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# Example Python plugin.
#
# This example can be freely used for any purpose.
# Run it from the build directory like this:
#
# ./nbdkit -f -v python ./plugins/python/examples/ramdisk.py test1=foo
#
# Or run it after installing nbdkit like this:
#
# nbdkit -f -v python ./plugins/python/examples/ramdisk.py test1=foo
#
# The -f -v arguments are optional. They cause the server to stay in
# the foreground and print debugging, which is useful when testing.
#
# You can connect to the server using guestfish or qemu, eg:
#
# guestfish --format=raw -a nbd://localhost
# ><fs> run
# ><fs> part-disk /dev/sda mbr
# ><fs> mkfs ext2 /dev/sda1
# ><fs> list-filesystems
# ><fs> mount /dev/sda1 /
# ><fs> [etc]
import nbdkit
import errno
# This is the string used to store the emulated disk (initially all
# zero bytes). There is one disk per nbdkit instance, so if you
# reconnect to the same server you should see the same disk. You
# could also put this into the handle, so there would be a fresh disk
# per handle.
disk = bytearray(1024 * 1024)
# There are several variants of the API. nbdkit will use this
# constant to determine which one you want to use. This is the latest
# version at the time this example was written.
API_VERSION = 2
# This just prints the extra command line parameters, but real plugins
# should parse them and reject any unknown parameters.
def config(key, value):
nbdkit.debug("ignored parameter %s=%s" % (key, value))
def open(readonly):
nbdkit.debug("open: readonly=%d, tls=%r" % (readonly, nbdkit.is_tls()))
# You can return any Python object from open (even None), and the
# same object will be passed as the first arg 'h' to the other
# callbacks below. To return an error from this method you must
# throw an exception.
return 1
def get_size(h):
return len(disk)
def pread(h, buf, offset, flags):
end = offset + len(buf)
buf[:] = disk[offset:end]
# or if reading from a file you can use:
# f.readinto(buf)
def pwrite(h, buf, offset, flags):
end = offset + len(buf)
disk[offset:end] = buf
def zero(h, count, offset, flags):
if flags & nbdkit.FLAG_MAY_TRIM:
disk[offset:offset+count] = bytearray(count)
else:
nbdkit.set_error(errno.EOPNOTSUPP)
raise Exception
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