//! Traits for stacks.
use core::prelude::*;

/// A trait for objects that hold ownership of a stack.
pub trait Stack {
  /// Returns the top of the stack.
  /// On all modern architectures, the stack grows downwards,
  /// so this is the highest address.
  fn top(&mut self) -> *mut u8;
  /// Returns the bottom of the stack.
  /// On all modern architectures, the stack grows downwards,
  /// so this is the lowest address.
  fn limit(&self) -> *const u8;
}

/// A trait for objects that provide stacks of arbitrary size.
pub trait StackSource {
  type Output: Stack;
  type Error = ();
  fn get_stack(size: usize) -> Result<Self::Output, Self::Error>;
}