1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/ipc/chromium/src/base/rand_util.cc Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,40 @@
1.4 +// Copyright (c) 2008 The Chromium Authors. All rights reserved.
1.5 +// Use of this source code is governed by a BSD-style license that can be
1.6 +// found in the LICENSE file.
1.7 +
1.8 +#include "base/rand_util.h"
1.9 +
1.10 +#include <math.h>
1.11 +
1.12 +#include <limits>
1.13 +
1.14 +#include "base/basictypes.h"
1.15 +#include "base/logging.h"
1.16 +
1.17 +namespace base {
1.18 +
1.19 +int RandInt(int min, int max) {
1.20 + DCHECK(min <= max);
1.21 +
1.22 + uint64_t range = static_cast<int64_t>(max) - min + 1;
1.23 + uint64_t number = base::RandUint64();
1.24 + int result = min + static_cast<int>(number % range);
1.25 + DCHECK(result >= min && result <= max);
1.26 + return result;
1.27 +}
1.28 +
1.29 +double RandDouble() {
1.30 + // We try to get maximum precision by masking out as many bits as will fit
1.31 + // in the target type's mantissa, and raising it to an appropriate power to
1.32 + // produce output in the range [0, 1). For IEEE 754 doubles, the mantissa
1.33 + // is expected to accommodate 53 bits.
1.34 +
1.35 + COMPILE_ASSERT(std::numeric_limits<double>::radix == 2, otherwise_use_scalbn);
1.36 + static const int kBits = std::numeric_limits<double>::digits;
1.37 + uint64_t random_bits = base::RandUint64() & ((GG_UINT64_C(1) << kBits) - 1);
1.38 + double result = ldexp(static_cast<double>(random_bits), -1 * kBits);
1.39 + DCHECK(result >= 0.0 && result < 1.0);
1.40 + return result;
1.41 +}
1.42 +
1.43 +} // namespace base
