Functions

Description

Core utility functions of the library.

Functions
template<typename Operation >
constexpr auto	ozo::get_operation_initiator (const Operation &op)
	Get asynchronous operation initiator. More...
template<typename Operation , typename Factory >
constexpr auto	ozo::construct_initiator (Factory &&f, const Operation &op)
	Create asynchronous operation initiator using factory. More...
template<typename T >
constexpr decltype(auto)	ozo::is_null (const T &v) noexcept(noexcept(is_null_impl< T >::apply(v)))
	Indicates if value is in null state. More...
template<typename T , typename Alloc >
void	ozo::allocate_nullable (T &out, const Alloc &a)
	Allocates nullable object of given type. More...
template<typename Map , typename Key >
constexpr decltype(auto)	ozo::get_option (Map &&map, ozo::option< Key > op)
	Get the option object from Hana.Map. More...
template<typename Map , typename Key , typename T >
constexpr decltype(auto)	ozo::get_option (Map &&map, ozo::option< Key > op, T &&default_)
	Get the option object from Hana.Map. More...
template<typename ... Options>
constexpr auto	ozo::make_options (Options &&...opts)
	Constructor for options map. More...
template<typename T >
constexpr decltype(auto)	ozo::unwrap_recursive (T &&v) noexcept
	Unwraps argument underlying value recursively. More...
template<typename T >
constexpr bool	ozo::is_null_recursive (T &&v) noexcept
	Indicates if one of unwrapped values is in null state. More...
template<typename T >
constexpr decltype(auto)	ozo::unwrap (T &&v) noexcept(noexcept(unwrap_impl< std::decay_t< T >>::apply(std::forward< T >(v))))
	Unwraps argument underlying value or forwards the argument. More...
constexpr time_traits::time_point	ozo::deadline (time_traits::time_point t) noexcept
	Dealdine calculation. More...
constexpr time_traits::time_point	ozo::deadline (time_traits::duration after, time_traits::time_point now) noexcept
	Dealdine calculation. More...
time_traits::time_point	ozo::deadline (time_traits::duration after) noexcept
	Dealdine calculation. More...
constexpr auto	ozo::deadline (none_t) noexcept
	Dealdine calculation. More...
constexpr time_traits::duration	ozo::time_left (time_traits::time_point t, time_traits::time_point now) noexcept
	Time left to deadline. More...
time_traits::duration	ozo::time_left (time_traits::time_point t) noexcept
	Time left to deadline. More...
bool	ozo::expired (time_traits::time_point t, time_traits::time_point now) noexcept
	Deadline is expired. More...
bool	ozo::expired (time_traits::time_point t) noexcept
	Deadline is expired. More...

Function Documentation

allocate_nullable()

template<typename T , typename Alloc >

void ozo::allocate_nullable	(	T &	out,
		const Alloc &	a
	)

Allocates nullable object of given type.

This function allocates memory and constructs nullable object of given type by means of given allocator if applicable. It uses ozo::allocate_nullable_impl functional object as an implementation.

Note

The function implementation may use no allocator and ignore the argument (e.g.: if it is not applicable to the given object type).

Parameters

out	— object to allocate to
a	— allocator to use

construct_initiator()

template<typename Operation , typename Factory >

constexpr auto ozo::construct_initiator ( Factory &&  f, const Operation &  op  )

constexpr

Create asynchronous operation initiator using factory.

The function constructs asynchronous operation initiator using factory object. The default behaviour is static assertion. The behaviour should be customized for a particular factory.

Parameters

f	— factory for asynchronous operation initiator object.
op	— asynchronous operation object.

Returns

initiator functional object.

Customization Point

Default implementation is static assertion

template <typename Factory, typename Operation>
struct construct_initiator_impl {
    constexpr static auto apply(const Factory&, const Operation&) {
        static_assert(std::is_void_v<Factory>, "Factory is not supported for the Operation");
    }
};

deadline() [1/4]

constexpr auto ozo::deadline ( none_t  )

constexprnoexcept

Dealdine calculation.

Calculates deadline from ozo::none_t.

Parameters

none_t

Returns

ozo::none

References ozo::none.

