entropy.psm1
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#requires -version 6 using namespace System.Reflection.Emit Set-Alias -Name ent -Value Get-Entropy function Get-Entropy { [CmdletBinding()] param( [Parameter(Mandatory)] [ValidateNotNullOrEmpty()] [Byte[]]$Bytes ) process { if (!($e = $ExecutionContext.SessionState.PSVariable.Get('PSEntropy').Value)) { $dm = [DynamicMethod]::new('Entropy', [Double], [Type[]]([Byte[]])) $il = $dm.GetILGenerator() # variables $i = $il.DeclareLocal([Int32]) $rng = $il.DeclareLocal([Type]::GetType('System.Int32*')) $pi = $il.DeclareLocal([Type]::GetType('System.Int32*')) $ent = $il.DeclareLocal([Double]) $src = $il.DeclareLocal([Double]) # labels (four totally) $labels = (0..3).ForEach{ $il.DefineLabel() } # function body $il.Emit([OpCodes]::ldc_i4, 0x100) $il.Emit([OpCodes]::conv_u) $il.Emit([OpCodes]::ldc_i4_4) $il.Emit([OpCodes]::mul_ovf_un) $il.Emit([OpCodes]::localloc) $il.Emit([OpCodes]::stloc_1) $il.Emit([OpCodes]::ldloc_1) $il.Emit([OpCodes]::ldc_i4, 0x400) $il.Emit([OpCodes]::conv_i) $il.Emit([OpCodes]::add) $il.Emit([OpCodes]::stloc_2) $il.Emit([OpCodes]::ldc_r8, 0.0) $il.Emit([OpCodes]::stloc_3) $il.Emit([OpCodes]::ldarg_0) $il.Emit([OpCodes]::ldlen) $il.Emit([OpCodes]::conv_i4) $il.Emit([OpCodes]::dup) $il.Emit([OpCodes]::stloc_0) $il.Emit([OpCodes]::conv_r8) $il.Emit([OpCodes]::stloc_s, $src) $il.Emit([OpCodes]::br_s, $labels[0]) $il.MarkLabel($labels[1]) # 0x28 $il.Emit([OpCodes]::ldloc_1) $il.Emit([OpCodes]::ldarg_0) $il.Emit([OpCodes]::ldloc_0) $il.Emit([OpCodes]::ldelem_u1) $il.Emit([OpCodes]::conv_i) $il.Emit([OpCodes]::ldc_i4_4) $il.Emit([OpCodes]::mul) $il.Emit([OpCodes]::add) $il.Emit([OpCodes]::dup) $il.Emit([OpCodes]::ldind_i4) $il.Emit([OpCodes]::ldc_i4_1) $il.Emit([OpCodes]::add) $il.Emit([OpCodes]::stind_i4) $il.MarkLabel($labels[0]) # 0x35 $il.Emit([OpCodes]::ldloc_0) $il.Emit([OpCodes]::ldc_i4_1) $il.Emit([OpCodes]::sub) $il.Emit([OpCodes]::dup) $il.Emit([OpCodes]::stloc_0) $il.Emit([OpCodes]::ldc_i4_0) $il.Emit([OpCodes]::bge_s, $labels[1]) $il.Emit([OpCodes]::br_s, $labels[2]) $il.MarkLabel($labels[3]) # 0x3f $il.Emit([OpCodes]::ldloc_2) $il.Emit([OpCodes]::ldind_i4) $il.Emit([OpCodes]::ldc_i4_0) $il.Emit([OpCodes]::ble_s, $labels[2]) $il.Emit([OpCodes]::ldloc_3) $il.Emit([OpCodes]::ldloc_2) $il.Emit([OpCodes]::ldind_i4) $il.Emit([OpCodes]::conv_r8) $il.Emit([OpCodes]::ldloc_2) $il.Emit([OpCodes]::ldind_i4) $il.Emit([OpCodes]::conv_r8) $il.Emit([OpCodes]::ldloc_s, $src) $il.Emit([OpCodes]::div) $il.Emit([OpCodes]::ldc_r8, 2.) $il.Emit([OpCodes]::call, [Math].GetMethod('Log', [Type[]]([Double], [Double]))) $il.Emit([OpCodes]::mul) $il.Emit([OpCodes]::add) $il.Emit([OpCodes]::stloc_3) $il.MarkLabel($labels[2]) # 0x5f $il.Emit([OpCodes]::ldloc_2) $il.Emit([OpCodes]::ldc_i4_4) $il.Emit([OpCodes]::conv_i) $il.Emit([OpCodes]::sub) $il.Emit([OpCodes]::dup) $il.Emit([OpCodes]::stloc_2) $il.Emit([OpCodes]::ldloc_1) $il.Emit([OpCodes]::bge_un_s, $labels[3]) $il.Emit([OpCodes]::ldloc_3) $il.Emit([OpCodes]::neg) $il.Emit([OpCodes]::ldloc_s, $src) $il.Emit([OpCodes]::div) $il.Emit([OpCodes]::ret) Set-Variable -Name PSEntropy -Value ( $e = $dm.CreateDelegate([Func[[Byte[]], Double]]) ) -Option Constant -Scope Global -Visibility Private } '{0:F3}' -f $e.Invoke($Bytes) } } Export-ModuleMember -Alias ent -Function Get-Entropy |