#autoload
local tmp
local dev_tmp dpath_tmp mp_tmp mline

case "$OSTYPE" in
linux*|irix*)
  tmp=( "${(@f)$(< /etc/mtab)}" )
  dev_tmp=( "${(@)${(@)tmp%% *}:#none}" )
  mp_tmp=( "${(@)${(@)tmp#* }%% *}" )
  ;;
freebsd*|dragonfly*)
  /sbin/mount | while read mline; do
    dev_tmp+=( $mline[(w)1] )
    mp_tmp+=( $mline[(w)3] )
  done
;;
darwin*)
  tmp=( "${(@f)$(/sbin/mount)}" )
  dev_tmp=( "${(@)${(@)tmp%% *}:#map}" )
  mp_tmp=( "${(@)${(@)tmp#* on }%% \(*}" )
  ;;
*)
  /sbin/mount | while read mline; do
    mp_tmp+=( $mline[(w)1] )
    dev_tmp+=( $mline[(w)3] )
  done
  ;;
esac

local MATCH MBEGIN MEND
# The complicated substitution for mount point names is required because
# characters in /etc/mtab that might confuse programs reading the names
# are encoded as exactly 3 octal digits, like for example \040 for space.
# The cleaner-looking ${(g::)mp_tmp} might consume too many digits.
# Both mp_tmp and dev_tmp are derived from /etc/mtab or "mount" output.
mp_tmp=("${(@)mp_tmp//(#m)\\[0-7](#c3)/${(#)$(( 8#${MATCH[2,-1]} ))}}")
dev_tmp=("${(@)dev_tmp//(#m)\\[0-7](#c3)/${(#)$(( 8#${MATCH[2,-1]} ))}}")
dpath_tmp=( "${(@M)dev_tmp:#/*}" )
dev_tmp=( "${(@)dev_tmp:#/*}" )

_alternative \
  'device-labels:device label:compadd -a dev_tmp' \
  'device-paths: device path:_canonical_paths -A dpath_tmp -N -M "r:|/=* r:|=*" device-paths device\ path' \
  'directories:mount point:_canonical_paths -A mp_tmp -N -M "r:|/=* r:|=*" directories mount\ point'