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function Get-FileHash
{
[CmdletBinding(DefaultParameterSetName = "Path")]
param(
[Parameter(Mandatory=$true, ParameterSetName="Path", Position = 0)]
[System.String[]]
$Path,
[Parameter(Mandatory=$true, ParameterSetName="LiteralPath", ValueFromPipelineByPropertyName = $true)]
[Alias("PSPath")]
[System.String[]]
$LiteralPath,
[Parameter(Mandatory=$true, ParameterSetName="Stream")]
[System.IO.Stream]
$InputStream,
[ValidateSet("SHA1", "SHA256", "SHA384", "SHA512", "MACTripleDES", "MD5", "RIPEMD160")]
[System.String]
$Algorithm="SHA256"
)
begin
{
# Construct the strongly-typed crypto object
$hasher = [System.Security.Cryptography.HashAlgorithm]::Create($Algorithm)
}
process
{
if($PSCmdlet.ParameterSetName -eq "Stream")
{
GetStreamHash -InputStream $InputStream -RelatedPath $null -Hasher $hasher
}
else
{
$pathsToProcess = @()
if($PSCmdlet.ParameterSetName -eq "LiteralPath")
{
$pathsToProcess += Resolve-Path -LiteralPath $LiteralPath | Foreach-Object { $_.ProviderPath }
}
if($PSCmdlet.ParameterSetName -eq "Path")
{
$pathsToProcess += Resolve-Path $Path | Foreach-Object { $_.ProviderPath }
}
foreach($filePath in $pathsToProcess)
{
if(Test-Path -LiteralPath $filePath -PathType Container)
{
continue
}
try
{
# Read the file specified in $FilePath as a Byte array
[system.io.stream]$stream = [system.io.file]::OpenRead($filePath)
GetStreamHash -InputStream $stream -RelatedPath $filePath -Hasher $hasher
}
catch [Exception]
{
$errorMessage = 'FileReadError {0}:{1}' -f $FilePath, $_
Write-Error -Message $errorMessage -Category ReadError -ErrorId "FileReadError" -TargetObject $FilePath
return
}
finally
{
if($stream)
{
$stream.Close()
}
}
}
}
}
}
function GetStreamHash
{
param(
[System.IO.Stream]
$InputStream,
[System.String]
$RelatedPath,
[System.Security.Cryptography.HashAlgorithm]
$Hasher)
# Compute file-hash using the crypto object
[Byte[]] $computedHash = $Hasher.ComputeHash($InputStream)
[string] $hash = [BitConverter]::ToString($computedHash) -replace '-',''
if ($RelatedPath -eq $null)
{
$retVal = [PSCustomObject] @{
Algorithm = $Algorithm.ToUpperInvariant()
Hash = $hash
}
$retVal.psobject.TypeNames.Insert(0, "Microsoft.Powershell.Utility.FileHash")
$retVal
}
else
{
$retVal = [PSCustomObject] @{
Algorithm = $Algorithm.ToUpperInvariant()
Hash = $hash
Path = $RelatedPath
}
$retVal.psobject.TypeNames.Insert(0, "Microsoft.Powershell.Utility.FileHash")
$retVal
}
}
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