Fixed-size array in shared memory with zero-overhead access. More...

#include <shm_array.h>

Inheritance diagram for shm_array< T, TableType >:

Collaboration diagram for shm_array< T, TableType >:

Public Types
STL Type Definitions
using	value_type = T
	Element type.

using	size_type = size_t
	Size type.

using	difference_type = std::ptrdiff_t
	Iterator difference.

using	reference = T &
	Reference type.

using	const_reference = const T &
	Const reference.

using	pointer = T *
	Pointer type.

using	const_pointer = const T *
	Const pointer.

using	iterator = T *
	Iterator type (raw pointer)

using	const_iterator = const T *
	Const iterator.

using	reverse_iterator = std::reverse_iterator< iterator >
	Reverse iterator.

using	const_reverse_iterator = std::reverse_iterator< const_iterator >
	Const reverse.

Public Member Functions
template<typename ShmType >
	shm_array (ShmType &shared_mem, std::string_view name, size_t count=0)
	Create new array or attach to existing array by name.

void	initialize (std::string_view name, size_t count=0)
	Internal initialization helper.

T &	at (size_t pos)
	Bounds-checked element access.

const T &	at (size_t pos) const
	Const version of at()

T &	front ()
	Access first element.

const T &	front () const
	Access first element (const)

T &	back ()
	Access last element.

const T &	back () const
	Access last element (const)

bool	empty () const noexcept
	Check if array is empty.

size_t	size () const noexcept
	Get number of elements.

void	fill (const T &value)
	Fill array with value.

std::span< T >	as_span () noexcept
	Convert to std::span for modern C++ usage.

std::span< const T >	as_span () const noexcept
	Convert to const span.

size_type	max_size () const noexcept
	Get maximum size (same as size() for fixed arrays)

pointer	data () noexcept
	Get pointer to underlying data.

const_pointer	data () const noexcept
	Get const pointer to underlying data.

std::string_view	name () const noexcept
	Get array name from metadata table.

Iterator Support
iterator	begin () noexcept
	Get iterator to beginning.

iterator	end () noexcept
	Get iterator to end.

const_iterator	begin () const noexcept
	Get const iterator to beginning.

const_iterator	end () const noexcept
	Get const iterator to end.

const_iterator	cbegin () const noexcept
	Get const iterator to beginning (explicit)

const_iterator	cend () const noexcept
	Get const iterator to end (explicit)

Reverse Iterator Support
reverse_iterator	rbegin () noexcept
	Get reverse iterator to beginning.

reverse_iterator	rend () noexcept
	Get reverse iterator to end.

const_reverse_iterator	rbegin () const noexcept
	Get const reverse iterator to beginning.

const_reverse_iterator	rend () const noexcept
	Get const reverse iterator to end.

const_reverse_iterator	crbegin () const noexcept
	Get const reverse iterator to beginning (explicit)

const_reverse_iterator	crend () const noexcept
	Get const reverse iterator to end (explicit)

Public Member Functions inherited from shm_span< T, ShmType >
	shm_span (ShmType &shm, size_t off, size_t count)

T *	data ()

const T *	data () const

size_t	size () const

T &	operator[] (size_t index)

const T &	operator[] (size_t index) const

Additional Inherited Members
Protected Attributes inherited from shm_span< T, ShmType >
ShmType &	shm

size_t	offset

size_t	num_elem

Detailed Description

template<typename T, typename TableType = shm_table>
requires std::is_trivially_copyable_v<T>
class shm_array< T, TableType >

Fixed-size array in shared memory with zero-overhead access.

Provides a fully STL-compliant array interface for shared memory. Key features:

Zero-overhead reads: Direct pointer access, no synchronization
Named discovery: Find arrays by name across processes
STL compatibility: Works with all standard algorithms
Range support: Full C++20 ranges support
Type safety: Compile-time checks via concepts

Memory layout:

[T][T][T][T]... // Contiguous array of T

shm_array::reverse_iterator

std::reverse_iterator< iterator > reverse_iterator

Reverse iterator.

