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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 argu- ment. Any unused pointer bits are leveraged for internal optimiza- tions. 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 ar- gument is a pointer to a key. The seed argument is the initial seed associ- ated 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 compar- ison function. If NULL is specified in this argument, then pointer equality will be used to determine key equality. A user-specified comparison func- tion takes two arguments representing pointers to the objects being com- pared 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 im- plementation is free to allocate more or less memory than necessary to con- tain 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 other- wise 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_re- build(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 CK_HS_INIT(3)
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO
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