lib/ccmap.h

   1 /*
   2  * Copyright (c) 2014, 2016 Nicira, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #ifndef CCMAP_H
  18 #define CCMAP_H 1
  19
  20 #include <stdbool.h>
  21 #include <stdint.h>
  22 #include "ovs-rcu.h"
  23 #include "util.h"
  24
  25 /* Concurrent hash map for numerical counts of given hash values.
  26  * ==============================================================
  27  *
  28  * A single-writer, multiple-reader count hash table that efficiently supports
  29  * duplicates.
  30  *
  31  *
  32  * Thread-safety
  33  * =============
  34  *
  35  * The general rules are:
  36  *
  37  *    - Only a single thread may safely call into ccmap_inc(),
  38  *      or ccmap_dec() at any given time.
  39  *
  40  *    - Any number of threads may use functions and macros that search
  41  *      a given ccmap, even in parallel with other threads
  42  *      calling ccmap_inc() or ccmap_dec().
  43  */
  44
  45 /* Concurrent hash map. */
  46 struct ccmap {
  47     OVSRCU_TYPE(struct ccmap_impl *) impl;
  48 };
  49
  50 /* Initialization. */
  51 void ccmap_init(struct ccmap *);
  52 void ccmap_destroy(struct ccmap *);
  53
  54 /* Count. */
  55 size_t ccmap_count(const struct ccmap *);
  56 bool ccmap_is_empty(const struct ccmap *);
  57
  58 /* Insertion and deletion.  Return the current count after the operation. */
  59 uint32_t ccmap_inc(struct ccmap *, uint32_t hash);
  60 uint32_t ccmap_dec(struct ccmap *, uint32_t hash);
  61
  62 uint32_t ccmap_find(const struct ccmap *, uint32_t hash);
  63
  64 #endif /* ccmap.h */