add basic single-file PS base script

sri.ps1

@@ -0,0 +1,48 @@
+param (
+    # Specifies a path to one or more locations.
+    [Parameter(Mandatory=$true,
+               HelpMessage="Path to resource for which to generate integrity hash.")]
+    [Alias("path", "resource")]
+    [ValidateNotNullOrEmpty()]
+    [string]
+    $filename,
+
+    [Parameter(HelpMessage="Desired hash algorithm.")]
+    [Alias("algorithm")]
+    [ValidateSet('sha256', 'sha384', 'sha512')]
+    [string]
+    $hashAlgo='sha384'
+)
+
+function hashSHA($type) {
+    switch($type) {
+        'sha256' { return [System.Security.Cryptography.SHA256]::Create() }
+        'sha384' { return [System.Security.Cryptography.SHA384]::Create() }
+        'sha512' { return [System.Security.Cryptography.SHA512]::Create() }
+        default {
+            Write-Host "`rUnknown hash algorithm.`r"
+            exit 2
+        }
+    }
+}
+
+$fileContents = Get-Content $filename -Raw
+$hashAlgo = $hashAlgo.ToLower()
+$hashValue = hashSHA $hashAlgo
+
+try {
+    $hashBytes = $hashValue.ComputeHash([System.Text.Encoding]::UTF8.GetBytes($fileContents))
+    $hashBase64 = [System.Convert]::ToBase64String($hashBytes)
+    Write-Host "`r$hashAlgo-$hashBase64`r"
+}
+catch {
+    Write-Host "There was a problem generating a hash value."
+    exit 1
+}
+finally {
+    $hashValue.Dispose()
+}
+
+exit 0
+
+#EOF