skiplistNode *slInsert(skiplist *sl, double score) { skiplistNode *update[SKIPLIST_MAXLEVEL]; skiplistNode *node; node = sl->header; int i, level; for ( i = sl->level-1; i >= 0; i--) { while(node->level[i].forward && node->level[i].forward->score < score) { node = node->level[i].forward; } update[i] = node; } level = slRandomLevel(); if (level > sl->level) { for (i = sl->level; i< level ;i++) { update[i] = sl->header; } sl->level = level; } node = slCreateNode(level, score); for (i = 0; i < level; i++) { node->level[i].forward = update[i]->level[i].forward; update[i]->level[i].forward = node; } node->backward = (update[0] == sl->header? NULL : update[0]); if (node->level[0].forward) node->level[0].forward->backward = node; else sl->tail = node; sl->length++; return node; }
skiplistNode *slInsert(skiplist *sl, void *obj) { skiplistNode *update[SKIPLIST_MAXLEVEL]={NULL}; skiplistNode *node; int i, level; node = sl->header; /* 从最高层次开始搜索,查找插入的位置。update数组用于记录各层次的插入点 */ for(i=sl->level-1; i>=0; i--){ while(node->forward[i] && sl->cmp(node->forward[i]->obj, obj)){ node = node->forward[i]; } update[i]=node; } /* 完全随机决定本次插入的元素所占的层数 */ level = slRandomLevel(); if(level>sl->level){ for(i=sl->level;i<level;i++){ update[i] = sl->header; } sl->level = level; } node = slCreateNode(level, obj); /* 分别在每一层执行链表插入动作 */ for(i=0; i<level; i++){ node->forward[i] = update[i]->forward[i]; update[i]->forward[i] = node; } sl->length++; return node; }
void slInsert(skiplist *sl, double score, slobj *obj) { skiplistNode *update[SKIPLIST_MAXLEVEL], *x; unsigned int rank[SKIPLIST_MAXLEVEL]; int i, level; x = sl->header; for (i = sl->level-1; i >= 0; i--) { /* store rank that is crossed to reach the insert position */ rank[i] = i == (sl->level-1) ? 0 : rank[i+1]; while (x->level[i].forward && (x->level[i].forward->score < score || (x->level[i].forward->score == score && compareslObj(x->level[i].forward->obj,obj) < 0))) { rank[i] += x->level[i].span; x = x->level[i].forward; } update[i] = x; } /* we assume the key is not already inside, since we allow duplicated * scores, and the re-insertion of score and redis object should never * happen since the caller of slInsert() should test in the hash table * if the element is already inside or not. */ level = slRandomLevel(); if (level > sl->level) { for (i = sl->level; i < level; i++) { rank[i] = 0; update[i] = sl->header; update[i]->level[i].span = sl->length; } sl->level = level; } x = slCreateNode(level,score,obj); for (i = 0; i < level; i++) { x->level[i].forward = update[i]->level[i].forward; update[i]->level[i].forward = x; /* update span covered by update[i] as x is inserted here */ x->level[i].span = update[i]->level[i].span - (rank[0] - rank[i]); update[i]->level[i].span = (rank[0] - rank[i]) + 1; } /* increment span for untouched levels */ for (i = level; i < sl->level; i++) { update[i]->level[i].span++; } x->backward = (update[0] == sl->header) ? NULL : update[0]; if (x->level[0].forward) x->level[0].forward->backward = x; else sl->tail = x; sl->length++; }
skiplist *slCreate(void) { int j; skiplist *sl; sl = malloc(sizeof(*sl)); sl->level = 1; sl->length = 0; sl->header = slCreateNode(SKIPLIST_MAXLEVEL, 0); for(j = 0; j < SKIPLIST_MAXLEVEL; j++) { sl->header->level[j].forward = NULL; } sl->header->backward = NULL; sl->tail = NULL; return sl; }
/* * 创建skiplist * */ skiplist *slCreate(cmp_func_t cmp) { int j; skiplist *sl; sl = malloc(sizeof(skiplist)); if(NULL==sl){ return NULL; } sl->level = 1; sl->length = 0; sl->header = slCreateNode(SKIPLIST_MAXLEVEL, 0); sl->cmp = cmp; for(j=0;j<SKIPLIST_MAXLEVEL;j++){ sl->header->forward[j] = NULL; } return sl; }