MemArena::Block Struct Reference

Simple internal arena block of memory. Maintains the underlying memory. More...

#include <MemArena.h>

Collaboration diagram for MemArena::Block:

Classes
struct	Linkage

Public Member Functions
char *	data ()
	Get the start of the data in this block.
const char *	data () const
	Get the start of the data in this block.
char *	allocated_data_end ()
const char *	allocated_data_end () const
size_t	remaining () const
	Amount of unallocated storage.
bool	satisfies (size_t n, size_t align) const
MemSpan< void >	remnant ()
	Span of unallocated storage.
MemSpan< void >	alloc (size_t n, size_t=DEFAULT_ALIGNMENT)
Block &	discard ()
bool	contains (const void *ptr) const
bool	is_full () const

Static Public Member Functions
static size_t	align_padding (void const *ptr, size_t align)

Static Public Attributes
static constexpr size_t	MIN_FREE_SPACE = 16
	A block must have at least this much free space to not be "full".

Protected Member Functions
	Block (size_t n) noexcept

Static Protected Member Functions
static void	operator delete (void *ptr) noexcept
static void	operator delete (void *ptr, void *place) noexcept

Protected Attributes
friend	MemArena
	Container.
size_t	size
	Actual block size.
size_t	allocated {0}
	Current allocated (in use) bytes.
struct swoc::MemArena::Block::Linkage	_link
	Intrusive list support.

Detailed Description

Simple internal arena block of memory. Maintains the underlying memory.

Definition at line 60 of file MemArena.h.

Constructor & Destructor Documentation

Block()

swoc::MemArena::Block::Block ( size_t n )

explicitprotectednoexcept

Construct to have n bytes of available storage.

Note this is descriptive - this presumes use via placement new and the size value describes memory already allocated immediately after this instance.

Parameters

n	The amount of storage.

Member Function Documentation

align_padding()

static size_t swoc::MemArena::Block::align_padding ( void const * ptr, size_t align )

static

Compute the padding needed such adding it to ptr is a multiple of align.

Parameters

ptr	Base pointer.
align	Alignment requirement (must be a power of 2).

Returns

Value to add to ptr to achieve align.

alloc()

MemSpan< void > swoc::MemArena::Block::alloc	(	size_t	n,
		size_t	= DEFAULT_ALIGNMENT )

Allocate n bytes from this block.

Parameters

n	Number of bytes to allocate.
align	Alignment requirement (default, no alignment).

Returns

The span of memory allocated.

allocated_data_end() [1/2]

char * swoc::MemArena::Block::allocated_data_end

(

)

Returns

The first byte past allocated storage.

allocated_data_end() [2/2]

const char * swoc::MemArena::Block::allocated_data_end

(

)

const

Returns

The first byte past allocated storage.

contains()

bool swoc::MemArena::Block::contains

(

const void *

ptr

)

const

Check if the byte at address ptr is in this block.

Parameters

ptr	Address of byte to check.

Returns

true if ptr is in this block, false otherwise.

discard()

Block & swoc::MemArena::Block::discard

(

)

Discard allocations.

Reset the block state to empty.

Returns

this.

is_full()

bool swoc::MemArena::Block::is_full

(

)

const

Returns

true if the block has at least MIN_FREE_SPACE bytes free.

operator delete() [1/2]

static void swoc::MemArena::Block::operator delete ( void * ptr )

staticprotectednoexcept

Override operator delete.

This is required because the allocated memory size is larger than the class size which requires calling free directly, skipping the destructor and avoiding complaints about size mismatches.

Parameters

ptr	Memory to be de-allocated.

operator delete() [2/2]

static void swoc::MemArena::Block::operator delete ( void * ptr, void * place )

staticprotectednoexcept

Override placement (non-allocated) delete.

Parameters

ptr	Pointer returned from new
place	Value passed to new.

This is called only when the class constructor throws an exception during placement new.

Note

I think the parameters are described correctly, the documentation I can find is a bit vague on the source of these values. It is required even if the constructor is marked noexcept. Both are kept in order to be documented.

satisfies()

bool swoc::MemArena::Block::satisfies ( size_t n, size_t align ) const

inline

Check if there is n bytes of space at align.

Parameters

n	Size required.
align	Alignment required.

Returns

true if there is space, false if not.

Definition at line 16 of file MemArena.cc.

Member Data Documentation

allocated

size_t swoc::MemArena::Block::allocated {0}

protected

Current allocated (in use) bytes.

Definition at line 163 of file MemArena.h.

MemArena

friend swoc::MemArena::Block::MemArena

protected

Container.

Definition at line 125 of file MemArena.h.

MIN_FREE_SPACE

size_t swoc::MemArena::Block::MIN_FREE_SPACE = 16

staticconstexpr

A block must have at least this much free space to not be "full".

Definition at line 62 of file MemArena.h.

size

size_t swoc::MemArena::Block::size

protected

Actual block size.

Definition at line 162 of file MemArena.h.

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

• MemArena.h
• MemArena.cc