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.help zfiobf May84 "System Interface"
.ih
NAME
zfiobf -- binary file driver
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SYNOPSIS
.nf
zopnbf (osfn, mode, chan) # open or create binary file
zclsbf (chan, status) # close binary file
zardbf (chan, buf, maxbytes, loffset) # asynchronous read
zawrbf (chan, buf, nbytes, loffset) # asynchronous write
zawtbf (chan, status) # wait for transfer
zsttbf (chan, param, lvalue) # get file/device status
packed char osfn[]
char buf[]
int mode, chan, maxbytes, nbytes, param, status
long loffset, lvalue
.fi
.ih
DESCRIPTION
A binary file is an extendable array of machine bytes. There are two types
of binary files: \fBblocked\fR files, which are randomly accessible in chunks
the size of a device block, and \fBstreaming\fR binary files, which are
restricted to sequential access and characterized by a variable block size.
A binary file is effectively an extension of host memory, i.e., arbitrary
regions of memory may be written to a binary file and later restored
(possibly at a different location) without modification of the data.
Unlike the text file, there are no restrictions on the contents of a binary
file.
.ih
RETURN VALUES
When a binary file is opened the kernel assigns a channel to the file
and all subsequent file operations refer to the file by the channel number.
The asynchronous read and write primitives do not return a status value;
the number of bytes read or written or ERR is returned in a subsequent
call to \fBzawtbf\fR. Every i/o transfer must be followed by a call to
\fBzawtbf\fR. Only one transfer is permitted on a file at a time.
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NOTES
If a file is accessed by name (rather than by channel number) while the file
is open the results are machine dependent.
If a file is blocked reads and writes must be aligned on block boundaries;
file offsets are one-indexed. A binary file may be extended by writing at
EOF or by overwriting EOF. All blocks but the last in a blocked file are the
same size; the last block may be partially full. A write to a streaming
file appends a new block of size \fInbytes\fR to the file; successive blocks
may vary in size. Each read from a streaming file returns a single variable
length block.
.ih
SEE ALSO
zfiotx, manual pages for the individual routines
.endhelp
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