Definition shm_array.h:278

Template Parameters

T	Element type (must be trivially copyable for shared memory)
TableType	Metadata table type (default: shm_table)

Note: Read performance identical to native arrays (~2.3ns per access); No synchronization provided - use external locking if needed

Warning: Cannot resize after creation (fixed-size)

Example:: // Process 1: Create and populate

posix_shm shm("sim", 10*1024*1024);

shm_array<double> temps(shm, "temperatures", 1000);

temps[0] = 25.5;

// Process 2: Discover and read

posix_shm shm("sim");

shm_array<double> temps(shm, "temperatures"); // Auto-discovers size

double t = temps[0]; // Zero-overhead read

posix_shm_impl< shm_table >

shm_span::shm
ShmType & shm
Definition shm_span.h:13

See also: shm_span Base class providing core functionality; shm_queue For FIFO operations; shm_object_pool For dynamic allocation

Definition at line 62 of file shm_array.h.

Member Typedef Documentation

◆ const_iterator

template<typename T , typename TableType = shm_table>

using shm_array< T, TableType >::const_iterator = const T*

Const iterator.

Definition at line 277 of file shm_array.h.

◆ const_pointer

template<typename T , typename TableType = shm_table>

using shm_array< T, TableType >::const_pointer = const T*

Const pointer.

Definition at line 275 of file shm_array.h.

◆ const_reference

template<typename T , typename TableType = shm_table>

using shm_array< T, TableType >::const_reference = const T&

Const reference.

Definition at line 273 of file shm_array.h.

◆ const_reverse_iterator

template<typename T , typename TableType = shm_table>

using shm_array< T, TableType >::const_reverse_iterator = std::reverse_iterator<const_iterator>

Const reverse.

Definition at line 279 of file shm_array.h.

◆ difference_type

template<typename T , typename TableType = shm_table>

using shm_array< T, TableType >::difference_type = std::ptrdiff_t

Iterator difference.

Definition at line 271 of file shm_array.h.

◆ iterator

template<typename T , typename TableType = shm_table>

using shm_array< T, TableType >::iterator = T*

Iterator type (raw pointer)

Definition at line 276 of file shm_array.h.

◆ pointer

template<typename T , typename TableType = shm_table>

using shm_array< T, TableType >::pointer = T*

Pointer type.

Definition at line 274 of file shm_array.h.

◆ reference

template<typename T , typename TableType = shm_table>

using shm_array< T, TableType >::reference = T&

Reference type.

Definition at line 272 of file shm_array.h.

◆ reverse_iterator

template<typename T , typename TableType = shm_table>

using shm_array< T, TableType >::reverse_iterator = std::reverse_iterator<iterator>

Reverse iterator.

Definition at line 278 of file shm_array.h.

◆ size_type

template<typename T , typename TableType = shm_table>

using shm_array< T, TableType >::size_type = size_t

Size type.

Definition at line 270 of file shm_array.h.

◆ value_type

template<typename T , typename TableType = shm_table>

using shm_array< T, TableType >::value_type = T

Element type.

Definition at line 269 of file shm_array.h.

Constructor & Destructor Documentation

◆ shm_array()

template<typename T , typename TableType = shm_table>

template<typename ShmType >

shm_array< T, TableType >::shm_array	(	ShmType &	shared_mem,
		std::string_view	name,
		size_t	count = `0`
	)

inline

Create new array or attach to existing array by name.

Template Parameters

ShmType Type of shared memory (must have matching TableType)

Parameters

shared_mem	Shared memory segment to allocate from
name	Unique identifier for the array (max TableType::MAX_NAME_SIZE chars)
count	Number of elements (0 = attach to existing)

Exceptions

std::runtime_error	if creation fails (insufficient space)
std::runtime_error	if name not found and count=0
std::runtime_error	if existing array has different size

Note: Name is truncated if longer than MAX_NAME_SIZE; Uses stack allocation - cannot be deallocated

Thread Safety:: Constructor is thread-safe for different names. Race condition possible for same name.

