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35 lines
776 B
C++
35 lines
776 B
C++
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// Copyright 2005-2009 The RE2 Authors. All Rights Reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Modified from Google perftools's tcmalloc_unittest.cc.
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#include "util/random.h"
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namespace re2 {
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int32 ACMRandom::Next() {
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const int32 M = 2147483647L; // 2^31-1
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const int32 A = 16807;
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// In effect, we are computing seed_ = (seed_ * A) % M, where M = 2^31-1
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uint32 lo = A * (int32)(seed_ & 0xFFFF);
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uint32 hi = A * (int32)((uint32)seed_ >> 16);
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lo += (hi & 0x7FFF) << 16;
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if (lo > M) {
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lo &= M;
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++lo;
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}
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lo += hi >> 15;
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if (lo > M) {
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lo &= M;
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++lo;
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}
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return (seed_ = (int32) lo);
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}
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int32 ACMRandom::Uniform(int32 n) {
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return Next() % n;
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}
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} // namespace re2
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