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simplify stacksize api

This commit is contained in:
Andrew Dirksen 2018-11-28 15:03:19 -08:00
parent ab67889223
commit b76ad46a94
3 changed files with 143 additions and 208 deletions
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235
src/common/stack.rs
View File

@ -26,26 +26,6 @@ impl<T> StackWithLimit<T> {
/// Create a StackWithLimit with `limit` max size and `initial_size` of pre-allocated
/// memory.
///
/// ```
/// # extern crate wasmi;
/// # use wasmi::{StackWithLimit, StackSize, FuncRef};
/// StackWithLimit::<FuncRef>::new(
/// StackSize::from_element_count(1024).into_initial(),
/// StackSize::from_element_count(2048).into_limit(),
/// );
/// ```
///
/// Unlimited
///
/// ```
/// # extern crate wasmi;
/// # use wasmi::{StackWithLimit, StackSize, RuntimeValue};
/// StackWithLimit::<RuntimeValue>::new(
/// StackSize::from_element_count(1024).into_initial(),
/// StackSize::unlimited(),
/// );
/// ```
///
/// # Panics
///
/// In debug mode, panics if `initial_size` is larger than `limit`.
@ -63,12 +43,6 @@ impl<T> StackWithLimit<T> {
}
/// Create an new StackWithLimit with `limit` max size and `limit` elements pre-allocated
///
/// ```
/// # extern crate wasmi;
/// # use wasmi::{StackWithLimit, StackSize};
/// let bstack = StackWithLimit::<i32>::with_size(StackSize::from_element_count(2));
/// ```
pub fn with_size(size: StackSize<T>) -> StackWithLimit<T> {
StackWithLimit::new(StackSizeInitial(size), StackSizeLimit(size))
}
@ -102,21 +76,11 @@ impl<T> StackWithLimit<T> {
}
/// 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()
}
/// Remove and Return top element. Does not check for emptyness.
/// Remove and return top element. Does not check for emptiness.
/// If this is called on a zero length stack, bad things will happen.
/// Do not call this method unless you can prove the stack has length.
#[inline]
@ -132,15 +96,6 @@ impl<T> StackWithLimit<T> {
/// `bstack.nth_from_top(0)` gets the top of the stack
///
/// `bstack.nth_from_top(1)` gets the item just below the stack
///
/// ```
/// # extern crate wasmi;
/// # use wasmi::{StackWithLimit, StackSize};
/// let mut bstack = StackWithLimit::<i32>::with_size(StackSize::from_element_count(2));
/// bstack.push(4);
/// assert_eq!(bstack.nth_from_top(0), Some(&4));
/// assert_eq!(bstack.nth_from_top(1), None);
/// ```
pub fn nth_from_top(&self, depth: usize) -> Option<&T> {
// Be cognizant of integer underflow and overflow here. Both are possible in this situation.
// len() is unsigned, so if len() == 0, subtraction is a problem
@ -176,54 +131,12 @@ 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));
/// bstack.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 stack and returns it.
///
/// The removed element is replaced by the element at the top of the stack.
///
/// # 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!(bstack.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()
}
@ -241,55 +154,17 @@ impl<T> StackWithLimit<T> {
}
/// 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()
}
}
// Why introduce the extra complexity of StackSizeLimit, StackSizeInitial, and StackSize?
// We want to make the user to do the correct thing using the type checker.
// Check out the excellent Rust API Guidelines (linked below) for suggestions
// about type safety in rust.
//
// By introducing the new typed arguments, we turn:
//
// ```
// pub fn new(initial_size: usize, limit: usize) -> StackWithLimit<T> { ... }
// ```
//
// into:
//
// ```
// pub fn new(initial_size: StackSizeInitial<T>, limit: StackSizeLimit<T>) -> StackWithLimit<T> { ... }
// ```
//
// https://rust-lang-nursery.github.io/api-guidelines/type-safety.html#c-custom-type
/// Type for communicating the size of some contigous container.
/// Used for constructing both [`StackSizeLimit`] and [`StackSizeInitial`].
#[derive(Eq, PartialEq, Hash, Debug)]
@ -314,13 +189,6 @@ impl<T> Copy for StackSize<T> {}
impl<T> StackSize<T> {
/// Create StackSize based on number of elements.
