PS array of Big Endian words.

Question

For my own edification I am attempting to convert a java function into .net (PowerShell). The problem is the function barfs before anything is produced and I am wondering what needs to be changed to make it produce the intended Big Endian word array, from a raw string input.

This is the Java function.

function convert(input)
{
  var output = Array(input.length >> 2);
  for(var i = 0; i < output.length; i++)

    output[i] = 0;

  for(var i = 0; i < input.length * 8; i += 8)
    output[i>>5] |= (input.charCodeAt(i / 8) & 0xFF) << (24 - i % 32);
  return output;
}

This is my PowerShell port of the function above, which as I say doesn't.

function convert($inp)
{
    $s = ($inp.Length) -shr 2
    $output = [system.collections.arraylist]::new($s)
    for($i = 0; $i -le $output.Capacity; $i++)
    {
        $output[$i] = 0
        for($i = 0; $i -lt ($inp.length * 8); $i += 8)
        {
            $output[$i -shr 5] -ne (([byte][char]$inp[($i/8)]) -band 0xFF) -shl (24 - $i % 32)
        }
    }
    return $output
}

I am looking for a PowerShell code level solution only.

Answer 1

How about this?

https://www.powershellgallery.com/packages/Convert/0.2.0.5/Content/Public%5CConvertFrom-StringToByteArray.ps1

$string = "abc"
"Unicode format"
$string | format-hex -Encoding Unicode
$bytes = ConvertFrom-StringToByteArray -String $string -Encoding BigEndianUnicode 
""
"BigEndian format"
$bytes | format-hex 

Produces...

Unicode format


           00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

00000000   61 00 62 00 63 00                                a.b.c.          

BigEndian format


           Path:  

           00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

00000000   00 61 00 62 00 63                                .a.b.c          



PS C:\> 

Answer 2

If you can convince PowerShell to give you chunks of memory in raw format, you could create, say, unsigned integers of the appropriate number of bits, and reverse the bytes.

[UInt64]$uvalue = 0x0102030405060708;

[byte[]]$bytes = [System.BitConverter]::GetBytes($uvalue)
[byte[]]$rbytes = @()
# reverse the bytes (sorry, but there's not "Reverse" method for a byte array)
for ($i = $bytes.GetUpperBound(0); $i -ge $bytes.GetLowerBound(0); --$i){
    $rbytes += $bytes[$i]
}

$ convert the reversed bytes into the original type
$to = "To" + $uvalue.GetType()
$swapped  = [System.BitConverter]::$to($rbytes, 0)
"{0:X}" -f $swapped

The value displayed will have the leading zero suppressed. :-(