Memory resource implementing the first fit, top-down allocation policies, using an existing arena. More...

#include <cmsis-plus/memory/first-fit-top.h>

Inheritance diagram for os::memory::first_fit_top:

Public Member Functions
Public Member Functions
void *	allocate (std::size_t bytes, std::size_t alignment=max_align)
	Allocate a memory block.

void	deallocate (void *addr, std::size_t bytes, std::size_t alignment=max_align) noexcept
	Deallocate the previously allocated memory block.

bool	is_equal (memory_resource const &other) const noexcept
	Compare for equality with another `memory_resource`.

void	reset (void) noexcept
	Reset the memory manager to the initial state.

bool	coalesce (void) noexcept
	Coalesce free blocks.

std::size_t	max_size (void) const noexcept
	Get the largest value that can be passed to `allocate()`.

out_of_memory_handler_t	out_of_memory_handler (out_of_memory_handler_t handler)
	Set the out of memory handler.

out_of_memory_handler_t	out_of_memory_handler (void)
	Get the out of memory handler.

std::size_t	total_bytes (void)
	Get the total size of managed memory.

std::size_t	allocated_bytes (void)
	Get the current size of all allocated chunks.

std::size_t	max_allocated_bytes (void)
	Get the maximum allocated size.

std::size_t	free_bytes (void)
	Get the current size of all free chunks.

std::size_t	allocated_chunks (void)
	Get the current number of allocated chunks.

std::size_t	free_chunks (void)
	Get the current number of free chunks.

std::size_t	allocations (void)
	Get the number of allocations.

std::size_t	deallocations (void)
	Get the number of deallocations.

void	trace_print_statistics (void)
	Print a long message with usage statistics.

Public Member Functions
const char *	name (void) const
	Get object name.

Static Public Attributes
static constexpr std::size_t	max_align = alignof(std::max_align_t)
	The largest alignment for the platform. Also default when supplied alignment is not supported.

Protected Member Functions
Private Member Functions
void	internal_construct_ (void *addr, std::size_t bytes)
	Internal function to construct the memory resource.

void	internal_reset_ (void) noexcept
	Internal function to reset the memory resource.

void *	internal_align_ (chunk_t *chunk, std::size_t bytes, std::size_t alignment)
	Internal function to align a chunk.

virtual void *	do_allocate (std::size_t bytes, std::size_t alignment) override
	Implementation of the memory allocator.

virtual void	do_deallocate (void *addr, std::size_t bytes, std::size_t alignment) noexcept override
	Implementation of the memory deallocator.

virtual std::size_t	do_max_size (void) const noexcept override
	Implementation of the function to get max size.

virtual void	do_reset (void) noexcept override
	Implementation of the function to reset the memory manager.

Private Member Functions
virtual bool	do_is_equal (memory_resource const &other) const noexcept
	Implementation of the equality comparator.

virtual bool	do_coalesce (void) noexcept
	Implementation of the function to coalesce free blocks.

void	internal_increase_allocated_statistics (std::size_t bytes) noexcept
	Update statistics after allocation.

void	internal_decrease_allocated_statistics (std::size_t bytes) noexcept
	Update statistics after deallocation.

Constructors & Destructor
	first_fit_top (void *addr, std::size_t bytes)
	Construct a memory resource object instance.

	first_fit_top (const char name, void addr, std::size_t bytes)
	Construct a named memory resource object instance.

virtual	~first_fit_top () override
	Destruct the memory resource object instance.

	first_fit_top ()=default
	Default constructor. Construct a memory resource object instance.

	first_fit_top (const char *name)
	Construct a named memory resource object instance.

Detailed Description

Memory resource implementing the first fit, top-down allocation policies, using an existing arena.

This memory manager was inspired by the newlib nano implementation of malloc() & free().

Neither allocation nor deallocation are deterministic, but are reasonably fast.

Definition at line 54 of file first-fit-top.h.

Constructor & Destructor Documentation

◆ first_fit_top() [1/4]

os::memory::first_fit_top::first_fit_top	(	void *	addr,
		std::size_t	bytes
	)

inline

Construct a memory resource object instance.

Parameters

[in]	addr	Begin of allocator arena.
[in]	bytes	Size of allocator arena, in bytes.

Definition at line 494 of file first-fit-top.h.

◆ first_fit_top() [2/4]

os::memory::first_fit_top::first_fit_top	(	const char *	name,
		void *	addr,
		std::size_t	bytes
	)

inline

Construct a named memory resource object instance.

Parameters

[in]	name	Pointer to name.
[in]	addr	Begin of allocator arena.
[in]	bytes	Size of allocator arena, in bytes.

Definition at line 501 of file first-fit-top.h.