///
/// ```
/// # extern crate wasmi;
/// # use wasmi::StackSize;
/// let ss = StackSize::<(u8, u8)>::from_element_count(10);
/// assert_eq!(ss.element_count(), 10);
/// ```
pub fn from_element_count(num_elements: usize) -> StackSize<T> {
StackSize {
num_elements,
@ -328,51 +196,12 @@ impl<T> StackSize<T> {
}
}
/// Compute StackSize based on allowable memory.
///
/// ```
/// # extern crate wasmi;
/// # use wasmi::StackSize;
/// let ss = StackSize::<(u8, u8)>::from_byte_count(10);
/// assert_eq!(ss.element_count(), 10 / 2);
/// ```
///
/// # Errors
///
/// In debug mode, panics if size of `T` is 0.
pub fn from_byte_count(num_bytes: usize) -> StackSize<T> {
// This debug_assert should catch logical errors.
debug_assert!(::core::mem::size_of::<T>() != 0, "That doesn't make sense.");
// In case a zero sized T still makes it into prod. We assume unlimited stack
// size instead of panicking.
let element_count = if ::core::mem::size_of::<T>() != 0 {
num_bytes / ::core::mem::size_of::<T>()
} else {
usize::MAX // Semi-relevant fun fact: Vec::<()>::new().capacity() == usize::MAX
};
StackSize::from_element_count(element_count)
}
/// Return number the of elements this StackSize indicates.
///
/// ```
/// # use wasmi::StackSize;
/// let ss = StackSize::<(u8, u8)>::from_element_count(10);
/// assert_eq!(ss.element_count(), 10);
/// ```
///
pub fn element_count(&self) -> usize {
self.num_elements
}
/// Create StackSizeLimit out of self
///
/// ```
/// # use wasmi::{StackSize, StackSizeLimit, RuntimeValue};
/// let values_limit: StackSizeLimit<RuntimeValue> = StackSize::from_element_count(1024).into_limit();
/// ```
pub fn into_limit(self) -> StackSizeLimit<T> {
StackSizeLimit(self)
}
@ -381,11 +210,6 @@ impl<T> StackSize<T> {
pub fn into_initial(self) -> StackSizeInitial<T> {
StackSizeInitial(self)
}
/// Create StackSizeLimit with no upper bound.
pub fn unlimited() -> StackSizeLimit<T> {
StackSize::from_element_count(usize::MAX).into_limit()
}
}
/// Max size a stack may become.
@ -492,4 +316,61 @@ mod test {
assert_eq!(unsafe { bstack.pop_unchecked() }, 0);
assert_eq!(unsafe { bstack.pop_unchecked() }, 8);
}
#[test]
fn misc() {
// These used to be doctests. They were moved here because StackWithLimit no longer
// public. Doctests can't test internal APIs.
StackWithLimit::<usize>::new(
StackSize::from_element_count(1024).into_initial(),
StackSize::from_element_count(2048).into_limit(),
);
let bstack = StackWithLimit::<i32>::with_size(StackSize::from_element_count(2));
let mut bstack = StackWithLimit::<i32>::with_size(StackSize::from_element_count(2));
bstack.push(2).unwrap();
assert_eq!(bstack.pop(), Some(2));
assert_eq!(bstack.len(), 0);
assert_eq!(bstack.pop(), None);
let mut bstack = StackWithLimit::<i32>::with_size(StackSize::from_element_count(2));
bstack.push(4).unwrap();
assert_eq!(bstack.nth_from_top(0), Some(&4));
assert_eq!(bstack.nth_from_top(1), None);
let mut bstack = StackWithLimit::<i32>::with_size(StackSize::from_element_count(2));
bstack.push(1).unwrap();
bstack.push(2).unwrap();
assert_eq!(bstack.top(), Some(&2));
bstack.swap(0, 1);
assert_eq!(bstack.top(), Some(&1));
let mut bstack = StackWithLimit::<i32>::with_size(StackSize::from_element_count(2));
bstack.push(1).unwrap();
bstack.push(2).unwrap();
assert_eq!(bstack.top(), Some(&2));
bstack.swap(0, 1);
assert_eq!(bstack.top(), Some(&1));
