docs and tests

src/common/stack.rs

@@ -80,6 +80,7 @@ impl<T> StackWithLimit<T> {
 	/// Returns Err(StackOverflow) if stack is already full.
 	#[inline]
 	pub fn push(&mut self, value: T) -> Result<(), StackOverflow> {
+		debug_assert!(self.stack.capacity() <= self.limit);
 		if self.stack.len() == self.stack.capacity() {
 			if self.stack.len() == self.limit {
 				return Err(StackOverflow);
@@ -100,6 +101,17 @@ impl<T> StackWithLimit<T> {
 		Ok(())
 	}
 
+	/// Remove item from the top of a stack and return it, or `None` if the stack is empty.
+	///
+	/// ```
+	/// # extern crate wasmi;
+	/// # use wasmi::{StackWithLimit, StackSize};
+	/// let mut bstack = StackWithLimit::<i32>::with_size(StackSize::from_element_count(2));
+	/// bstack.push(2);
+	/// assert_eq!(bstack.pop(), Some(2));
+	/// assert_eq!(bstack.len(), 0);
+	/// assert_eq!(bstack.pop(), None);
+	/// ```
 	pub fn pop(&mut self) -> Option<T> {
 		self.stack.pop()
 	}
@@ -159,42 +171,96 @@ impl<T> StackWithLimit<T> {
 	/// # Panics
 	///
 	/// Panics if `a` or `b` are out of bound.
+	///
+	/// ```
+	/// # extern crate wasmi;
+	/// # use wasmi::{StackWithLimit, StackSize};
+	/// let mut bstack = StackWithLimit::<i32>::with_size(StackSize::from_element_count(2));
+	/// bstack.push(1);
+	/// bstack.push(2);
+	/// assert_eq!(bstack.top(), Some(&2));
+	/// stack.swap(0, 1);
+	/// assert_eq!(bstack.top(), Some(&1));
+	/// ```
 	#[inline]
 	pub fn swap(&mut self, a: usize, b: usize) {
 		self.stack.swap(a, b)
 	}
 
-	/// Removes an element from the vector and returns it.
+	/// Removes an element from the stack and returns it.
 	///
-	/// The removed element is replaced by the last element of the vector.
+	/// The removed element is replaced by the element at the top of the stack.
-	///
-	/// This does not preserve ordering, but is O(1).
 	///
 	/// # Panics
 	///
 	/// Panics if `index` is out of bounds.
+	///
+	/// ```
+	/// # extern crate wasmi;
+	/// # use wasmi::{StackWithLimit, StackSize};
+	/// let mut bstack = StackWithLimit::<i32>::with_size(StackSize::from_element_count(2));
+	/// bstack.push(1);
+	/// bstack.push(2);
+	/// assert_eq!(bstack.top(), Some(&2));
+	/// assert_eq!(stack.swap_remove(0), 1);
+	/// assert_eq!(bstack.top(), Some(&2));
+	/// ```
 	pub fn swap_remove(&mut self, index: usize) -> T {
 		self.stack.swap_remove(index)
 	}
 
+	/// Get a reference to the top of the stack, or `None` if the stack is empty.
+	///
+	/// ```
+	/// # extern crate wasmi;
+	/// # use wasmi::{StackWithLimit, StackSize};
+	/// let mut bstack = StackWithLimit::<i32>::with_size(StackSize::from_element_count(2));
+	/// assert_eq!(bstack.top(), None);
+	/// bstack.push(2);
+	/// assert_eq!(bstack.top(), Some(&2));
+	/// ```
 	pub fn top(&self) -> Option<&T> {
 		self.stack.last()
 	}
 
+	/// Get a mutable reference to the top of the stack, or `None` if the stack is empty.
 	pub fn top_mut(&mut self) -> Option<&mut T> {
 		self.stack.last_mut()
 	}
 
-	// Same as Vec::[truncate](https://doc.rust-lang.org/std/vec/struct.Vec.html#method.truncate)
+	/// Shorten the stack, keeping the bottom len elements and dropping the rest.
+	///
+	/// If new_size is greater then the current stack size, this has no effect.
 	pub fn truncate(&mut self, new_size: usize) {
 		self.stack.truncate(new_size)
 	}
 
