Open System Services System Calls Reference Manual (G06.29+, H06.08+, J06.03+)

SPT_READUPDATEX(2) OSS System Calls Reference Manual
NAME
SPT_READUPDATEX - Reads data from a Guardian disk or process file in anticipation of a
subsequent write to the file
LIBRARY
G-series native OSS processes: /G/system/sysnn/zsptsrl
H-series OSS processes: /G/system/zdllnnn/zsptdll
SYNOPSIS
[#include <cextdecs.h>]
#include <spthread.h>
short SPT_READUPDATEX (
short filenum,
char *buffer,
unsigned short read_count,
[unsigned short *count_read ],
[long tag ]
);
PARAMETERS
filenum specifies the file number of a Guardian file open instance that identifies the file to
be read.
buffer specifies an array in the application process in which the information read from
the file is returned.
read_count specifies the number of bytes to be read.
count_read is for waited I/O only. This parameter returns a count of the number of bytes
returned from the file into buffer.
tag is for nowait I/O only. The tag value you define uniquely identifies the operation
associated with this call.
This parameter is supported only for program compatibility; if you provide it, it
is ignored.
DESCRIPTION
The SPT_READUPDATEX() function is the thread-aware version of the Guardian READUP-
DATEX procedure.
This function reads data from a disk or process file in anticipation of a subsequent write to the
file. The values of the current-record and next-record pointers do not change. This function has
the following uses:
Disk files SPT_READUPDATEX( ) is used for random processing. Data is read from the
file at the position of the current-record pointer. A call to this function typically
follows a corresponding call to the Guardian POSITION or KEYPOSITION pro-
cedure.
Queue Files SPT_READUPDATEX() is not supported on queue files. An attempt to use
SPT_READUPDATEX( ) is rejected with Guardian file-system error 2.
Interprocess communication
SPT_READUPDATEX( ) reads a message from the $RECEIVE file that is
answered in a later call to the Guardian REPLYX procedure. Each message read
by SPT_READUPDATEX( ) must be replied to in a corresponding call to
REPLYX.
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