Line data Source code
1 : /*
2 : * Copyright (c) 2010, Andrea Mazzoleni. All rights reserved.
3 : *
4 : * Redistribution and use in source and binary forms, with or without
5 : * modification, are permitted provided that the following conditions
6 : * are met:
7 : *
8 : * 1. Redistributions of source code must retain the above copyright
9 : * notice, this list of conditions and the following disclaimer.
10 : *
11 : * 2. Redistributions in binary form must reproduce the above copyright
12 : * notice, this list of conditions and the following disclaimer in the
13 : * documentation and/or other materials provided with the distribution.
14 : *
15 : * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
16 : * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 : * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 : * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
19 : * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
20 : * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
21 : * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
22 : * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
23 : * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
24 : * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
25 : * POSSIBILITY OF SUCH DAMAGE.
26 : */
27 :
28 : /** \file
29 : * Chain of nodes.
30 : * A chain of nodes is an abstraction used to implements complex list operations
31 : * like sorting.
32 : *
33 : * Do not use this directly. Use lists instead.
34 : */
35 :
36 : #ifndef __TOMMYCHAIN_H
37 : #define __TOMMYCHAIN_H
38 :
39 : #include "tommytypes.h"
40 :
41 : /******************************************************************************/
42 : /* chain */
43 :
44 : /**
45 : * Chain of nodes.
46 : * A chain of nodes is a sequence of nodes with the following properties:
47 : * - It contains at least one node. A chains of zero nodes cannot exist.
48 : * - The next field of the tail is of *undefined* value.
49 : * - The prev field of the head is of *undefined* value.
50 : * - All the other inner prev and next fields are correctly set.
51 : */
52 : typedef struct tommy_chain_struct {
53 : tommy_node* head; /**< Pointer to the head of the chain. */
54 : tommy_node* tail; /**< Pointer to the tail of the chain. */
55 : } tommy_chain;
56 :
57 : /**
58 : * Splices a chain in the middle of another chain.
59 : */
60 4513683 : tommy_inline void tommy_chain_splice(tommy_node* first_before, tommy_node* first_after, tommy_node* second_head, tommy_node* second_tail)
61 : {
62 : /* set the prev list */
63 4513683 : first_after->prev = second_tail;
64 4513683 : second_head->prev = first_before;
65 :
66 : /* set the next list */
67 4513683 : first_before->next = second_head;
68 4513683 : second_tail->next = first_after;
69 4513683 : }
70 :
71 : /**
72 : * Concats two chains.
73 : */
74 1279685 : tommy_inline void tommy_chain_concat(tommy_node* first_tail, tommy_node* second_head)
75 : {
76 : /* set the prev list */
77 1279685 : second_head->prev = first_tail;
78 :
79 : /* set the next list */
80 1279685 : first_tail->next = second_head;
81 1279685 : }
82 :
83 : /**
84 : * Merges two chains.
85 : */
86 474382 : tommy_inline void tommy_chain_merge(tommy_chain* first, tommy_chain* second, tommy_compare_func* cmp)
87 : {
88 474382 : tommy_node* first_i = first->head;
89 474382 : tommy_node* second_i = second->head;
90 :
91 : /* merge */
92 : while (1) {
93 9828371 : if (cmp(first_i->data, second_i->data) > 0) {
94 4751400 : tommy_node* next = second_i->next;
95 4751400 : if (first_i == first->head) {
96 237717 : tommy_chain_concat(second_i, first_i);
97 237717 : first->head = second_i;
98 : } else {
99 4513683 : tommy_chain_splice(first_i->prev, first_i, second_i, second_i);
100 : }
101 4751400 : if (second_i == second->tail)
102 239530 : break;
103 4511870 : second_i = next;
104 : } else {
105 5076971 : if (first_i == first->tail) {
106 234852 : tommy_chain_concat(first_i, second_i);
107 234852 : first->tail = second->tail;
108 234852 : break;
109 : }
110 4842119 : first_i = first_i->next;
111 : }
112 : }
113 474382 : }
114 :
115 : /**
116 : * Merges two chains managing special degenerated cases.
