server/AyaNova/util/Hasher.cs

@@ -1,4 +1,6 @@
 using System;
+using System.Collections.Generic;
+using System.Linq;
 using System.Security.Cryptography;
 using Microsoft.AspNetCore.Cryptography.KeyDerivation;
 namespace AyaNova.Util
@@ -32,6 +34,39 @@ namespace AyaNova.Util
             return Convert.ToBase64String(salt);
         }
 
+
+
+        public static string GetRandomAlphanumericString(int length)
+        {
+            const string alphanumericCharacters = "0123456789abcdefghijkmnopqrstuvwxyz";
+            return GetRandomString(length, alphanumericCharacters);
+        }
+
+        public static string GetRandomString(int length, IEnumerable<char> characterSet)
+        {
+            if (length < 0)
+                throw new ArgumentException("length must not be negative", "length");
+            if (length > int.MaxValue / 8) // 250 million chars ought to be enough for anybody
+                throw new ArgumentException("length is too big", "length");
+            if (characterSet == null)
+                throw new ArgumentNullException("characterSet");
+            var characterArray = characterSet.Distinct().ToArray();
+            if (characterArray.Length == 0)
+                throw new ArgumentException("characterSet must not be empty", "characterSet");
+
+            var bytes = new byte[length * 8];
+            new RNGCryptoServiceProvider().GetBytes(bytes);
+            var result = new char[length];
+            for (int i = 0; i < length; i++)
+            {
+                ulong value = BitConverter.ToUInt64(bytes, i * 8);
+                result[i] = characterArray[value % (uint)characterArray.Length];
+            }
+            return new string(result);
+        }
+
+
+
     }//eoc
 
 }//eons