Example:: // Create new array of 1000 floats

shm_array<float> arr(shm, "sensor_data", 1000);

// Attach to existing array (size auto-discovered)

shm_array<float> arr2(shm, "sensor_data");

Definition at line 97 of file shm_array.h.

References shm_array< T, TableType >::initialize(), and shm_array< T, TableType >::name().

Member Function Documentation

◆ as_span() [1/2]

template<typename T , typename TableType = shm_table>

std::span< const T > shm_array< T, TableType >::as_span ( ) const

inlinenoexcept

Convert to const span.

Definition at line 262 of file shm_array.h.

References shm_array< T, TableType >::data(), and shm_span< T, ShmType >::num_elem.

◆ as_span() [2/2]

template<typename T , typename TableType = shm_table>

std::span< T > shm_array< T, TableType >::as_span ( )

inlinenoexcept

Convert to std::span for modern C++ usage.

Returns: std::span view of the array

Note: Allows use with C++20 ranges and algorithms

Example:: auto span = arr.as_span();

std::ranges::sort(span);

Definition at line 256 of file shm_array.h.

References shm_array< T, TableType >::data(), and shm_span< T, ShmType >::num_elem.

◆ at() [1/2]

template<typename T , typename TableType = shm_table>

T & shm_array< T, TableType >::at ( size_t pos )

inline

Bounds-checked element access.

Parameters

pos	Index to access

Returns: Reference to element

Exceptions

std::out_of_range if pos >= size()

Note: Use operator[] for unchecked access (faster)

Complexity: O(1)

Definition at line 179 of file shm_array.h.

References shm_span< T, ShmType >::num_elem.

◆ at() [2/2]

template<typename T , typename TableType = shm_table>

const T & shm_array< T, TableType >::at ( size_t pos ) const

inline

Const version of at()

See also: at(size_t)

Definition at line 190 of file shm_array.h.

References shm_span< T, ShmType >::num_elem.

◆ back() [1/2]

template<typename T , typename TableType = shm_table>

T & shm_array< T, TableType >::back ( )

inline

Access last element.

Returns: Reference to last element

Precondition: !empty()

Definition at line 210 of file shm_array.h.

References shm_array< T, TableType >::data(), and shm_span< T, ShmType >::num_elem.

◆ back() [2/2]

template<typename T , typename TableType = shm_table>

const T & shm_array< T, TableType >::back ( ) const

inline

Access last element (const)

Definition at line 213 of file shm_array.h.

References shm_array< T, TableType >::data(), and shm_span< T, ShmType >::num_elem.

◆ begin() [1/2]

template<typename T , typename TableType = shm_table>

const_iterator shm_array< T, TableType >::begin ( ) const

inlinenoexcept

Get const iterator to beginning.

Definition at line 292 of file shm_array.h.

References shm_array< T, TableType >::data().

◆ begin() [2/2]

template<typename T , typename TableType = shm_table>

iterator shm_array< T, TableType >::begin ( )

inlinenoexcept

Get iterator to beginning.

Definition at line 286 of file shm_array.h.

References shm_array< T, TableType >::data().

Referenced by shm_array< T, TableType >::cbegin(), main(), shm_array< T, TableType >::rend(), and shm_array< T, TableType >::rend().

◆ cbegin()

template<typename T , typename TableType = shm_table>

const_iterator shm_array< T, TableType >::cbegin ( ) const

inlinenoexcept

Get const iterator to beginning (explicit)

Definition at line 298 of file shm_array.h.

References shm_array< T, TableType >::begin().

◆ cend()

template<typename T , typename TableType = shm_table>

const_iterator shm_array< T, TableType >::cend ( ) const

inlinenoexcept

Get const iterator to end (explicit)

Definition at line 301 of file shm_array.h.

