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