Overview

Abstract interface for variable-layout memory allocation.

The interface makes no guarantees about its implementation. Consumers of the generic interface must not make any assumptions around allocator behavior, thread safety, or performance.

Inheritance diagram for pw::Allocator:

Public Types
using	Fragmentation = allocator::Fragmentation

Public Types inherited from pw::Deallocator
using	Capabilities = allocator::Capabilities

using	Capability = allocator::Capability

using	Layout = allocator::Layout

Public Member Functions
void *	Allocate (Layout layout)

template<typename T , int &... kExplicitGuard, std::enable_if_t<!std::is_array_v< T >, int > = 0, typename... Args>
T *	New (Args &&... args)

template<typename T , int &... kExplicitGuard, typename ElementType = std::remove_extent_t<T>, std::enable_if_t< is_bounded_array_v< T >, int > = 0>
ElementType *	New ()

template<typename T , int &... kExplicitGuard, typename ElementType = std::remove_extent_t<T>, std::enable_if_t< is_unbounded_array_v< T >, int > = 0>
ElementType *	New (size_t count)

template<typename T , int &... kExplicitGuard, typename ElementType = std::remove_extent_t<T>, std::enable_if_t< is_unbounded_array_v< T >, int > = 0>
ElementType *	New (size_t count, size_t alignment)
	Constructs an `alignment`-byte aligned array of `count` objects.

template<typename T , int &... kExplicitGuard, std::enable_if_t<!std::is_array_v< T >, int > = 0, typename... Args>
UniquePtr< T >	MakeUnique (Args &&... args)

template<typename T , std::enable_if_t< is_unbounded_array_v< T >, int > = 0>
UniquePtr< T >	MakeUnique (size_t size)

template<typename T , std::enable_if_t< is_unbounded_array_v< T >, int > = 0>
UniquePtr< T >	MakeUnique (size_t size, size_t alignment)

template<typename T , std::enable_if_t< is_bounded_array_v< T >, int > = 0>
UniquePtr< T >	MakeUnique ()

template<typename T , int &... kExplicitGuard, std::enable_if_t<!std::is_array_v< T >, int > = 0, typename... Args>
SharedPtr< T >	MakeShared (Args &&... args)

template<typename T , std::enable_if_t< is_unbounded_array_v< T >, int > = 0>
SharedPtr< T >	MakeShared (size_t size)

template<typename T , std::enable_if_t< is_unbounded_array_v< T >, int > = 0>
SharedPtr< T >	MakeShared (size_t size, size_t alignment)

template<typename T , std::enable_if_t< is_bounded_array_v< T >, int > = 0>
SharedPtr< T >	MakeShared ()

bool	Resize (void *ptr, size_t new_size)

void *	Reallocate (void *ptr, Layout new_layout)

size_t	GetAllocated () const

std::optional< Fragmentation >	MeasureFragmentation () const
	Returns fragmentation information for the allocator's memory region.

Public Member Functions inherited from pw::Deallocator
constexpr const Capabilities &	capabilities () const

constexpr bool	HasCapability (Capability capability) const
	Returns whether a given capability is enabled for this object.

void	Deallocate (void *ptr)

template<typename ElementType >
void	DeleteArray (ElementType *ptr, size_t count)

StatusWithSize	GetCapacity () const

bool	IsEqual (const Deallocator &other) const

template<typename T , int &... kExplicitGuard, std::enable_if_t<!std::is_array_v< T >, int > = 0>
void	Delete (T *ptr)

template<typename T , int &... kExplicitGuard, typename ElementType = std::remove_extent_t<T>, std::enable_if_t< is_bounded_array_v< T >, int > = 0>
void	Delete (ElementType *ptr)

template<typename T , int &... kExplicitGuard, typename ElementType = std::remove_extent_t<T>, std::enable_if_t< is_unbounded_array_v< T >, int > = 0>
void	Delete (ElementType *ptr, size_t count)

Protected Member Functions
constexpr	Allocator () noexcept=default
	TODO(b/326509341): Remove when downstream consumers migrate.

constexpr	Allocator (const Capabilities &capabilities) noexcept

virtual void *	DoAllocate (Layout layout)=0

virtual bool	DoResize (void *ptr, size_t new_size)

virtual void *	DoReallocate (void *ptr, Layout new_layout)

virtual void	DoBeforeReallocate (void *ptr, Layout new_layout)

virtual void	DoAfterReallocateCopy (void ptr, Layout new_layout, void new_ptr)

virtual void	DoAfterReallocateDone (Layout new_layout, void *new_ptr)

virtual size_t	DoGetAllocated () const

virtual std::optional< Fragmentation >	DoMeasureFragmentation () const
	Returns fragmentation information for the allocator's memory region.