References shm_array< T, TableType >::end().

◆ crbegin()

template<typename T , typename TableType = shm_table>

const_reverse_iterator shm_array< T, TableType >::crbegin ( ) const

inlinenoexcept

Get const reverse iterator to beginning (explicit)

Definition at line 320 of file shm_array.h.

References shm_array< T, TableType >::rbegin().

◆ crend()

template<typename T , typename TableType = shm_table>

const_reverse_iterator shm_array< T, TableType >::crend ( ) const

inlinenoexcept

Get const reverse iterator to end (explicit)

Definition at line 323 of file shm_array.h.

References shm_array< T, TableType >::rend().

◆ data() [1/2]

template<typename T , typename TableType = shm_table>

const_pointer shm_array< T, TableType >::data ( ) const

inlinenoexcept

Get const pointer to underlying data.

Definition at line 336 of file shm_array.h.

References shm_array< T, TableType >::data().

◆ data() [2/2]

template<typename T , typename TableType = shm_table>

pointer shm_array< T, TableType >::data ( )

inlinenoexcept

Get pointer to underlying data.

Returns: Pointer to first element (or nullptr if empty)

Note: Direct memory access - use with caution

Definition at line 333 of file shm_array.h.

References shm_array< T, TableType >::data().

◆ empty()

template<typename T , typename TableType = shm_table>

bool shm_array< T, TableType >::empty ( ) const

inlinenoexcept

Check if array is empty.

Returns: true if size() == 0

Definition at line 217 of file shm_array.h.

References shm_span< T, ShmType >::num_elem.

◆ end() [1/2]

template<typename T , typename TableType = shm_table>

const_iterator shm_array< T, TableType >::end ( ) const

inlinenoexcept

Get const iterator to end.

Definition at line 295 of file shm_array.h.

References shm_array< T, TableType >::data(), and shm_span< T, ShmType >::num_elem.

◆ end() [2/2]

template<typename T , typename TableType = shm_table>

iterator shm_array< T, TableType >::end ( )

inlinenoexcept

Get iterator to end.

Definition at line 289 of file shm_array.h.

References shm_array< T, TableType >::data(), and shm_span< T, ShmType >::num_elem.

Referenced by shm_array< T, TableType >::cend(), main(), shm_array< T, TableType >::rbegin(), and shm_array< T, TableType >::rbegin().

◆ fill()

template<typename T , typename TableType = shm_table>

void shm_array< T, TableType >::fill ( const T & value )

inline

Fill array with value.

Parameters

value Value to fill with

Note: No synchronization - use external locking if needed

Complexity: O(n)

Example:: shm_array<int> arr(shm, "data", 1000);

arr.fill(42); // All elements = 42

Definition at line 238 of file shm_array.h.

References shm_array< T, TableType >::data(), and shm_span< T, ShmType >::num_elem.

◆ front() [1/2]

template<typename T , typename TableType = shm_table>

T & shm_array< T, TableType >::front ( )

inline

Access first element.

Returns: Reference to first element

Precondition: !empty()

Definition at line 202 of file shm_array.h.

References shm_array< T, TableType >::data().

◆ front() [2/2]

template<typename T , typename TableType = shm_table>

const T & shm_array< T, TableType >::front ( ) const

inline

Access first element (const)

Definition at line 205 of file shm_array.h.

References shm_array< T, TableType >::data().

◆ initialize()

template<typename T , typename TableType = shm_table>

void shm_array< T, TableType >::initialize	(	std::string_view	name,
		size_t	count = `0`
	)

inline

Internal initialization helper.

Definition at line 114 of file shm_array.h.

References shm_array< T, TableType >::name(), shm_span< T, ShmType >::num_elem, shm_span< T, ShmType >::offset, and shm_span< T, ShmType >::shm.

Referenced by shm_array< T, TableType >::shm_array().

