#include <unistd.h> /* for standard unix functions */
#include <fcntl.h> /* for file operation flags like O_RDONLY */
#include <sys/stat.h> /* for fstat */
#include <sys/types.h> /* implementation specific system types */
#include <sys/dir.h> /* for implementation of struct direct */
#include "dirent.h" /* portable structures and functions */

/* opendir: open a directory for readdir calls */
DIR *opendir(char *dirname) {
     int fd;
     struct stat stbuf;
     DIR *dp;

     if ((fd = open(dirname, O_RDONLY, 0)) == -1
	 || fstat(fd, &stbuf) == -1
	 || (stbuf.st_mode & S_IFMT) != S_IFDIR
	 || (dp = (DIR *) malloc(sizeof(DIR))) == NULL)
	  return NULL;
     dp->fd = fd;
     return dp;
}

/* closedir: close directory opened by opendir */
void (closedir(DIR *dp)) {
     
     if (dp) {
	  close(dp->fd);
	  free(dp);
     }
}

/* readdir: read directory entries in sequence */
Dirent *readdir(DIR *dp) {
     struct direct dirbuf; /* local directory structure */
     static Dirent d; /* return: portable structure */

     while (read(dp->fd, (char *) &dirbuf, sizeof(dirbuf))
	    == sizeof(dirbuf)) {
	  if (dirbuf.d_ino == 0) /* slot not in use */
	       continue;
	  d.ino = dirbuf.d_ino;
	  strncpy(d.name, dirbuf.d_name, DIRSIZE);
	  d.name[DIRSIZE] = '\0'; /* ensure termination */
	  return &d;
     }
     return NULL;
}