oidset.h

   1 #ifndef OIDSET_H
   2 #define OIDSET_H
   3
   4 #include "hashmap.h"
   5 #include "khash.h"
   6
   7 /**
   8  * This API is similar to sha1-array, in that it maintains a set of object ids
   9  * in a memory-efficient way. The major differences are:
  10  *
  11  *   1. It uses a hash, so we can do online duplicate removal, rather than
  12  *      sort-and-uniq at the end. This can reduce memory footprint if you have
  13  *      a large list of oids with many duplicates.
  14  *
  15  *   2. The per-unique-oid memory footprint is slightly higher due to hash
  16  *      table overhead.
  17  */
  18
  19 /**
  20  * A single oidset; should be zero-initialized (or use OIDSET_INIT).
  21  */
  22 struct oidset {
  23         kh_oid_t set;
  24 };
  25
  26 #define OIDSET_INIT { { 0 } }
  27
  28
  29 /**
  30  * Initialize the oidset structure `set`.
  31  *
  32  * If `initial_size` is bigger than 0 then preallocate to allow inserting
  33  * the specified number of elements without further allocations.
  34  */
  35 void oidset_init(struct oidset *set, size_t initial_size);
  36
  37 /**
  38  * Returns true iff `set` contains `oid`.
  39  */
  40 int oidset_contains(const struct oidset *set, const struct object_id *oid);
  41
  42 /**
  43  * Insert the oid into the set; a copy is made, so "oid" does not need
  44  * to persist after this function is called.
  45  *
  46  * Returns 1 if the oid was already in the set, 0 otherwise. This can be used
  47  * to perform an efficient check-and-add.
  48  */
  49 int oidset_insert(struct oidset *set, const struct object_id *oid);
  50
  51 /**
  52  * Remove the oid from the set.
  53  *
  54  * Returns 1 if the oid was present in the set, 0 otherwise.
  55  */
  56 int oidset_remove(struct oidset *set, const struct object_id *oid);
  57
  58 /**
  59  * Remove all entries from the oidset, freeing any resources associated with
  60  * it.
  61  */
  62 void oidset_clear(struct oidset *set);
  63
  64 struct oidset_iter {
  65         kh_oid_t *set;
  66         khiter_t iter;
  67 };
  68
  69 static inline void oidset_iter_init(struct oidset *set,
  70                                     struct oidset_iter *iter)
  71 {
  72         iter->set = &set->set;
  73         iter->iter = kh_begin(iter->set);
  74 }
  75
  76 static inline struct object_id *oidset_iter_next(struct oidset_iter *iter)
  77 {
  78         for (; iter->iter != kh_end(iter->set); iter->iter++) {
  79                 if (kh_exist(iter->set, iter->iter))
  80                         return &kh_key(iter->set, iter->iter++);
  81         }
  82         return NULL;
  83 }
  84
  85 static inline struct object_id *oidset_iter_first(struct oidset *set,
  86                                                   struct oidset_iter *iter)
  87 {
  88         oidset_iter_init(set, iter);
  89         return oidset_iter_next(iter);
  90 }
  91
  92 #endif /* OIDSET_H */