Protected Member Functions inherited from pw::Deallocator
constexpr	Deallocator ()=default
	TODO(b/326509341): Remove when downstream consumers migrate.

constexpr	Deallocator (const Capabilities &capabilities)

Result< Layout >	GetInfo (InfoType info_type, const void *ptr) const

Result< Layout >	GetRequestedLayout (const void *ptr) const

Result< Layout >	GetUsableLayout (const void *ptr) const

Result< Layout >	GetAllocatedLayout (const void *ptr) const

bool	Recognizes (const void *ptr) const

virtual void	DoDeallocate (void *ptr)=0

virtual Result< Layout >	DoGetInfo (InfoType, const void *) const

Static Protected Member Functions
static void	BeforeReallocate (Allocator &allocator, void *ptr, Layout new_layout)

static void	AfterReallocateCopy (Allocator &allocator, void ptr, Layout new_layout, void new_ptr)

static void	AfterReallocateDone (Allocator &allocator, Layout new_layout, void *new_ptr)

Static Protected Member Functions inherited from pw::Deallocator
static Result< Layout >	GetInfo (const Deallocator &deallocator, InfoType info_type, const void *ptr)

static Result< Layout >	GetRequestedLayout (const Deallocator &deallocator, const void *ptr)

static Result< Layout >	GetUsableLayout (const Deallocator &deallocator, const void *ptr)

static Result< Layout >	GetAllocatedLayout (const Deallocator &deallocator, const void *ptr)

static bool	Recognizes (const Deallocator &deallocator, const void *ptr)

Additional Inherited Members
Protected Types inherited from pw::Deallocator
enum class	InfoType { kRequestedLayoutOf , kUsableLayoutOf , kAllocatedLayoutOf , kCapacity , kRecognizes }

Static Protected Attributes inherited from pw::Deallocator
template<typename T >
static constexpr bool	is_bounded_array_v = ::pw::is_bounded_array_v<T>

template<typename T >
static constexpr bool	is_unbounded_array_v = ::pw::is_unbounded_array_v<T>

Member Function Documentation

◆ AfterReallocateCopy()

static void pw::Allocator::AfterReallocateCopy	(	Allocator &	allocator,
		void *	ptr,
		Layout	new_layout,
		void *	new_ptr
	)

inlinestaticprotected

Static version of DoAfterReallocateCopy that allows forwarding allocators to call it on wrapped allocators.

◆ AfterReallocateDone()

static void pw::Allocator::AfterReallocateDone	(	Allocator &	allocator,
		Layout	new_layout,
		void *	new_ptr
	)

inlinestaticprotected

Static version of DoAfterReallocateDone that allows forwarding allocators to call it on wrapped allocators.

◆ Allocate()

void * pw::Allocator::Allocate ( Layout layout )

inline

Allocates a block of memory with the specified size and alignment.

Returns nullptr if the allocation cannot be made, or the layout has a size of 0.

Parameters

[in] layout Describes the memory to be allocated.

◆ BeforeReallocate()

static void pw::Allocator::BeforeReallocate	(	Allocator &	allocator,
		void *	ptr,
		Layout	new_layout
	)

inlinestaticprotected

Static version of DoBeforeReallocate that allows forwarding allocators to call it on wrapped allocators.

◆ DoAfterReallocateCopy()

virtual void pw::Allocator::DoAfterReallocateCopy	(	void *	ptr,
		Layout	new_layout,
		void *	new_ptr
	)

inlineprotectedvirtual

Called as part of the default implementation of DoReallocate once the data from ptr has been resized or copied to new_ptr.

By default, does nothing. Derived types may implement this method to add additional behavior. If they do, they must call DoAfterReallocateCopy on their base type before performing any other action.

ptr and new_ptr are guaranteed to be non-null, and new_layout.size() is guaranteed to be non-zero.

Reimplemented in pw::allocator::ForwardingAllocator.

