R.I.P. needless PowerShell script to extract a resource from Windows EXE

extract.ps1

function SeekPos
{
  param([System.IO.BinaryReader]$br, $offset)
  $br.BaseStream.Seek($offset, [System.IO.SeekOrigin]::Begin)
}

function SeekDiff
{
  param([System.IO.BinaryReader]$br, $offset)
  $br.BaseStream.Seek($offset, [System.IO.SeekOrigin]::Current)
}

$br = [System.IO.BinaryReader]::new(
        [System.IO.FileStream]::new(
          "$(Get-Location)\calibre-portable-installer-6.24.0.exe",
          [System.IO.FileMode]::Open,
          [System.IO.FileAccess]::Read)
      )

SeekPos $br 0x3c
$peOffset = $br.ReadInt16()
SeekPos $br $peOffset
if ($br.ReadUInt32() -eq 0x00004550) { # PE\x00\x00
  SeekDiff $br 2
  $sections = $br.ReadUInt16()
  Write-Host Sections $sections
  SeekDiff $br 16
  $peOpt = $br.ReadUInt16()
  if ($peOpt -eq 0x20b) {
    SeekPos $br ($peOffset + 4 + 20 + 108)
    $rvas = $br.ReadUInt32()
    Write-Host $rvas
    SeekDiff $br ($rvas * 8)
    $sectionHeader = $br.BaseStream.Position
    foreach ($_ in 1..$sections) {
      SeekPos $br ($sectionHeader + ($_ - 1) * 40)
      $name1 = $br.ReadUInt32()
      $name2 = $br.ReadUInt32()
      if (($name1 -eq 0x7273722e) -and ($name2 -eq 0x00000063)) { # .rsrc
        SeekDiff $br 4
        $rsrcRva = $br.ReadUInt32()
        $rsrcSize = $br.ReadUInt32()
        $rsrcOffset = $br.ReadUInt32()
        Write-Host $rsrcRva $rsrcSize $rsrcOffset
        SeekPos $br ($rsrcOffset + 12)
        $numName = $br.ReadUInt16()
        if ($numName -eq 1) {
          SeekDiff $br 2
          $nameOffset = $br.ReadUInt32()
          $sdOffset = $br.ReadUInt32()

          Write-Host $nameOffset $sdOffset
          SeekPos $br ($rsrcOffset + ($sdOffset -band 0x7fffffff) + 12)
          $numName = $br.ReadUInt16()
          if ($numName -eq 1) {
            SeekDiff $br 2
            $nameOffset = $br.ReadUInt32()
            $sdOffset = $br.ReadUInt32()

            SeekPos $br ($rsrcOffset + ($sdOffset -band 0x7fffffff) + 12)
            $numName = $br.ReadUInt16()
            $numId = $br.ReadUInt16()
            if ($numName -eq 0 -and $numId -eq 1) {
              $id = $br.ReadUInt32()
              $entryOffset = $br.ReadUInt32()

              SeekPos $br ($rsrcOffset + $entryOffset)
              $rvaOffset = $br.ReadUInt32()
              $actualSize = $br.ReadUInt32()
              $actualOffset = $rvaOffset + $rsrcOffset - $rsrcRva
              Write-Host $actualOffset $actualSize
            }
          }
        }
      }
    }
  }
  if(-not($null -eq $actualOffset)) {
    # 18 = lzip header(6) + lzip footer(12), 13 = lzma header
    $buffer = [System.Array]::CreateInstance([byte], $actualSize - 18 + 13)
    SeekPos $br ($actualOffset + 4) # skip lzip signature (4bytes)
    if(-not ($br.ReadByte() -eq 0)) { throw "lzip version is not 0" }
    $dictBits = $br.ReadByte()
    $bytesToRead = $actualSize - 18
    $bytesRead = 13
    $bufSize = 4*1024*1024
    while ($bytesToRead -gt 0) {
      if ($bytesToRead -gt $bufSize) {
        $readLength = $bufSize
      } else {
        $readLength = $bytesToRead
      }
      $ret = $br.BaseStream.Read($buffer, $bytesRead, $readLength)
      if($ret -eq 0) { break }
      $bytesRead += $ret
      $bytesToRead -= $ret
    }
    $crc = $br.ReadUInt32()
    $length = $br.ReadUInt64()
    $buffer[0] = 0x5d # =93=(pb*5+lp)*9+lc (pb=2,lp=0,lc=3)
    $dictSize = [Math]::pow(2, $dictBits)
    foreach ($_ in 0..3) {
      $buffer[1+$_] = ($dictSize -shr (8 * $_)) -band 0xFF
    }
    foreach ($_ in 0..7) {
      $buffer[5+$_] = ($length -shr (8 * $_)) -band 0xFF
    }
    [System.IO.File]::WriteAllBytes("$(Get-Location)\temp.zip.lzma", $buffer);
  }
}

$br.Dispose()
$br.Close()