#!/bin/bash
exit 1

DISK=/dev/mapper/36090a028407d6e2b2589a45cdb971489

# The name of the LVM archive to get data from
ARCHIVE=/etc/lvm/archive/xenvg_00685.vg

# Extract the first block of an lv to a file named part-$lv
getfirstblock () {
  lvname="$1"
  offset=$(grep -A16 $'\t'$lvname $ARCHIVE  | grep pv0 | cut -f 2 -d ,);
  if [ -z "$offset" ]; then echo "WARNING: LV not found";
  else
    echo "Extracting $lvname from offset $offset"
    dd if=$DISK of=part-$lvname bs=1M skip=$(( $offset * 8192 + 384 )) bs=512 count=1;
  fi
}

lvinfo () {
  perl -ne 'print if ( /^(\s*)'"$1"' \{/ ... /^$1\}/ )' $ARCHIVE
}
segment2 () {
  perl -ne 'print if ( /^(\s*)segment2 \{/ ... /^$1\}/ )'
}


# Generate a dd command to copy the LV data to /dev/xenvg/$lv
# Only works for single-segment LVs.
ddlv () {
  lvname="$1"
  if ! lvinfo $lvname | grep -q 'segment_count = 1'; then
    echo "# WARNING: LV $lvname has more than one segment, skipping" >&2
    return 1
  fi
  offset=$(lvinfo $lvname | perl -lne 'print $1 if (/"pv0", ([0-9]+)/)')
  length=$(lvinfo $lvname | perl -lne 'print $1 if (/extent_count = ([0-9]+)/)')

  if [ -z "$offset" ]; then
    echo "# WARNING: LV $lvname not found";
  else
    echo "# Extracting $lvname from offset $offset PEs with length $length PEs"
    echo dd if=$DISK of=/dev/xenvg/$lvname \
      skip=$(( $offset * 64 + 3 )) bs=64K count=$(( $length * 64 ))
  fi
}

# Generate a dd command to copy the LV data for the second segment.
ddlv2 () {
  lvname="$1"
  if ! lvinfo $lvname | grep -q 'segment_count = 2'; then
    echo "# WARNING: LV $lvname has other than two segments, skipping" >&2
    return 1
  fi
  offset=$(lvinfo $lvname | segment2 | perl -lne 'print $1 if (/"pv0", ([0-9]+)/)')
  length=$(lvinfo $lvname | segment2 | perl -lne 'print $1 if (/extent_count = ([0-9]+)/)')
  seek=$(lvinfo $lvname | segment2 | perl -lne 'print $1 if (/start_extent = ([0-9]+)/)')

  if [ -z "$offset" ]; then
    echo "# WARNING: LV $lvname not found";
  else
    echo "# Extracting $lvname segment 2 from offset $offset PEs with length $length PEs"
    echo dd if=$DISK of=/dev/xenvg/$lvname bs=64K \
      skip=$(($offset*64 + 3)) count=$(($length*64)) seek=$(($seek*64))
  fi
}