examples/libsmbclient/smbwrapper/select.c

   1 /*
   2    Unix SMB/Netbios implementation.
   3    Version 3.0
   4    Samba select/poll implementation
   5    Copyright (C) Andrew Tridgell 1992-1998
   6    Copyright (C) Derrell Lipman 2003-2005
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program; if not, write to the Free Software
  20    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21 */
  22
  23 /*
  24  * WHY THIS FILE?
  25  *
  26  * This file implements the two functions in the select() family, as required
  27  * by samba.  The samba native functions, though, implement a pipe to help
  28  * alleviate a deadlock problem, but which creates problems of its own (the
  29  * timeout stops working correctly).  Those functions also require that all
  30  * signal handlers call a function which writes to the pipe -- a task which is
  31  * difficult to do in the smbwrapper environment.
  32  */
  33
  34
  35 #include <sys/select.h>
  36 #include <errno.h>
  37 #include <stdio.h>
  38
  39 int sys_select(int maxfd, fd_set *readfds, fd_set *writefds, fd_set *errorfds, struct timeval *tval)
  40 {
  41         int ret;
  42         fd_set *readfds2, readfds_buf;
  43
  44         /* If readfds is NULL we need to provide our own set. */
  45         if (readfds) {
  46                 readfds2 = readfds;
  47         } else {
  48                 readfds2 = &readfds_buf;
  49                 FD_ZERO(readfds2);
  50         }
  51
  52         errno = 0;
  53         ret = select(maxfd,readfds2,writefds,errorfds,tval);
  54
  55         if (ret <= 0) {
  56                 FD_ZERO(readfds2);
  57                 if (writefds)
  58                         FD_ZERO(writefds);
  59                 if (errorfds)
  60                         FD_ZERO(errorfds);
  61         }
  62
  63         return ret;
  64 }
  65
  66 /*******************************************************************
  67  Similar to sys_select() but catch EINTR and continue.
  68  This is what sys_select() used to do in Samba.
  69 ********************************************************************/
  70
  71 int sys_select_intr(int maxfd, fd_set *readfds, fd_set *writefds, fd_set *errorfds, struct timeval *tval)
  72 {
  73         int ret;
  74         fd_set *readfds2, readfds_buf, *writefds2, writefds_buf, *errorfds2, errorfds_buf;
  75         struct timeval tval2, *ptval, end_time, now_time;
  76         extern void GetTimeOfDay(struct timeval *tval);
  77
  78         readfds2 = (readfds ? &readfds_buf : NULL);
  79         writefds2 = (writefds ? &writefds_buf : NULL);
  80         errorfds2 = (errorfds ? &errorfds_buf : NULL);
  81         if (tval) {
  82                 GetTimeOfDay(&end_time);
  83                 end_time.tv_sec += tval->tv_sec;
  84                 end_time.tv_usec += tval->tv_usec;
  85                 end_time.tv_sec += end_time.tv_usec / 1000000;
  86                 end_time.tv_usec %= 1000000;
  87                 ptval = &tval2;
  88         } else {
  89                 ptval = NULL;
  90         }
  91
  92         do {
  93                 if (readfds)
  94                         readfds_buf = *readfds;
  95                 if (writefds)
  96                         writefds_buf = *writefds;
  97                 if (errorfds)
  98                         errorfds_buf = *errorfds;
  99                 if (tval) {
 100                         GetTimeOfDay(&now_time);
 101                         tval2.tv_sec = end_time.tv_sec - now_time.tv_sec;
 102                         tval2.tv_usec = end_time.tv_usec - now_time.tv_usec;
 103                         if ((signed long) tval2.tv_usec < 0) {
 104                                 tval2.tv_usec += 1000000;
 105                                 tval2.tv_sec--;
 106                         }
 107                         if ((signed long) tval2.tv_sec < 0) {
 108                                 ret = 0;
 109                                 break;          /* time has already elapsed */
 110                         }
 111                 }
 112
 113                 ret = sys_select(maxfd, readfds2, writefds2, errorfds2, ptval);
 114         } while (ret == -1 && errno == EINTR);
 115
 116         if (readfds)
 117                 *readfds = readfds_buf;
 118         if (writefds)
 119                 *writefds = writefds_buf;
 120         if (errorfds)
 121                 *errorfds = errorfds_buf;
 122
 123         return ret;
 124 }