external/ibm-public/postfix/dist/src/util/non_blocking.c

   1 /*      $NetBSD$        */
   2
   3 /*++
   4 /* NAME
   5 /*      non_blocking 3
   6 /* SUMMARY
   7 /*      set/clear non-blocking flag
   8 /* SYNOPSIS
   9 /*      #include <iostuff.h>
  10 /*
  11 /*      int     non_blocking(int fd, int on)
  12 /* DESCRIPTION
  13 /*      the \fInon_blocking\fR() function manipulates the non-blocking
  14 /*      flag for the specified open file, and returns the old setting.
  15 /*
  16 /*      Arguments:
  17 /* .IP fd
  18 /*      A file descriptor.
  19 /* .IP on
  20 /*      For non-blocking I/O, specify a non-zero value (or use the
  21 /*      NON_BLOCKING constant); for blocking I/O, specify zero
  22 /*      (or use the BLOCKING constant).
  23 /*
  24 /*      The result is non-zero when the non-blocking flag was enabled.
  25 /* DIAGNOSTICS
  26 /*      All errors are fatal.
  27 /* LICENSE
  28 /* .ad
  29 /* .fi
  30 /*      The Secure Mailer license must be distributed with this software.
  31 /* AUTHOR(S)
  32 /*      Wietse Venema
  33 /*      IBM T.J. Watson Research
  34 /*      P.O. Box 704
  35 /*      Yorktown Heights, NY 10598, USA
  36 /*--*/
  37
  38 /* System interfaces. */
  39
  40 #include "sys_defs.h"
  41 #include <fcntl.h>
  42
  43 /* Utility library. */
  44
  45 #include "msg.h"
  46 #include "iostuff.h"
  47
  48 /* Backwards compatibility */
  49 #ifndef O_NONBLOCK
  50 #define PATTERN FNDELAY
  51 #else
  52 #define PATTERN O_NONBLOCK
  53 #endif
  54
  55 /* non_blocking - set/clear non-blocking flag */
  56
  57 int     non_blocking(fd, on)
  58 int     fd;
  59 int     on;
  60 {
  61     int     flags;
  62
  63     if ((flags = fcntl(fd, F_GETFL, 0)) < 0)
  64         msg_fatal("fcntl: get flags: %m");
  65     if (fcntl(fd, F_SETFL, on ? flags | PATTERN : flags & ~PATTERN) < 0)
  66         msg_fatal("fcntl: set non-blocking flag %s: %m", on ? "on" : "off");
  67     return ((flags & PATTERN) != 0);
  68 }