Memory Manager

As mentioned in the previous section, each stable structure requires its own dedicated Memory instance. This is an intentional design decision that limits the blast radius of potential bugs, ensuring that issues only affect the specific stable structure and its associated memory, not other stable structures.

Overview

The Memory Manager enables the creation of up to 255 virtual memories from a single underlying memory instance. When used with stable memory, this allows you to maintain up to 255 separate stable structures, each with its own isolated memory space.

Usage Example

The following example demonstrates how to use the Memory Manager to create multiple stable structures:

#![allow(unused)]
fn main() {
use ic_stable_structures::{
   memory_manager::{MemoryId, MemoryManager},
   BTreeMap, DefaultMemoryImpl,
};

// Initialize a MemoryManager with DefaultMemoryImpl as the underlying memory
let mem_mgr = MemoryManager::init(DefaultMemoryImpl::default());

// Create two separate BTreeMaps, each with its own virtual memory
let mut map_1: BTreeMap<u64, u64, _> = BTreeMap::init(mem_mgr.get(MemoryId::new(0)));
let mut map_2: BTreeMap<u64, u64, _> = BTreeMap::init(mem_mgr.get(MemoryId::new(1)));

// Demonstrate independent operation of the two maps
map_1.insert(1, 2);
map_2.insert(1, 3);
assert_eq!(map_1.get(&1), Some(2)); // Succeeds as expected
}