zskiplistNode *zn = zmalloc(sizeof(*zn));
zn->forward = zmalloc(sizeof(zskiplistNode*) * level);
- zn->span = zmalloc(sizeof(unsigned int) * level);
+ if (level > 0)
+ zn->span = zmalloc(sizeof(unsigned int) * (level - 1));
zn->score = score;
zn->obj = obj;
return zn;
static void zslInsert(zskiplist *zsl, double score, robj *obj) {
zskiplistNode *update[ZSKIPLIST_MAXLEVEL], *x;
- unsigned int span[ZSKIPLIST_MAXLEVEL];
+ unsigned int rank[ZSKIPLIST_MAXLEVEL];
int i, level;
x = zsl->header;
for (i = zsl->level-1; i >= 0; i--) {
- /* store span that is crossed to reach the insert position */
- span[i] = i == (zsl->level-1) ? 0 : span[i+1];
+ /* store rank that is crossed to reach the insert position */
+ rank[i] = i == (zsl->level-1) ? 0 : rank[i+1];
while (x->forward[i] &&
(x->forward[i]->score < score ||
(x->forward[i]->score == score &&
compareStringObjects(x->forward[i]->obj,obj) < 0))) {
- span[i] += x->span[i];
+ rank[i] += i > 0 ? x->span[i-1] : 1;
x = x->forward[i];
}
update[i] = x;
level = zslRandomLevel();
if (level > zsl->level) {
for (i = zsl->level; i < level; i++) {
- span[i] = 0;
+ rank[i] = 0;
update[i] = zsl->header;
- update[i]->span[i] = zsl->length;
+ update[i]->span[i-1] = zsl->length;
}
zsl->level = level;
}
update[i]->forward[i] = x;
/* update span covered by update[i] as x is inserted here */
- x->span[i] = update[i]->span[i] - (span[0] - span[i]);
- update[i]->span[i] = (span[0] - span[i]) + 1;
+ if (i > 0) {
+ x->span[i-1] = update[i]->span[i-1] - (rank[0] - rank[i]);
+ update[i]->span[i-1] = (rank[0] - rank[i]) + 1;
+ }
}
/* increment span for untouched levels */
for (i = level; i < zsl->level; i++) {
- update[i]->span[i]++;
+ update[i]->span[i-1]++;
}
x->backward = (update[0] == zsl->header) ? NULL : update[0];
if (x && score == x->score && compareStringObjects(x->obj,obj) == 0) {
for (i = 0; i < zsl->level; i++) {
if (update[i]->forward[i] == x) {
- update[i]->span[i] += x->span[i] - 1;
+ if (i > 0) {
+ update[i]->span[i-1] += x->span[i-1] - 1;
+ }
update[i]->forward[i] = x->forward[i];
} else {
- update[i]->span[i] -= 1;
+ /* invariant: i > 0, because update[0]->forward[0]
+ * is always equal to x */
+ update[i]->span[i-1] -= 1;
}
}
if (x->forward[0]) {
for (i = 0; i < zsl->level; i++) {
if (update[i]->forward[i] == x) {
- update[i]->span[i] += x->span[i] - 1;
+ if (i > 0) {
+ update[i]->span[i-1] += x->span[i-1] - 1;
+ }
update[i]->forward[i] = x->forward[i];
} else {
- update[i]->span[i] -= 1;
+ /* invariant: i > 0, because update[0]->forward[0]
+ * is always equal to x */
+ update[i]->span[i-1] -= 1;
}
}
if (x->forward[0]) {
return x->forward[0];
}
+/* Find the rank for an element by both score and key.
+ * Returns 0 when the element cannot be found, rank otherwise.