◆ max_size()

template<typename T , typename TableType = shm_table>

size_type shm_array< T, TableType >::max_size ( ) const

inlinenoexcept

Get maximum size (same as size() for fixed arrays)

Returns: Maximum number of elements (equals size())

Definition at line 328 of file shm_array.h.

References shm_span< T, ShmType >::num_elem.

◆ name()

template<typename T , typename TableType = shm_table>

std::string_view shm_array< T, TableType >::name ( ) const

inlinenoexcept

Get array name from metadata table.

Returns: Name used to create/find this array

Note: Returns empty string_view if table entry lost

Complexity: O(1) - cached lookup

Example:: shm_array<int> arr(shm, "sensor_data", 100);

std::cout << arr.name(); // Prints: sensor_data

Definition at line 353 of file shm_array.h.

Referenced by example_large_simulation(), example_minimal_overhead(), shm_array< T, TableType >::initialize(), and shm_array< T, TableType >::shm_array().

◆ rbegin() [1/2]

template<typename T , typename TableType = shm_table>

const_reverse_iterator shm_array< T, TableType >::rbegin ( ) const

inlinenoexcept

Get const reverse iterator to beginning.

Definition at line 314 of file shm_array.h.

References shm_array< T, TableType >::end().

◆ rbegin() [2/2]

template<typename T , typename TableType = shm_table>

reverse_iterator shm_array< T, TableType >::rbegin ( )

inlinenoexcept

Get reverse iterator to beginning.

Definition at line 308 of file shm_array.h.

References shm_array< T, TableType >::end().

Referenced by shm_array< T, TableType >::crbegin().

◆ rend() [1/2]

template<typename T , typename TableType = shm_table>

const_reverse_iterator shm_array< T, TableType >::rend ( ) const

inlinenoexcept

Get const reverse iterator to end.

Definition at line 317 of file shm_array.h.

References shm_array< T, TableType >::begin().

◆ rend() [2/2]

template<typename T , typename TableType = shm_table>

reverse_iterator shm_array< T, TableType >::rend ( )

inlinenoexcept

Get reverse iterator to end.

Definition at line 311 of file shm_array.h.

References shm_array< T, TableType >::begin().

Referenced by shm_array< T, TableType >::crend().

◆ size()

template<typename T , typename TableType = shm_table>

size_t shm_array< T, TableType >::size ( ) const

inlinenoexcept

Get number of elements.

Returns: Number of elements in array

Definition at line 221 of file shm_array.h.

References shm_span< T, ShmType >::num_elem.

Referenced by shm_simd::SimdArray< TableType >::dot(), example_custom_config(), example_minimal_overhead(), main(), shm_simd::SimdArray< TableType >::max(), shm_simd::SimdArray< TableType >::min(), shm_simd::SimdArray< TableType >::scale(), and shm_simd::SimdArray< TableType >::sum().

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

include/shm_array.h

Public Types

Public Member Functions

Additional Inherited Members

Detailed Description

Member Typedef Documentation

◆ const_iterator

◆ const_pointer

◆ const_reference

◆ const_reverse_iterator

◆ difference_type

◆ iterator

◆ pointer

◆ reference

◆ reverse_iterator

◆ size_type

◆ value_type

Constructor & Destructor Documentation

◆ shm_array()

Member Function Documentation

◆ as_span() [1/2]

◆ as_span() [2/2]

◆ at() [1/2]

◆ at() [2/2]

◆ back() [1/2]

◆ back() [2/2]

◆ begin() [1/2]

◆ begin() [2/2]

◆ cbegin()

◆ cend()

◆ crbegin()

◆ crend()

◆ data() [1/2]

◆ data() [2/2]

◆ empty()

◆ end() [1/2]

◆ end() [2/2]

◆ fill()

◆ front() [1/2]

◆ front() [2/2]

◆ initialize()

◆ max_size()

◆ name()

◆ rbegin() [1/2]

◆ rbegin() [2/2]

◆ rend() [1/2]

◆ rend() [2/2]

◆ size()