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In some of the following intrinsics, a parameter contains more
than one piece of information within a word. When this
is the case, data fields are described in the format
(n:m), where n is the first
bit of the field and m is the number
of consecutive bits in the field.
For example, the FOPTION field
for File Type occupies bits (2:3), or bits 2, 3
and 4. Parameters not discussed in the following descriptions retain
their normal value range and defaults. For more information
about these intrinsics,
refer to the MPE/iX Intrinsics Reference Manual
(32650-90028). HPFOPEN | |
| | | |  | NOTE:
The following discussion also applies to the
FOPEN intrinsic, which is the equivalent within MPE V/E
of HPFOPEN. The FOPEN parameter name
follows the HPFOPEN parameter name. For
more information on FOPEN, refer to the MPE/iX Intrinsics
Reference Manual (32650-90028). | | | | |
- Item #6, record format option; FOPTION (8:2)
Message files are always formatted internally as variable-length record files (option=1). If fixed-length records are requested (option=0), the file can appear fixed when it is opened. There is no difference for a writer; for a reader, the portion of the target area that exceeds the record is filled with blanks (for an ASCII file) or zeros (for a binary file). Files accessed in copy mode are always formatted as variable. (See item #17 for more information on copy mode.) - Item #11, access type option; AOPTION (12:4)
The type of access allowed for
this file is specified by the following values:
0 - READ-only access. A process that has opened a file with this access type is a "reader." (FWRITE calls will not be allowed.) 1 - WRITE-only access. If this is the only current open of the file, any data written in the file prior to the current HPFOPEN request is deleted. If this is not the only current open of the file, the file is treated as if Access Type 3 has been specified. A process that has opened a file with this access type is a "writer." (FREAD calls will not be allowed.) 2 - WRITE-SAVE access. The file system sets this to APPEND access for message files. 3 - APPEND-only access. The FREAD intrinsic cannot reference this file. Calls to FWRITE will add data to the end of the file. A process that has opened a file with this access type is a "writer." For a file accessed in copy mode, any access type other than READ-only access (option = 0) is changed to WRITE-only access (option = 1) by the file system. - Item #13, exclusive option; AOPTION (8:2)
The values for this option are the same as for any other file. However, the significance of each value is different:
| User | Value | Meaning |
|---|
| EXCLUSIVE | 1 | One reader, one writer | | SEMI | 2 | One reader, multiple writers | | SHARE | 3 | Multiple readers and writers | | Default | 0 | Same as 1 |
In copy mode, the value is always 1. - Item #14, multiaccess mode;AOPTION (5:2)
This feature permits processes located in different jobs or sessions to open the same file. 0 - No multiaccess. The file system changes this value to 2 to allow global multiaccess. 1 - Only intrajob multiaccess allowed; this is the same as specifying the MULTI option in a :FILE command. 2 - Interjob multiaccess allowed; this is the same as specifying the GMULTI option in a :FILE command. In copy mode, the value is always 0 (no multiaccess). - Item #15, multirecord option; AOPTION (11:1)
For message files, the file system sets this bit to 0, except in copy mode. This option is available only if you also select the inhibit buffering option, Item #46. - Item #17, copy mode option;
AOPTION (3:1)
This feature permits a message
file to be treated as a standard sequential
file, so that it can be copied by logical record
or physical block to another file. 0 - The file is accessed in its own
mode; that is, a message (MSG) file is
treated as a message file. 1 - The file is to be treated as a standard (STD),
sequential file with variable-length
records. For message files, this allows nondestructive
reading of an old message file at either
the logical record or the physical block
level. Only block level access is
permitted if the file is being written in
message-file format. This prevents incorrectly
formatted data from being written to the
message file while that file is unprotected.
In order to access a message file in copy
mode, a process must have EXCLUSIVE access
to the file. - Item #22, volume class option,
Item #23, volume name option;
DEVICE field
These fields are relevant only if this is a new file.
If you specify volume class field, you must specify
a disc; specification of any device other than a
disc opens the device, and the file
is no longer a message file. - Item #35, filesize option;
FILESIZE field
For message files, the number of records is rounded
up to completely fill the last block and to make the last
extent the same size as the other extents. Two additional
records are included for the open and close records.
