Struct WasmLimits 

pub struct WasmLimits {
    pub max_wasm_stack: usize,
    pub memory_size: usize,
    pub max_single_alloc: usize,
    pub max_total_memory: usize,
    pub max_table_elements: usize,
    pub aggressive_compilation: bool,
}

Resolved wasmtime resource limits, ready to configure the engine and stores.

All limits are security upper-bounds. Typical digital-twin contracts use kilobytes of state — these caps prevent runaway allocations by malicious or buggy contracts.

Fields

max_wasm_stack: usize

Maximum WASM stack depth in bytes. Fixed for security regardless of RAM.

memory_size: usize

Maximum WASM linear memory per contract instance (demand-paged virtual).

max_single_alloc: usize

Maximum single host-side I/O allocation (state_in, event_in, or result_out).

max_total_memory: usize

Maximum total host-side I/O buffer per contract call.

max_table_elements: usize

WASM function-table cap. Scales with CPU: more cores → heavier contracts supported.

aggressive_compilation: bool

Use Cranelift SpeedAndSize opt level (true when cpu_cores ≥ 4). Produces smaller, faster code at the cost of longer JIT compilation.

Implementations

impl WasmLimits

pub fn build(ram_mb: u64, cpu_cores: usize) -> Self

Derive resource limits from total machine RAM and CPU cores.

Scaling rationale

• memory_size (WASM linear memory): virtual and demand-paged, so the cost is proportional to pages actually touched, not the cap. Scales from 4 MB (Nano) to 32 MB (Large+) to bound worst-case VM RSS per instance.

• max_total_memory (host I/O): bounds the total byte-transfer between host and WASM per call (state_in + event_in + result_out). Scales from 3 MB (Nano) to 24 MB (Medium+).

• max_single_alloc: cap on a single buffer; ≈ ⅓ of total I/O budget.

• max_wasm_stack: fixed at 1 MB — a security/correctness bound independent of available RAM.

• max_table_elements (WASM function table): scales with CPU cores. Each Rust contract uses <50 real entries; this cap prevents runaway tables in adversarial modules. 256 entries per core, floor 512, cap 2 048.

• aggressive_compilation: enables Cranelift SpeedAndSize when cpu_cores ≥ 4. Produces smaller, faster JIT code at the cost of longer compilation time — only worthwhile when spare cores are available.

• Fuel limits (MAX_FUEL, MAX_FUEL_COMPILATION): DOS-prevention constants, machine-independent.

Trait Implementations

impl Clone for WasmLimits

fn clone(&self) -> WasmLimits

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for WasmLimits

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

Formats the value using the given formatter.

impl Default for WasmLimits

fn default() -> Self

Returns the “default value” for a type.