Private/ConvertFrom-Base64Url.ps1
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function ConvertFrom-Base64Url { [CmdletBinding()] [OutputType('System.String', ParameterSetName='String')] [OutputType('System.Byte[]', ParameterSetName='Bytes')] param( [Parameter(ParameterSetName='Bytes',Mandatory,Position=0,ValueFromPipeline)] [Parameter(ParameterSetName='String',Mandatory,Position=0,ValueFromPipeline)] [AllowEmptyString()] [string]$Base64Url, [Parameter(ParameterSetName='Bytes',Mandatory)] [switch]$AsByteArray ) Process { # short circuit on empty strings if ($Base64Url -eq [string]::Empty) { return [string]::Empty } # put the standard unsafe characters back $s = $Base64Url.Replace('-', '+').Replace('_', '/') # put the padding back switch ($s.Length % 4) { 0 { break; } # no padding needed 2 { $s += '=='; break; } # two pad chars 3 { $s += '='; break; } # one pad char default { throw "Invalid Base64Url string" } } # convert it using standard base64 stuff if ($AsByteArray) { return [Convert]::FromBase64String($s) } else { return [Text.Encoding]::UTF8.GetString([Convert]::FromBase64String($s)) } } } |