319 lines
8.3 KiB
C
319 lines
8.3 KiB
C
/* xf86drmSL.c -- Skip list support
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* Created: Mon May 10 09:28:13 1999 by faith@precisioninsight.com
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*
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* Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
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* All Rights Reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* PRECISION INSIGHT AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
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* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*
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* Authors: Rickard E. (Rik) Faith <faith@valinux.com>
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*
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* DESCRIPTION
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*
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* This file contains a straightforward skip list implementation.n
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*
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* FUTURE ENHANCEMENTS
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*
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* REFERENCES
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*
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* [Pugh90] William Pugh. Skip Lists: A Probabilistic Alternative to
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* Balanced Trees. CACM 33(6), June 1990, pp. 668-676.
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include "xf86drm.h"
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#define SL_LIST_MAGIC 0xfacade00LU
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#define SL_ENTRY_MAGIC 0x00fab1edLU
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#define SL_FREED_MAGIC 0xdecea5edLU
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#define SL_MAX_LEVEL 16
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#define SL_RANDOM_SEED 0xc01055a1LU
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#define SL_RANDOM_DECL static void *state = NULL
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#define SL_RANDOM_INIT(seed) if (!state) state = drmRandomCreate(seed)
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#define SL_RANDOM drmRandom(state)
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typedef struct SLEntry {
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unsigned long magic; /* SL_ENTRY_MAGIC */
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unsigned long key;
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void *value;
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int levels;
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struct SLEntry *forward[1]; /* variable sized array */
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} SLEntry, *SLEntryPtr;
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typedef struct SkipList {
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unsigned long magic; /* SL_LIST_MAGIC */
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int level;
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int count;
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SLEntryPtr head;
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SLEntryPtr p0; /* Position for iteration */
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} SkipList, *SkipListPtr;
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static SLEntryPtr SLCreateEntry(int max_level, unsigned long key, void *value)
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{
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SLEntryPtr entry;
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if (max_level < 0 || max_level > SL_MAX_LEVEL) max_level = SL_MAX_LEVEL;
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entry = drmMalloc(sizeof(*entry)
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+ (max_level + 1) * sizeof(entry->forward[0]));
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if (!entry) return NULL;
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entry->magic = SL_ENTRY_MAGIC;
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entry->key = key;
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entry->value = value;
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entry->levels = max_level + 1;
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return entry;
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}
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static int SLRandomLevel(void)
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{
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int level = 1;
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SL_RANDOM_DECL;
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SL_RANDOM_INIT(SL_RANDOM_SEED);
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while ((SL_RANDOM & 0x01) && level < SL_MAX_LEVEL) ++level;
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return level;
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}
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void *drmSLCreate(void)
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{
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SkipListPtr list;
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int i;
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list = drmMalloc(sizeof(*list));
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if (!list) return NULL;
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list->magic = SL_LIST_MAGIC;
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list->level = 0;
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list->head = SLCreateEntry(SL_MAX_LEVEL, 0, NULL);
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list->count = 0;
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for (i = 0; i <= SL_MAX_LEVEL; i++) list->head->forward[i] = NULL;
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return list;
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}
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int drmSLDestroy(void *l)
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{
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SkipListPtr list = (SkipListPtr)l;
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SLEntryPtr entry;
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SLEntryPtr next;
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if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
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for (entry = list->head; entry; entry = next) {
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if (entry->magic != SL_ENTRY_MAGIC) return -1; /* Bad magic */
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next = entry->forward[0];
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entry->magic = SL_FREED_MAGIC;
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drmFree(entry);
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}
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list->magic = SL_FREED_MAGIC;
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drmFree(list);
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return 0;
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}
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static SLEntryPtr SLLocate(void *l, unsigned long key, SLEntryPtr *update)
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{
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SkipListPtr list = (SkipListPtr)l;
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SLEntryPtr entry;
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int i;
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if (list->magic != SL_LIST_MAGIC) return NULL;
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for (i = list->level, entry = list->head; i >= 0; i--) {
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while (entry->forward[i] && entry->forward[i]->key < key)
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entry = entry->forward[i];
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update[i] = entry;
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}
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return entry->forward[0];
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}
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int drmSLInsert(void *l, unsigned long key, void *value)
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{
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SkipListPtr list = (SkipListPtr)l;
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SLEntryPtr entry;
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SLEntryPtr update[SL_MAX_LEVEL + 1];
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int level;
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int i;
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if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
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entry = SLLocate(list, key, update);
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if (entry && entry->key == key) return 1; /* Already in list */
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level = SLRandomLevel();
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if (level > list->level) {
