Get-HashValues-New.ps1

Get-HashValues-New.ps1

# Start Hash value function
Function Get-HashValues {
[CmdletBinding()]
Param(
      [Parameter(Mandatory=$True,ValueFromPipeline=$True)]
      [ValidateScript({If ((-Not (Test-Path -Path "$_")) -and ((Get-Item -Path "$_").Length -ne 0)) {  } return $true })]
      [String]$FilePath,
      [Parameter(Mandatory=$False,ValueFromPipeline=$True)]
      [Int]$SByte = 0,
      [Parameter(Mandatory=$False,ValueFromPipeline=$True)]
      [Int]$Bytes
      )

Begin {
       $Script:HashValues = $NULL
       $Script:HashValues = [ordered]@{"Name"="";"Size"="";"CRC32"="";"MD5"="";"SHA1"=""}  # Removed: ;"SHA256"=""

       If (!($Bytes)) {
                       [String]$HashValues.Name = "$($FilePath | Split-Path -Leaf)"
                       [Int]$HashValues.Size = $((Get-Item $FilePath).Length)
                       } Else {
                               [String]$HashValues.Name = "bootsec"
                               [Int]$HashValues.Size = $($Bytes)
                               }
       
       # Setup CRC32 function
Add-Type -TypeDefinition @"
		using System;
		using System.Diagnostics;
		using System.Runtime.InteropServices;
		using System.Security.Principal;
	
		public static class CRC32
		{
			[DllImport("ntdll.dll")]
			public static extern UInt32 RtlComputeCrc32(
				UInt32 InitialCrc,
				Byte[] Buffer,
				Int32 Length);
		}
"@

       # Setup Remaining Hash Collections
       $MD5    = New-Object -TypeName System.Security.Cryptography.MD5CryptoServiceProvider
       $SHA1   = New-Object -TypeName System.Security.Cryptography.SHA1CryptoServiceProvider
       # $SHA256 = New-Object -TypeName System.Security.Cryptography.SHA256CryptoServiceProvider

       $InputObject1   = [System.IO.File]::Open("$($FilePath)",[System.IO.Filemode]::Open, [System.IO.FileAccess]::Read)

       $Buffer = [System.Byte[]]::new($($HashValues.Size))

       $InputObject1.Position = 0
       
       [void]$InputObject1.Read($Buffer,$SByte,$HashValues.Size)
       
       }
Process {
         
         Foreach ($i in $($HashValues.Keys.Clone())) {

         Switch ($i) {
          "CRC32" {
                   Try {
                        $HashValues[$i] = ('{0:X}' -f [CRC32]::RtlComputeCrc32(0, $Buffer, $HashValues.Size)).PadLeft(8,'0')
                        } Catch { $HashValues[$i] = "Error" }
                   }
            "MD5" {
                   $HashValues[$i] = ([System.BitConverter]::ToString($MD5.ComputeHash($Buffer))).Replace("-","")
                   }
           "SHA1" {
                   $HashValues[$i] = ([System.BitConverter]::ToString($SHA1.ComputeHash($Buffer))).Replace("-","")
                   }
#         "SHA256" {
#                   $HashValues[$i] = ([System.BitConverter]::ToString($SHA256.ComputeHash($Buffer))).Replace("-","")
#                   }
         }

         }

         }
End {
     $InputObject1.Close()
     $InputObject1.Dispose()

     [System.GC]::Collect()
     [GC]::Collect()
     [GC]::WaitForPendingFinalizers()
     }

}
# End Hash value function

This script passes "$HashValues" to another script with all file and hash data for use in your script.

***** Warning: This has a high risk of crashing Powershell until I add size validation for "$SByte" and "$Bytes" *****