src/runtime/hopscotch.h

   1 /*
   2  * This software is part of the SBCL system. See the README file for
   3  * more information.
   4  *
   5  * This software is derived from the CMU CL system, which was
   6  * written at Carnegie Mellon University and released into the
   7  * public domain. The software is in the public domain and is
   8  * provided with absolutely no warranty. See the COPYING and CREDITS
   9  * files for more information.
  10  */
  11
  12 #ifndef _HOPSCOTCH_H_
  13 #define _HOPSCOTCH_H_
  14
  15 struct hopscotch_table {
  16     uword_t*   keys;
  17     unsigned*  hops;
  18     unsigned*  values;
  19     unsigned   mask;
  20     int hop_range;
  21     int count;
  22     int mem_size;  // in bytes, for zero-filling when done using
  23     // Statistics
  24     struct { int n_seeks, n_probes; } hit, miss;
  25     int  prev_size;  // in cells, as specified to hopscotch_create()
  26     char resized;    // set to 1 if sized up since last reset
  27     char rehashing;  // set to 1 during rehash
  28 };
  29
  30 void hopscotch_init();
  31 void hopscotch_create(struct hopscotch_table*,boolean,int,char);
  32 int hopscotch_put(struct hopscotch_table*,uword_t,unsigned);
  33 int hopscotch_get(struct hopscotch_table*,uword_t);
  34 int hopscotch_containsp(struct hopscotch_table*,uword_t);
  35 void hopscotch_reset(struct hopscotch_table*);
  36 void hopscotch_log_stats(struct hopscotch_table*);
  37
  38 /* This confuses me every time I look at it, so here's an example-
  39  * Suppose (unrealistically) that a table has a hop range of 4,
  40  * and 16 logical bins. The largest logical bin index (= the table mask)
  41  * is 15, and there are 3 (not 4) more cells at the end.
  42  * So the largest physical index in which you can probe without
  43  * overrunning the key array is (mask + range - 1).
  44  * i.e. the neighborhood of logical cell index 15 is {15,16,17,18}.
  45  * The total count of physical key cells is (mask + 1) + (range - 1)
  46  * where (mask + 1) is the logical bin count.
  47  */
  48 #define hopscotch_max_key_index(table) ((table).mask+(table).hop_range-1)
  49
  50 #define for_each_hopscotch_cell(loopvar, tablevar) \
  51   for(loopvar=hopscotch_max_key_index(tablevar) ; loopvar >= 0 ; --loopvar)
  52
  53 #endif