◆ first_fit_top() [3/4]

os::memory::first_fit_top::first_fit_top ( )

protecteddefault

Default constructor. Construct a memory resource object instance.

◆ first_fit_top() [4/4]

os::memory::first_fit_top::first_fit_top ( const char * name )

inlineprotected

Construct a named memory resource object instance.

Parameters

[in] name Pointer to name.

Definition at line 487 of file first-fit-top.h.

◆ ~first_fit_top()

os::memory::first_fit_top::~first_fit_top ( )

overridevirtual

Destruct the memory resource object instance.

Definition at line 35 of file first-fit-top.cpp.

Member Function Documentation

◆ allocate()

void * os::rtos::memory::memory_resource::allocate	(	std::size_t	bytes,
		std::size_t	alignment = `max_align`
	)

inlineinherited

Allocate a memory block.

Parameters

bytes	Number of bytes to allocate.
alignment	Alignment constraint (power of 2).

Returns: Pointer to newly allocated block, or nullptr.

Allocate storage with a size of at least bytes bytes. The returned storage is aligned to the specified alignment if such alignment is supported, and to alignof(std::max_align_t) otherwise.

If the storage of the requested size and alignment cannot be obtained:

if the out of memory handler is not set, return nullptr;
if the out of memory handler is set, call it and retry.

Equivalent to return do_allocate(bytes, alignment);.

Exceptions: The code itself throws nothing, but if the out of memory handler is set, it may throw a bad_alloc() exception.

See also: do_allocate();

Definition at line 1289 of file os-memory.h.

◆ allocated_bytes()

std::size_t os::rtos::memory::memory_resource::allocated_bytes ( void )

inlineinherited

Get the current size of all allocated chunks.

Parameters: None.

Returns: Number of bytes.

Definition at line 1401 of file os-memory.h.

◆ allocated_chunks()

std::size_t os::rtos::memory::memory_resource::allocated_chunks ( void )

inlineinherited

Get the current number of allocated chunks.

Parameters: None.

Returns: Number of chunks.

Definition at line 1419 of file os-memory.h.

◆ allocations()

std::size_t os::rtos::memory::memory_resource::allocations ( void )

inlineinherited

Get the number of allocations.

Parameters: None.

Returns: Number of allocations.

Definition at line 1431 of file os-memory.h.

◆ coalesce()

bool os::rtos::memory::memory_resource::coalesce ( void )

inlinenoexceptinherited

Coalesce free blocks.

Parameters: None.

Return values

true	if the operation freed more memory.
false	if the operation was ineffective.

In case the memory manager does not coalesce during deallocation, traverse the list of free blocks and coalesce.

Return true if the operation was successful and at least one larger block resulted.

See also: do_coalesce();

Definition at line 1364 of file os-memory.h.

◆ deallocate()

void os::rtos::memory::memory_resource::deallocate	(	void *	addr,
		std::size_t	bytes,
		std::size_t	alignment = `max_align`
	)

inlinenoexceptinherited

Deallocate the previously allocated memory block.

Parameters

addr	Address of the block to free.
bytes	Number of bytes to deallocate (may be 0 if unknown).
alignment	Alignment constraint (power of 2).

Returns: Nothing.

Deallocate the storage pointed to by addr. The address shall have been returned by a prior call to allocate() on a memory_resource that compares equal to *this, and the storage it points to shall not yet have been deallocated.

Equivalent to return do_deallocate(p, bytes, alignment);.

Exceptions: Throws nothing.

See also: do_deallocate();

Definition at line 1311 of file os-memory.h.

◆ deallocations()

std::size_t os::rtos::memory::memory_resource::deallocations ( void )

inlineinherited

Get the number of deallocations.

Parameters: None.

Returns: Number of deallocations

Definition at line 1437 of file os-memory.h.

◆ do_allocate()

void * os::memory::first_fit_top::do_allocate	(	std::size_t	bytes,
		std::size_t	alignment
	)

overrideprotectedvirtual

Implementation of the memory allocator.

Parameters

[in]	bytes	Number of bytes to allocate.
[in]	alignment	Alignment constraint (power of 2).

Returns: Pointer to newly allocated block, or nullptr.

The allocator tries to be fast and grasps the first block large enough, possibly splitting large blocks and increasing fragmentation. If the block is only slightly larger (the remaining space is not large enough for a minimum chunk) the block is not split, but left partly unused.

When large blocks are split, the top sub-block is returned; in other words, memory is allocated top-down. This speeds up deallocation for blocks allocated recently.

Exceptions: Throws nothing by itself, but the out of memory handler may throw bad_alloc().

Implements os::rtos::memory::memory_resource.

Reimplemented in os::memory::lifo.

Definition at line 113 of file first-fit-top.cpp.

