31.4 getpmsg and
putpmsg Functions
When support for different priority bands was
added to STREAMS with SVR4, the following two variants of
getmsg and putmsg were added:
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#include <stropts.h>
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int getpmsg(int fd, struct strbuf *ctlptr, struct strbuf *dataptr, int *bandp, int *flagsp) ;
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int putpmsg(int fd, const struct strbuf *ctlptr, const struct strbuf
*dataptr, int
band, int flags) ;
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Both return: non-negative value if OK, 鈥? on
error
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The band
argument to putpmsg must be between 0 and 255, inclusive.
If the flags argument is
MSG_BAND, then a message is generated in the specified
priority band. Setting flags to
MSG_BAND and specifying a band of 0 is equivalent to
calling putmsg. If flags
is MSG_HIPRI, band must
be 0, and a high-priority message is generated. (Note that this
flag is named differently from the RS_HIPRI flag for
putmsg.)
The two integers pointed to by bandp and flagsp are value-result arguments for
getpmsg. The integer pointed to by flagsp for getpmsg can be
MSG_HIPRI (to read a high-priority message),
MSG_BAND (to read a message whose priority band is at
least equal to the integer pointed to by bandp), or MSG_ANY (to read any
message). On return, the integer pointed to by bandp contains the band of the message that
was read and the integer pointed to by flagsp contains MSG_HIPRI (if a
high-priority message was read) or MSG_BAND (if some other
message was read).
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