#!/bin/bash
exit 1

SOURCE=/dev/mapper/36090a028407d6e2b2589a45cdb971489

# The name of the LVM archive to get data from
ARCHIVE=/etc/lvm/archive/xenvg_01514.vg

lvmextractsection () {
  perl -ne 'print if ( /^(\s*)'"$1"' [\{[]/ ... /^$1[\}\]]/ )'
}
lvmextractint () {
  perl -lne 'print $1 if (/'"$1"' = ([0-9]+)/)'
}

# 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 $offset"
    dd if=$SOURCE 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\}/ )'
}

# Extract the first block of an lv to a file named part-$lv
getfirstblock () {
  lvname="$1"
  lvinfo=$(lvinfo "$lvname")
  firststripe=$(echo "$lvinfo" | lvmextractsection 'stripes =' | tail -n +2 | head -n 1)
  offset=$(echo "$firststripe" | cut -f 2 -d ,);
  if [ -z "$offset" ]; then echo "WARNING: LV $lvname not found";
  else
    pvname=$(echo "$firststripe" | perl -pe 's/.*"([^"]+)".*/\1/')
    pvdevice=$(cat $ARCHIVE | lvmextractsection "$pvname" | perl -lne 'print $1 if (/device = "(.+)"/)')
    pe_start=$(cat $ARCHIVE | lvmextractsection "$pvname" | lvmextractint "pe_start")
    echo "Extracting $lvname from PE offset $offset on $pvname ($pvdevice)"
    dd if=$pvdevice of=part-$lvname bs=1M skip=$(( $offset * 8192 + $pe_start )) bs=512 count=1;
  fi
}

if /bin/false; then
# Usage:
mkdir new
mkdir old
(cd old; for i in $(listlvs); do getfirstblock "$i"; done)
(cd new; for i in $(listlvs); do dd if=/dev/xenvg/$i of=part-$i bs=512 count=1; done)

diff -u <(cd old && sfdisk -l * 2>/dev/null) <(cd new && sfdisk -l * 2>/dev/null)
(cd old && md5sum *) | (cd new && md5sum -c) | grep -v OK
# end usage
fi

# Get a list of LVs in an LVM archive
listlvs () {
  cat $ARCHIVE | lvmextractsection "logical_volumes" | tail -n +2 | perl -lne 'if (/^(\s+)\S+\s+{/) { $indent ||= $1; }; print "$1" if /^$indent(\S+)\s+{/;'
}


# 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 $length PEs"
    echo dd if=$SOURCE 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 $length PEs"
    echo dd if=$SOURCE of=/dev/xenvg/$lvname bs=64K \
      skip=$(($offset*64 + 3)) count=$(($length*64)) seek=$(($seek*64))
  fi
}