MMappedVector< T > Class Template Reference

Append-only, mmap-backed vector of elements of type T. More...

#include "MMappedVector.h"

Collaboration diagram for MMappedVector< T >:

Classes
struct	data_t
	On-disk layout stored at the start of the backing file. More...

Public Member Functions
	MMappedVector (const char *filename, bool read_only, uint64_t magic)
	Open (or create) the mmap-backed vector.
	~MMappedVector ()
	Sync and unmap the file.
const T &	operator[] (unsigned long k) const
	Read-only element access by index.
T &	operator[] (unsigned long k)
	Read-write element access by index.
void	add (const T &value)
	Append an element to the end of the vector.
unsigned long	nbElements () const
	Return the number of elements currently stored.
void	sync ()
	Flush dirty pages to the backing file with msync().

Private Member Functions
void	mmap (size_t length, bool read_only)
	Map length bytes from the backing file.
void	grow ()
	Double the backing file and remap.
void	set (pg_uuid_t u, unsigned long i)
	Unused overload kept for interface compatibility.

Private Attributes
int	fd
	File descriptor of the backing mmap file.
data_t *	data
	Pointer to the memory-mapped data header.

Static Private Attributes
static constexpr unsigned	STARTING_CAPACITY =(1u << 16)
	Initial number of element slots allocated.

Detailed Description

template<typename T>
class MMappedVector< T >

Append-only, mmap-backed vector of elements of type T.

Template Parameters

T	The element type. Must be trivially copyable.

Definition at line 37 of file MMappedVector.h.

Constructor & Destructor Documentation

MMappedVector()

template<typename T>

MMappedVector< T >::MMappedVector	(	const char *	filename,
		bool	read_only,
		uint64_t	magic )

Open (or create) the mmap-backed vector.

Parameters

filename	Path to the backing file (created with STARTING_CAPACITY slots if absent).
read_only	If true, map the file read-only.
magic	Expected magic value for format validation.

Definition at line 42 of file MMappedVector.hpp.

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~MMappedVector()

template<typename T>

MMappedVector< T >::~MMappedVector

(

)

Sync and unmap the file.

Definition at line 110 of file MMappedVector.hpp.

Member Function Documentation

add()

template<typename T>

void MMappedVector< T >::add

(

const T &

value

)

Append an element to the end of the vector.

Grows the backing file if the current capacity is exhausted.

Parameters

value

Element to append.

Definition at line 129 of file MMappedVector.hpp.

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grow()

template<typename T>

void MMappedVector< T >::grow ( )

private

Double the backing file and remap.

Definition at line 95 of file MMappedVector.hpp.

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mmap()

template<typename T>

void MMappedVector< T >::mmap ( size_t length, bool read_only )

private

Map length bytes from the backing file.

Parameters

length	Number of bytes to map.
read_only	If true, map read-only.

Definition at line 81 of file MMappedVector.hpp.

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nbElements()

template<typename T>

unsigned long MMappedVector< T >::nbElements ( ) const

inline

Return the number of elements currently stored.

Returns

Element count.

Definition at line 114 of file MMappedVector.h.

operator[]() [1/2]

template<typename T>

T & MMappedVector< T >::operator[] ( unsigned long k )

inline

Read-write element access by index.

Parameters

k	Zero-based element index.

Returns

Reference to element k.

Definition at line 123 of file MMappedVector.hpp.

operator[]() [2/2]

template<typename T>

const T & MMappedVector< T >::operator[] ( unsigned long k ) const

inline

Read-only element access by index.

Parameters

k	Zero-based element index.

Returns

Const reference to element k.

Definition at line 117 of file MMappedVector.hpp.

set()

template<typename T>

void MMappedVector< T >::set ( pg_uuid_t u, unsigned long i )

private

Unused overload kept for interface compatibility.

Parameters

u	Ignored UUID parameter.
i	Ignored integer parameter.

sync()

template<typename T>

void MMappedVector< T >::sync

(

)

Flush dirty pages to the backing file with msync().

Definition at line 138 of file MMappedVector.hpp.

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Member Data Documentation

data

template<typename T>

data_t* MMappedVector< T >::data

private

Pointer to the memory-mapped data header.

Definition at line 54 of file MMappedVector.h.

fd

template<typename T>

int MMappedVector< T >::fd

private

File descriptor of the backing mmap file.

Definition at line 53 of file MMappedVector.h.

STARTING_CAPACITY

template<typename T>

unsigned MMappedVector< T >::STARTING_CAPACITY =(1u << 16)

staticconstexprprivate

Initial number of element slots allocated.

Definition at line 57 of file MMappedVector.h.

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

• /home/pierre/git/software/provsql/src/MMappedVector.h
• /home/pierre/git/software/provsql/src/MMappedVector.hpp