Base64 Decode in Powershell

Decode-Base64.ps1

function Decode-Base64Ascii ($data) {
    $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
    $ss = "[^" + $chars + "=]"
    $data = $data -replace $ss, ""

    $pad = ""
    $r = ""
    if (($data[$data.Length - 1]) -eq '=') {
        if (($data[$data.Length - 2]) -eq '=') {
            $pad = "AA"
        } else {
            $pad = "A"
        }
    }

    $data = $data.Substring(0, $data.Length - $pad.Length) + $pad

    for($c = 0; $c -lt $data.Length ; $c += 4) {
        $n = ($chars.IndexOf($data[$c]) -shl 18) `
            +  ($chars.IndexOf($data[$c + 1]) -shl 12) `
            +  ($chars.IndexOf($data[$c + 2]) -shl 6) `
            +  ($chars.IndexOf($data[$c + 3]))

        $r += "" + [char](($n -shr 16) -band 0xff)
        $r += "" + [char](($n -shr 8) -band 0xff)
        $r += "" + [char]($n -band 0xff)
    }

    return $r.Substring(0, $r.Length - $pad.Length)
}

function Decode-Base64 ($data) {
    $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
    $ss = "[^" + $chars + "=]"
    $data = $data -replace $ss, ""

    $pad = ""
    [byte[]]$r = @()
    if (($data[$data.Length - 1]) -eq '=') {
        if (($data[$data.Length - 2]) -eq '=') {
            $pad = "AA"
        } else {
            $pad = "A"
        }
    }

    $data = $data.Substring(0, $data.Length - $pad.Length) + $pad

    for($c = 0; $c -lt $data.Length ; $c += 4) {
        $n = ($chars.IndexOf($data[$c]) -shl 18) `
            +  ($chars.IndexOf($data[$c + 1]) -shl 12) `
            +  ($chars.IndexOf($data[$c + 2]) -shl 6) `
            +  ($chars.IndexOf($data[$c + 3]))

        $r += [byte](($n -shr 16) -band 0xff)
        $r += [byte](($n -shr 8) -band 0xff)
        $r += [byte]($n -band 0xff)
    }

    $dif = $r.Length - $pad.Length
    return $r[0..$dif]
}

# Set-Content -Path $Env:Temp\foo.bin -Encoding Byte -Value $someEncodedValue