The Tor Browser: ipc/chromium/src/base/rand

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

     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.

     5 #include "base/rand_util.h"

     7 #include <math.h>

     9 #include <limits>

    11 #include "base/basictypes.h"

    12 #include "base/logging.h"

    14 namespace base {

    16 int RandInt(int min, int max) {

    17   DCHECK(min <= max);

    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 }

    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.

    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 }

    40 }  // namespace base

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