STREAMS/UX for the HP 9000 Reference Manual

Differences Between STREAMS/UX and System V Release 4 STREAMS

HP-UX Changes to STREAMS/UX System Calls

A select exception event is returned if a poll event POLLPRI or

POLLRDBAND exists on the STREAM. More speciﬁcally, an exception

event is returned if a high-priority message or a banded message is waiting

to be read.

signal Modifications

STREAMS/UX supports signals and the HP-UX signal system call.

However, STREAMS/UX does not support extended signals or the siginfo_t

structure described in the siginfo(5) manpage.

write and writev Modifications

Maximum and Minimum Data Buffer Size

The size of the user's data buffer must be within the minimum and maximum

packet size range speciﬁed in the topmost STREAM module's streamtab. If

the number of bytes to transfer is not in this range, ERANGE will be

returned. Two exceptions exist in which no error occurs. The ﬁrst exception

is if the data buffer is too large and either the maximum packet size is

inﬁnite or the minimum packet size is less than or equal to zero. (An inﬁnite

packet size is speciﬁed using the deﬁne INFPSZ in the stream.h ﬁle.) The

second exception occurs if the buffer is too small and the minimum packet

size is less than or equal to zero. With either exception, ERANGE is not

returned, and the data is transferred.

Data Buffer Segmentation

The user's data buffer may be sent in multiple messages. The maximum

amount of data that can be sent in one message is the lower value of the

topmost module's maximum packet size and STRMSGSZ. If the maximum

packet size is inﬁnite, then the top module’s high water mark is taken into

consideration. If the high water mark is more than zero, half of the high

water mark is used; otherwise the page size is used.