117 : * It's functionally equivalent at tommy_chain_merge() but faster with already ordered chains.
118 : */
119 1281498 : tommy_inline void tommy_chain_merge_degenerated(tommy_chain* first, tommy_chain* second, tommy_compare_func* cmp)
120 : {
121 : /* identify the condition first <= second */
122 1281498 : if (cmp(first->tail->data, second->head->data) <= 0) {
123 469455 : tommy_chain_concat(first->tail, second->head);
124 469455 : first->tail = second->tail;
125 469455 : return;
126 : }
127 :
128 : /* identify the condition second < first */
129 : /* here we must be strict on comparison to keep the sort stable */
130 812043 : if (cmp(second->tail->data, first->head->data) < 0) {
131 337661 : tommy_chain_concat(second->tail, first->head);
132 337661 : first->head = second->head;
133 337661 : return;
134 : }
135 :
136 474382 : tommy_chain_merge(first, second, cmp);
137 : }
138 :
139 : /**
140 : * Sorts a chain.
141 : * It's a stable merge sort using power of 2 buckets, with O(N*log(N)) complexity,
142 : * similar at the one used in the SGI STL libraries and in the Linux Kernel,
143 : * but faster on degenerated cases like already ordered lists.
144 : *
145 : * SGI STL stl_list.h
146 : * http://www.sgi.com/tech/stl/stl_list.h
147 : *
148 : * Linux Kernel lib/list_sort.c
149 : * http://lxr.linux.no/#linux+v2.6.36/lib/list_sort.c
150 : */
151 1691 : tommy_inline void tommy_chain_mergesort(tommy_chain* chain, tommy_compare_func* cmp)
152 : {
153 : /*
154 : * Bit buckets of chains.
155 : * Each bucket contains 2^i nodes or it's empty.
156 : * The chain at address TOMMY_BIT_MAX is an independent variable operating as "carry".
157 : * We keep it in the same "bit" vector to avoid reports from the valgrind tool sgcheck.
158 : */
159 : tommy_chain bit[TOMMY_SIZE_BIT + 1];
160 :
161 : /**
162 : * Value stored inside the bit bucket.
163 : * It's used to know which bucket is empty of full.
164 : */
165 : tommy_size_t counter;
166 1691 : tommy_node* node = chain->head;
167 1691 : tommy_node* tail = chain->tail;
168 : tommy_size_t mask;
169 : tommy_size_t i;
170 :
171 1691 : counter = 0;
172 1281498 : while (1) {
173 : tommy_node* next;
174 : tommy_chain* last;
175 :
176 : /* carry bit to add */
177 1283189 : last = &bit[TOMMY_SIZE_BIT];
178 1283189 : bit[TOMMY_SIZE_BIT].head = node;
179 1283189 : bit[TOMMY_SIZE_BIT].tail = node;
180 1283189 : next = node->next;
181 :
182 : /* add the bit, propagating the carry */
183 1283189 : i = 0;
184 1283189 : mask = counter;
185 2558643 : while ((mask & 1) != 0) {
186 1275454 : tommy_chain_merge_degenerated(&bit[i], last, cmp);
187 1275454 : mask >>= 1;
188 1275454 : last = &bit[i];
189 1275454 : ++i;
190 : }
191 :
192 : /* copy the carry in the first empty bit */
193 1283189 : bit[i] = *last;
194 :
195 : /* add the carry in the counter */
196 1283189 : ++counter;
197 :
198 1283189 : if (node == tail)
199 1691 : break;
200 1281498 : node = next;
201 : }
202 :
203 : /* merge the buckets */
204 1691 : i = tommy_ctz(counter);
205 1691 : mask = counter >> i;
206 10705 : while (mask != 1) {
207 9014 : mask >>= 1;
208 9014 : if (mask & 1)
209 6044 : tommy_chain_merge_degenerated(&bit[i + 1], &bit[i], cmp);
210 : else
211 2970 : bit[i + 1] = bit[i];
212 9014 : ++i;
213 : }
214 :
215 1691 : *chain = bit[i];
216 1691 : }
217 :
218 : #endif
219 :
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