unixdev.net


Switch to SpeakEasy.net DSL

The Modular Manual Browser

Home Page
Manual: (SunOS-5.9)
Page:
Section:
Apropos / Subsearch:
optional field



System Calls                                            putmsg(2)



NAME
     putmsg, putpmsg - send a message on a stream

SYNOPSIS
     #include <stropts.h>

     int putmsg(int fildes, const struct  strbuf  *ctlptr,  const
     struct strbuf *dataptr, int flags);

     int putpmsg(int fildes, const struct strbuf  *ctlptr,  const
     struct strbuf *dataptr, int band, int flags);

DESCRIPTION
     The putmsg() function creates a message  from user-specified
     buffer(s) and sends the message to a  STREAMS file. The mes-
     sage may contain either a data  part,  a  control  part,  or
     both.   The  data  and  control  parts  to  be sent are dis-
     tinguished by placement in separate  buffers,  as  described
     below.  The semantics of each part is defined by the STREAMS
     module that receives  the message.

     The  putpmsg() function does the same thing as putmsg(), but
     provides  the user the ability to send messages in different
     priority bands. Except where noted, all information pertain-
     ing to putmsg() also pertains to putpmsg().

     The fildes argument specifies a file descriptor  referencing
     an open stream.  The ctlptr and dataptr arguments each point
     to a strbuf structure, which contains the following members:

     int      maxlen;     /* not used here */
     int      len;        /* length of data */
     void     *buf;       /* ptr to buffer */

     The ctlptr argument points to the structure  describing  the
     control part, if any, to be included in the message. The buf
     member in the strbuf structure points to  the  buffer  where
     the  control  information  resides, and the len member indi-
     cates the number of bytes to be sent. The maxlen  member  is
     not  used  in putmsg() (see getmsg(2)). In a similar manner,
     dataptr specifies the data, if any, to be included  in   the
     message.   The flags argument indicates what type of message
     should be sent and is described later.

     To send the data part of a  message,  dataptr  must  not  be
     NULL,  and  the len member of dataptr must have a value of 0
     or greater. To send the  control  part  of  a  message,  the
     corresponding  values must be set for  ctlptr. No data (con-
     trol) part is sent if either dataptr (ctlptr)  is   NULL  or
     the len member of dataptr (ctlptr) is negative.





SunOS 5.9           Last change: 17 Oct 1996                    1






System Calls                                            putmsg(2)



     For putmsg(), if a control part is specified, and  flags  is
     set  to   RS_HIPRI,  a  high priority message is sent. If no
     control part is specified, and flags  is  set  to  RS_HIPRI,
     putmsg()  fails and sets errno to EINVAL. If flags is set to
     0, a normal (non-priority) message is sent.  If  no  control
     part  and no data part are specified, and flags is set to 0,
     no message is sent, and 0 is returned.

     The stream head guarantees that the control part of  a  mes-
     sage generated by putmsg() is at least 64 bytes in length.

     For putpmsg(), the flags are different.  The flags  argument
     is  a  bitmask  with  the following mutually-exclusive flags
     defined: MSG_HIPRI and MSG_BAND.  If  flags  is  set  to  0,
     putpmsg()  fails and sets errno to EINVAL. If a control part
     is specified and flags is set to MSG_HIPRI and band  is  set
     to  0,  a  high-priority message is sent. If flags is set to
     MSG_HIPRI and either no control part is specified or band is
     set  to  a non-zero value, putpmsg() fails and sets errno to
     EINVAL. If flags is set to MSG_BAND, then a message is  sent
     in  the  priority  band specified by band. If a control part
     and data  part  are  not  specified  and  flags  is  set  to
     MSG_BAND, no message is sent and 0 is returned.

     Normally, putmsg() will block if the stream write  queue  is
     full   due  to  internal  flow control conditions. For high-
     priority messages,  putmsg() does not block on  this  condi-
     tion.  For other messages,  putmsg() does not block when the
     write queue is full and   O_NDELAY  or  O_NONBLOCK  is  set.
     Instead, it fails and sets  errno to EAGAIN.

     The putmsg()  or  putpmsg()  function  also  blocks,  unless
     prevented  by  lack  of internal resources, waiting  for the
     availability of message blocks in the stream, regardless  of
     priority   or whether O_NDELAY or O_NONBLOCK has been speci-
     fied. No partial message is sent.

RETURN VALUES
     Upon successful completion, 0 is returned. Otherwise, -1  is
     returned and errno is set to indicate the error.

ERRORS
     The putmsg() and putpmsg() functions will fail if:

     EAGAIN
           A non-priority message was specified, the O_NDELAY  or
           O_NONBLOCK  flag is  set and the stream write queue is
           full due to internal flow control conditions.

     EBADF The fildes argument is not  a  valid  file  descriptor
           open for writing.




SunOS 5.9           Last change: 17 Oct 1996                    2






System Calls                                            putmsg(2)



     EFAULT
           The ctlptr or dataptr argument points  to  an  illegal
           address.

     EINTR A signal  was  caught  during  the  execution  of  the
           putmsg() function.

     EINVAL
           An undefined value was specified in  flags;  flags  is
           set  to  RS_HIPRI and no control part was supplied; or
           the stream referenced by fildes is linked below a mul-
           tiplexor.

     ENOSR Buffers could not be allocated for  the  message  that
           was  to  be created due to insufficient STREAMS memory
           resources.

     ENOSTR
           The fildes argument is not associated with a STREAM.

     ENXIO A hangup condition was generated  downstream  for  the
           specified  stream,  or  the  other  end of the pipe is
           closed.

     EPIPE or EIO
           The fildes argument refers to a STREAMS-based pipe and
           the other end of the pipe is closed.  A SIGPIPE signal
           is generated for the calling process. This error  con-
           dition  occurs  only  with SUS-compliant applications.
           See standards(5).

     ERANGE
           The size of the data part of the message does not fall
           within  the range specified by the maximum and minimum
           packet sizes of the topmost stream module. This  value
           is also returned if the control part of the message is
           larger than the maximum configured size of the control
           part of a message, or if the data part of a message is
           larger than the maximum configured size  of  the  data
           part of a message.

     In addition, putmsg() and putpmsg() will fail if the  STREAM
     head  had  processed  an asynchronous error before the call.
     In this case, the value of errno does not reflect the result
     of putmsg() or putpmsg() but reflects the prior error.

     The putpmsg() function will fail if:

     EINVAL
           The flags argument is set to  MSG_HIPRI  and  band  is
           non-zero.




SunOS 5.9           Last change: 17 Oct 1996                    3






System Calls                                            putmsg(2)



SEE ALSO
     intro(2),  getmsg(2),  poll(2),  read(2),  write(2),   stan-
     dards(5)

     STREAMS Programming Guide


















































SunOS 5.9           Last change: 17 Oct 1996                    4