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1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #include "base/rand_util.h" | 5 #include "base/rand_util.h" |
6 | 6 |
7 #include <math.h> | 7 #include <math.h> |
| 8 #include <stdint.h> |
8 | 9 |
9 #include <algorithm> | 10 #include <algorithm> |
10 #include <limits> | 11 #include <limits> |
11 | 12 |
12 #include "base/basictypes.h" | 13 #include "base/basictypes.h" |
13 #include "base/logging.h" | 14 #include "base/logging.h" |
14 #include "base/strings/string_util.h" | 15 #include "base/strings/string_util.h" |
15 | 16 |
16 namespace base { | 17 namespace base { |
17 | 18 |
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30 } | 31 } |
31 | 32 |
32 double BitsToOpenEndedUnitInterval(uint64 bits) { | 33 double BitsToOpenEndedUnitInterval(uint64 bits) { |
33 // We try to get maximum precision by masking out as many bits as will fit | 34 // We try to get maximum precision by masking out as many bits as will fit |
34 // in the target type's mantissa, and raising it to an appropriate power to | 35 // in the target type's mantissa, and raising it to an appropriate power to |
35 // produce output in the range [0, 1). For IEEE 754 doubles, the mantissa | 36 // produce output in the range [0, 1). For IEEE 754 doubles, the mantissa |
36 // is expected to accommodate 53 bits. | 37 // is expected to accommodate 53 bits. |
37 | 38 |
38 COMPILE_ASSERT(std::numeric_limits<double>::radix == 2, otherwise_use_scalbn); | 39 COMPILE_ASSERT(std::numeric_limits<double>::radix == 2, otherwise_use_scalbn); |
39 static const int kBits = std::numeric_limits<double>::digits; | 40 static const int kBits = std::numeric_limits<double>::digits; |
40 uint64 random_bits = bits & ((GG_UINT64_C(1) << kBits) - 1); | 41 uint64 random_bits = bits & ((UINT64_C(1) << kBits) - 1); |
41 double result = ldexp(static_cast<double>(random_bits), -1 * kBits); | 42 double result = ldexp(static_cast<double>(random_bits), -1 * kBits); |
42 DCHECK_GE(result, 0.0); | 43 DCHECK_GE(result, 0.0); |
43 DCHECK_LT(result, 1.0); | 44 DCHECK_LT(result, 1.0); |
44 return result; | 45 return result; |
45 } | 46 } |
46 | 47 |
47 uint64 RandGenerator(uint64 range) { | 48 uint64 RandGenerator(uint64 range) { |
48 DCHECK_GT(range, 0u); | 49 DCHECK_GT(range, 0u); |
49 // We must discard random results above this number, as they would | 50 // We must discard random results above this number, as they would |
50 // make the random generator non-uniform (consider e.g. if | 51 // make the random generator non-uniform (consider e.g. if |
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62 } | 63 } |
63 | 64 |
64 std::string RandBytesAsString(size_t length) { | 65 std::string RandBytesAsString(size_t length) { |
65 DCHECK_GT(length, 0u); | 66 DCHECK_GT(length, 0u); |
66 std::string result; | 67 std::string result; |
67 RandBytes(WriteInto(&result, length + 1), length); | 68 RandBytes(WriteInto(&result, length + 1), length); |
68 return result; | 69 return result; |
69 } | 70 } |
70 | 71 |
71 } // namespace base | 72 } // namespace base |
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