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comparison: ipc/chromium/src/base/rand_util.cc
ipc/chromium/src/base/rand_util.cc
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| -1:000000000000 | 0:cc421900528e |
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| 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 int RandInt(int min, int max) { | |
| 17 DCHECK(min <= max); | |
| 18 | |
| 19 uint64_t range = static_cast<int64_t>(max) - min + 1; | |
| 20 uint64_t number = base::RandUint64(); | |
| 21 int result = min + static_cast<int>(number % range); | |
| 22 DCHECK(result >= min && result <= max); | |
| 23 return result; | |
| 24 } | |
| 25 | |
| 26 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 uint64_t random_bits = base::RandUint64() & ((GG_UINT64_C(1) << kBits) - 1); | |
| 35 double result = ldexp(static_cast<double>(random_bits), -1 * kBits); | |
| 36 DCHECK(result >= 0.0 && result < 1.0); | |
| 37 return result; | |
| 38 } | |
| 39 | |
| 40 } // namespace base |
