Add a rand_util method for generating a random string.

base/rand_util.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/rand_util.h"
 
 #include <math.h>
 
 #include <limits>
 
@@ skipping 23 matching lines @@
   double result = ldexp(static_cast<double>(random_bits), -1 * kBits);
   DCHECK(result >= 0.0 && result < 1.0);
   return result;
 }
 
 uint64 RandGenerator(uint64 max) {
   DCHECK_GT(max, 0ULL);
   return base::RandUint64() % max;
 }
 
+std::string RandBytesAsString(size_t length) {
+  const size_t kBitsPerChar = 8;
+  const int kCharsPerInt64 = sizeof(uint64)/sizeof(char);
+
+  std::string result(length, '\0');
+  uint64 entropy = 0;
+  for (size_t i = 0; i < result.size(); ++i) {
+    if (i % kCharsPerInt64 == 0)
+      entropy = RandUint64();
+    result[i] = static_cast<char>(entropy);
+    entropy >>= kBitsPerChar;
+  }
+
+  return result;
+}
+
 }  // namespace base