let mut bstack = StackWithLimit::<i32>::with_size(StackSize::from_element_count(2));
assert_eq!(bstack.len(), 0);
bstack.push(1).unwrap();
bstack.push(2).unwrap();
assert_eq!(bstack.len(), 2);
let mut bstack = StackWithLimit::<i32>::with_size(StackSize::from_element_count(2));
assert_eq!(bstack.is_empty(), true);
bstack.push(1).unwrap();
assert_eq!(bstack.is_empty(), false);
let ss = StackSize::<(u8, u8)>::from_element_count(10);
assert_eq!(ss.element_count(), 10);
let ss = StackSize::<(u8, u8)>::from_element_count(10);
assert_eq!(ss.element_count(), 10);
let values_limit: StackSizeLimit<usize> = StackSize::from_element_count(1024).into_limit();
}
}

3
src/lib.rs
View File

@ -404,8 +404,7 @@ pub use self::module::{ModuleInstance, ModuleRef, ExternVal, NotStartedModuleRef
pub use self::global::{GlobalInstance, GlobalRef};
pub use self::func::{FuncInstance, FuncRef, FuncInvocation, ResumableError};
pub use self::types::{Signature, ValueType, GlobalDescriptor, TableDescriptor, MemoryDescriptor};
pub use self::common::stack::{StackWithLimit, StackSize, StackSizeLimit, StackSizeInitial};
pub use self::runner::Interpreter;
pub use self::runner::{Interpreter, InterpreterStackConfig};
/// WebAssembly-specific sizes and units.
pub mod memory_units {

113
src/runner.rs
View File

@ -19,11 +19,8 @@ use value::{
};
use {Signature, Trap, TrapKind, ValueType};
/// Maximum number of entries in value stack.
pub const DEFAULT_VALUE_STACK_LIMIT: usize = (1024 * 1024) / ::core::mem::size_of::<RuntimeValue>();
// TODO: Make these parameters changeble.
pub const DEFAULT_CALL_STACK_LIMIT: usize = 64 * 1024;
const DEFAULT_VALUE_STACK_LIMIT: usize = (1024 * 1024) / 8;
const DEFAULT_CALL_STACK_LIMIT: usize = 64 * 1024;
/// This is a wrapper around u64 to allow us to treat runtime values as a tag-free `u64`
/// (where if the runtime value is <64 bits the upper bits are 0). This is safe, since
@ -37,7 +34,7 @@ pub const DEFAULT_CALL_STACK_LIMIT: usize = 64 * 1024;
/// at these boundaries.
#[derive(Copy, Clone, Debug, PartialEq, Default)]
#[repr(transparent)]
pub struct RuntimeValueInternal(pub u64);
struct RuntimeValueInternal(pub u64);
impl RuntimeValueInternal {
pub fn with_type(self, ty: ValueType) -> RuntimeValue {
@ -164,6 +161,54 @@ enum RunResult {
NestedCall(FuncRef),
}
/// Stack pre-allocation and size limit settings for [`Interpreter`].
///
/// Sizes indicate number of elements, not number of bytes.
///
/// When an interpreter exceeds the size limit on either stack, [`Trapkind::StackOverflow`] is returned.
///
/// The following example initializes an Interpreter with space pre-allocated for 1024
/// values and 1024 function calls. The value stack has a maximum size of
/// 2048 and the call stack has unlimited size (bounded only by available addressable memory).
///
/// ```
/// # extern crate wasmi;
/// # use wasmi::{Interpreter, InterpreterStackConfig};
/// use std::usize;
/// let config = InterpreterStackConfig {
/// value_stack_size_initial: 1024,
/// value_stack_size_limit: 2048,
/// call_stack_size_initial: 1024,
/// call_stack_size_limit: usize::MAX,
/// };
/// let interpreter = Interpreter::with_stacks(config);
/// ```
///
/// [`Interpreter`]: struct.Interpreter.html
/// [`Trapkind::StackOverflow`]: enum.TrapKind.html
#[derive(Clone, PartialEq, PartialOrd, Debug)]
pub struct InterpreterStackConfig {
/// Number of spots to be pre-allocated for the value stack.
