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// Copyright 2010 Google Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Glorified C++ version of Bob Jenkins' random number generator.
// See http://burtleburtle.net/bob/rand/smallprng.html for more details.
#ifndef CRCUTIL_BOB_JENKINS_RNG_H_
#define CRCUTIL_BOB_JENKINS_RNG_H_
#include "base_types.h"
#if !defined(_MSC_VER)
#define _rotl(value, bits) \
static_cast<uint32>(((value) << (bits)) + ((value) >> (32 - (bits))))
#define _rotl64(value, bits) \
static_cast<uint64>(((value) << (bits)) + ((value) >> (64 - (bits))))
#endif // !defined(_MSC_VER)
namespace crcutil {
#pragma pack(push, 8)
template<typename T> class BobJenkinsRng;
template<> class BobJenkinsRng<uint32> {
public:
typedef uint32 value;
value Get() {
value e = a_ - _rotl(b_, 23);
a_ = b_ ^ _rotl(c_, 16);
b_ = c_ + _rotl(d_, 11);
c_ = d_ + e;
d_ = e + a_;
return (d_);
}
void Init(value seed) {
a_ = 0xf1ea5eed;
b_ = seed;
c_ = seed;
d_ = seed;
for (size_t i = 0; i < 20; ++i) {
(void) Get();
}
}
explicit BobJenkinsRng(value seed) {
Init(seed);
}
BobJenkinsRng() {
Init(0x1234567);
}
private:
value a_;
value b_;
value c_;
value d_;
};
#if HAVE_UINT64
template<> class BobJenkinsRng<uint64> {
public:
typedef uint64 value;
value Get() {
value e = a_ - _rotl64(b_, 7);
a_ = b_ ^ _rotl64(c_, 13);
b_ = c_ + _rotl64(d_, 37);
c_ = d_ + e;
d_ = e + a_;
return d_;
}
void Init(value seed) {
a_ = 0xf1ea5eed;
b_ = seed;
c_ = seed;
d_ = seed;
for (size_t i = 0; i < 20; ++i) {
(void) Get();
}
}
explicit BobJenkinsRng(value seed) {
Init(seed);
}
BobJenkinsRng() {
Init(0x1234567);
}
private:
value a_;
value b_;
value c_;
value d_;
};
#endif // HAVE_UINT64
#if !defined(_MSC_VER)
#undef _rotl
#undef _rotl64
#endif // !defined(_MSC_VER)
#pragma pack(pop)
} // namespace crcutil
#endif // CRCUTIL_BOB_JENKINS_RNG_H_
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