◆ do_coalesce()

bool os::rtos::memory::memory_resource::do_coalesce ( void )

protectedvirtualnoexceptinherited

Implementation of the function to coalesce free blocks.

Parameters: None.

Return values

true	if the operation resulted in larger blocks.
false	if the operation was ineffective.

The default implementation of this virtual function returns false, meaning the operation was ineffective.

Override this function to perform the action.

Standard compliance: Extension to standard.

Definition at line 464 of file os-memory.cpp.

◆ do_deallocate()

void os::memory::first_fit_top::do_deallocate	(	void *	addr,
		std::size_t	bytes,
		std::size_t	alignment
	)

overrideprotectedvirtualnoexcept

Implementation of the memory deallocator.

Parameters

[in]	addr	Address of a previously allocated block to free.
[in]	bytes	Number of bytes to deallocate (may be 0 if unknown).
[in]	alignment	Alignment constraint (power of 2).

Returns: Nothing.

Deallocation is not guaranteed to be deterministic, but if done in strict reverse allocation order, it becomes deterministic, otherwise a traversal of the free list is required, the older the block, the more nodes to traverse (the free list is kept in ascending addresses order).

If the block is already in the free list, issue a trace message, but otherwise ignore the condition.

Exceptions: Throws nothing.

Implements os::rtos::memory::memory_resource.

Definition at line 228 of file first-fit-top.cpp.

◆ do_is_equal()

bool os::rtos::memory::memory_resource::do_is_equal ( memory_resource const & other ) const

protectedvirtualnoexceptinherited

Implementation of the equality comparator.

Parameters

other Reference to another memory_resource.

Return values

true	The `memory_resource` objects are equal.
false	The `memory_resource` objects are not equal.

Compares *this for equality with other. Two memory_resources compare equal if and only if memory allocated from one memory_resource can be deallocated from the other and vice versa.

The most-derived type of other may not match the most derived type of *this. A derived class implementation therefore must typically check whether the most derived types of *this and other match using dynamic_cast, and immediately return false if the cast fails.

Exceptions: Throws nothing.

Definition at line 416 of file os-memory.cpp.

◆ do_max_size()

std::size_t os::memory::first_fit_top::do_max_size ( void ) const

overrideprotectedvirtualnoexcept

Implementation of the function to get max size.

Parameters: None.

Returns: Integer with size in bytes, or 0 if unknown.

Reimplemented from os::rtos::memory::memory_resource.

Definition at line 388 of file first-fit-top.cpp.

◆ do_reset()

void os::memory::first_fit_top::do_reset ( void )

overrideprotectedvirtualnoexcept

Implementation of the function to reset the memory manager.

Parameters: None.

Returns: Nothing.

Reimplemented from os::rtos::memory::memory_resource.

Definition at line 83 of file first-fit-top.cpp.

◆ free_bytes()

std::size_t os::rtos::memory::memory_resource::free_bytes ( void )

inlineinherited

Get the current size of all free chunks.

Parameters: None.

Returns: Number of bytes.

Definition at line 1413 of file os-memory.h.

◆ free_chunks()

std::size_t os::rtos::memory::memory_resource::free_chunks ( void )

inlineinherited

Get the current number of free chunks.

Parameters: None.

Returns: Number of chunks.

Definition at line 1425 of file os-memory.h.

◆ internal_align_()

void * os::memory::first_fit_top::internal_align_	(	chunk_t *	chunk,
		std::size_t	bytes,
		std::size_t	alignment
	)

protected

Internal function to align a chunk.

Parameters

[in]	chunk	Pointer to chunk.
[in]	bytes	Bytes to allocate.
[in]	alignment	Power of two.

Returns: Pointer to aligned payload.

Definition at line 394 of file first-fit-top.cpp.

◆ internal_construct_()

void os::memory::first_fit_top::internal_construct_	(	void *	addr,
		std::size_t	bytes
	)

protected

Internal function to construct the memory resource.

Parameters

[in]	addr	Begin of allocator arena.
[in]	bytes	Size of allocator arena, in bytes.

Returns: Nothing.

Definition at line 41 of file first-fit-top.cpp.

◆ internal_decrease_allocated_statistics()

void os::rtos::memory::memory_resource::internal_decrease_allocated_statistics ( std::size_t bytes )

protectednoexceptinherited

Update statistics after deallocation.

Parameters

[in] bytes Number of deallocated bytes.

Returns: Nothing.

Definition at line 486 of file os-memory.cpp.

◆ internal_increase_allocated_statistics()

void os::rtos::memory::memory_resource::internal_increase_allocated_statistics ( std::size_t bytes )

protectednoexceptinherited

Update statistics after allocation.

Parameters

[in] bytes Number of allocated bytes.

