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

pipes on the system will be STREAMS-based. However, ﬁfos will not be

STREAMS-based. STREAMS/UX does not support STREAMS-based

ﬁfos.

The STREAMS/UX device pipedev is only for internal STREAMS/UX use

in implementing STREAMS-based pipes. Opening a device ﬁle with

pipedev's major number will not result in a STREAMS-based pipe, or even a

properly functioning stream. STREAMS-based pipes must be created using

the pipe(2) system call.

PIPE_BUF is a pathname variable value, and SVID, XPG4, POSIX, etc.

deﬁne it as the maximum number of bytes that is guaranteed to be written

atomically. To obtain the correct value of PIPE_BUF, use fpathconf() (see

pathconf()). For STREAMS-based pipes, the value of PIPE_BUF depends

on the conﬁgurable parameter STRMSGZ (by default, 8KB). For example,

PIPE_BUF is set to 4KB if STRMSGSZ is 4KB, 8KB if STRMSGSZ is

8KB, and 16KB if STRMSGSZ is 16KB. There is one exception. If

STRMSGSZ is set to 0 (i.e. inﬁnite size), then PIPE_BUF for

STREAMS/UX pipes is set to 8KB.

putmsg and putpmsg 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. It must also be less than or equal to STRMSGSZ. If the number

of bytes to transfer is not in this range, ERANGE will be returned.

Maximum and Minimum Control Buffer Size

The size of the user's control buffer must be less than or equal to both

STRCTLSZ and STRMSGSZ. If STRCTLSZ is less than or equal to zero,

the page size is used instead of STRCTLSZ for this check.

Data Buffer Segmentation

The user's data buffer may be sent in multiple data blocks chained together

to form a message. The maximum number of bytes, including the write

offset, that can be sent in one data block is equal to the page size.