosts file    */


extern char    *strchr();


/*
**  Close the host file.
*/
void
endhostent()
{
    if (HostFile) {
    (void)fclose(HostFile);
    HostFile = NULL;
    }
}


/*
**  Read the next line from the host file.
*/
static struct hostent *
gethostent()
{
    static struct hostent    E;
    static char            buff[200];
    static char            *aliases[MAXALIASES];
    static char            addr[ADDRLEN];
    register int        i;
    register char        *q;
    register char        *p;

    /* Open the file if necessary, reset state. */
    if (HostFile == NULL) {
    if ((HostFile = fopen(HOSTFILENAME, "r")) == NULL)
        return NULL;
    E.h_addrtype = AF_INET;
    E.h_length = ADDRLEN;
    E.h_addr = addr;
        E.h_aliases = aliases;
    }

    /* Loop until we get a good line. */
    for ( ; ; ) {
    if (fgets(buff, sizeof buff, HostFile) == NULL)
        return NULL;

    /* Kill the comment and newline character, skip blank lines. */
    if (p = strchr(buff, '#'))
        *p = '\0';
    if (p = strchr(buff, '\n'))
        *p = '\0';
    if (buff[0] == '\0')
        continue;

    /* Parse the first field as a dotted quad. */
    for (q = p = buff, i = 0; i < ADDRLEN; i++) {
        while (*p && *p != '.' && !WHITE(*p))
        p++;
        if (*p == '\0')
        break;
        *p = '\0';
        addr[i] = atoi(q);
        q = ++p;
    }
    if (i == ADDRLEN)
        break;
    }

    /* Skip whitespace, get the second field as the full name. */
    while (*q && WHITE(*q))
    q++;
    for (E.h_name = q; *q && !WHITE(*q); )
    q++;
    if (*q)
    *q++ = '\0';

    /* Parse any aliases. */
    for (i = 0; i < MAXALIASES - 1 && *q; i++) {
        while (*q && WHITE(*q))
        q++;
    for (aliases[i] = q; *q && !WHITE(*q); )
        q++;
        if (*q)
        *q++ = '\0';
    }
    aliases[i] = NULL;

    return &E;
}


/*
**  Compare two strings, ignoring case.
*/
static int
samehostname(n1, n2)
    register char    *n1;
    register char    *n2;
{
    register char    c1;
    register char    c2;

    for ( ; ; ) {
    if ((c1 = *n1++) == (c2 = *n2++)) {
        if (c1 || c2)
        continue;
        return TRUE;
    }
    if (islower(c1))
        c1 = toupper(c1);
    if (islower(c2))
        c2 = toupper(c2);
    if (c1 != c2)
        return FALSE;
    }
}


/*
**  Given a name, find the hostent structure.
*/
struct hostent *
gethostbyname(name)
    register char        *name;
{
    register struct hostent    *E;
    register int        i;

    while (E = gethostent()) {
    if (samehostname(name, E->h_name))
        break;
    for (i = 0; E->h_aliases[i]; i++)
        if (samehostname(name, E->h_aliases[i]))
        break;
    if (E->h_aliases[i])
        break;
    }
    endhostent();

    return E;
}


#if    0
/*
**  Given an address, find the hostent structure.
*/
struct hostent *
gethostbyaddr(p, length, type)
    register char        *p;
    int                length;
    int                type;
{
    register struct hostent    *E;

    /* We only handle Internet addresses here. */
    if (length != ADDRLEN || type != AF_INET)
    return NULL;

    while (E = gethostent())
    if (he->h_addr[0] == p[0] && he->h_addr[1] == p[1]
     && he->h_addr[2] == p[2] && he->h_addr[3] == p[3])
        break;
    endhostent();

    return E;
}
#endif    /* 0 */