1 : // Copyright (c) 2008 The Chromium Authors. All rights reserved.
2 : // Use of this source code is governed by a BSD-style license that can be
3 : // found in the LICENSE file.
4 :
5 : #include "base/rand_util.h"
6 :
7 : #include <math.h>
8 :
9 : #include <limits>
10 :
11 : #include "base/basictypes.h"
12 : #include "base/logging.h"
13 :
14 : namespace base {
15 :
16 0 : int RandInt(int min, int max) {
17 0 : DCHECK(min <= max);
18 :
19 0 : uint64 range = static_cast<int64>(max) - min + 1;
20 0 : uint64 number = base::RandUint64();
21 0 : int result = min + static_cast<int>(number % range);
22 0 : DCHECK(result >= min && result <= max);
23 0 : return result;
24 : }
25 :
26 0 : double RandDouble() {
27 : // We try to get maximum precision by masking out as many bits as will fit
28 : // in the target type's mantissa, and raising it to an appropriate power to
29 : // produce output in the range [0, 1). For IEEE 754 doubles, the mantissa
30 : // is expected to accommodate 53 bits.
31 :
32 : COMPILE_ASSERT(std::numeric_limits<double>::radix == 2, otherwise_use_scalbn);
33 : static const int kBits = std::numeric_limits<double>::digits;
34 0 : uint64 random_bits = base::RandUint64() & ((GG_UINT64_C(1) << kBits) - 1);
35 0 : double result = ldexp(static_cast<double>(random_bits), -1 * kBits);
36 0 : DCHECK(result >= 0.0 && result < 1.0);
37 0 : return result;
38 : }
39 :
40 : } // namespace base
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