Added random string generation functions to a separate file

rand_string.inc.php

@@ -0,0 +1,29 @@
+<?php
+
+function gen_rand_shortlink($len) {
+        $to_return = '';
+        $possible_chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
+        while (mb_strlen($to_return) < $len) {
+                $to_return = $to_return . $possible_chars[rand(0, mb_strlen($possible_chars)-1)];
+        }
+
+        return $to_return;
+
+}
+
+function gen_base62_rand_shortlink($len) {
+        $rand_bytes = random_bytes(intval(($len * 2) / 3));
+        $rand_string = base64_encode($rand_bytes);
+        $rand_string = str_replace("+","",$rand_string);
+        $rand_string = str_replace("/","",$rand_string);
+        $rand_string = str_replace("=","",$rand_string);
+
+        if (mb_strlen($rand_string) < $len) {
+                $curlen = mb_strlen($rand_string);
+                $rand_string = $rand_string . gen_rand_shortlink($len - $curlen);
+        }
+
+        return $rand_string;
+}
+
+?>