lmdb::value_stream< T, D > Class Template Reference

#include <value_stream.h>

Public Member Functions
	value_stream (std::unique_ptr< MDB_cursor, D > cur)
	Take ownership of cur without changing position. nullptr valid.
	value_stream (value_stream &&)=default
	value_stream (value_stream const &)=delete
	~value_stream ()=default
value_stream &	operator= (value_stream &&)=default
value_stream &	operator= (value_stream const &)=delete
std::unique_ptr< MDB_cursor, D >	give_cursor () noexcept
void	reset ()
std::size_t	count () const
template<typename U = T, typename F = U, std::size_t offset = 0>
value_iterator< U, F, offset >	make_iterator () const
template<typename U = T, typename F = U, std::size_t offset = 0>
boost::iterator_range< value_iterator< U, F, offset > >	make_range () const

Detailed Description

template<typename T, typename D>
class lmdb::value_stream< T, D >

C++ wrapper for a LMDB read-only cursor on a fixed-sized value T.

Template Parameters

T	value type being stored by each record.
D	cleanup functor for the cursor; usually unique per db/table.

Definition at line 186 of file value_stream.h.

Constructor & Destructor Documentation

value_stream() [1/3]

template<typename T, typename D>

lmdb::value_stream< T, D >::value_stream ( std::unique_ptr< MDB_cursor, D > cur )

inlineexplicit

Take ownership of cur without changing position. nullptr valid.

Definition at line 192 of file value_stream.h.

          : cur(std::move(cur))
        {}

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value_stream() [2/3]

template<typename T, typename D>

lmdb::value_stream< T, D >::value_stream ( value_stream< T, D > && )

default

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value_stream() [3/3]

template<typename T, typename D>

lmdb::value_stream< T, D >::value_stream ( value_stream< T, D > const & )

delete

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~value_stream()

template<typename T, typename D>

lmdb::value_stream< T, D >::~value_stream ( )

default

Member Function Documentation

count()

template<typename T, typename D>

std::size_t lmdb::value_stream< T, D >::count ( ) const

inline

Exceptions

std::system_error

if LMDB has unexpected errors.

Returns

Number of values at this key.

Definition at line 230 of file value_stream.h.

        {
            return lmdb::stream::count(cur.get());
        }

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give_cursor()

template<typename T, typename D>

std::unique_ptr< MDB_cursor, D > lmdb::value_stream< T, D >::give_cursor ( )

inlinenoexcept

Give up ownership of the cursor. count(), make_iterator() and make_range() can still be invoked, but return the empty set.

Returns

Currently owned LMDB cursor.

Definition at line 208 of file value_stream.h.

        {
            return {std::move(cur)};
        }

make_iterator()

template<typename T, typename D>

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

value_iterator< U, F, offset > lmdb::value_stream< T, D >::make_iterator ( ) const

inline

Return a C++ iterator over database values from current cursor position that will reach .is_end() after the last duplicate key record. Calling make_iterator() will return an iterator whose operator* will return entire value (T). make_iterator<ELECTRONEUM_FIELD(account, id)>() will return an iterator whose operator* will return a decltype(account.id) object - the other fields in the struct account are never copied from the database.

Exceptions

std::system_error

if LMDB has unexpected errors.

Returns

C++ iterator starting at current cursor position.

Definition at line 249 of file value_stream.h.

        {
            static_assert(std::is_same<U, T>(), "was ELECTRONEUM_FIELD used with wrong type?");
            return {cur.get()};
        }

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make_range()

template<typename T, typename D>

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

boost::iterator_range< value_iterator< U, F, offset > > lmdb::value_stream< T, D >::make_range ( ) const

inline

Return a range from current cursor position until last duplicate key record. Useful in for-each range loops or in templated code expecting a range of elements. Calling make_range() will return a range of T objects. make_range<ELECTRONEUM_FIELD(account, id)>() will return a range of decltype(account.id) objects - the other fields in the struct account are never copied from the database.

Exceptions

std::system_error

if LMDB has unexpected errors.

Returns

An InputIterator range over values at cursor position.

Definition at line 267 of file value_stream.h.

        {
            return {make_iterator<U, F, offset>(), value_iterator<U, F, offset>{}};
        }

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operator=() [1/2]

template<typename T, typename D>

value_stream & lmdb::value_stream< T, D >::operator= ( value_stream< T, D > && )

default

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operator=() [2/2]

template<typename T, typename D>

value_stream & lmdb::value_stream< T, D >::operator= ( value_stream< T, D > const & )

delete

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reset()

template<typename T, typename D>

void lmdb::value_stream< T, D >::reset ( )

inline

Place the stream back at the first value. Newly created iterators will start at the first value again.

Note

Invalidates all current iterators from this, including those created with make_iterator or make_range.

Definition at line 220 of file value_stream.h.

        {
            if (cur)
                lmdb::stream::get(*cur, MDB_FIRST_DUP, 0, 0);
        }

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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