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CK_HS_INIT(3)         DragonFly Library Functions Manual         CK_HS_INIT(3)


NAME

     ck_hs_init - initialize a hash set


LIBRARY

     Concurrency Kit (libck, -lck)


SYNOPSIS

     #include <ck_hs.h>

     typedef unsigned long
     ck_hs_hash_cb_t(const void *key, unsigned long seed);

     typedef bool
     ck_hs_compare_cb_t(const void *c1, const void *c2);

     bool
     ck_hs_init(ck_hs_t *hs, unsigned int mode,
         ck_hs_hash_cb_t *hash_function, ck_hs_compare_cb_t *compare,
         struct ck_malloc *allocator, unsigned long capacity,
         unsigned long seed);


DESCRIPTION

     The ck_hs_init() function initializes the hash set pointed to by the hs
     pointer.

     The argument mode specifies the type of key-value pairs to be stored in
     the hash set as well as the expected concurrent access model.  The value
     of mode consists of a bitfield of one of the following:

     CK_HS_MODE_OBJECT
             The hash set is meant to store pointers to objects. This provides
             a hint that only CK_MD_VMA_BITS are necessary to encode the key
             argument. Any unused pointer bits are leveraged for internal
             optimizations.

     CK_HS_MODE_DIRECT
             The hash set is meant to directly store key values and that all
             bits of the key are used to encode values.

     The concurrent access model is specified by:

     CK_HS_MODE_SPMC
             The hash set should allow for concurrent readers in the presence
             of a single writer.

     CK_HS_MODE_MPMC
             The hash set should allow for concurrent readers in the presence
             of concurrent writers. This is currently unsupported.

     The developer is free to specify additional workload hints.  These hints
     are one of:

     CK_HS_MODE_DELETE
             The hash set is expected to have a delete-heavy workload.  At the
             cost of approximately 13% increased memory usage, allow for
             stronger per-slot probe bounds to combat the effects of tombstone
             accumulation.

     The argument hash_function is a mandatory pointer to a user-specified
     hash function.  A user-specified hash function takes two arguments. The
     key argument is a pointer to a key. The seed argument is the initial seed
     associated with the hash set.  This initial seed is specified by the user
     in ck_hs_init(3).

     The compare argument is an optional pointer to a user-specified key
     comparison function. If NULL is specified in this argument, then pointer
     equality will be used to determine key equality. A user-specified
     comparison function takes two arguments representing pointers to the
     objects being compared for equality. It is expected to return true if the
     keys are of equal value and false otherwise.

     The allocator argument is a pointer to a structure containing malloc and
     free function pointers which respectively define the memory allocation
     and destruction functions to be used by the hash set being initialized.

     The argument capacity represents the initial number of keys the hash set
     is expected to contain. This argument is simply a hint and the underlying
     implementation is free to allocate more or less memory than necessary to
     contain the number of entries capacity specifies.

     The argument seed specifies the initial seed used by the underlying hash
     function.  The user is free to choose a value of their choice.


RETURN VALUES

     Upon successful completion ck_hs_init() returns a value of true and
     otherwise returns a value of false to indicate an error.


ERRORS

     The behavior of ck_hs_init() is undefined if hs is not a pointer to a
     ck_hs_t object.


SEE ALSO

     ck_hs_move(3), ck_hs_destroy(3), CK_HS_HASH(3), ck_hs_iterator_init(3),
     ck_hs_next(3), ck_hs_get(3), ck_hs_put(3), ck_hs_put_unique(3),
     ck_hs_set(3), ck_hs_fas(3), ck_hs_remove(3), ck_hs_grow(3),
     ck_hs_rebuild(3), ck_hs_gc(3), ck_hs_count(3), ck_hs_reset(3),
     ck_hs_reset_size(3), ck_hs_stat(3)

     Additional information available at http://concurrencykit.org/

                              September 17, 2012

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