~drizzle-trunk/drizzle/development

/* -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-

 *  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:

 *

 *  Copyright (C) 2008 Sun Microsystems, Inc.

 *  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 &registry)

{

  rand_function= new plugin::Create_function<RandFunction>("rand");

  registry.add(rand_function);

  return 0;

}

DRIZZLE_PLUGIN(initialize, NULL, NULL);