mirror of
https://github.com/MariaDB/server.git
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159 lines
3.7 KiB
C++
159 lines
3.7 KiB
C++
/***************************************************************************//**
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Copyright (c) 2010, 2011, Oracle and/or its affiliates. All Rights Reserved.
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This program is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free Software
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Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along with
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this program; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA
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*****************************************************************************/
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/******************************************************************//**
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@file ut/ut0bh.cc
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Binary min-heap implementation.
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Created 2010-05-28 by Sunny Bains
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*******************************************************/
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#include "ut0bh.h"
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#include "ut0mem.h"
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#ifdef UNIV_NONINL
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#include "ut0bh.ic"
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#endif
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#include <string.h>
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/**********************************************************************//**
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Create a binary heap.
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@return a new binary heap */
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UNIV_INTERN
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ib_bh_t*
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ib_bh_create(
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/*=========*/
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ib_bh_cmp_t compare, /*!< in: comparator */
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ulint sizeof_elem, /*!< in: size of one element */
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ulint max_elems) /*!< in: max elements allowed */
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{
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ulint sz;
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ib_bh_t* ib_bh;
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sz = sizeof(*ib_bh) + (sizeof_elem * max_elems);
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ib_bh = (ib_bh_t*) ut_malloc(sz);
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memset(ib_bh, 0x0, sz);
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ib_bh->compare = compare;
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ib_bh->max_elems = max_elems;
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ib_bh->sizeof_elem = sizeof_elem;
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return(ib_bh);
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}
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/**********************************************************************//**
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Free a binary heap.
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@return a new binary heap */
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UNIV_INTERN
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void
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ib_bh_free(
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/*=======*/
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ib_bh_t* ib_bh) /*!< in/own: instance */
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{
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ut_free(ib_bh);
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}
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/**********************************************************************//**
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Add an element to the binary heap. Note: The element is copied.
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@return pointer to added element or NULL if full. */
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UNIV_INTERN
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void*
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ib_bh_push(
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/*=======*/
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ib_bh_t* ib_bh, /*!< in/out: instance */
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const void* elem) /*!< in: element to add */
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{
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void* ptr;
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if (ib_bh_is_full(ib_bh)) {
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return(NULL);
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} else if (ib_bh_is_empty(ib_bh)) {
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++ib_bh->n_elems;
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return(ib_bh_set(ib_bh, 0, elem));
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} else {
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ulint i;
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i = ib_bh->n_elems;
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++ib_bh->n_elems;
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for (ptr = ib_bh_get(ib_bh, i >> 1);
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i > 0 && ib_bh->compare(ptr, elem) > 0;
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i >>= 1, ptr = ib_bh_get(ib_bh, i >> 1)) {
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ib_bh_set(ib_bh, i, ptr);
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}
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ptr = ib_bh_set(ib_bh, i, elem);
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}
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return(ptr);
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}
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/**********************************************************************//**
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Remove the first element from the binary heap. */
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UNIV_INTERN
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void
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ib_bh_pop(
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/*======*/
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ib_bh_t* ib_bh) /*!< in/out: instance */
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{
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byte* ptr;
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byte* last;
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ulint parent = 0;
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if (ib_bh_is_empty(ib_bh)) {
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return;
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} else if (ib_bh_size(ib_bh) == 1) {
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--ib_bh->n_elems;
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return;
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}
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last = (byte*) ib_bh_last(ib_bh);
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/* Start from the child node */
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ptr = (byte*) ib_bh_get(ib_bh, 1);
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while (ptr < last) {
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/* If the "right" child node is < "left" child node */
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if (ib_bh->compare(ptr + ib_bh->sizeof_elem, ptr) < 0) {
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ptr += ib_bh->sizeof_elem;
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}
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if (ib_bh->compare(last, ptr) <= 0) {
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break;
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}
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ib_bh_set(ib_bh, parent, ptr);
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parent = (ptr - (byte*) ib_bh_first(ib_bh))
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/ ib_bh->sizeof_elem;
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if ((parent << 1) >= ib_bh_size(ib_bh)) {
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break;
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}
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ptr = (byte*) ib_bh_get(ib_bh, parent << 1);
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}
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--ib_bh->n_elems;
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ib_bh_set(ib_bh, parent, last);
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}
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