/***************************************************************************//**
Copyright (c) 2010, 2011, Oracle Corpn. All Rights Reserved.

Portions of this file contain modifications contributed and copyrighted by
Sun Microsystems, Inc. Those modifications are gratefully acknowledged and
are described briefly in the InnoDB documentation. The contributions by
Sun Microsystems are incorporated with their permission, and subject to the
conditions contained in the file COPYING.Sun_Microsystems.

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

*****************************************************************************/

/******************************************************************//**
@file ut/ut0bh.c
Binary min-heap implementation.

Created 2010-05-28 by Sunny Bains
*******************************************************/

#include "ut0bh.h"
#include "ut0mem.h"

#ifdef UNIV_NONINL
#include "ut0bh.ic"
#endif

#include <string.h>

/**********************************************************************//**
Create a binary heap.
@return a new binary heap */
UNIV_INTERN
ib_bh_t*
ib_bh_create(
/*=========*/
	ib_bh_cmp_t	compare,		/*!< in: comparator */
	ulint		sizeof_elem,		/*!< in: size of one element */
	ulint		max_elems)		/*!< in: max elements allowed */
{
	ulint		sz;
	ib_bh_t*	ib_bh;

	sz = sizeof(*ib_bh) + (sizeof_elem * max_elems);

	ib_bh = (ib_bh_t*) ut_malloc(sz);
	memset(ib_bh, 0x0, sz);

	ib_bh->compare = compare;
	ib_bh->max_elems = max_elems;
	ib_bh->sizeof_elem = sizeof_elem;

	return(ib_bh);
}

/**********************************************************************//**
Free a binary heap.
@return a new binary heap */
UNIV_INTERN
void
ib_bh_free(
/*=======*/
	ib_bh_t*	ib_bh)			/*!< in/own: instance */
{
	ut_free(ib_bh);
}

/**********************************************************************//**
Add an element to the binary heap. Note: The element is copied.
@return pointer to added element or NULL if full. */
UNIV_INTERN
void*
ib_bh_push(
/*=======*/
	ib_bh_t*	ib_bh,			/*!< in/out: instance */
	const void*	elem)			/*!< in: element to add */
{
	void*		ptr;

	if (ib_bh_is_full(ib_bh)) {
		return(NULL);
	} else if (ib_bh_is_empty(ib_bh)) {
		++ib_bh->n_elems;
		return(ib_bh_set(ib_bh, 0, elem));
	} else {
		ulint	i;

		i = ib_bh->n_elems;

		++ib_bh->n_elems;

		for (ptr = ib_bh_get(ib_bh, i >> 1);
		     i > 0 && ib_bh->compare(ptr, elem) > 0;
		     i >>= 1, ptr = ib_bh_get(ib_bh, i >> 1)) {

			ib_bh_set(ib_bh, i, ptr);
		}

		ptr = ib_bh_set(ib_bh, i, elem);
	}

	return(ptr);
}

/**********************************************************************//**
Remove the first element from the binary heap. */
UNIV_INTERN
void
ib_bh_pop(
/*======*/
	ib_bh_t*	ib_bh)			/*!< in/out: instance */
{
	byte*		ptr;
	byte*		last;
	ulint		parent = 0;

	if (ib_bh_is_empty(ib_bh)) {
		return;
	} else if (ib_bh_size(ib_bh) == 1) {
		--ib_bh->n_elems;
		return;
	}

	last = (byte*) ib_bh_last(ib_bh);

	/* Start from the child node */
	ptr = (byte*) ib_bh_get(ib_bh, 1);

	while (ptr < last) {
		/* If the "right" child node is < "left" child node */
		if (ib_bh->compare(ptr + ib_bh->sizeof_elem, ptr) < 0) {
			ptr += ib_bh->sizeof_elem;
		}

		if (ib_bh->compare(last, ptr) <= 0) {
			break;
		}

		ib_bh_set(ib_bh, parent, ptr);

		parent = (ptr - (byte*) ib_bh_first(ib_bh))
		       / ib_bh->sizeof_elem;

		if ((parent << 1) >= ib_bh_size(ib_bh)) {
			break;
		}

		ptr = (byte*) ib_bh_get(ib_bh, parent << 1);
	}

	--ib_bh->n_elems;

	ib_bh_set(ib_bh, parent, last);
}