◆ DoAfterReallocateDone()

virtual void pw::Allocator::DoAfterReallocateDone	(	Layout	new_layout,
		void *	new_ptr
	)

inlineprotectedvirtual

Called as part of the default implementation of DoReallocate just before returning.

By default, does nothing. Derived types may implement this method to add additional behavior. If they do, they must call DoAfterReallocateDone on their base type before performing any other action.

new_ptr is guaranteed to be non-null, and new_layout.size() is guaranteed to be non-zero.

Reimplemented in pw::allocator::ForwardingAllocator, and pw::allocator::TrackingAllocator< MetricsType >.

◆ DoAllocate()

virtual void * pw::Allocator::DoAllocate ( Layout layout )

protectedpure virtual

Allocates a block of memory with the specified size and alignment.

Returns nullptr if the allocation cannot be made, or the layout has a size of 0.

Parameters

[in] layout Describes the memory to be allocated.

◆ DoBeforeReallocate()

virtual void pw::Allocator::DoBeforeReallocate	(	void *	ptr,
		Layout	new_layout
	)

inlineprotectedvirtual

Called at the start of the default implementation of DoReallocate.

By default, does nothing. Derived types may implement this method to add additional behavior. If they do, they must call DoBeforeReallocate on their base type just before returning.

ptr is guaranteed to be non-null, and new_layout.size() is guaranteed to be non-zero.

Reimplemented in pw::allocator::ForwardingAllocator, pw::allocator::test::AllocatorForTest< kBufferSize, BlockType_, MetricsType_ >, and pw::allocator::TrackingAllocator< MetricsType >.

◆ DoGetAllocated()

virtual size_t pw::Allocator::DoGetAllocated ( ) const

inlineprotectedvirtual

Returns the total bytes that have been allocated by this allocator, or size_t(-1) if this allocator does not track its total allocated bytes.

The default implementation simply returns size_t(-1), indicating that tracking total allocated bytes is not supported.

◆ DoMeasureFragmentation()

virtual std::optional< Fragmentation > pw::Allocator::DoMeasureFragmentation ( ) const

inlineprotectedvirtual

Returns fragmentation information for the allocator's memory region.

The default implementation simply returns std::nullopt, indicating that tracking memory fragmentation is not supported.

◆ DoReallocate()

virtual void * pw::Allocator::DoReallocate	(	void *	ptr,
		Layout	new_layout
	)

protectedvirtual

Modifies the size of a previously-allocated block of memory.

Returns pointer to the modified block of memory, or nullptr if the memory could not be modified.

The data stored by the memory being modified must be trivially copyable. If it is not, callers should themselves attempt to Resize, then Allocate, move the data, and Deallocate as needed.

If nullptr is returned, the block of memory is unchanged. In particular, if the new_layout has a size of 0, the given pointer will NOT be deallocated.

TODO(b/331290408): This error condition needs to be better communicated to module users, who may assume the pointer is freed.

Unlike Resize, providing a null pointer will return a new allocation.

If the request can be satisfied using Resize, the alignment parameter may be ignored.

Parameters

[in]	ptr	Pointer to previously-allocated memory.
[in]	new_layout	Describes the memory to be allocated.

The default implementation will first try to Resize the data. If that is unsuccessful, it will allocate an entirely new block, copy existing data, and deallocate the given block.

Derived allocators should avoid overiding this method unless absolutely necessary, and instead override the DoBeforeReallocate, DoAfterReallocateCopy, and DoAfterReallocateDone methods below that are called as part of the default implementation. By using the default implementation, the derived types guarantees its own implementations of DoAllocate, DoDeallocate and DoResize will be used for the reallocation. This is especially important for allocators such as ForwardingAllocator that use composition instead of inheritance.

Reimplemented in pw::allocator::test::FaultInjectingAllocator, pw::allocator::LibCAllocator, and pw::allocator::SynchronizedAllocator< LockType >.

◆ DoResize()

virtual bool pw::Allocator::DoResize	(	void *	ptr,
		size_t	new_size
	)

protectedvirtual

Modifies the size of an previously-allocated block of memory without copying any data.

Returns true if its size was changed without copying data to a new allocation; otherwise returns false.

In particular, it always returns true if the old_layout.size() equals new_size, and always returns false if the given pointer is null, the old_layout.size() is 0, or the new_size is 0.

Parameters

[in]	ptr	Pointer to previously-allocated memory.
[in]	new_size	Requested new size for the memory allocation.

