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/***************************************************************************
* lib/common/seed.cpp
*
* Part of the STXXL. See http://stxxl.sourceforge.net
*
* Copyright (C) 2007, 2008 Andreas Beckmann <beckmann@cs.uni-frankfurt.de>
* Copyright (C) 2008 Roman Dementiev <dementiev@ira.uka.de>
*
* Distributed under the Boost Software License, Version 1.0.
* (See accompanying file LICENSE_1_0.txt or copy at
* http://www.boost.org/LICENSE_1_0.txt)
**************************************************************************/
#include <cassert>
#include <stxxl/bits/config.h>
#include <stxxl/bits/common/mutex.h>
#include <stxxl/bits/namespace.h>
#if STXXL_WINDOWS
#ifndef NOMINMAX
#define NOMINMAX
#endif
#include <io.h>
#include <windows.h>
#else
#include <unistd.h>
#include <sys/time.h>
#endif
STXXL_BEGIN_NAMESPACE
inline unsigned initial_seed();
struct seed_generator_t {
unsigned seed;
mutex mtx;
seed_generator_t(unsigned s) : seed(s)
{ }
};
seed_generator_t & seed_generator()
{
static seed_generator_t sg(initial_seed());
return sg;
}
inline unsigned initial_seed()
{
#ifndef NDEBUG
static bool initialized = false;
assert(!initialized); // this should only be called once!
initialized = true;
#endif // NDEBUG
#if STXXL_WINDOWS
// GetTickCount(): ms since system start
return GetTickCount() ^ GetCurrentProcessId();
#else
struct timeval tv;
gettimeofday(&tv, 0);
return tv.tv_sec ^ tv.tv_usec ^ (getpid() << 16);
#endif
}
void set_seed(unsigned seed)
{
scoped_mutex_lock Lock(seed_generator().mtx);
seed_generator().seed = seed;
}
unsigned get_next_seed()
{
scoped_mutex_lock Lock(seed_generator().mtx);
return seed_generator().seed++;
}
STXXL_END_NAMESPACE
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