12.26

struct hostent *gethostbyname(const char *name)

struct hostent {
  char *h_name;
  char **h_aliases;
  int  h_addrtype;
  int  h_length;
  char **h_addr_list;
}

/*
 * 12.26.c
 */
#include <stdio.h>
#include "csapp.h"

/*
 * struct hostent *gethostbyname(const char *name)
 *
 * struct hostent {
 *   char *h_name;
 *   char **h_aliases;
 *   int  h_addrtype;
 *   int  h_length;
 *   char **h_addr_list;
 * }
 */
static sem_t mutex;

static void init_mutex(void) {
  Sem_init(&mutex, 0, 1);
}

struct hostent *gethostbyname_ts(const char *name, struct hostent *host) {
  struct hostent *sharehost;

  P(&mutex);
  sharehost = gethostbyname(name);
  // copy int
  host->h_addrtype = sharehost->h_addrtype;
  host->h_length = sharehost->h_length;
  // copy char *
  host->h_name = (char*)Malloc(strlen(sharehost->h_name));
  strcpy(host->h_name, sharehost->h_name);
  // copy char **
  int i;
  for (i = 0; sharehost->h_aliases[i] != NULL; i++) {}
  host->h_aliases = (char**)Malloc(sizeof(char*) * (i+1));
  for (i = 0; sharehost->h_aliases[i] != NULL; i++) {
    // copy every char *
    host->h_aliases[i] = (char*)Malloc(strlen(sharehost->h_aliases[i]));
    strcpy(host->h_aliases[i], sharehost->h_aliases[i]);
  }
  host->h_aliases[i] = NULL;

  for (i = 0; sharehost->h_addr_list[i] != NULL; i++) {}
  host->h_addr_list = (char**)Malloc(sizeof(char*) * (i+1));
  for (i = 0; sharehost->h_addr_list[i] != NULL; i++) {
    // copy every char *
    host->h_addr_list[i] = (char*)Malloc(strlen(sharehost->h_addr_list[i]));
    strcpy(host->h_addr_list[i], sharehost->h_addr_list[i]);
  }
  host->h_addr_list[i] = NULL;
  V(&mutex);

  return host;
}

int main(int argc, char* argv[]) {
  init_mutex();

  struct hostent host;
  gethostbyname_ts("127.0.0.1", &host);
  // result in &host

  return 0;
}