param(
  [Parameter(Mandatory = $true)] [int] $ProcessId,
  [Parameter(Mandatory = $true)] [UInt64] $Address,
  [Parameter(Mandatory = $true)] [int] $Length,
  [Parameter(Mandatory = $true)] [string] $OutputPath
)

Add-Type -TypeDefinition @'
using System;
using System.Runtime.InteropServices;

public static class ProcessMemoryDumpNative
{
    [DllImport("kernel32.dll", SetLastError = true)]
    public static extern IntPtr OpenProcess(uint access, bool inheritHandle, int processId);

    [DllImport("kernel32.dll", SetLastError = true)]
    public static extern bool ReadProcessMemory(IntPtr process, UIntPtr address, byte[] buffer,
                                                UIntPtr size, out UIntPtr bytesRead);

    [DllImport("kernel32.dll")]
    public static extern bool CloseHandle(IntPtr handle);
}
'@

$handle = [ProcessMemoryDumpNative]::OpenProcess(0x410, $false, $ProcessId)
if ($handle -eq [IntPtr]::Zero) {
  throw "OpenProcess failed: $([Runtime.InteropServices.Marshal]::GetLastWin32Error())"
}

try {
  $buffer = [byte[]]::new($Length)
  $bytesRead = [UIntPtr]::Zero
  if (-not [ProcessMemoryDumpNative]::ReadProcessMemory(
      $handle, [UIntPtr]::new($Address), $buffer, [UIntPtr]::new([UInt64]$Length), [ref]$bytesRead)) {
    throw "ReadProcessMemory failed: $([Runtime.InteropServices.Marshal]::GetLastWin32Error())"
  }
  if ($bytesRead.ToUInt64() -ne [UInt64]$Length) {
    throw "Short read: requested $Length bytes, got $($bytesRead.ToUInt64())"
  }
  [IO.File]::WriteAllBytes((Join-Path (Get-Location) $OutputPath), $buffer)
}
finally {
  [void][ProcessMemoryDumpNative]::CloseHandle($handle)
}