Struct Stack 

pub(crate) struct Stack {
    values: FixedCapacityVec<Value>,
    frames: FixedCapacityVec<CallFrame>,
}

The stack at runtime containing

1. Values
2. Labels
3. Activations

See https://webassembly.github.io/spec/core/exec/runtime.html#stack

Fields

values: FixedCapacityVec<Value>

WASM values on the stack, i.e. the actual data that instructions operate on

frames: FixedCapacityVec<CallFrame>

Call frames

Each time a function is called, a new frame is pushed, whenever a function returns, a frame is popped

Implementations

impl Stack

pub fn new<T: Config>( params_to_base_call_frame: Vec<Value>, base_call_frame_func_ty: &FuncType, base_call_frame_remaining_locals: &[ValType], ) -> Result<Self, RuntimeError>

pub(super) fn into_values(self) -> Vec<Value>

pub fn pop_value(&mut self) -> Value

Pop a value from the value stack

unsafe fn pop_value_unchecked(&mut self) -> Value

Pop a Value from the value stack

Safety

This will underflow the stack and cause undefined behavior, if the stack is empty. To check, before pushing, assure that Self::values is not empty.

pub fn peek_value(&self) -> Option<Value>

Returns a cloned copy of the top value on the stack, or None if the stack is empty

pub fn push_value(&mut self, value: Value) -> Result<(), RuntimeError>

Push a value to the value stack after veryfing that this will not overflow the stack

unsafe fn push_value_unchecked(&mut self, value: Value)

Push a Value to the value stack

Safety

This will overflow the stack and cause undefined behavior, if the stack is already full. To check, before pushing, assure that the Self::values is not full.

pub fn get_local(&self, idx: LocalIdx) -> &Value

Returns a shared reference to a specific local by its index in the current call frame.

pub fn get_local_mut(&mut self, idx: LocalIdx) -> &mut Value

Returns a mutable reference to a specific local by its index in the current call frame.

pub fn current_call_frame(&self) -> &CallFrame

Get a shared reference to the current CallFrame

Safety

This will underflow if no active call frame is on the stack.

pub fn pop_call_frame(&mut self) -> Option<(FuncAddr, usize, usize)>

Pop a CallFrame from the call stack, returning the caller function store address, return address, and the return stp

Returns None if the base call frame was popped. Its information cannot be retrieved.

pub fn push_call_frame<C: Config>( &mut self, return_func_addr: FuncAddr, func_ty: &FuncType, remaining_locals: &[ValType], return_addr: usize, return_stp: usize, ) -> Result<(), RuntimeError>

Push a call frame to the call stack

Takes the current Self::values’s length as CallFrame::value_stack_base_idx.

pub fn call_frame_count(&self) -> usize

Returns how many call frames are on the stack, in total.

pub fn pop_tail_iter(&mut self, n: usize) -> Vec<Value>

Pop n elements from the value stack’s tail as an iterator, with the first element being closest to the bottom of the value stack

Note that this is providing the values in reverse order compared to popping n values (which would yield the element closest to the top of the value stack first).

pub fn remove_in_between(&mut self, remove_count: usize, keep_count: usize)

Remove remove_count values from the stack, keeping the topmost keep_count values

From the stack, remove remove_count elements, by sliding down the keep_count topmost values remove_count positions.

Effects

• after the operation, Stack will contain remove_count fewer elements
• keep_count topmost elements will be identical before and after the operation
• all elements below the remove_count + keep_count topmost stack entry remain

Trait Implementations

impl Clone for Stack

fn clone(&self) -> Stack

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Stack

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

Formats the value using the given formatter.