Merge branch 'zsl-get-rank' of git://github.com/pietern/redis

diff --combined redis.c
index fd1cb0a532a46374d86aa8fb35797af74ad079d3,4f7d3efcd0e2e57627c97e65bf5d983e0c449371..331aaaa03d7424999ab8156ab9dfa1d3b2d607ca
--- 1/redis.c
--- 2/redis.c
+++ b/redis.c
@@@ -4075,7 -4075,7 +4075,7 @@@ static void pushGenericCommand(redisCli
      lobj = lookupKeyWrite(c->db,c->argv[1]);
      if (lobj == NULL) {
          if (handleClientsWaitingListPush(c,c->argv[1],c->argv[2])) {
 -            addReply(c,shared.ok);
 +            addReply(c,shared.cone);
              return;
          }
          lobj = createListObject();
@@@ -4094,7 -4094,7 +4094,7 @@@
              return;
          }
          if (handleClientsWaitingListPush(c,c->argv[1],c->argv[2])) {
 -            addReply(c,shared.ok);
 +            addReply(c,shared.cone);
              return;
          }
          list = lobj->ptr;
@@@ -4106,7 -4106,7 +4106,7 @@@
          incrRefCount(c->argv[2]);
      }
      server.dirty++;
 -    addReply(c,shared.ok);
 +    addReplySds(c,sdscatprintf(sdsempty(),":%d\r\n",listLength(list)));
  }
  
  static void lpushCommand(redisClient *c) {
@@@ -4844,7 -4844,8 +4844,8 @@@ static zskiplistNode *zslCreateNode(in
      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;
@@@ -4897,19 -4898,19 +4898,19 @@@ static int zslRandomLevel(void) 
  
  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;
@@@ -4921,9 -4922,9 +4922,9 @@@
      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;
      }
@@@ -4933,13 -4934,15 +4934,15 @@@
          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];
@@@ -4970,10 -4973,14 +4973,14 @@@ static int zslDelete(zskiplist *zsl, do
      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]) {
@@@ -5015,10 -5022,14 +5022,14 @@@ static unsigned long zslDeleteRange(zsk
  
          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]) {
@@@ -5054,6 -5065,53 +5065,53 @@@ static zskiplistNode *zslFirstWithScore
      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.
@@@ -5253,17 -5311,15 +5311,15 @@@ static void zrangeGenericCommand(redisC
              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++) {
@@@ -5467,42 -5523,26 +5523,26 @@@ static void zrankCommand(redisClient *c
      }
      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  ==================== */