◆ GetAllocated()

size_t pw::Allocator::GetAllocated ( ) const

inline

Returns the total bytes that have been allocated by this allocator, or size_t(-1) if this allocator does not track its total allocated bytes.

◆ MakeShared() [1/4]

template<typename T , std::enable_if_t< is_bounded_array_v< T >, int > = 0>

SharedPtr< T > pw::Allocator::MakeShared ( )

inline

Constructs an array of objects and wraps it in a SharedPtr.

The returned value may contain null if allocating memory for the object fails. Callers must check for null before using the SharedPtr.

Template Parameters

T	A bounded array type, like `int[3]`.

◆ MakeShared() [2/4]

template<typename T , int &... kExplicitGuard, std::enable_if_t<!std::is_array_v< T >, int > = 0, typename... Args>

SharedPtr< T > pw::Allocator::MakeShared ( Args &&... args )

inline

Constructs and object of type T from the given args, and wraps it in a SharedPtr

The returned value may contain null if allocating memory for the object fails. Callers must check for null before using the SharedPtr.

Parameters

[in] args Arguments passed to the object constructor.

◆ MakeShared() [3/4]

template<typename T , std::enable_if_t< is_unbounded_array_v< T >, int > = 0>

SharedPtr< T > pw::Allocator::MakeShared ( size_t size )

inline

Constructs an array of size objects, and wraps it in a SharedPtr.

The returned value may contain null if allocating memory for the object fails. Callers must check for null before using the SharedPtr.

Template Parameters

T	An array type.

Parameters

[in] size Number of objects to allocate.

◆ MakeShared() [4/4]

template<typename T , std::enable_if_t< is_unbounded_array_v< T >, int > = 0>

SharedPtr< T > pw::Allocator::MakeShared	(	size_t	size,
		size_t	alignment
	)

inline

Constructs an alignment-byte aligned array of size objects, and wraps it in a SharedPtr

The returned value may contain null if allocating memory for the object fails. Callers must check for null before using the SharedPtr.

Template Parameters

T	An array type.

Parameters

[in]	size	Number of objects to allocate.
[in]	alignment	Object alignment.

◆ MakeUnique() [1/4]

template<typename T , std::enable_if_t< is_bounded_array_v< T >, int > = 0>

UniquePtr< T > pw::Allocator::MakeUnique ( )

inline

Constructs an array of objects and wraps it in a UniquePtr.

The returned value may contain null if allocating memory for the object fails. Callers must check for null before using the UniquePtr.

Template Parameters

T	A bounded array type, like `int[3]`.

◆ MakeUnique() [2/4]

template<typename T , int &... kExplicitGuard, std::enable_if_t<!std::is_array_v< T >, int > = 0, typename... Args>

UniquePtr< T > pw::Allocator::MakeUnique ( Args &&... args )

inline

Constructs and object of type T from the given args, and wraps it in a UniquePtr

The returned value may contain null if allocating memory for the object fails. Callers must check for null before using the UniquePtr.

Template Parameters

T	A non-array object type, like `int`.

Parameters

[in] args Arguments passed to the object constructor.

◆ MakeUnique() [3/4]

template<typename T , std::enable_if_t< is_unbounded_array_v< T >, int > = 0>

UniquePtr< T > pw::Allocator::MakeUnique ( size_t size )

inline

Constructs an array of size objects, and wraps it in a UniquePtr

The returned value may contain null if allocating memory for the object fails. Callers must check for null before using the UniquePtr.

Template Parameters

T	An unbounded array type, like `int[]`.

Parameters

[in] size Number of objects to allocate.

◆ MakeUnique() [4/4]

template<typename T , std::enable_if_t< is_unbounded_array_v< T >, int > = 0>

UniquePtr< T > pw::Allocator::MakeUnique	(	size_t	size,
		size_t	alignment
	)

inline

Constructs an alignment-byte aligned array of size objects and wraps it in a UniquePtr.

The returned value may contain null if allocating memory for the object fails. Callers must check for null before using the UniquePtr.

Template Parameters

T	An unbounded array type, like `int[]`.

Parameters

[in]	size	Number of objects to allocate.
[in]	alignment	Object alignment.

◆ New() [1/4]

template<typename T , int &... kExplicitGuard, typename ElementType = std::remove_extent_t<T>, std::enable_if_t< is_bounded_array_v< T >, int > = 0>

ElementType * pw::Allocator::New ( )

inline

Constructs an array of objects.