+ * Note that the rank is 1-based due to the span of zsl->header to the
+ * first element. */
+static unsigned long zslGetRank(zskiplist *zsl, double score, robj *o) {
+ zskiplistNode *x;
+ unsigned long rank = 0;
+ int i;
+
+ x = zsl->header;
+ for (i = zsl->level-1; i >= 0; i--) {
+ while (x->forward[i] &&
+ (x->forward[i]->score < score ||
+ (x->forward[i]->score == score &&
+ compareStringObjects(x->forward[i]->obj,o) <= 0))) {
+ rank += i > 0 ? x->span[i-1] : 1;
+ x = x->forward[i];
+ }
+
+ /* x might be equal to zsl->header, so test if obj is non-NULL */
+ if (x->obj && compareStringObjects(x->obj,o) == 0) {
+ return rank;
+ }
+ }
+ return 0;
+}
+
+/* Finds an element by its rank. The rank argument needs to be 1-based. */
+zskiplistNode* zslGetElementByRank(zskiplist *zsl, unsigned long rank) {
+ zskiplistNode *x;
+ unsigned long traversed = 0;
+ int i;
+
+ x = zsl->header;
+ for (i = zsl->level-1; i >= 0; i--) {
+ while (x->forward[i] && (traversed + (i > 0 ? x->span[i-1] : 1)) <= rank) {
+ traversed += i > 0 ? x->span[i-1] : 1;
+ x = x->forward[i];
+ }
+
+ if (traversed == rank) {
+ return x;
+ }
+ }
+ return NULL;
+}
+
/* The actual Z-commands implementations */
/* This generic command implements both ZADD and ZINCRBY.
if (end >= llen) end = llen-1;
rangelen = (end-start)+1;
- /* Return the result in form of a multi-bulk reply */
+ /* check if starting point is trivial, before searching
+ * the element in log(N) time */
if (reverse) {
- ln = zsl->tail;
- while (start--)
- ln = ln->backward;
+ ln = start == 0 ? zsl->tail : zslGetElementByRank(zsl, llen - start);
} else {
- ln = zsl->header->forward[0];
- while (start--)
- ln = ln->forward[0];
+ ln = start == 0 ? zsl->header->forward[0] : zslGetElementByRank(zsl, start + 1);
}
+ /* Return the result in form of a multi-bulk reply */
addReplySds(c,sdscatprintf(sdsempty(),"*%d\r\n",
withscores ? (rangelen*2) : rangelen));
for (j = 0; j < rangelen; j++) {
}
if (o->type != REDIS_ZSET) {
addReply(c,shared.wrongtypeerr);
- return;
- }
-
- zset *zs = o->ptr;
- zskiplist *zsl = zs->zsl;
- dictEntry *de = dictFind(zs->dict,c->argv[2]);
- if (!de) {
- addReply(c,shared.nullbulk);
- return;
- }
-
- double *score = dictGetEntryVal(de);
- zskiplistNode *x;
- unsigned int rank = 0;
- int i;
+ } else {
+ zset *zs = o->ptr;
+ zskiplist *zsl = zs->zsl;
+ dictEntry *de;
+ unsigned long rank;
- x = zsl->header;
- for (i = zsl->level-1; i >= 0; i--) {
- while (x->forward[i] &&
- (x->forward[i]->score < *score ||
- (x->forward[i]->score == *score &&
- compareStringObjects(x->forward[i]->obj,c->argv[2]) <= 0))) {
- rank += x->span[i];
- x = x->forward[i];
+ de = dictFind(zs->dict,c->argv[2]);
+ if (!de) {
+ addReply(c,shared.nullbulk);
+ return;
}
- /* x might be equal to zsl->header, so test if obj is non-NULL */
- if (x->obj && compareStringObjects(x->obj,c->argv[2]) == 0) {
- /* the pointer from zsl->header to the first element also spans one,
- * which makes the rank 1-based */
+ double *score = dictGetEntryVal(de);
+ rank = zslGetRank(zsl, *score, c->argv[2]);
+ if (rank) {
addReplyLong(c, rank-1);
- return;
+ } else {
+ addReply(c,shared.nullbulk);
}
}
-
- addReply(c,shared.nullbulk);
}
/* ========================= Non type-specific commands ==================== */
projects / redis.git / blobdiff