Referenced by ozo::deadline().

deadline() [2/4]

time_traits::time_point ozo::deadline ( time_traits::duration  after )

noexcept

Dealdine calculation.

Calculates deadline time point in a given duration from now. The result value is limited by time_traits::time_point::max(). Literally: time_traits::now() + after.

Parameters

after

— duration to a deadline time point

Returns

calculated deadline time point

References ozo::deadline(), and ozo::time_traits::now().

deadline() [3/4]

constexpr time_traits::time_point ozo::deadline ( time_traits::duration  after, time_traits::time_point  now  )

constexprnoexcept

Dealdine calculation.

Calculates deadline time point in a given duration from a given time point. The result value range is [now, time_traits::time_point::max()]. Literally: now + after.

Parameters

after	— duration to a deadline time point
now	— start time point for the duration

Returns

calculated deadline time point

deadline() [4/4]

constexpr time_traits::time_point ozo::deadline ( time_traits::time_point  t )

constexprnoexcept

Dealdine calculation.

Calculate deadline from time point. Literally returns it's argument.

Parameters

t	— time point of a deadline

Returns

it's argument

Referenced by ozo::failover::retry_strategy< Options >::get_first_try().

expired() [1/2]

bool ozo::expired ( time_traits::time_point  t )

noexcept

Deadline is expired.

Indicates if a given dedline is expired. Deadline is expired then time left duration to the deadline is 0.

Parameters

t	— deadline time point

Returns

true — deadline has been expired

false — there is time left to deadline

References ozo::time_traits::now().

expired() [2/2]

bool ozo::expired ( time_traits::time_point  t, time_traits::time_point  now  )

noexcept

Deadline is expired.

Indicates if a given dedline is expired for a given time point. Deadline is expired then time left duration to the deadline is 0.

Parameters

t	— deadline time point

Returns

true — deadline has been expired

false — there is time left to deadline

References ozo::time_left().

get_operation_initiator()

template<typename Operation >

constexpr auto ozo::get_operation_initiator ( const Operation &  op )

constexpr

Get asynchronous operation initiator.

Initiator is a functional object which may be used with boost::asio::async_initiate to start an asynchronous operation. Typically this is detail zone of an operation, but in OZO this is a part of operations customization for extentions like failover.

Parameters

op	— asynchronous operation object

Returns

initiator functional object

Customization Point

The function is implemented via ozo::get_operation_initiator_impl. The default implementation is:

template <typename Operation>
struct get_operation_initiator_impl {
    constexpr static auto apply(const Operation& op) {
        return op.get_initiator();
    }
};

So this behaviour may be changed via specialization of the template.

Referenced by ozo::begin(), ozo::execute(), ozo::get_connection(), and ozo::request().

get_option() [1/2]

template<typename Map , typename Key >

constexpr decltype(auto) ozo::get_option ( Map &&  map, ozo::option< Key >  op  )

constexpr

Get the option object from Hana.Map.

This function is similar to map[op] call, but it makes a static assert that map should contain an option. This produces human readable compile error in case of no option found.

Parameters

map	— map to get option from
op	— the option

Returns

option value reference

Referenced by ozo::failover::basic_try< Options, Context >::get_conditions(), ozo::failover::basic_try< Options, Context >::get_next_try(), ozo::get_transaction_deferrability(), ozo::get_transaction_isolation_level(), ozo::get_transaction_mode(), and ozo::failover::basic_try< Options, Context >::tries_remain().

get_option() [2/2]

template<typename Map , typename Key , typename T >

constexpr decltype(auto) ozo::get_option ( Map &&  map, ozo::option< Key >  op, T &&  default_  )

constexpr

Get the option object from Hana.Map.

This function is similar to map[op] call, but returns default value if no such option has been found.

Parameters

map	— map to get option from
op	— the option
default_	— the default value for the option which is not found

Returns

option value reference or forwarded default value

Referenced by ozo::options_factory_base< options_factory< decltype(hana::make_map()) >, decltype(hana::make_map()) >::get().

is_null()

template<typename T >

constexpr decltype(auto) ozo::is_null ( const T &  v )

constexprnoexcept

Indicates if value is in null state.

