X-Git-Url: https://git.saurik.com/redis.git/blobdiff_plain/2ebd2720b37dcca3b6e0c18377bd69e9eaf541fc..18aa2b87b6db7fa79b0596590aa385adcbc64e53:/src/t_zset.c?ds=sidebyside diff --git a/src/t_zset.c b/src/t_zset.c index f42e5a31..d2535c72 100644 --- a/src/t_zset.c +++ b/src/t_zset.c @@ -17,7 +17,7 @@ /* This skiplist implementation is almost a C translation of the original * algorithm described by William Pugh in "Skip Lists: A Probabilistic * Alternative to Balanced Trees", modified in three ways: - * a) this implementation allows for repeated values. + * a) this implementation allows for repeated scores. * b) the comparison is not just by key (our 'score') but by satellite data. * c) there is a back pointer, so it's a doubly linked list with the back * pointers being only at "level 1". This allows to traverse the list @@ -64,6 +64,10 @@ void zslFree(zskiplist *zsl) { zfree(zsl); } +/* Returns a random level for the new skiplist node we are going to create. + * The return value of this function is between 1 and ZSKIPLIST_MAXLEVEL + * (both inclusive), with a powerlaw-alike distribution where higher + * levels are less likely to be returned. */ int zslRandomLevel(void) { int level = 1; while ((random()&0xFFFF) < (ZSKIPLIST_P * 0xFFFF))