thodg/libgit2/src/vector.c

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• Hash : de18f276
  Author :
  Date : 2011-07-07T01:46:20
  

  vector: Timsort all of the things Drop the GLibc implementation of Merge Sort and replace it with Timsort. The algorithm has been tuned to work on arrays of pointers (void **), so there's no longer a need to abstract the byte-width of each element in the array. All the comparison callbacks now take pointers-to-elements, not pointers-to-pointers, so there's now one less level of dereferencing. E.g. int index_cmp(const void *a, const void *b) { - const git_index_entry *entry_a = *(const git_index_entry **)(a); + const git_index_entry *entry_a = (const git_index_entry *)(a); The result is up to a 40% speed-up when sorting vectors. Memory usage remains lineal. A new `bsearch` implementation has been added, whose callback also supplies pointer-to-elements, to uniform the Vector API again.

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• src/vector.c

• /*
   * This file is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License, version 2,
   * as published by the Free Software Foundation.
   *
   * In addition to the permissions in the GNU General Public License,
   * the authors give you unlimited permission to link the compiled
   * version of this file into combinations with other programs,
   * and to distribute those combinations without any restriction
   * coming from the use of this file.  (The General Public License
   * restrictions do apply in other respects; for example, they cover
   * modification of the file, and distribution when not linked into
   * a combined executable.)
   *
   * This file 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; see the file COPYING.  If not, write to
   * the Free Software Foundation, 51 Franklin Street, Fifth Floor,
   * Boston, MA 02110-1301, USA.
   */
  
  #include "common.h"
  #include "repository.h"
  #include "vector.h"
  
  static const double resize_factor = 1.75;
  static const size_t minimum_size = 8;
  
  static int resize_vector(git_vector *v)
  {
  	v->_alloc_size = ((unsigned int)(v->_alloc_size * resize_factor)) + 1;
  	if (v->_alloc_size < minimum_size)
  		v->_alloc_size = minimum_size;
  
  	v->contents = realloc(v->contents, v->_alloc_size * sizeof(void *));
  	if (v->contents == NULL)
  		return GIT_ENOMEM;
  
  	return GIT_SUCCESS;
  }
  
  
  void git_vector_free(git_vector *v)
  {
  	assert(v);
  	free(v->contents);
  }
  
  int git_vector_init(git_vector *v, unsigned int initial_size, git_vector_cmp cmp)
  {
  	assert(v);
  
  	memset(v, 0x0, sizeof(git_vector));
  
  	if (initial_size == 0)
  		initial_size = minimum_size;
  
  	v->_alloc_size = initial_size;
  	v->_cmp = cmp;
  
  	v->length = 0;
  	v->sorted = 1;
  
  	v->contents = git__malloc(v->_alloc_size * sizeof(void *));
  	if (v->contents == NULL)
  		return GIT_ENOMEM;
  
  	return GIT_SUCCESS;
  }
  
  int git_vector_insert(git_vector *v, void *element)
  {
  	assert(v);
  
  	if (v->length >= v->_alloc_size) {
  		if (resize_vector(v) < 0)
  			return GIT_ENOMEM;
  	}
  
  	v->contents[v->length++] = element;
  	v->sorted = 0;
  
  	return GIT_SUCCESS;
  }
  
  void git_vector_sort(git_vector *v)
  {
  	assert(v);
  
  	if (v->sorted || v->_cmp == NULL)
  		return;
  
  	git__tsort(v->contents, v->length, v->_cmp);
  	v->sorted = 1;
  }
  
  int git_vector_bsearch2(git_vector *v, git_vector_cmp key_lookup, const void *key)
  {
  	void **find;
  
  	assert(v && key && key_lookup);
  
  	/* need comparison function to sort the vector */
  	if (v->_cmp == NULL)
  		return git__throw(GIT_ENOTFOUND, "Can't sort vector. No comparison function set");
  
  	git_vector_sort(v);
  
  	find = git__bsearch(key, v->contents, v->length, key_lookup);
  	if (find != NULL)
  		return (int)(find - v->contents);
  
  	return git__throw(GIT_ENOTFOUND, "Can't find element");
  }
  
  int git_vector_search2(git_vector *v, git_vector_cmp key_lookup, const void *key)
  {
  	unsigned int i;
  
  	assert(v && key && key_lookup);
  
  	for (i = 0; i < v->length; ++i) {
  		if (key_lookup(key, v->contents[i]) == 0)
  			return i;
  	}
  
  	return git__throw(GIT_ENOTFOUND, "Can't find element");
  }
  
  static int strict_comparison(const void *a, const void *b)
  {
  	return (a == b) ? 0 : -1;
  }
  
  int git_vector_search(git_vector *v, const void *entry)
  {
  	return git_vector_search2(v, v->_cmp ? v->_cmp : strict_comparison, entry);
  }
  
  int git_vector_bsearch(git_vector *v, const void *key)
  {
  	return git_vector_bsearch2(v, v->_cmp, key);
  }
  
  int git_vector_remove(git_vector *v, unsigned int idx)
  {
  	unsigned int i;
  
  	assert(v);
  
  	if (idx >= v->length || v->length == 0)
  		return git__throw(GIT_ENOTFOUND, "Can't remove element. Index out of bounds");
  
  	for (i = idx; i < v->length - 1; ++i)
  		v->contents[i] = v->contents[i + 1];
  
  	v->length--;
  	return GIT_SUCCESS;
  }
  
  void git_vector_uniq(git_vector *v)
  {
  	git_vector_cmp cmp;
  	unsigned int i, j;
  
  	if (v->length <= 1)
  		return;
  
  	git_vector_sort(v);
  	cmp = v->_cmp ? v->_cmp : strict_comparison;
  
  	for (i = 0, j = 1 ; j < v->length; ++j)
  		if (!cmp(v->contents[i], v->contents[j]))
  			v->contents[i] = v->contents[j];
  		else
  			v->contents[++i] = v->contents[j];
  
  	v->length -= j - i - 1;
  }
  
  void git_vector_clear(git_vector *v)
  {
  	assert(v);
  	v->length = 0;
  	v->sorted = 1;
  }
  
  
  

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