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level = ++list->level;
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update[level] = list->head;
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}
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entry = SLCreateEntry(level, key, value);
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/* Fix up forward pointers */
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for (i = 0; i <= level; i++) {
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entry->forward[i] = update[i]->forward[i];
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update[i]->forward[i] = entry;
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}
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++list->count;
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return 0; /* Added to table */
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}
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int drmSLDelete(void *l, unsigned long key)
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{
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SkipListPtr list = (SkipListPtr)l;
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SLEntryPtr update[SL_MAX_LEVEL + 1];
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SLEntryPtr entry;
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int i;
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if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
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entry = SLLocate(list, key, update);
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if (!entry || entry->key != key) return 1; /* Not found */
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/* Fix up forward pointers */
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for (i = 0; i <= list->level; i++) {
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if (update[i]->forward[i] == entry)
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update[i]->forward[i] = entry->forward[i];
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}
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entry->magic = SL_FREED_MAGIC;
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drmFree(entry);
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while (list->level && !list->head->forward[list->level]) --list->level;
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--list->count;
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return 0;
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}
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int drmSLLookup(void *l, unsigned long key, void **value)
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{
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SkipListPtr list = (SkipListPtr)l;
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SLEntryPtr update[SL_MAX_LEVEL + 1];
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SLEntryPtr entry;
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entry = SLLocate(list, key, update);
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if (entry && entry->key == key) {
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*value = entry;
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return 0;
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}
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*value = NULL;
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return -1;
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}
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int drmSLLookupNeighbors(void *l, unsigned long key,
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unsigned long *prev_key, void **prev_value,
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unsigned long *next_key, void **next_value)
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{
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SkipListPtr list = (SkipListPtr)l;
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SLEntryPtr update[SL_MAX_LEVEL + 1] = {0};
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int retcode = 0;
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SLLocate(list, key, update);
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*prev_key = *next_key = key;
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*prev_value = *next_value = NULL;
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if (update[0]) {
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*prev_key = update[0]->key;
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*prev_value = update[0]->value;
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++retcode;
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if (update[0]->forward[0]) {
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*next_key = update[0]->forward[0]->key;
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*next_value = update[0]->forward[0]->value;
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++retcode;
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}
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}
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return retcode;
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}
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int drmSLNext(void *l, unsigned long *key, void **value)
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{
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SkipListPtr list = (SkipListPtr)l;
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SLEntryPtr entry;
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if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
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entry = list->p0;
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if (entry) {
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list->p0 = entry->forward[0];
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*key = entry->key;
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*value = entry->value;
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return 1;
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}
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list->p0 = NULL;
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return 0;
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}
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int drmSLFirst(void *l, unsigned long *key, void **value)
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{
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SkipListPtr list = (SkipListPtr)l;
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if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
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list->p0 = list->head->forward[0];
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return drmSLNext(list, key, value);
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}
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/* Dump internal data structures for debugging. */
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void drmSLDump(void *l)
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{
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SkipListPtr list = (SkipListPtr)l;
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SLEntryPtr entry;
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int i;
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if (list->magic != SL_LIST_MAGIC) {
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printf("Bad magic: 0x%08lx (expected 0x%08lx)\n",
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list->magic, SL_LIST_MAGIC);
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return;
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}
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printf("Level = %d, count = %d\n", list->level, list->count);
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for (entry = list->head; entry; entry = entry->forward[0]) {
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if (entry->magic != SL_ENTRY_MAGIC) {
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printf("Bad magic: 0x%08lx (expected 0x%08lx)\n",
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list->magic, SL_ENTRY_MAGIC);
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}
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printf("\nEntry %p <0x%08lx, %p> has %2d levels\n",
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entry, entry->key, entry->value, entry->levels);
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for (i = 0; i < entry->levels; i++) {
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if (entry->forward[i]) {
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printf(" %2d: %p <0x%08lx, %p>\n",
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i,
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entry->forward[i],
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entry->forward[i]->key,
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entry->forward[i]->value);
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} else {
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printf(" %2d: %p\n", i, entry->forward[i]);
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}
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}
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}
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}
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