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|
#!/bin/sh
#
# Copyright (C) 2014 Codethink Limited
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#
# =*= License: GPL-2 =*=
# Receive a data stream describing a sparse file, and reproduce it,
# either to a named file or stdout.
#
# The data stream is simple: it's a sequence of DATA or HOLE records:
#
# DATA
# 123
# <123 bytes of binary data, NOT including newline at the end>
#
# HOLE
# 123
#
# This shell script can be executed over ssh (given to ssh as an arguemnt,
# with suitable escaping) on a different computer. This allows a large
# sparse file (e.g., disk image) be transferred quickly.
#
# This script should be called in one of the following ways:
#
# recv-hole file FILENAME
# recv-hole vbox FILENAME DISKSIZE
#
# In both cases, FILENAME is the pathname of the disk image on the
# receiving end. DISKSIZE is the size of the disk image in bytes. The
# first form is used when transferring a disk image to become an
# identical file on the receiving end.
#
# The second form is used when the disk image should be converted for
# use by VirtualBox. In this case, we want to avoid writing a
# temporary file on disk, and then calling the VirtualBox VBoxManage
# tool to do the conversion, since that would involve large amounts of
# unnecessary I/O and disk usage. Instead we pipe the file directly to
# VBoxManage, avoiding those issues. The piping is done here in this
# script, instead of in the caller, to make it easier to run things
# over ssh.
#
# However, since it's not possible seek in a Unix pipe, we have to
# explicitly write the zeroes into the pipe. This is not
# super-efficient, but the way to avoid that would be to avoid sending
# a sparse file, and do the conversion to a VDI on the sending end.
# That is out of scope for xfer-hole and recv-hole.
set -eu
die()
{
echo "$@" 1>&2
exit 1
}
recv_hole_to_file()
{
local n
read n
truncate --size "+$n" "$1"
}
recv_data_to_file()
{
local n
read n
local blocksize=1048576
local blocks=$(($n / $blocksize))
local extra=$(($n % $blocksize))
xfer_data_to_stdout "$blocksize" "$blocks" >> "$1"
xfer_data_to_stdout 1 "$extra" >> "$1"
}
recv_hole_to_stdout()
{
local n
read n
(echo "$n"; cat /dev/zero) | recv_data_to_stdout
}
recv_data_to_stdout()
{
local n
read n
local blocksize=1048576
local blocks=$(($n / $blocksize))
local extra=$(($n % $blocksize))
xfer_data_to_stdout "$blocksize" "$blocks"
xfer_data_to_stdout 1 "$extra"
}
xfer_data_to_stdout()
{
local log="$(mktemp)"
if ! dd "bs=$1" count="$2" iflag=fullblock status=noxfer 2> "$log"
then
cat "$log" 1>&2
rm -f "$log"
exit 1
else
rm -f "$log"
fi
}
type="$1"
case "$type" in
file)
output="$2"
truncate --size=0 "$output"
while read what
do
case "$what" in
DATA) recv_data_to_file "$output" ;;
HOLE) recv_hole_to_file "$output" ;;
*) die "Unknown instruction: $what" ;;
esac
done
;;
vbox)
output="$2"
disk_size="$3"
while read what
do
case "$what" in
DATA) recv_data_to_stdout ;;
HOLE) recv_hole_to_stdout ;;
*) die "Unknown instruction: $what" ;;
esac
done |
VBoxManage convertfromraw stdin "$output" "$disk_size"
;;
esac
|
