Struct holochain_core::nucleus::ribosome::memory::SinglePageManager

pub struct SinglePageManager { /* fields omitted */ }

Struct for managing a WASM Memory Instance as a single page memory stack

Methods

impl SinglePageManager

A Memory Manager limited to one wasm memory page that works like a stack. With this Memory Manager, the WASM host (i.e. the Ribosome) and WASM module (i.e. the Zome) only need to pass around an i32 to communicate any data. That i32 is the last memory allocation on the stack: it is split in an i16 'offset' in the upper bits and an i16 'length' in the lower bits. This fits with the 64KiB sized of a memory Page. Complex input arguments should be stored on the latest allocation on the stack. Complex output arguments can be stored anywhere on stack. Since zero sized allocations are not allowed, it is possible to pass around a return and/or error code with the following convention: using the i16 'offset' as return code and i16 'length' set to zero to indicate its a return code. Return code of 0 means success, while any other value means a failure and gives the error code. In the future, to handle bigger memory needs, we could do same with an i64 instead and handle multiple memory Pages.

pub fn new(wasm_instance: &ModuleRef) -> Self

pub fn allocate(     &mut self,     length: u16 ) -> Result<SinglePageAllocation, RibosomeErrorCode>

Allocate on stack without writing in it

pub fn write(     &mut self,     data: &[u8] ) -> Result<SinglePageAllocation, RibosomeErrorCode>

Write data on top of stack

pub fn read(&self, allocation: SinglePageAllocation) -> Vec<u8>

Read data somewhere in stack

Trait Implementations

impl Clone for SinglePageManager

fn clone(&self) -> SinglePageManager

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for SinglePageManager

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.