Powershell ipcalc cidrsubnet helper

PSIPCalc.ps1

Function Convert-IpAddressStringToBinString {
	[CmdletBinding()]
	param(
		[Parameter(Mandatory)]
		[string]$IpAddress
	)

	$IpAddressFullBin = ""
	foreach ($octet in $IPAddress.Split(".")) {
		# make sure this is a valid byte octet
		$v = [convert]::ToInt32($octet)
		if ( ($v -lt 0) -or ($v -gt 255)) {
			throw "Invalid ip address octet"
		}
		$s = [convert]::ToString($octet, 2)
		$IpAddressFullBin += $s.PadLeft(8, "0")
	}
	$IpAddressFullBin
}

Function Convert-IpAddressBinStringToString {
	[CmdletBinding()]
	param(
		[Parameter(Mandatory)]
		[string]$IpAddressBinString
	)

	@( 0, 8, 16, 24 ) | ForEach-Object {
		$o = $IpAddressBinString.substring($_, 8)
		"{0}" -f [convert]::ToInt32($o,2)
	} | Join-String -Separator "."
}

Function Test-CidrValid {
	<#

	.SYNOPSIS
	Checks if a given CIDR string is valid

	#>
	return $false
}

Function Measure-Cidr {
	[CmdletBinding()]
	param (
		[Parameter(Mandatory=$true)]
		[string]$Prefix,

		[Parameter(Mandatory=$true)]
		[byte]$NewBits
	)

	$m = $Prefix -match "^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\/[0-9]{1,2}$"
	if (-not $m) {
		throw "Prefix not a valid CIDR"
	}

	$s = $Prefix.split("/")

	$IpCidr = $s[0]
	$NetmaskBits = [convert]::ToUint16($s[1])
	if ($NetmaskBits -gt 32) {
		throw "Prefix not a valid CIDR, invalid netmask"
	}

	if ($NewBits -gt 32) {
		throw "NewBits must be <= 32"
	}

	if ($NewBits -lt $NetMaskBits) {
		throw "NewBits must be larger that netmask of prefix"
	}

	$d = [math]::pow(2, $NewBits - $NetmaskBits)

	$res = New-Object PSCustomObject @{
		Prefix = $Prefix
		IP = $IpCidr
		NetmaskBits = $NetmaskBits
		NumberOfNetworks = $d
	}
	$res
}

Function Get-CidrSubnets {
	<#
	.SYNPOSIS

	.EXAMPLE

	#>

	[CmdletBinding()]
	param (
		[Parameter(Mandatory=$true)]
		[string]$Prefix,

		[Parameter(Mandatory=$true)]
		[byte]$NewBits
	)

	$m = Measure-Cidr -Prefix $Prefix -NewBits $NewBits
	for ($i = 0; $i -lt $m.NumberOfNetworks; $i++) {
		Split-CidrSubnet -Prefix $Prefix -NewBits $NewBits -NetNum $i
	}
}

Function Split-CidrSubnet {
	<#

	.EXAMPLE
	> Update-CidrSubnet -Prefix "192.168.10.0/24" -NewBits 26 -NetNum 3
	192.168.10.192

	#>

	[CmdletBinding()]
	param (
		[Parameter(Mandatory=$true)]
		[string]$Prefix,

		[Parameter(Mandatory=$true)]
		[byte]$NewBits,

		[Parameter(Mandatory=$true)]
		[byte]$NetNum
	)

	$m = Measure-Cidr -Prefix $Prefix -NewBits $NewBits

	$f = Convert-IpAddressStringToBinString $m.IP

	# given the $NewBits parameter, determine the size of the new bits
	# begin patched in. bin-format the $NetNum to the length of bits to replace
	$d = $NewBits - $m.NetmaskBits
	Write-Verbose ("d: {0}" -f $d)

	$maxNets = $m.NumberOfNetworks
	Write-Verbose ("NetNum: {0}, maxNets: {1}" -f $NetNum, $MaxNets)
 	if ($NetNum -ge $maxNets) {
		throw ("NetNum must be <={0}" -f $maxNets)
	}

	$patch = ("{0}" -f [convert]::ToString($NetNum,2)).PadLeft($d,"0")
	if ($d -eq 0) {
		# if the same subnet length is requested, the patch is empty
		$patch = ""
	}
	Write-Verbose ("f: {0}" -f $f)
	Write-Verbose ("patch: {0}" -f $patch)

	# combine the old net-part, patch and rest into new bitmask
	$fPatched = $f.substring(0,$m.NetMaskBits) + $patch + $f.substring($NewBits, 32-$NewBits)
	Write-Verbose ("Patch: {0} l:{1}" -f $fPatched, $fPatched.Length)
	if ($fPatched.Length -ne 32) {
		throw "Internal error"
	}

	# convert bitmask back into octet IP string
	$result = Convert-IpAddressBinStringToString $fPatched
	Write-Verbose ("RES: {0}" -f $result)

	$result
}