1 files changed, 47 insertions, 0 deletions
diff --git a/base/rand_util.cc b/base/rand_util.cc
new file mode 100644
index 0000000..89b5b32
--- /dev/null
+++ b/base/rand_util.cc
@@ -0,0 +1,47 @@
+// Copyright (c) 2008 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 "base/basictypes.h"
+#include "base/logging.h"
+
+namespace {
+
+union uint64_splitter {
+  uint64 normal;
+  uint16 split[4];
+};
+
+}  // namespace
+
+namespace base {
+
+int RandInt(int min, int max) {
+  DCHECK(min <= max);
+
+  uint64 range = static_cast<int64>(max) - min + 1;
+  uint64 number = base::RandUInt64();
+  int result = min + static_cast<int>(number % range);
+  DCHECK(result >= min && result <= max);
+  return result;
+}
+
+double RandDouble() {
+  uint64_splitter number;
+  number.normal = base::RandUInt64();
+
+  // Standard code based on drand48 would give only 48 bits of precision.
+  // We try to get maximum precision for IEEE 754 double (52 bits).
+  double result = ldexp(static_cast<double>(number.split[0] & 0xf), -52) +
+                  ldexp(static_cast<double>(number.split[1]), -48) +
+                  ldexp(static_cast<double>(number.split[2]), -32) +
+                  ldexp(static_cast<double>(number.split[3]), -16);
+  DCHECK(result >= 0.0 && result < 1.0);
+  return result;
+}
+
+}  // namespace base