memory.md

Namespace memory

Table of Contents

• API
  • Type Handle
  • Interface Shareable
  • Interface Allocator
    • allocator.allocate(size: number): Handle
    • allocator.deallocate(handle: Handle, sizeHint: number): void
    • allocator.type: string
  • Interface AllocatorDebugger
    • allocatorDebugger.getDebugInfo(): string
  • Function debugAllocator(allocator: Allocator): AllocatorDebugger
  • Object crtAllocator
  • Object defaultAllocator
  • Memory allocation in C++ addon

API

Type Handle

Handle is defined in TypeScript as below:

type Handle = [number, number]

It is a standard way to represent a 64-bit pointer in Napa.

Interface Shareable

Interface for native object wrap that can be shared across multiple JavaScript threads.

Interface Allocator

Interface for memory allocator that allocates memory for native objects.

allocator.allocate(size: number): Handle

It allocates memory of requested size.

var handle = allocator.allocate(10);

allocator.deallocate(handle: Handle, sizeHint: number): void

It deallocates memory from a input handle, with a size hint which is helpful for some C++ allocator implementations for deallocating memory.

allocator.deallocate(handle, 10);

allocator.type: string

It gets a string type identifier for the allocator, which will be useful during debugging purpose.

Interface AllocatorDebugger

AllocatorDebugger extends interface Allocator, with a member function getDebugInfo to expose debug information. Basically an allocator debugger will use a pass-in allocator for memory allocation, meanwhile intercepting it to keep track of allocation count and size.

allocatorDebugger.getDebugInfo(): string

It gets the debug information for allocation. Implementations of interface AllocatorDebugger can have different schema on debug info.

debugAllocator(allocator: Allocator): AllocatorDebugger

It returns a simple allocator debugger, which returns debug information like below:

{
    "allocate": 10,
    "allocateSize": 1024,
    "deallocate": 8,
    "deallocateSize": 912
}

Object crtAllocator

It returns a C-runtime allocator from Napa.js shared library. Its corresponding C++ part is napa::memory::GetCrtAllocator().

Object defaultAllocator

It returns the default allocator from Napa.js shared library. Its corresponding C++ part is napa::memory::GetDefaultAllocator().

Users can set default allocation/deallocation callback in napa_allocator_set API.

Memory allocation in C++ addon

Memory allocation in C++ addon is tricky. A common pitfall is to allocate memory in one dll, but deallocate in another. This can cause issue if C-runtime in these 2 dlls are not compiled the same way.

There are also advanced scenarios that user want to customize memory allocation. Napa.js provides APIs for customizing memory allocator as well.

Recommended way of allocate memory

TBD

Customize memory allocation

TBD