cds::container::feldman_hashset::traits Struct Reference

FeldmanHashSet traits More...

#include <cds/container/details/feldman_hashset_base.h>

Public Types
typedef cds::opt::none	hash_accessor
	Mandatory functor to get hash value from data node. More...
typedef cds::opt::none	hash_splitter
	Hash splitter. More...
typedef cds::opt::none	compare
	Hash comparing functor. More...
typedef cds::opt::none	less
	Specifies binary predicate used for hash compare. More...
typedef cds::atomicity::item_counter	item_counter
	Item counter. More...
typedef CDS_DEFAULT_ALLOCATOR	allocator
	Item allocator. More...
typedef CDS_DEFAULT_ALLOCATOR	node_allocator
	Array node allocator. More...
typedef cds::opt::v::relaxed_ordering	memory_model
	C++ memory ordering model. More...
typedef cds::backoff::Default	back_off
	Back-off strategy.
typedef empty_stat	stat
	Internal statistics. More...
typedef cds::opt::v::rcu_throw_deadlock	rcu_check_deadlock
	RCU deadlock checking policy (only for RCU-based FeldmanHashSet) More...

Static Public Attributes
static constexpr size_t const	hash_size = 0
	The size of hash value in bytes. More...

Detailed Description

FeldmanHashSet traits

Member Typedef Documentation

allocator

typedef CDS_DEFAULT_ALLOCATOR cds::container::feldman_hashset::traits::allocator

Item allocator.

Default is CDS_DEFAULT_ALLOCATOR

compare

typedef cds::opt::none cds::container::feldman_hashset::traits::compare

Hash comparing functor.

No default functor is provided. If the option is not specified, the less option is used.

hash_accessor

typedef cds::opt::none cds::container::feldman_hashset::traits::hash_accessor

Mandatory functor to get hash value from data node.

It is most-important feature of FeldmanHashSet. That functor must return a reference to fixed-sized hash value of data node. The return value of that functor specifies the type of hash value.

Example:

typedef uint8_t hash_type[32]; // 256-bit hash type
struct foo {
    hash_type  hash; // 256-bit hash value
    // ... other fields
};

// Hash accessor
struct foo_hash_accessor {
    hash_type const& operator()( foo const& d ) const
    {
        return d.hash;
    }
};

hash_splitter

typedef cds::opt::none cds::container::feldman_hashset::traits::hash_splitter

Hash splitter.

This trait specifies hash bit-string splitter algorithm. By default, cds::algo::number_splitter is used if HashType is a number, cds::algo::split_bitstring otherwise.

item_counter

typedef cds::atomicity::item_counter cds::container::feldman_hashset::traits::item_counter

Item counter.

The item counting is an important part of FeldmanHashSet algorithm: the empty() member function depends on correct item counting. Therefore, atomicity::empty_item_counter is not allowed as a type of the option.

Default is atomicity::item_counter. To avoid false sharing you can aldo use atomicity::cache_friendly_item_counter

less

typedef cds::opt::none cds::container::feldman_hashset::traits::less

Specifies binary predicate used for hash compare.

If less and compare are not specified, memcmp() -like bit-wise hash comparator is used because the hash value is treated as fixed-sized bit-string.

memory_model

typedef cds::opt::v::relaxed_ordering cds::container::feldman_hashset::traits::memory_model

C++ memory ordering model.

Can be opt::v::relaxed_ordering (relaxed memory model, the default) or opt::v::sequential_consistent (sequentially consisnent memory model).

node_allocator

typedef CDS_DEFAULT_ALLOCATOR cds::container::feldman_hashset::traits::node_allocator

Array node allocator.

Allocator for array nodes. The allocator is used for creating headNode and arrayNode when the set grows. Default is CDS_DEFAULT_ALLOCATOR

rcu_check_deadlock

typedef cds::opt::v::rcu_throw_deadlock cds::container::feldman_hashset::traits::rcu_check_deadlock

RCU deadlock checking policy (only for RCU-based FeldmanHashSet)

List of available policy see opt::rcu_check_deadlock

stat

typedef empty_stat cds::container::feldman_hashset::traits::stat

Internal statistics.

By default, internal statistics is disabled (feldman_hashset::empty_stat). Use feldman_hashset::stat to enable it.

Field Documentation

hash_size

constexpr size_t const cds::container::feldman_hashset::traits::hash_size = 0

static

The size of hash value in bytes.

By default, the size of hash value is sizeof( hash_type ). Sometimes it is not correct, for example, for that 6-byte struct static_assert will be thrown:

struct key_type {
    uint32_t    key1;
    uint16_t    subkey;
};

static_assert( sizeof( key_type ) == 6, "Key type size mismatch" );

For that case you can specify hash_size explicitly.

Value 0 means sizeof( hash_type ).

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The documentation for this struct was generated from the following file:

• cds/container/details/feldman_hashset_base.h