lmdb::value_iterator< T, F, offset > Class Template Reference

#include <value_stream.h>

Public Types
using	value_type = F
using	reference = value_type
using	pointer = void
using	difference_type = std::size_t
using	iterator_category = std::input_iterator_tag

Public Member Functions
	value_iterator () noexcept
	Construct an "end" iterator.
	value_iterator (MDB_cursor *cur)
	value_iterator (value_iterator const &)=default
	~value_iterator ()=default
value_iterator &	operator= (value_iterator const &)=default
bool	is_end () const noexcept
bool	equal (value_iterator const &rhs) const noexcept
value_iterator &	operator++ ()
	Invalidates all prior copies of the iterator.
value_iterator	operator++ (int)
template<typename U, typename G = U, std::size_t uoffset = 0>
G	get_value () const noexcept
value_type	operator* () const noexcept

Detailed Description

template<typename T, typename F = T, std::size_t offset = 0>
class lmdb::value_iterator< T, F, offset >

An InputIterator for a fixed-sized LMDB value at a specific key.

Template Parameters

T	The value type at the specific key.
F	The value type being returned when dereferenced.
offset	to F within T.

Note

This meets requirements for an InputIterator only. The iterator can only be incremented and dereferenced. All copies of an iterator share the same LMDB cursor, and therefore incrementing any copy will change the cursor state for all (incrementing an iterator will invalidate all prior copies of the iterator). Usage is identical to std::istream_iterator.

Definition at line 82 of file value_stream.h.

Member Typedef Documentation

difference_type

template<typename T, typename F = T, std::size_t offset = 0>

using lmdb::value_iterator< T, F, offset >::difference_type = std::size_t

Definition at line 98 of file value_stream.h.

iterator_category

template<typename T, typename F = T, std::size_t offset = 0>

using lmdb::value_iterator< T, F, offset >::iterator_category = std::input_iterator_tag

Definition at line 99 of file value_stream.h.

pointer

template<typename T, typename F = T, std::size_t offset = 0>

using lmdb::value_iterator< T, F, offset >::pointer = void

Definition at line 97 of file value_stream.h.

reference

template<typename T, typename F = T, std::size_t offset = 0>

using lmdb::value_iterator< T, F, offset >::reference = value_type

Definition at line 96 of file value_stream.h.

value_type

template<typename T, typename F = T, std::size_t offset = 0>

using lmdb::value_iterator< T, F, offset >::value_type = F

Definition at line 95 of file value_stream.h.

Constructor & Destructor Documentation

value_iterator() [1/3]

template<typename T, typename F = T, std::size_t offset = 0>

lmdb::value_iterator< T, F, offset >::value_iterator ( )

inlinenoexcept

Construct an "end" iterator.

Definition at line 102 of file value_stream.h.

          : cur(nullptr), values()
        {}

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value_iterator() [2/3]

template<typename T, typename F = T, std::size_t offset = 0>

lmdb::value_iterator< T, F, offset >::value_iterator ( MDB_cursor * cur )

inline

Parameters

cur	Iterate over values starting at this cursor position.

Exceptions

std::system_error

if unexpected LMDB error. This can happen if cur is invalid.

Definition at line 111 of file value_stream.h.

          : cur(cur), values()
        {
            if (cur)
                values = lmdb::stream::get(*cur, MDB_GET_CURRENT, 0, sizeof(T)).second;
        }

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value_iterator() [3/3]

template<typename T, typename F = T, std::size_t offset = 0>

lmdb::value_iterator< T, F, offset >::value_iterator ( value_iterator< T, F, offset > const & )

default

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~value_iterator()

template<typename T, typename F = T, std::size_t offset = 0>

lmdb::value_iterator< T, F, offset >::~value_iterator ( )

default

Member Function Documentation

equal()

template<typename T, typename F = T, std::size_t offset = 0>

bool lmdb::value_iterator< T, F, offset >::equal ( value_iterator< T, F, offset > const & rhs ) const

inlinenoexcept

Returns

True iff rhs is referencing this value.

Definition at line 126 of file value_stream.h.

        {
            return
                (values.empty() && rhs.values.empty()) ||
                values.data() == rhs.values.data();
        }

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get_value()

template<typename T, typename F = T, std::size_t offset = 0>

template<typename U, typename G = U, std::size_t uoffset = 0>

G lmdb::value_iterator< T, F, offset >::get_value ( ) const

inlinenoexcept

Get a specific field within F. Default behavior is to return the entirety of U, despite the filtering logic of operator*.

Precondition

!is_end()

Template Parameters

U	must match T, used for ELECTRONEUM_FIELD sanity checking.
G	field type to extract from the value
uoffset	to G type, or 0 when std::is_same<U, G>().

Returns

The field G, at uoffset within U.

Definition at line 161 of file value_stream.h.

        {
            static_assert(std::is_same<U, T>(), "bad ELECTRONEUM_FIELD usage?");
            static_assert(std::is_pod<U>(), "value type must be pod");
            static_assert(std::is_pod<G>(), "field type must be pod");
            static_assert(sizeof(G) + uoffset <= sizeof(U), "bad field and/or offset");
            assert(sizeof(G) + uoffset <= values.size());
            assert(!is_end());
 
            G value;
            std::memcpy(std::addressof(value), values.data() + uoffset, sizeof(value));
            return value;
        }

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is_end()

template<typename T, typename F = T, std::size_t offset = 0>

bool lmdb::value_iterator< T, F, offset >::is_end ( ) const

inlinenoexcept

Returns

True if this is one-past the last value.

Definition at line 123 of file value_stream.h.

{ return values.empty(); }

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operator*()

template<typename T, typename F = T, std::size_t offset = 0>

value_type lmdb::value_iterator< T, F, offset >::operator* ( ) const

inlinenoexcept

Precondition

!is_end()

Returns

The field F, at offset, within T.

Definition at line 176 of file value_stream.h.

{ return get_value<T, F, offset>(); }

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operator++() [1/2]

template<typename T, typename F = T, std::size_t offset = 0>

value_iterator & lmdb::value_iterator< T, F, offset >::operator++ ( )

inline

Invalidates all prior copies of the iterator.

Definition at line 134 of file value_stream.h.

        {
            increment();
            return *this;
        }

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operator++() [2/2]

template<typename T, typename F = T, std::size_t offset = 0>

value_iterator lmdb::value_iterator< T, F, offset >::operator++ ( int )

inline

Returns

A copy that is already invalidated, ignore

Definition at line 141 of file value_stream.h.

        {
            value_iterator out{*this};
            increment();
            return out;
        }

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operator=()

template<typename T, typename F = T, std::size_t offset = 0>

value_iterator & lmdb::value_iterator< T, F, offset >::operator= ( value_iterator< T, F, offset > const & )

default

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

• /home/abuild/rpmbuild/BUILD/electroneum-5.1.3.1-build/electroneum-5.1.3.1/src/lmdb/value_stream.h