The Datafile PD-CD 4/DATAFILE_PDCD4.iso/languages/netlib/NetLibSrc/c/host

Text File | 1995-05-24 | 4.9 KB | 247 lines

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "arpa/inet.h"
#include "netdb.h"
#include "netinet/in.h"
#include "sys/socket.h"

#include "socketlib.h"

/*
 * Veneers to the InetDB routines
 */
extern struct hostent *_gethostbyname(const char *name);
extern struct hostent *_gethostbyaddr(const char *addr, int len, int type);

/*
 * File handle for the hosts file
 */
static FILE *hostfile = NULL;

/*
 * Keep the file open between calls to these routines?
 */
static int keepopen = 0;

/*
 * Local routines
 */
static int __sethostent(int allowrewind);
static struct hostent *__gethostent(void);

/*
 * Open and rewind the hosts file
 */
int sethostent(int stayopen)
{
  /* Record whether the file should be kept open */
  keepopen = stayopen;

  return __sethostent(1);
}

/*
 * Do the real work of opening/rewinding the hosts file
 */
static int __sethostent(int allowrewind)
{
  /* Open or rewind the file as necessary */
  if (hostfile) {
    if (allowrewind)
      rewind(hostfile);
  } else {
    hostfile = fopen("InetDBase:Hosts", "r");
  }

  return (hostfile == NULL) ? -1 : 0;
}

/*
 * Fetch the next entry from the hosts file
 */
struct hostent *gethostent()
{
  struct hostent *host;

  /* Open the file if necessary */
  if (hostfile == NULL)
    if (__sethostent(0) == -1)
      return NULL;

  /* Do the actual read */
  host = __gethostent();

  /* Close the file unless the user has prohibited it */
  if (!keepopen)
    endhostent();

  return host;
}

/*
 * Do the real work of getting an entry from the file
 */
struct hostent *__gethostent()
{
  static struct hostent host = {
    NULL, NULL, AF_INET, sizeof(struct in_addr), NULL
  };

  char **item;
  char *line;
  char *element;
  int  aliases;

  /* Free up any memory in use */
  if (host.h_name)
  {
    for (item = host.h_aliases; *item; item++)
      free(*item);
    for (item = host.h_addr_list; *item; item++)
      free(*item);
    free(host.h_name);
    free(host.h_aliases);
    free(host.h_addr_list);

    host.h_name = NULL;
  }

  /* Read a line from the file */
  if ((line = __socketlib_readline(hostfile)) == NULL)
    return NULL;

  /* Extract the address from the line */
  host.h_addr_list = malloc(2 * sizeof(struct in_addr *));
  host.h_addr_list[0] = malloc(sizeof(struct in_addr));
  host.h_addr_list[1] = NULL;
  element = strtok(line, " \t");
  ((struct in_addr *)(host.h_addr_list[0]))->s_addr = inet_addr(element);

  /* Extract the offical hostname from the line */
  element = strtok(NULL, " \t");
  host.h_name = strdup(element);

  /* Initialialise the alias list */
  host.h_aliases = malloc(sizeof(char *));
  host.h_aliases[0] = NULL;
  aliases = 1;

  /* Extract the aliases */
  while ((element = strtok(NULL, " \t")) != NULL)
  {
     aliases += 1;
     host.h_aliases = realloc(host.h_aliases, aliases * sizeof(char *));
     host.h_aliases[aliases-2] = strdup(element);
     host.h_aliases[aliases-1] = NULL;
  }

  return &host;
}

/*
 * Close the hosts file
 */
int endhostent()
{
  int status = 0;

  /* If its open, close it */
  if (hostfile) {
    status = fclose(hostfile);
    hostfile = 0;
  }

  return status;
}

/*
 * Search the hosts file for a given host name
 */
struct hostent *gethostbyname(const char *name)
{
  struct hostent *host;
  char           **alias;

  /* Try the resolver first */
  if ((host = _gethostbyname(name)) != NULL)
  {
    return host;
  }

  /* Open/rewind the file */
  if (__sethostent(1) == -1)
    return NULL;

  /* Look through the file for a match */
  while ((host = __gethostent()) != NULL)
  {
    /* Does the offical name match? */
    if (strcmp(host->h_name, name) == 0)
      break;

    /* Do any of the aliases match? */
    for (alias = host->h_aliases; *alias; alias++)
    {
      if (strcmp(*alias, name) == 0)
        break;
    }

    /* Did any of the aliases match? */
    if (*alias)
      break;
  }

  /* Close the file unless the user has prohibited it */
  if (!keepopen)
    endhostent();

  return host;
}

/*
 * Search the hosts file for a given address
 */
struct hostent *gethostbyaddr(const char *addr, int len, int type)
{
  struct hostent *host;
  char           **address;

  /* Try the resolver first */
  if ((host = _gethostbyaddr(addr, len, type)) != NULL)
  {
    return host;
  }

  /* Open/rewind the file */
  if (__sethostent(1) == -1)
    return NULL;

  /* Look through the file for a match */
  while ((host = __gethostent()) != NULL) {

    /* If the type and length don't match, try the next one */
    if ((host->h_length != len) || (host->h_addrtype != type))
      continue;

    /* Do any of the addresses match? */
    for (address = host->h_addr_list; *address; address++)
    {
      if (memcmp(*address, addr, len) == 0)
        break;
    }

    /* Did any of the aliases match? */
    if (*address)
      break;
  }

  /* Close the file unless the user has prohibited it */
  if (!keepopen)
    endhostent();

  return host;
}