This utility function indicates if given value is in null state. If argument is not #Nullable it always returns false

Parameters

value

— object to examine

Returns

true — object is in null-state,

false — overwise.

Referenced by ozo::send(), and ozo::size_of().

is_null_recursive()

template<typename T >

constexpr bool ozo::is_null_recursive ( T &&  v )

constexprnoexcept

Indicates if one of unwrapped values is in null state.

This utility function recursively examines the value for a null state. The function is useful to examine Connection object for a null state because it is normal for such object to be wrapped.

The function is equal to this pesudo-code:

constexpr bool is_null_recursive(auto&& arg) noexcept {
    while (decltype(arg) != unwrap_type<decltype(arg)>) {
        if (is_null(arg)) {
            return true;
        }
        arg = unwrap(arg);
    }
    return false;
}

Parameters

v	— object to examine

Returns

true — one of the objects is in null-state,

false — overwise.

See also

ozo::is_null(), ozo::unwrap()

Referenced by ozo::defer_close_connection(), and ozo::error_message().

make_options()

template<typename ... Options>

constexpr auto ozo::make_options ( Options &&...  opts )

constexpr

Constructor for options map.

This function is a semantic wrapper for boost::hana::make_map.

Example

namespace demo {
 
constexpr ozo::option<class foo_tag> foo;
constexpr ozo::option<class buzz_tag> buzz;
 
}
 
using namespace std::literals;
 
auto options = ozo::make_options(demo::foo="Foo"s, demo::buzz=777);

Parameters

opts	— pairs of options and its' values

Returns

— constructed boost::hana::map

time_left() [1/2]

time_traits::duration ozo::time_left ( time_traits::time_point  t )

noexcept

Time left to deadline.

Calculates time left to a given deadline time point.

Parameters

t	— deadline time point

Returns

time left to the time point which is more or equal to a zero.

References ozo::time_traits::now().

Referenced by ozo::expired().

time_left() [2/2]

constexpr time_traits::duration ozo::time_left ( time_traits::time_point  t, time_traits::time_point  now  )

constexprnoexcept

Time left to deadline.

Calculates time left form given now time point to a given deadline time point t.

Parameters

t	— deadline time point
now	— time point to calculate duration from

Returns

time left to the time point which is more or equal to a zero.

unwrap()

template<typename T >

constexpr decltype(auto) ozo::unwrap ( T &&  v )

constexprnoexcept

Unwraps argument underlying value or forwards the argument.

This utility function returns underlying value of it's argument as defined by the operation implementation ozo::unwrap_impl.

In-library implementations returns:

• reference on an underlying value - std::reference_wrapper and other types like pointers, optional values which are defined via External adaptors,
• argument itself by default.

Parameters

value

— object to unwrap

Returns

implementation depended result of unwrap_impl<std::decay_t<T>>::apply(std::forward<T>(v)) call

Referenced by ozo::pooled_connection< Rep, Executor >::close(), ozo::failover::basic_try< Options, Context >::get_context(), ozo::pooled_connection< Rep, Executor >::get_error_context(), ozo::failover::get_next_try(), ozo::failover::get_try_context(), ozo::failover::initiate_next_try(), ozo::transaction< Connection, Options >::lowest_layer(), ozo::pooled_connection< Rep, Executor >::native_handle(), ozo::pooled_connection< Rep, Executor >::oid_map(), ozo::failover::role_based_connection_provider< Source >::rebind_role(), ozo::send(), and ozo::size_of().

unwrap_recursive()

template<typename T >

constexpr decltype(auto) ozo::unwrap_recursive ( T &&  v )

constexprnoexcept

Unwraps argument underlying value recursively.

This utility function unwraps argument recursively applying ozo::unwrap() function until the type of unwrapped value and type of it's argument become the same.

Note

Before applying the function it is better to check the object recursively for a null state via ozo::is_null_recursive().

The function is equal to this pesudo-code:

constexpr decltype(auto) unwrap_recursive(auto&& arg) noexcept {
    while (decltype(arg) != unwrap_type<decltype(arg)>) {
        arg = unwrap(arg);
    }
    return arg;
}

Parameters

value

— object to unwrap

Returns

implementation depended result of recursively applied ozo::unwrap()

See also

ozo::is_null_recursive()