ConvertTo-BinaryString.ps1

# ConvertTo-BinaryString.ps1
# Written by Bill Stewart (bstewart AT iname.com)

# I wrote this for two main reasons...
# * "b" format specifier not universally available
# * [Convert]::ToString() doesn't support UInt64 values

<#
.SYNOPSIS
Converts an unsigned integer to a binary string.

.DESCRIPTION
Converts an unsigned integer to a binary string.

.PARAMETER Value
Specifies the unsigned integer value.

.PARAMETER Width
Specifies the minimum width of the output string. This parmameter must be in the range 1 through 64.

.PARAMETER LeadingZeros
Specifies that the binary string should include leading zeros.
#>

param(
  [Parameter(Position = 0,Mandatory,ValueFromPipeline)]
  [UInt64]
  $Value,

  [Parameter(Position = 1)]
  [ValidateRange(1,64)]
  [Int]
  $Width = 1,

  [Switch]
  $LeadingZeros
)

# Zero is zero...
if ( $Value -eq 0 ) {
  ('0',('0' * $Width))[$LeadingZeros.IsPresent]
  return
}

# Outputs the number of bits in the specified value
function Get-BitWidth {
  [CmdletBinding()]
  param(
    [Parameter(Position = 0,Mandatory)]
    [UInt64]
    $value
  )
  $width = 1
  while ( $value -gt 0 ) {
    $value = $value -shr 1
    if ( $value -gt 0 ) { $width++ }
  }
  $width
}

# Get number of bits in the value
$valueWidth = Get-BitWidth $Value

# Widen if specified width too small
$Width = ($Width,$valueWidth)[$valueWidth -gt $Width]

# Populate character array with set bits
$chars = New-Object Char[] $Width
for ( $i = $Width - 1; $i -ge 0; $i-- ) {
  $chars[$i] = ('0','1')[$Value -band 1]
  $Value = $Value -shr 1
}

if ( $LeadingZeros ) {
  $chars -join ''
}
else {
  $chars[$chars.IndexOf([Char] '1')..$chars.GetUpperBound(0)] -join ''
}