Openwrt/openwrt/package/base-files/default/etc/functions.sh

#!/bin/sh
. /etc/nvram.sh

alias debug=${DEBUG:-:}

# valid interface?
if_valid () (
  ifconfig "$1" >&- 2>&- ||
  [ "${1%%[0-9]}" = "br" ] ||
  { debug "# missing interface '$1' ignored"; false; }
)

hotplug_dev() {
	env -i ACTION=$1 INTERFACE=$2 /sbin/hotplug net
}

bitcount () {
  local c=$1
  echo $((
  c=((c>> 1)&0x55555555)+(c&0x55555555),
  c=((c>> 2)&0x33333333)+(c&0x33333333),
  c=((c>> 4)&0x0f0f0f0f)+(c&0x0f0f0f0f),
  c=((c>> 8)&0x00ff00ff)+(c&0x00ff00ff),
  c=((c>>16)&0x0000ffff)+(c&0x0000ffff)
  ))
}

valid_netmask () {
  return $((-($1)&~$1))
}

ip2int () (
  set $(echo $1 | tr '\.' ' ')
  echo $(($1<<24|$2<<16|$3<<8|$4))
)

int2ip () {
  echo $(($1>>24&255)).$(($1>>16&255)).$(($1>>8&255)).$(($1&255))
}