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7001 :: help use mq posix

• JPLRouge (orginal) [2020-10-28T13:35:42+01:00] view original

  hello,

  I apply what we do in C but it does not work moreover I cannot do O_CREAT | O_RDWR

  le resultat:

  
   myPid--> 98118
  mq_flags
  mq_maxmsg
  mq_msgsize
  mq_curmsgs
  Init-->  0 -- 9999 -- 1024 -- 0
  mq_open
  mqd_t--> -1   *****error
  ctrl--> -1 *****error
  getattr-->  0 -- 9999 -- 1024 -- 0
  Run

  source:

   posix
  import strformat
  
  let QUEUE_NAME  = "QMname"
  let MAX_MSG     = 9999    # nbr max de message
  let MSGTXTLEN   = 1024  # msg text length
  var myPid : Pid
  var mqd_t : Mqd
  
  var mqd_a : MqAttr
  
  proc main() =
    echo "getpid"
    myPid = getpid()
    echo fmt" myPid--> {myPid}"
    
    # initialize the queue attributes
    echo "mq_flags"
    mqd_a.mq_flags = 0
    echo "mq_maxmsg"
    mqd_a.mq_maxmsg = MAX_MSG
    echo "mq_msgsize"
    mqd_a.mq_msgsize = MSGTXTLEN
    echo "mq_curmsgs"
    mqd_a.mq_curmsgs = 0
    echo fmt"Init-->  {mqd_a.mq_flags} -- {mqd_a.mq_maxmsg} -- {mqd_a.mq_msgsize} -- { mqd_a.mq_curmsgs}"
    
    # create the message
    echo "mq_open"
    mqd_t = mq_open(QUEUE_NAME, O_RDWR) # impossible  O_CREAT | O_RDWR
    echo fmt"mqd_t--> {mqd_t}"
    
    var ctrl = mq_getattr(mqd_t, mqd_a.addr)
    echo fmt"ctrl--> {ctrl}"
    echo fmt"getattr-->  {mqd_a.mq_flags} -- {mqd_a.mq_maxmsg} -- {mqd_a.mq_msgsize} -- { mqd_a.mq_curmsgs}"
  main()
  Run

  compil :

   [ "$mode" == "TEST" ] ; then
          ( set -x ; \
                  nim  c -f --gc:orc -d:useMalloc --panics:on \
                          --hint[Performance]:off  --warning[Deprecated]:on --warning[EachIdentIsTuple]:on \
                          --threads:on \
                          --passL:-no-pie \
                          -o:$projet_bin   $projet_src ; \
          )
  fi
  Run

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• Araq (orginal) [2020-10-28T17:53:55+01:00] view original

  O_CREAT | O_RDWR would be O_CREAT or O_RDWR.

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• JPLRouge (orginal) [2020-10-28T18:31:19+01:00] view original

  yes it compiles correctly but the execution is not correct result -1 in fact we cannot give permissions 0644 etc ...

  regarde svp:

  is good example:

  https://www.softprayog.in/programming/interprocess-communication-using-posix-message-queues-in-linux

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• shirleyquirk (orginal) [2020-10-28T23:07:14+01:00] view original

  mqd_t = mq_open(QUEUE_NAME,O_CREAT or O_RDWR,0o644,null) #or mqd_a.mq_maxnmsg = 10 mqd_t = mq_open(QUEUE_NAME,O_CREAT or O_RDWR,0o644,mqd_a.addr)

  Run

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• JPLRouge (orginal) [2020-10-29T01:00:55+01:00] view original

  min import posix

  only :

   mq_open(a1: cstring; a2: cint): Mqd {...}
  Run

  https://github.com/nim-lang/Nim/blob/version-1-4/lib/posix/posix.nim#L249

  my book development Linux

  _open(const char *name,int flags, mode_t mode, struct mq_attr* attr);
  Run

  very different from Nim

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• shirleyquirk (orginal) [2020-10-29T13:50:04+01:00] view original

  il ne faut pas definir une nouvelle proc: mq_open in posix.nim c'est varargs, alors elle va accepter (cstring,cint...)

  You don't need a new proc: {.importc varargs.} procs accept multiple arguments. The documentation for posix could be revised to reflect that.

  import posix, strformat
  const QMname = "/QMname"
  template check(assertion: untyped, msg: typed): untyped =
    if not assertion: echo msg, &": {strerror(errno)}"
  proc main() =
    let attr = MqAttr(mq_maxmsg: 99, mq_msgsize: 1024)
    let p_attr = attr.addr
    let mq = mq_open(QMname, O_CREAT or O_RDWR or O_EXCL, 0o644, p_attr)
    check(mq >= 0, "Error opening queue")
    check(mq_getattr(mq, p_attr) >= 0, "Error getting attrs")
    echo &"getattr--> {attr.mq_flags} -- {attr.mq_maxmsg} -- {attr.mq_msgsize} -- {attr.mq_curmsgs}"
    
    #cleanup
    dealloc(attr)
    discard mq_close(mq)
    discard mq_unlink(QMname)
  
  main()
  Run

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