thodg/libgit2/src/pqueue.c

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• Hash : 931b8b70
  Author :
  Date : 2013-01-03T22:16:37
  

  Add Apache license header back to libpqueue files The original libpqueue file were licensed under Apache 2.0 so therefore should retain their copyrights and header as per the license terms at http://www.apache.org/licenses/LICENSE-2.0

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• src/pqueue.c

• /*
   * Copyright (C) 2009-2012 the libgit2 contributors
   *
   * This file is part of libgit2, distributed under the GNU GPL v2 with
   * a Linking Exception. For full terms see the included COPYING file.
   *
   * This file is based on a modified version of the priority queue found
   * in the Apache project and libpqueue library.
   * 
   * https://github.com/vy/libpqueue
   * 
   * Original file notice:
   * 
   * Copyright 2010 Volkan Yazici <volkan.yazici@gmail.com>
   * Copyright 2006-2010 The Apache Software Foundation
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not
   * use this file except in compliance with the License. You may obtain a copy of
   * the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
   * License for the specific language governing permissions and limitations under
   * the License.
   */
  
  #include "common.h"
  #include "pqueue.h"
  
  #define left(i)	((i) << 1)
  #define right(i) (((i) << 1) + 1)
  #define parent(i) ((i) >> 1)
  
  int git_pqueue_init(git_pqueue *q, size_t n, git_pqueue_cmp cmppri)
  {
  	assert(q);
  
  	/* Need to allocate n+1 elements since element 0 isn't used. */
  	q->d = git__malloc((n + 1) * sizeof(void *));
  	GITERR_CHECK_ALLOC(q->d);
  
  	q->size = 1;
  	q->avail = q->step = (n + 1); /* see comment above about n+1 */
  	q->cmppri = cmppri;
  
  	return 0;
  }
  
  
  void git_pqueue_free(git_pqueue *q)
  {
  	git__free(q->d);
  	q->d = NULL;
  }
  
  void git_pqueue_clear(git_pqueue *q)
  {
  	q->size = 1;
  }
  
  size_t git_pqueue_size(git_pqueue *q)
  {
  	/* queue element 0 exists but doesn't count since it isn't used. */
  	return (q->size - 1);
  }
  
  
  static void bubble_up(git_pqueue *q, size_t i)
  {
  	size_t parent_node;
  	void *moving_node = q->d[i];
  
  	for (parent_node = parent(i);
  			((i > 1) && q->cmppri(q->d[parent_node], moving_node));
  			i = parent_node, parent_node = parent(i)) {
  		q->d[i] = q->d[parent_node];
  	}
  
  	q->d[i] = moving_node;
  }
  
  
  static size_t maxchild(git_pqueue *q, size_t i)
  {
  	size_t child_node = left(i);
  
  	if (child_node >= q->size)
  		return 0;
  
  	if ((child_node + 1) < q->size &&
  		q->cmppri(q->d[child_node], q->d[child_node + 1]))
  		child_node++; /* use right child instead of left */
  
  	return child_node;
  }
  
  
  static void percolate_down(git_pqueue *q, size_t i)
  {
  	size_t child_node;
  	void *moving_node = q->d[i];
  
  	while ((child_node = maxchild(q, i)) != 0 &&
  			q->cmppri(moving_node, q->d[child_node])) {
  		q->d[i] = q->d[child_node];
  		i = child_node;
  	}
  
  	q->d[i] = moving_node;
  }
  
  
  int git_pqueue_insert(git_pqueue *q, void *d)
  {
  	void *tmp;
  	size_t i;
  	size_t newsize;
  
  	if (!q) return 1;
  
  	/* allocate more memory if necessary */
  	if (q->size >= q->avail) {
  		newsize = q->size + q->step;
  		tmp = git__realloc(q->d, sizeof(void *) * newsize);
  		GITERR_CHECK_ALLOC(tmp);
  
  		q->d = tmp;
  		q->avail = newsize;
  	}
  
  	/* insert item */
  	i = q->size++;
  	q->d[i] = d;
  	bubble_up(q, i);
  
  	return 0;
  }
  
  
  void *git_pqueue_pop(git_pqueue *q)
  {
  	void *head;
  
  	if (!q || q->size == 1)
  		return NULL;
  
  	head = q->d[1];
  	q->d[1] = q->d[--q->size];
  	percolate_down(q, 1);
  
  	return head;
  }
  
  
  void *git_pqueue_peek(git_pqueue *q)
  {
  	if (!q || q->size == 1)
  		return NULL;
  	return q->d[1];
  }
  

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