+	/// Get number of items in a stack.
+	///
+	/// ```
+	/// # extern crate wasmi;
+	/// # use wasmi::{StackWithLimit, StackSize};
+	/// let mut bstack = StackWithLimit::<i32>::with_size(StackSize::from_element_count(2));
+	/// assert_eq!(bstack.len(), 0);
+	/// bstack.push(1);
+	/// bstack.push(2);
+	/// assert_eq!(bstack.len(), 2);
+	/// ```
 	#[inline]
 	pub fn len(&self) -> usize {
 		self.stack.len()
 	}
 
+	/// Check whether the stack is empty.
+	///
+	/// ```
+	/// # extern crate wasmi;
+	/// # use wasmi::{StackWithLimit, StackSize};
+	/// let mut bstack = StackWithLimit::<i32>::with_size(StackSize::from_element_count(2));
+	/// assert_eq!(bstack.is_empty(), true);
+	/// bstack.push(1);
+	/// assert_eq!(bstack.is_empty(), false);
+	/// ```
 	pub fn is_empty(&self) -> bool {
 		self.stack.is_empty()
 	}

src/runner.rs

@@ -216,6 +216,7 @@ impl Interpreter {
 		self.state = InterpreterState::Initialized;
 	}
 
+	/// Get current state of interpreter.
 	pub fn state(&self) -> &InterpreterState {
 		&self.state
 	}

src/validation/func.rs

@@ -1404,13 +1404,14 @@ fn pop_value(
 	let actual_value = if stack_is_empty && is_stack_polymorphic {
 		StackValueType::Any
 	} else {
-		let value_stack_min = frame_stack.top().expect("Expected a non-empty frame stack.").value_stack_len;
+		let value_stack_min = frame_stack
+			.top()
+			.expect("Expected a non-empty frame stack.")
+			.value_stack_len;
 		if value_stack.len() <= value_stack_min {
 			return Err(Error("Trying to access parent frame stack values.".into()));
 		}
-		value_stack
+		value_stack.pop().ok_or_else(underflow_err)?
-			.pop()
-			.ok_or_else(|| Error("non-empty stack expected".into()))?
 	};
 	match actual_value {
 		StackValueType::Specific(stack_value_type) if stack_value_type == value_type => Ok(actual_value),
@@ -1456,10 +1457,7 @@ fn pop_label(
 	// Don't pop frame yet. This is essential since we still might pop values from the value stack
 	// and this in turn requires current frame to check whether or not we've reached
 	// unreachable.
-	let block_type = frame_stack
+	let block_type = frame_stack.top().ok_or_else(underflow_err)?.block_type;
-		.top()
-		.ok_or_else(|| Error("non-empty stack expected".into()))?
-		.block_type;
 	match block_type {
 		BlockType::NoResult => (),
 		BlockType::Value(required_value_type) => {
@@ -1467,9 +1465,7 @@ fn pop_label(
 		}
 	}
 
-	let frame = frame_stack
+	let frame = frame_stack.pop().ok_or_else(underflow_err)?;
-		.pop()
-		.ok_or_else(|| Error("non-empty stack expected".into()))?;
 	if value_stack.len() != frame.value_stack_len {
 		return Err(Error(format!(
 			"Unexpected stack height {}, expected {}",
@@ -1488,9 +1484,7 @@ fn top_label(frame_stack: &StackWithLimit<BlockFrame>) -> &BlockFrame {
 }
 
 fn require_label(depth: u32, frame_stack: &StackWithLimit<BlockFrame>) -> Result<&BlockFrame, Error> {
-	frame_stack
+	frame_stack.nth_from_top(depth as usize).ok_or_else(underflow_err)
-		.nth_from_top(depth as usize)
-		.ok_or_else(|| Error("non-empty stack expected".into()))
 }
 
 fn require_target(
@@ -1718,3 +1712,7 @@ impl Sink {
 		self.ins
 	}
 }
+
+fn underflow_err() -> Error {
+	Error("non-empty stack expected".into())
+}