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.\" ========================================================================
.\"
.IX Title "nbdkit-swab-filter 1"
.TH nbdkit-swab-filter 1 "2021-01-20" "nbdkit-1.24.1" "NBDKIT"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
nbdkit\-swab\-filter \- nbdkit filter for swapping byte order
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& nbdkit \-\-filter=swab PLUGIN [PLUGIN\-ARGS...] [swab\-bits=8|16|32|64]
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\f(CW\*(C`nbdkit\-swab\-filter\*(C'\fR is a filter for \fBnbdkit\fR\|(1) which swaps bytes
in the underlying plugin.
.PP
One use for this is to read disk images which were formatted on the
Atari Falcon, where the \s-1IDE\s0 controller is wired in reverse order.
.SH "EXAMPLE"
.IX Header "EXAMPLE"
.SS "Swap bytes from a disk image"
.IX Subsection "Swap bytes from a disk image"
.Vb 1
\& nbdkit \-\-filter=swab file file=disk.img
.Ve
.PP
The above command serves the disk image \fIdisk.img\fR, swapping even and
odd bytes:
.PP
.Vb 3
\& disk.img   0   1   2   3   4   5 ...
\&              ╳       ╳       ╳
\&   output   1   0   3   2   5   4 ...
.Ve
.PP
This filter truncates the size of the plugin down to the alignment
determined by swab-bits (since operating on an unaligned tail would be
awkward).  If you need to round the image size up instead to access
the last few bytes, combine this filter with
\&\fBnbdkit\-truncate\-filter\fR\|(1); fortunately, sector-based disk images
are already suitably sized.
.SH "PARAMETERS"
.IX Header "PARAMETERS"
.IP "\fBswab\-bits=8\fR" 4
.IX Item "swab-bits=8"
This turns off the filter.
.IP "\fBswab\-bits=16\fR" 4
.IX Item "swab-bits=16"
This is the default setting which swaps pairs of bytes.  This is
suitable when reading and writing to Atari Falcon drives.
.IP "\fBswab\-bits=32\fR" 4
.IX Item "swab-bits=32"
This swaps the endianness of each 4 byte word in the disk, ie:
.Sp
.Vb 1
\&  input    0   1   2   3   4   5   6   7
\&
\& output    3   2   1   0   7   6   5   4
.Ve
.IP "\fBswab\-bits=64\fR" 4
.IX Item "swab-bits=64"
This swaps the endianness of each 8 byte word in the disk, ie:
.Sp
.Vb 1
\&  input    0   1   2   3   4   5   6   7
\&
\& output    7   6   5   4   3   2   1   0
.Ve
.Sp
This can be used to make \fBnbdkit\-pattern\-plugin\fR\|(1) little endian
instead of big endian.
.SH "FILES"
.IX Header "FILES"
.IP "\fI\f(CI$filterdir\fI/nbdkit\-swab\-filter.so\fR" 4
.IX Item "$filterdir/nbdkit-swab-filter.so"
The filter.
.Sp
Use \f(CW\*(C`nbdkit \-\-dump\-config\*(C'\fR to find the location of \f(CW$filterdir\fR.
.SH "VERSION"
.IX Header "VERSION"
\&\f(CW\*(C`nbdkit\-swab\-filter\*(C'\fR first appeared in nbdkit 1.22.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBnbdkit\fR\|(1),
\&\fBnbdkit\-file\-plugin\fR\|(1),
\&\fBnbdkit\-pattern\-plugin\fR\|(1),
\&\fBnbdkit\-filter\fR\|(3),
\&\fBnbdkit\-truncate\-filter\fR\|(1).
.SH "AUTHORS"
.IX Header "AUTHORS"
François Revol
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright (C) 2020 François Revol
.SH "LICENSE"
.IX Header "LICENSE"
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
.IP "\(bu" 4
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
.IP "\(bu" 4
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
.IP "\(bu" 4
Neither the name of Red Hat nor the names of its contributors may be
used to endorse or promote products derived from this software without
specific prior written permission.
.PP
\&\s-1THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS\s0 ''\s-1AS IS\s0'' \s-1AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES\s0 (\s-1INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES\s0; \s-1LOSS OF
USE, DATA, OR PROFITS\s0; \s-1OR BUSINESS INTERRUPTION\s0) \s-1HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT\s0 (\s-1INCLUDING NEGLIGENCE OR OTHERWISE\s0) \s-1ARISING IN ANY WAY OUT
OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.\s0