HP 3000 Manuals HP 3000 Manuals
HPSELECT
Determine whether a file or group of files is ready to perform reads,
writes, or if it has an exception condition, and whether to block on one
or more of these events if the condition is not currently true.
Syntax
_____________________________________________________________
| |
| I16 IV CA CA |
| numselect:=HPSELECT(numfiles,readmask,writemask, |
| CA R I32 |
| exceptionmask,timeout,status)|
_____________________________________________________________
Functional Return
numselect 16-bit signed integer (assigned functional return)
Returns a value representing the number of files
that have selected true. The following values are
returned:
Value Meaning
n The number of files that have selected true.
0 If a timeout value was assigned and the select "timed
out".
-1 If an error occurred in the call, an internal error
occurred, or if a soft interrupt occurred before any
selected events or before the time limit expired.
Parameters
numfiles integer by value (required)
Passes the number of files (number of files -1)
whose bits will be checked by HPSELECT.
Note that this parameter does not represent the
number of files where a bit in one of the masks is
being set. It represents the highest file number
(minus 1) that will be examined by HPSELECT.
readmask character array by reference (optional)
Specifies which file numbers will be examined to
see if the file that is ready for reading should be
passed. The least significant bit of each 32-bit
word represents the lowest file number in the word.
The first word contains the bits for the first 32
files. Subsequent words contain the bits for
additional groups of 32 files.
For each file number less than numfiles, the
corresponding bit in the mask is set at return if
the bit was set at entry and the file is ready for
reading.
Bits representing file numbers greater than
numfiles (minus 1) are ignored. The buffer
containing the bit mask only needs to be as large
as the number of 32-bit words required to contain
the bits for numfiles files.
If a timeout is specified and the time limit has
elapsed, the mask is cleared on return.
Default: No files are checked for reading.
writemask character array by reference (optional)
Specifies which file numbers are to be examined to
see if the file is ready for writing. The last
significant bit of each 32-bit word represents the
lowest file number in the word. The first word
contains the bits for the first 32 files.
Subsequent words contain the bits for additional
groups of 32 files.
For each file number less than numfiles, the
corresponding bit in the mask is set at return if
the bit was set at entry and the file is ready for
writing.
Bits representing file numbers greater than
numfiles (minus 1) are ignored. The buffer
containing the bit mask only needs to be as large
as the number of 32-bit words required to contain
the bits for numfiles files.
If a timeout is specified and the time limit has
elapsed, the mask is cleared on return.
Default: No files are checked for writing.
exceptionmask character array by reference (optional)
Specifies which file numbers are to be examined to
see if the file has detected an exception
condition. The last significant bit of each 32-bit
word represents the lowest file number in the word.
The first word contains the bits for the first 32
files. Subsequent words contain the bits for
additional groups of 32 files.
For each file number less than numfiles, the
corresponding bit in the mask is set at return if
the bit was set at entry and the file has detected
an exception condition.
Bits representing file numbers greater than
numfiles (minus 1) are ignored. The buffer
containing the bit mask only needs to be as large
as the number of 32-bit words required to contain
the bits for numfiles files.
If a timeout is specified and the time limit has
elapsed, the mask is cleared on return.
Default: No files are checked for exception
conditions.
timeout record by reference (optional)
Specifies a maximum interval to wait for the
selection to complete. If a timeout value of 0 is
supplied, HPSELECT checks for the specified
conditions, sets the return mask, and returns
without blocking even if none of the specified
conditions are true. If a timeout value is not
specified, HPSELECT waits until an event causes one
of the masks to be returned with a non-zero value.
The timeout value is specified by a 64-bit record
containing the following two fields:
32-bit unsigned integer seconds
=
32-bit integer = microseconds
Values up to 2**32 seconds can be specified.
Default: HPSELECT blocks until one of the
specified conditions is true.
status 32-bit integer by reference (optional)
Returns the status of the HPSELECT call. If no
errors or warnings are encountered, status returns
32 bits of zero. If errors or warnings are
encountered, status is interpreted as two 16-bit
fields.
Bits (0:16) comprise status.info. A negative value
indicates an error condition, and a positive value
indicates a warning condition. Refer to the MPE/iX
Error Message Manual Volumes 1, 2 and 3
(32650-90066, 32650-90152, and 32650-90368) for a
description of its value.
Bits (16:16) comprise status.subsys. The value
represented by these bits defines the subsystem
that set the status information. The subsystem
identifier for HPSELECT is 143.
Possible error values of status.info are:
Value Meaning
-9 Illegal parameter - the value of numfiles is negative
or an invalid timeout value was specified.
-18 Bounds violation - one or more parameters point to an
invalid address or to an address the user does not
have access to.
-30 Invalid file reference - one or more of the bit masks
specified an invalid file number.
-90 Timeout - the time limit expired before any selected
events occurred.
-91 Soft interrupt - a soft interrupt occurred before any
selected events occurred or before the time limit
expired.
No status If status is not passed in, no status is returned.
NOTE HPSELECT will not ESCAPE if an error is detected and the status
parameter was not supplied. Errors are also indicated by a -1 in
the numselect parameter (functional return). For assurance of a
successful completion, check the functional return.
The only file type supported by HPSELECT is Net IPC. For all other
file types, HPSELECT always returns TRUE.
Related Information
Intrinsics IOWAIT
Commands None
Manuals None