pub value_stack_size_initial: usize,
/// Maximum nuber of elements allowed in the value stack.
pub value_stack_size_limit: usize,
/// Number of spots to be pre-allocated for the call stack.
pub call_stack_size_initial: usize,
/// Maximum nuber of elements allowed in the value stack.
pub call_stack_size_limit: usize,
}
impl Default for InterpreterStackConfig {
fn default() -> Self {
InterpreterStackConfig {
value_stack_size_initial: DEFAULT_VALUE_STACK_LIMIT,
value_stack_size_limit: DEFAULT_VALUE_STACK_LIMIT,
call_stack_size_initial: DEFAULT_CALL_STACK_LIMIT,
call_stack_size_limit: DEFAULT_CALL_STACK_LIMIT,
}
}
}
/// Function interpreter.
pub struct Interpreter {
value_stack: ValueStack,
@ -172,36 +217,46 @@ pub struct Interpreter {
}
impl Interpreter {
/// Initialize an interpreter with defaults stack sizes.
/// Initialize an interpreter with default stack sizes.
pub fn new() -> Interpreter {
Interpreter::with_stacks(
StackWithLimit::with_size(StackSize::from_element_count(DEFAULT_VALUE_STACK_LIMIT)),
StackWithLimit::with_size(StackSize::from_element_count(DEFAULT_CALL_STACK_LIMIT)),
)
Interpreter::with_stacks(InterpreterStackConfig::default())
}
/// Initialize an interpreter that will use `value_stack` and `call_stack`.
/// Initialize an interpreter with value stack and call stack configured according to
/// `stack_sizes`.
///
/// `value_stack` `call_stack` determine the allowed stack size during later executions.
/// # Panics
///
/// In debug mode, panics if `stack_sizes.value_stack_size_initial` is larger than
/// `stack_sizes.value_stack_size_limit` or if `stack_sizes.frame_stack_size_initial` is larger
/// than `stack_sizes.frame_stack_size_limit`.
///
/// ```
/// # extern crate wasmi;
/// use wasmi::{Interpreter, StackWithLimit, StackSize};
/// let interpreter = Interpreter::with_stacks(
/// StackWithLimit::with_size(StackSize::from_byte_count(8192)),
/// StackWithLimit::with_size(StackSize::from_element_count(2048)),
/// );
/// # let value_stack_size = StackSize::from_byte_count(8192);
/// # let value_stack = StackWithLimit::with_size(value_stack_size);
/// # let interpreter = Interpreter::with_stacks(
/// # value_stack,
/// # StackWithLimit::with_size(StackSize::from_element_count(2048)),
/// # );
/// use wasmi::{Interpreter, InterpreterStackConfig};
/// let config = InterpreterStackConfig {
/// value_stack_size_initial: 8192,
/// value_stack_size_limit: 8192,
/// call_stack_size_initial: 2048,
/// call_stack_size_limit: 2048,
/// };
/// let interpreter = Interpreter::with_stacks(config);
/// ```
pub fn with_stacks(
value_stack: StackWithLimit<RuntimeValueInternal>,
call_stack: StackWithLimit<FunctionContext>,
) -> Interpreter {
pub fn with_stacks(stack_sizes: InterpreterStackConfig) -> Interpreter {
let InterpreterStackConfig {
value_stack_size_initial,
value_stack_size_limit,
call_stack_size_initial,
call_stack_size_limit,
} = stack_sizes;
let value_stack = StackWithLimit::new(
StackSize::from_element_count(value_stack_size_initial).into_initial(),
StackSize::from_element_count(value_stack_size_limit).into_limit(),
); // debug panic may occur here
let call_stack = StackWithLimit::new(
StackSize::from_element_count(call_stack_size_initial).into_initial(),
StackSize::from_element_count(call_stack_size_limit).into_limit(),
); // debug panic may occur here
Interpreter {
value_stack: ValueStack(value_stack),
call_stack,
@ -1217,7 +1272,7 @@ impl Interpreter {
}
/// Function execution context.
pub struct FunctionContext {
struct FunctionContext {
/// Is context initialized.
pub is_initialized: bool,
/// Internal function reference.