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-rw-r--r--src/pqueue.c134
1 files changed, 134 insertions, 0 deletions
diff --git a/src/pqueue.c b/src/pqueue.c
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+/*
+ Copyright (c) 2012-2015, Matthias Schiffer <mschiffer@universe-factory.net>
+ All rights reserved.
+
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions are met:
+
+ 1. Redistributions of source code must retain the above copyright notice,
+ this list of conditions and the following disclaimer.
+ 2. Redistributions in binary form must reproduce the above copyright notice,
+ this list of conditions and the following disclaimer in the documentation
+ and/or other materials provided with the distribution.
+
+ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+/**
+ \file
+
+ Priority queue implementation
+
+ Priority queues implemented using pairing heaps.
+*/
+
+
+#include "pqueue.h"
+#include "log.h"
+
+
+static inline void pqueue_link(fastd_pqueue_t **pqueue, fastd_pqueue_t *elem) {
+ if (elem->next)
+ exit_bug("pqueue_link: element already linked");
+
+ elem->pprev = pqueue;
+ elem->next = *pqueue;
+ if (elem->next)
+ elem->next->pprev = &elem->next;
+
+ *pqueue = elem;
+}
+
+static inline void pqueue_unlink(fastd_pqueue_t *elem) {
+ *elem->pprev = elem->next;
+ if (elem->next)
+ elem->next->pprev = elem->pprev;
+
+ elem->pprev = NULL;
+ elem->next = NULL;
+}
+
+
+static fastd_pqueue_t * pqueue_merge(fastd_pqueue_t *pqueue1, fastd_pqueue_t *pqueue2) {
+ if (!pqueue1)
+ exit_bug("pqueue_merge: pqueue1 unset");
+ if (pqueue1->next)
+ exit_bug("pqueue_merge: pqueue1 has successor");
+
+ if (!pqueue2)
+ return pqueue1;
+
+ if (pqueue2->next)
+ exit_bug("pqueue_merge: pqueue2 has successor");
+
+ fastd_pqueue_t *lo, *hi;
+
+ if (pqueue1->value < pqueue2->value) {
+ lo = pqueue1;
+ hi = pqueue2;
+ }
+ else {
+ lo = pqueue2;
+ hi = pqueue1;
+ }
+
+ pqueue_link(&lo->children, hi);
+
+ return lo;
+}
+
+static fastd_pqueue_t * pqueue_merge_pairs(fastd_pqueue_t *pqueue0) {
+ if (!pqueue0)
+ return NULL;
+
+ if (!pqueue0->pprev)
+ exit_bug("pqueue_merge_pairs: unlinked pqueue");
+
+ fastd_pqueue_t *pqueue1 = pqueue0->next;
+
+ if (!pqueue1)
+ return pqueue0;
+
+ fastd_pqueue_t *pqueue2 = pqueue1->next;
+
+ pqueue0->next = pqueue1->next = NULL;
+ pqueue0->pprev = pqueue1->pprev = NULL;
+
+ return pqueue_merge(pqueue_merge(pqueue0, pqueue1), pqueue_merge_pairs(pqueue2));
+}
+
+void fastd_pqueue_insert(fastd_pqueue_t **pqueue, fastd_pqueue_t *elem) {
+ if (elem->pprev || elem->next || elem->children)
+ exit_bug("fastd_pqueue_insert: tried to insert linked pqueue element");
+
+ *pqueue = pqueue_merge(elem, *pqueue);
+ (*pqueue)->pprev = pqueue;
+}
+
+void fastd_pqueue_remove(fastd_pqueue_t *elem) {
+ if (!fastd_pqueue_linked(elem)) {
+ if (elem->children || elem->next)
+ exit_bug("fastd_pqueue_remove: corrupted pqueue item");
+
+ return;
+ }
+
+ fastd_pqueue_t **pprev = elem->pprev;
+
+ pqueue_unlink(elem);
+
+ fastd_pqueue_t *merged = pqueue_merge_pairs(elem->children);
+ if (merged)
+ pqueue_link(pprev, merged);
+
+ elem->children = NULL;
+}