Converts an indirect string to the actual string value

ConvertFrom-IndirectString.ps1

# Copyright: (c) 2020, Jordan Borean (@jborean93) <jborean93@gmail.com>
# MIT License (see LICENSE or https://opensource.org/licenses/MIT)

Function ConvertFrom-IndirectString {
    <#
    .SYNOPSIS
    Converts a indirect string identifier to the actual string value it represents.

    .PARAMETER IndirectString
    The indirect string that begins with '@' to convert to the proper string value.

    .EXAMPLE
    An example

    .NOTES
    An indirect string can be provided in several forms:

    File name and resource ID

        '@filename,resource'


    File name and resource ID with a version modifier

        '@filename,resource;v2'


    PRI file path and resource ID

        '@{PRIFilepath?resource}'


    Package name and resource ID

        '@{PackageFullName?resource}'
    #>
    [CmdletBinding()]
    param (
        [Parameter(Mandatory=$true, ValueFromPipeline=$true)]
        [String]
        $IndirectString
    )

    begin {
        Add-Type -Namespace Shlwapi -Name NativeMethods -UsingNamespace System.Text -MemberDefinition @'
[DllImport("Shlwapi.dll", CharSet = CharSet.Unicode)]
public static extern int SHLoadIndirectString(
    string pszSource,
    StringBuilder pszOutBuf,
    int cchOutBuf,
    IntPtr ppvReserved);
'@
    }

    process {
        $buffer = [System.Text.StringBuilder]::new()
        $res = [Shlwapi.NativeMethods]::SHLoadIndirectString(
            $IndirectString,
            $buffer,
            $buffer.MaxCapacity,
            [IntPtr]::Zero
        )
        if ($res -ne 0) {
            $msg = "Failed to convert indirect string '{0}': HRESULT 0x{1:X8}" -f ($IndirectString, $res)
            Write-Error -Message $msg
            return
        }

        $buffer.ToString()
    }
}