Originální popis anglicky:
putmsg, putpmsg - send a message on a STREAM (
STREAMS)
Návod, kniha: POSIX Programmer's Manual
#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);
The
putmsg() function shall create a message from a process buffer(s) and
send the message to a STREAMS file. The message may contain either a data
part, a control part, or both. The data and control parts are distinguished by
placement in separate buffers, as described below. The semantics of each part
are defined by the STREAMS module that receives the message.
The
putpmsg() function is equivalent to
putmsg(), except that the
process can send messages in different priority bands. Except where noted, all
requirements on
putmsg() also pertain to
putpmsg().
The
fildes argument specifies a file descriptor referencing an open
STREAM. The
ctlptr and
dataptr arguments each point to a
strbuf structure.
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 indicates the number of bytes to be sent.
The
maxlen member is not used by
putmsg(). In a similar manner,
the argument
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 further below.
To send the data part of a message, the application shall ensure that
dataptr is not a null pointer and the
len member of
dataptr is 0 or greater. To send the control part of a message, the
application shall ensure that the corresponding values are set for
ctlptr. No data (control) part shall be sent if either
dataptr(
ctlptr) is a null pointer or the
len member of
dataptr(
ctlptr) is set to -1.
For
putmsg(), if a control part is specified and
flags is set to
RS_HIPRI, a high priority message shall be sent. If no control part is
specified, and
flags is set to RS_HIPRI,
putmsg() shall fail and
set
errno to [EINVAL]. If
flags is set to 0, a normal message
(priority band equal to 0) shall be sent. If a control part and data part are
not specified and
flags is set to 0, no message shall be sent and 0
shall be returned.
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() shall fail and set
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 shall be
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() shall
fail and set
errno to [EINVAL]. If
flags is set to MSG_BAND,
then a message shall be 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 shall be sent and 0 shall be returned.
The
putmsg() function shall block if the STREAM write queue is full due
to internal flow control conditions, with the following exceptions:
- *
- For high-priority messages, putmsg() shall not block
on this condition and continues processing the message.
- *
- For other messages, putmsg() shall not block but
shall fail when the write queue is full and O_NONBLOCK is set.
The
putmsg() function shall also block, unless prevented by lack of
internal resources, while waiting for the availability of message blocks in
the STREAM, regardless of priority or whether O_NONBLOCK has been specified.
No partial message shall be sent.
Upon successful completion,
putmsg() and
putpmsg() shall return 0;
otherwise, they shall return -1 and set
errno to indicate the error.
The
putmsg() and
putpmsg() functions shall fail if:
- EAGAIN
- A non-priority message was specified, the O_NONBLOCK flag
is set, and the STREAM write queue is full due to internal flow control
conditions; or buffers could not be allocated for the message that was to
be created.
- EBADF
- fildes is not a valid file descriptor open for
writing.
- EINTR
- A signal was caught during putmsg().
- EINVAL
- An undefined value is specified in flags, or
flags is set to RS_HIPRI or MSG_HIPRI and no control part is
supplied, or the STREAM or multiplexer referenced by fildes is
linked (directly or indirectly) downstream from a multiplexer, or
flags is set to MSG_HIPRI and band is non-zero (for
putpmsg() only).
- ENOSR
- Buffers could not be allocated for the message that was to
be created due to insufficient STREAMS memory resources.
- ENOSTR
- A STREAM is not associated with fildes.
- ENXIO
- A hangup condition was generated downstream for the
specified STREAM.
- 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 thread.
- 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() shall 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 following sections are informative.
The value of
fd is assumed to refer to an open STREAMS file. This call to
putmsg() does the following:
- 1.
- Creates a high-priority message with a control part and a
data part, using the buffers pointed to by ctrlbuf and
databuf, respectively.
- 2.
- Sends the message to the STREAMS file identified by
fd.
#include <stropts.h>
#include <string.h>
...
int fd;
char *ctrlbuf = "This is the control part";
char *databuf = "This is the data part";
struct strbuf ctrl;
struct strbuf data;
int ret;
ctrl.buf = ctrlbuf;
ctrl.len = strlen(ctrlbuf);
data.buf = databuf;
data.len = strlen(databuf);
ret = putmsg(fd, &ctrl, &data, MSG_HIPRI);
This example has the same effect as the previous example. In this example,
however, the
putpmsg() function creates and sends the message to the
STREAMS file.
#include <stropts.h>
#include <string.h>
...
int fd;
char *ctrlbuf = "This is the control part";
char *databuf = "This is the data part";
struct strbuf ctrl;
struct strbuf data;
int ret;
ctrl.buf = ctrlbuf;
ctrl.len = strlen(ctrlbuf);
data.buf = databuf;
data.len = strlen(databuf);
ret = putpmsg(fd, &ctrl, &data, 0, MSG_HIPRI);
None.
None.
None.
STREAMS ,
getmsg() ,
poll() ,
read() ,
write() , the Base Definitions volume of
IEEE Std 1003.1-2001,
<stropts.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
