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Public Member Functions | Static Public Attributes | List of all members
pw::allocator::BumpAllocator Class Reference

#include <bump_allocator.h>

Public Member Functions

constexpr BumpAllocator ()
 Constructs a BumpAllocator without initializing it.
 
 BumpAllocator (ByteSpan region)
 Constructs a BumpAllocator and initializes it.
 
void Init (ByteSpan region)
 Sets the memory region to be used by the allocator.
 
template<typename T , int &... ExplicitGuard, typename... Args>
T * NewOwned (Args &&... args)
 
template<typename T , int &... ExplicitGuard, typename... Args>
UniquePtr< T > MakeUniqueOwned (Args &&... args)
 
- Public Member Functions inherited from pw::Allocator
void * Allocate (Layout layout)
 
template<typename T , int &... ExplicitGuard, typename... Args>
T * New (Args &&... args)
 
template<typename T , int &... ExplicitGuard, typename... Args>
UniquePtr< T > MakeUnique (Args &&... args)
 
bool Resize (void *ptr, size_t new_size)
 
bool Resize (void *ptr, Layout layout, size_t new_size)
 
void * Reallocate (void *ptr, Layout new_layout)
 
void * Reallocate (void *ptr, Layout old_layout, size_t new_size)
 
allocator::AsPmrAllocator as_pmr ()
 
- Public Member Functions inherited from pw::Deallocator
const Capabilities & capabilities () const
 
bool HasCapability (Capability capability) const
 Returns whether a given capabilityis enabled for this object.
 
void Deallocate (void *ptr)
 
void Deallocate (void *ptr, Layout layout)
 
template<typename T >
void Delete (T *ptr)
 
StatusWithSize GetCapacity () const
 
bool IsEqual (const Deallocator &other) const
 

Static Public Attributes

static constexpr Capabilities kCapabilities = kSkipsDestroy
 

Additional Inherited Members

- Public Types inherited from pw::Deallocator
using Capabilities = allocator::Capabilities
 
using Capability = allocator::Capability
 
using Layout = allocator::Layout
 
- Protected Member Functions inherited from pw::Allocator
constexpr Allocator ()=default
 TODO(b/326509341): Remove when downstream consumers migrate.
 
constexpr Allocator (const Capabilities &capabilities)
 
- Protected Member Functions inherited from pw::Deallocator
constexpr Deallocator ()=default
 TODO(b/326509341): Remove when downstream consumers migrate.
 
constexpr Deallocator (const Capabilities &capabilities)
 
template<typename T >
UniquePtr< T > WrapUnique (T *ptr)
 

Detailed Description

Allocator that does not automatically delete.

A "bump" or "arena" allocator provides memory by simply incrementing a pointer to a memory region in order to "allocate" memory for requests, and doing nothing on deallocation. All memory is freed only when the allocator itself is destroyed. As a result, this allocator is extremely fast.

Bump allocators are useful when short-lived to allocate objects from small buffers with almost zero overhead. Since memory is not deallocated, a bump allocator with a longer lifespan than any of its allocations will end up holding unusable memory. An example of a good use case might be decoding RPC messages that may require a variable amount of space only for as long as it takes to decode a single message.

On destruction, the destructors for any objects allocated using New or MakeUnique are NOT called. To have these destructors invoked, you can allocate "owned" objects using NewOwned and MakeUniqueOwned. This adds a small amount of overhead to the allocation.

Member Function Documentation

◆ MakeUniqueOwned()

template<typename T , int &... ExplicitGuard, typename... Args>
UniquePtr< T > pw::allocator::BumpAllocator::MakeUniqueOwned ( Args &&...  args)
inline

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

Owned objects will have their destructors invoked when the allocator goes out of scope.

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

Parameters
[in]args...Arguments passed to the object constructor.

◆ NewOwned()

template<typename T , int &... ExplicitGuard, typename... Args>
T * pw::allocator::BumpAllocator::NewOwned ( Args &&...  args)
inline

Constructs an "owned" object of type T from the given args

Owned objects will have their destructors invoked when the allocator goes out of scope.

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

Parameters
[in]args...Arguments passed to the object constructor.
The documentation for this class was generated from the following file: