gen/readdir_r.c

   1 #include <sys/types.h>
   2 #include <dirent.h>
   3 #include <pthread.h>
   4
   5 /*
   6  * Synopsis:
   7  * dir_table is a global static array of pthread mutexes.  The array is NMUTEXES
   8  * in length (NMUTEXES * sizeof(pthread_mutex_t)).
   9  *
  10  * Whenever a call to readdir_r is made, the element in the array indexed by the
  11  * modulus of the file descriptor associated with dirp is locked, and readdir is
  12  * called on dirp.  The result is returned in readdir_r semantics and the
  13  * element in dir_table is unlocked.
  14  */
  15
  16 static pthread_mutex_t dir_table[]  = {
  17         PTHREAD_MUTEX_INITIALIZER,
  18         PTHREAD_MUTEX_INITIALIZER,
  19         PTHREAD_MUTEX_INITIALIZER,
  20         PTHREAD_MUTEX_INITIALIZER,
  21         PTHREAD_MUTEX_INITIALIZER,
  22         PTHREAD_MUTEX_INITIALIZER,
  23         PTHREAD_MUTEX_INITIALIZER,
  24         PTHREAD_MUTEX_INITIALIZER
  25 #define NMUTEXES        8
  26 };
  27
  28 int readdir_r(DIR *dirp, struct dirent *entry, struct dirent **result)
  29 {
  30         int ret;
  31         int mindex = dirp->dd_fd % NMUTEXES;
  32         struct dirent *tmpdp;
  33
  34         pthread_mutex_lock(&dir_table[mindex]);
  35
  36         tmpdp = readdir(dirp);
  37         if( tmpdp == NULL ) {
  38                 *result = NULL;
  39                 ret = errno;
  40                 pthread_mutex_unlock(&dir_table[mindex]);
  41                 return ret;
  42         }
  43
  44         memcpy(entry, tmpdp, sizeof(struct dirent));
  45         *result = entry;
  46
  47         pthread_mutex_unlock(&dir_table[mindex]);
  48         return 0;
  49 }
  50
  51