Returns: Nothing.

Definition at line 470 of file os-memory.cpp.

◆ internal_reset_()

void os::memory::first_fit_top::internal_reset_ ( void )

protectednoexcept

Internal function to reset the memory resource.

Parameters: None.

Definition at line 63 of file first-fit-top.cpp.

◆ is_equal()

bool os::rtos::memory::memory_resource::is_equal ( memory_resource const & other ) const

inlinenoexceptinherited

Compare for equality with another memory_resource.

Parameters

other Reference to another memory_resource.

Return values

true	The `memory_resource` objects are equal.
false	The `memory_resource` objects are not equal.

Compare *this for equality with other. Two memory_resources compare equal if and only if memory allocated from one memory_resource can be deallocated from the other and vice versa.

Exceptions: Throws nothing.

See also: do_is_equal();

Definition at line 1330 of file os-memory.h.

◆ max_allocated_bytes()

std::size_t os::rtos::memory::memory_resource::max_allocated_bytes ( void )

inlineinherited

Get the maximum allocated size.

Parameters: None.

Returns: Number of bytes.

Definition at line 1407 of file os-memory.h.

◆ max_size()

std::size_t os::rtos::memory::memory_resource::max_size ( void ) const

inlinenoexceptinherited

Get the largest value that can be passed to allocate().

Parameters: None.

Returns: Number of bytes or 0 if unknown.

See also: do_max_size();

Definition at line 1339 of file os-memory.h.

◆ name()

const char * os::rtos::internal::object_named::name ( void ) const

inlineinherited

Get object name.

Parameters: None.

Returns: A null terminated string.

All objects return a non-null string; anonymous objects return "-".

Note: Can be invoked from Interrupt Service Routines.

Definition at line 759 of file os-decls.h.

◆ out_of_memory_handler() [1/2]

out_of_memory_handler_t os::rtos::memory::memory_resource::out_of_memory_handler ( out_of_memory_handler_t handler )

inlineinherited

Set the out of memory handler.

Parameters

handler Pointer to new handler.

Returns: Pointer to old handler.

Standard compliance: Extension to standard.

Definition at line 1374 of file os-memory.h.

◆ out_of_memory_handler() [2/2]

out_of_memory_handler_t os::rtos::memory::memory_resource::out_of_memory_handler ( void )

inlineinherited

Get the out of memory handler.

Parameters: None.

Returns: Pointer to existing handler.

Standard compliance: Extension to standard.

Definition at line 1389 of file os-memory.h.

◆ reset()

void os::rtos::memory::memory_resource::reset ( void )

inlinenoexceptinherited

Reset the memory manager to the initial state.

Parameters: None.

Returns: Nothing.

See also: do_reset();

Definition at line 1348 of file os-memory.h.

◆ total_bytes()

std::size_t os::rtos::memory::memory_resource::total_bytes ( void )

inlineinherited

Get the total size of managed memory.

Returns: Number of bytes.

Definition at line 1395 of file os-memory.h.

◆ trace_print_statistics()

void os::rtos::memory::memory_resource::trace_print_statistics ( void )

inlineinherited

Print a long message with usage statistics.

Parameters: None.

Returns: Nothing.

Definition at line 1443 of file os-memory.h.

Member Data Documentation

◆ max_align

constexpr std::size_t os::rtos::memory::memory_resource::max_align = alignof(std::max_align_t)

staticconstexprinherited

The largest alignment for the platform. Also default when supplied alignment is not supported.

Definition at line 168 of file os-memory.h.

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

Public Member Functions

Static Public Attributes

Protected Member Functions

Constructors & Destructor

Detailed Description

Constructor & Destructor Documentation

◆ first_fit_top() [1/4]

◆ first_fit_top() [2/4]

◆ first_fit_top() [3/4]

◆ first_fit_top() [4/4]

◆ ~first_fit_top()

Member Function Documentation

◆ allocate()

◆ allocated_bytes()

◆ allocated_chunks()

◆ allocations()

◆ coalesce()

◆ deallocate()

◆ deallocations()

◆ do_allocate()

◆ do_coalesce()

◆ do_deallocate()

◆ do_is_equal()

◆ do_max_size()

◆ do_reset()

◆ free_bytes()

◆ free_chunks()

◆ internal_align_()

◆ internal_construct_()

◆ internal_decrease_allocated_statistics()

◆ internal_increase_allocated_statistics()

◆ internal_reset_()

◆ is_equal()

◆ max_allocated_bytes()

◆ max_size()

◆ name()

◆ out_of_memory_handler() [1/2]

◆ out_of_memory_handler() [2/2]

◆ reset()

◆ total_bytes()

◆ trace_print_statistics()

Member Data Documentation

◆ max_align