Move crypto_helpers from sync to base

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;
 }
 
+void RandBytes(void* output, size_t output_length) {
+  uint64 random_int;
+  const char* random_int_bytes = reinterpret_cast<const char*>(&random_int);
+  size_t random_int_size = sizeof(random_int);
+  for (size_t i = 0; i < output_length; i += random_int_size) {
+    random_int = base::RandUint64();
+    size_t copy_count = std::min(output_length - i, random_int_size);
+    memcpy(((uint8*)output) + i, random_int_bytes, copy_count);
+  }

[abarth-chromium, 2011/05/02 18:23:20]

I'd recommend re-implementing RandBytesAsString in terms of this function.  You
can use the WriteInto function from string_util to make that a one-liner.

+}
+
 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