The return value is nullable, as allocating memory for the object may fail. Callers must check for this error before using the resulting pointer.

Template Parameters

T	A bounded array type, like `int[3]`.

◆ New() [2/4]

template<typename T , int &... kExplicitGuard, std::enable_if_t<!std::is_array_v< T >, int > = 0, typename... Args>

T * pw::Allocator::New ( Args &&... args )

inline

Constructs an object of type T from the given args.

The return value is nullable, as allocating memory for the object may fail. Callers must check for this error before using the resulting pointer.

Template Parameters

T	A non-array object type, like `int`.

Parameters

[in] args Arguments passed to the object constructor.

◆ New() [3/4]

template<typename T , int &... kExplicitGuard, typename ElementType = std::remove_extent_t<T>, std::enable_if_t< is_unbounded_array_v< T >, int > = 0>

ElementType * pw::Allocator::New ( size_t count )

inline

Constructs an array of count objects.

The return value is nullable, as allocating memory for the object may fail. Callers must check for this error before using the resulting pointer.

Template Parameters

T	An unbounded array type, like `int[]`.

Parameters

[in] count Number of objects to allocate.

◆ New() [4/4]

template<typename T , int &... kExplicitGuard, typename ElementType = std::remove_extent_t<T>, std::enable_if_t< is_unbounded_array_v< T >, int > = 0>

ElementType * pw::Allocator::New	(	size_t	count,
		size_t	alignment
	)

inline

Constructs an alignment-byte aligned array of count objects.

The return value is nullable, as allocating memory for the object may fail. Callers must check for this error before using the resulting pointer.

Template Parameters

T	An unbounded array type, like `int[]`.

Parameters

[in]	count	Number of objects to allocate.
[in]	alignment	Alignment to use for the start of the array.

◆ Reallocate()

void * pw::Allocator::Reallocate	(	void *	ptr,
		Layout	new_layout
	)

inline

Modifies the size of a previously-allocated block of memory.

Returns pointer to the modified block of memory, or nullptr if the memory could not be modified.

The data stored by the memory being modified must be trivially copyable. If it is not, callers should themselves attempt to Resize, then Allocate, move the data, and Deallocate as needed.

If nullptr is returned, the block of memory is unchanged. In particular, if the new_layout has a size of 0, the given pointer will NOT be deallocated.

TODO(b/331290408): This error condition needs to be better communicated to module users, who may assume the pointer is freed.

Unlike Resize, providing a null pointer will return a new allocation.

If the request can be satisfied using Resize, the alignment parameter may be ignored.

Parameters

[in]	ptr	Pointer to previously-allocated memory.
[in]	new_layout	Describes the memory to be allocated.

◆ Resize()

bool pw::Allocator::Resize	(	void *	ptr,
		size_t	new_size
	)

inline

Modifies the size of an previously-allocated block of memory without copying any data.

Returns true if its size was changed without copying data to a new allocation; otherwise returns false.

In particular, it always returns true if the old_layout.size() equals new_size, and always returns false if the given pointer is null, the old_layout.size() is 0, or the new_size is 0.

Parameters

[in]	ptr	Pointer to previously-allocated memory.
[in]	new_size	Requested new size for the memory allocation.

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

pw_allocator/public/pw_allocator/allocator.h

Overview

Public Types

Public Member Functions

Protected Member Functions

Static Protected Member Functions

Additional Inherited Members

Member Function Documentation

◆ AfterReallocateCopy()

◆ AfterReallocateDone()

◆ Allocate()

◆ BeforeReallocate()

◆ DoAfterReallocateCopy()

◆ DoAfterReallocateDone()

◆ DoAllocate()

◆ DoBeforeReallocate()

◆ DoGetAllocated()

◆ DoMeasureFragmentation()

◆ DoReallocate()

◆ DoResize()

◆ GetAllocated()

◆ MakeShared() [1/4]

◆ MakeShared() [2/4]

◆ MakeShared() [3/4]

◆ MakeShared() [4/4]

◆ MakeUnique() [1/4]

◆ MakeUnique() [2/4]

◆ MakeUnique() [3/4]

◆ MakeUnique() [4/4]

◆ New() [1/4]

◆ New() [2/4]

◆ New() [3/4]

◆ New() [4/4]

◆ Reallocate()

◆ Resize()