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