nbdkit-swab-filter - Man Page

nbdkit filter for swapping byte order

Synopsis

 nbdkit --filter=swab PLUGIN [PLUGIN-ARGS...] [swab-bits=8|16|32|64]

Description

nbdkit-swab-filter is a filter for nbdkit(1) which swaps bytes in the underlying plugin.

One use for this is to read disk images which were formatted on the Atari Falcon, where the IDE controller is wired in reverse order.

Example

Swap bytes from a disk image

 nbdkit --filter=swab file file=disk.img

The above command serves the disk image disk.img, swapping even and odd bytes:

 disk.img   0   1   2   3   4   5 ...
              ╳       ╳       ╳
   output   1   0   3   2   5   4 ...

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 nbdkit-truncate-filter(1); fortunately, sector-based disk images are already suitably sized.

Parameters

swab-bits=8

This turns off the filter.

swab-bits=16

This is the default setting which swaps pairs of bytes.  This is suitable when reading and writing to Atari Falcon drives.

swab-bits=32

This swaps the endianness of each 4 byte word in the disk, ie:

  input    0   1   2   3   4   5   6   7

 output    3   2   1   0   7   6   5   4
swab-bits=64

This swaps the endianness of each 8 byte word in the disk, ie:

  input    0   1   2   3   4   5   6   7

 output    7   6   5   4   3   2   1   0

This can be used to make nbdkit-pattern-plugin(1) little endian instead of big endian.

Files

$filterdir/nbdkit-swab-filter.so

The filter.

Use nbdkit --dump-config to find the location of $filterdir.

Version

nbdkit-swab-filter first appeared in nbdkit 1.22.

See Also

nbdkit(1), nbdkit-file-plugin(1), nbdkit-pattern-plugin(1), nbdkit-filter(3), nbdkit-truncate-filter(1).

Authors

François Revol

License

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND 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 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Referenced By

nbdkit(1), nbdkit-filter(3), nbdkit-pattern-plugin(1), nbdkit-release-notes-1.22(1).

2021-11-25 nbdkit-1.29.7