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 static inline unsigned int oid_hash(struct object_id oid)
  20 {
  21         return sha1hash(oid.hash);
  22 }
  23
  24 static inline int oid_equal(struct object_id a, struct object_id b)
  25 {
  26         return oideq(&a, &b);
  27 }
  28
  29 KHASH_INIT(oid, struct object_id, int, 0, oid_hash, oid_equal)
  30
  31 /**
  32  * A single oidset; should be zero-initialized (or use OIDSET_INIT).
  33  */
  34 struct oidset {
  35         kh_oid_t set;
  36 };
  37
  38 #define OIDSET_INIT { { 0 } }
  39
  40
  41 /**
  42  * Initialize the oidset structure `set`.
  43  *
  44  * If `initial_size` is bigger than 0 then preallocate to allow inserting
  45  * the specified number of elements without further allocations.
  46  */
  47 void oidset_init(struct oidset *set, size_t initial_size);
  48
  49 /**
  50  * Returns true iff `set` contains `oid`.
  51  */
  52 int oidset_contains(const struct oidset *set, const struct object_id *oid);
  53
  54 /**
  55  * Insert the oid into the set; a copy is made, so "oid" does not need
  56  * to persist after this function is called.
  57  *
  58  * Returns 1 if the oid was already in the set, 0 otherwise. This can be used
  59  * to perform an efficient check-and-add.
  60  */
  61 int oidset_insert(struct oidset *set, const struct object_id *oid);
  62
  63 /**
  64  * Remove the oid from the set.
  65  *
  66  * Returns 1 if the oid was present in the set, 0 otherwise.
  67  */
  68 int oidset_remove(struct oidset *set, const struct object_id *oid);
  69
  70 /**
  71  * Remove all entries from the oidset, freeing any resources associated with
  72  * it.
  73  */
  74 void oidset_clear(struct oidset *set);
  75
  76 struct oidset_iter {
  77         kh_oid_t *set;
  78         khiter_t iter;
  79 };
  80
  81 static inline void oidset_iter_init(struct oidset *set,
  82                                     struct oidset_iter *iter)
  83 {
  84         iter->set = &set->set;
  85         iter->iter = kh_begin(iter->set);
  86 }
  87
  88 static inline struct object_id *oidset_iter_next(struct oidset_iter *iter)
  89 {
  90         for (; iter->iter != kh_end(iter->set); iter->iter++) {
  91                 if (kh_exist(iter->set, iter->iter))
  92                         return &kh_key(iter->set, iter->iter++);
  93         }
  94         return NULL;
  95 }
  96
  97 static inline struct object_id *oidset_iter_first(struct oidset *set,
  98                                                   struct oidset_iter *iter)
  99 {
 100         oidset_iter_init(set, iter);
 101         return oidset_iter_next(iter);
 102 }
 103
 104 #endif /* OIDSET_H */