Because of spare tracks or remapped tracks, the logical
size is usually smaller than the physical size. - Item #44, numbuffers option;
NUMBUFFERS field
The number of buffers you wish to allocate to the file.
Value must be between 2 and 31; default is 2. IPC needs at least two buffers; if fewer than two are specified, the field is changed to two. Also, IPC
never uses more buffers than there are blocks in
the file. If more are specified, the lower number is
used (except in copy mode). - Item #46, inhibit buffering option;
AOPTION (7:1)
For message files, the
file system sets this value to 0. Readers may open a message file with
NOBUF if they are in copy mode. This option
determines whether the reader will be accessing
the file record by record or block by block: 0 - read by logical record 1 - read by physical block Writers must open message files with NOBUF
if they are in copy mode; they access
the file block by block.
FCONTROL | |
A few control codes deal specifically
with message files. Those not
mentioned here are invalid when message files are being used. | Code | Param | Description |
|---|
| 2 | | Complete all I/O; ignored in the case of
message files. | | 4 | Integer | Set timeout interval. Indicates that a
timeout interval is to be applied to
a file. In the case of message files,
param specifies the length of time
(in seconds) that a process waits when reading from an
empty file or writing to a full one. The
timeout remains enabled until it is
explicitly cancelled. (Refer to Chapter 4.) | | 6 | | Write End-Of-File. For message files, this
is used to verify the state of the file by
writing the file label and buffer area to disc.
This ensures that the message file can
survive system crashes. No EOF is
written. (Refer to Chapter 4.) | | 43 | | Abort NOWAIT I/O. For message files, CCG is returned
when an outstanding I/O operation has
completed. You must issue an IOWAIT call
to finish the request. (Refer to Chapter 5.) | | 45 | 1 or 0 | Enable/disable extended wait. For message files, a
param value of 1 enables extended wait.
This permits a reader to wait on an empty file
that is not currently opened by any writer, or
a writer to wait on a full file that has no
reader. This parameter remains in effect until you issue
an FCONTROL call with a controlcode of 45
and a param value of 0. | | 46 | 1 or 0 | Enable/disable reading the writer's ID. For
message files, a param value of 1 enables reading the
writer's ID. Each record read has a one-word header.
The first 16 bits indicate the type of record with the
following codes:
The second 16 bits contain the
writer's ID number. If the record is a
data record, the data follows the
header. Open and close records contain
no more information. If the param value is 0, reading the writer's
ID is disabled. Only data is read to the reader's
target area. The open and close records are skipped
and deleted by the file system
when they come to the head of the
message queue, and the one-word header
is transparent to the reader. (Refer to Chapter 4.) | | 47 | 1 or 0 | Nondestructive read. If the param value is 1,
the next FREAD by
this reader will not delete the record.
Subsequent FREAD calls are unaffected.
If the param value is 0, the next FREAD
by this reader deletes the record. (Refer to Chapter 4.) | | 48 | plabel | Arm/disarm software interrupts. The param
parameter must pass the
external label (plabel) of your interrupt procedure.
If the value of param is 0, the interrupt mechanism is
disabled for this file. Also, if AOPTIONS (4:1) was set to 0, option 48 resets it
to 1. Be sure to use IOWAIT or IODONTWAIT if you use
controlcode 48. (Refer to Chapter 6.) |
| | | | | NOTE:
Native Mode plabels
are 32 bits long, while Compatibility Mode
plabels are 16 bits. Therefore,
the interrupt handler and the FCONTROL call to it must
be compiled in the same mode. Arming software interrupts in
cross-mode programming can be unpredictable, and you should
avoid this whenever possible.
| | | | |
FCHECK | |
One error message is returned only when using IPC:
151 CURRENT RECORD WAS LAST RECORD WRITTEN BEFORE SYSTEM
CRASHED.
|
This error is returned when for some reason (usually a system
failure, or running out of disc space), the system was unable
to close the file cleanly. (An FREAD of the record
returns a CCL, and you can then use FCHECK to read the
message.) FFILEINFO | |
Three values for itemvalue are specifically for use with IPC: | Item # | Type | Description |
|---|
| 34 | I16 | The current number of writers. | | 35 | I16 | The current number of readers. | | 49 | I16 | Software interrupt plabel. A value
of zero implies that software
interrupts are not being used. |
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