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/* -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-
* vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
*
* Copyright (C) 2008 Sun Microsystems
* Copyright (C) 2010 Stewart Smith
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "config.h"
#include <drizzled/plugin/function.h>
#include <drizzled/item/func.h>
#include <drizzled/function/math/real.h>
#include <drizzled/session.h>
using namespace std;
using namespace drizzled;
class RandFunction :public Item_real_func
{
uint64_t seed1;
uint64_t seed2;
uint64_t max_value;
double max_value_dbl;
void _seed_random_int(uint64_t new_seed1, uint64_t new_seed2);
public:
RandFunction() :Item_real_func() {}
double val_real();
const char *func_name() const { return "rand"; }
bool const_item() const { return 0; }
void update_used_tables();
bool fix_fields(Session *session, Item **ref);
bool check_argument_count(int n)
{
return (n == 0 || n == 1);
}
private:
void seed_random (Item * val);
};
static uint32_t sql_rnd()
{
return (uint32_t) (rand() * 0xffffffff); /* make all bits random */
}
void RandFunction::seed_random(Item *arg)
{
/*
TODO: do not do reinit 'rand' for every execute of PS/SP if
args[0] is a constant.
*/
uint64_t tmp= (uint64_t) arg->val_int();
_seed_random_int(tmp * 0x10001L + 55555555L, tmp * 0x10000001L);
}
void RandFunction::_seed_random_int(uint64_t new_seed1, uint64_t new_seed2)
{
max_value= 0x3FFFFFFFL;
max_value_dbl=(double) max_value;
seed1= new_seed1 % max_value;
seed2= new_seed2 % max_value;
}
bool RandFunction::fix_fields(Session *session,Item **ref)
{
if (Item_real_func::fix_fields(session, ref))
return true;
used_tables_cache|= RAND_TABLE_BIT;
if (arg_count)
{ // Only use argument once in query
/*
No need to send a Rand log event if seed was given eg: RAND(seed),
as it will be replicated in the query as such.
*/
if (args[0]->const_item())
seed_random(args[0]);
}
else
{
uint64_t tmp= sql_rnd();
_seed_random_int(tmp + (uint64_t) ref, tmp + (uint64_t) session->thread_id);
}
return false;
}
void RandFunction::update_used_tables()
{
Item_real_func::update_used_tables();
used_tables_cache|= RAND_TABLE_BIT;
}
double RandFunction::val_real()
{
assert(fixed == 1);
if (arg_count && !args[0]->const_item())
seed_random(args[0]);
seed1= (seed1 * 3 + seed2) % max_value;
seed2= (seed1 + seed2 + 33) % max_value;
return (((double) seed1) / max_value_dbl);
}
plugin::Create_function<RandFunction> *rand_function= NULL;
static int initialize(module::Context ®istry)
{
rand_function= new plugin::Create_function<RandFunction>("rand");
registry.add(rand_function);
return 0;
}
DRIZZLE_PLUGIN(initialize, NULL, NULL);
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