Check that table evenly divides 256 when generating random string.

webrtc/base/helpers.h

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 18 matching lines @@
 std::string CreateRandomString(size_t length);
 
 // Generates a (cryptographically) random string of the given length.
 // We generate base64 values so that they will be printable.
 // Return false if the random number generator failed.
 bool CreateRandomString(size_t length, std::string* str);
 
 // Generates a (cryptographically) random string of the given length,
 // with characters from the given table. Return false if the random
 // number generator failed.
+// For ease of implementation, the function requires that the table
+// size evenly divide 256; otherwise, it returns false.
 bool CreateRandomString(size_t length, const std::string& table,
                         std::string* str);
 
 // Generates (cryptographically) random data of the given length.
 // Return false if the random number generator failed.
 bool CreateRandomData(size_t length, std::string* data);
 
 // Generates a (cryptographically) random UUID version 4 string.
 std::string CreateRandomUuid();
 
 // Generates a random id.
 uint32_t CreateRandomId();
 
 // Generates a 64 bit random id.
 uint64_t CreateRandomId64();
 
 // Generates a random id > 0.
 uint32_t CreateRandomNonZeroId();
 
 // Generates a random double between 0.0 (inclusive) and 1.0 (exclusive).
 double CreateRandomDouble();
 
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_HELPERS_H_