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use crate::budget;
use crate::internal;
use crate::{GeneratorState, Value, Vm, VmError, VmErrorKind, VmHalt, VmHaltInfo};
use std::future::Future;
/// The execution environment for a virtual machine.
pub struct VmExecution {
vms: Vec<Vm>,
}
impl VmExecution {
/// Construct an execution from a virtual machine.
pub(crate) fn new(vm: Vm) -> Self {
Self { vms: vec![vm] }
}
/// Get the current virtual machine.
pub fn vm(&self) -> Result<&Vm, VmError> {
match self.vms.last() {
Some(vm) => Ok(vm),
None => Err(VmError::from(VmErrorKind::NoRunningVm)),
}
}
/// Get the current virtual machine mutably.
pub fn vm_mut(&mut self) -> Result<&mut Vm, VmError> {
match self.vms.last_mut() {
Some(vm) => Ok(vm),
None => Err(VmError::from(VmErrorKind::NoRunningVm)),
}
}
/// Complete the current execution without support for async instructions.
///
/// This will error if the execution is suspended through yielding.
pub async fn async_complete(&mut self) -> Result<Value, VmError> {
match self.async_resume().await? {
GeneratorState::Complete(value) => Ok(value),
GeneratorState::Yielded(..) => Err(VmError::from(VmErrorKind::Halted {
halt: VmHaltInfo::Yielded,
})),
}
}
/// Complete the current execution without support for async instructions.
///
/// If any async instructions are encountered, this will error. This will
/// also error if the execution is suspended through yielding.
pub fn complete(&mut self) -> Result<Value, VmError> {
match self.resume()? {
GeneratorState::Complete(value) => Ok(value),
GeneratorState::Yielded(..) => Err(VmError::from(VmErrorKind::Halted {
halt: VmHaltInfo::Yielded,
})),
}
}
/// Resume the current execution with support for async instructions.
pub async fn async_resume(&mut self) -> Result<GeneratorState, VmError> {
loop {
let len = self.vms.len();
let vm = self.vm_mut()?;
match Self::run(vm)? {
VmHalt::Exited => (),
VmHalt::Awaited(awaited) => {
awaited.into_vm(vm).await?;
continue;
}
VmHalt::VmCall(vm_call) => {
vm_call.into_execution(self)?;
continue;
}
VmHalt::Yielded => return Ok(GeneratorState::Yielded(vm.stack_mut().pop()?)),
halt => {
return Err(VmError::from(VmErrorKind::Halted {
halt: halt.into_info(),
}))
}
}
if len == 1 {
let value = vm.stack_mut().pop()?;
debug_assert!(vm.stack().is_empty(), "the final vm should be empty");
self.vms.clear();
return Ok(GeneratorState::Complete(value));
}
self.pop_vm()?;
}
}
/// Resume the current execution without support for async instructions.
///
/// If any async instructions are encountered, this will error.
pub fn resume(&mut self) -> Result<GeneratorState, VmError> {
loop {
let len = self.vms.len();
let vm = self.vm_mut()?;
match Self::run(vm)? {
VmHalt::Exited => (),
VmHalt::VmCall(vm_call) => {
vm_call.into_execution(self)?;
continue;
}
VmHalt::Yielded => return Ok(GeneratorState::Yielded(vm.stack_mut().pop()?)),
halt => {
return Err(VmError::from(VmErrorKind::Halted {
halt: halt.into_info(),
}))
}
}
if len == 1 {
let value = vm.stack_mut().pop()?;
debug_assert!(vm.stack().is_empty(), "the final vm should be empty");
self.vms.clear();
return Ok(GeneratorState::Complete(value));
}
self.pop_vm()?;
}
}
/// Step the single execution for one step without support for async
/// instructions.
///
/// If any async instructions are encountered, this will error.
pub fn step(&mut self) -> Result<Option<Value>, VmError> {
let len = self.vms.len();
let vm = self.vm_mut()?;
match budget::with(1, || Self::run(vm)).call()? {
VmHalt::Exited => (),
VmHalt::VmCall(vm_call) => {
vm_call.into_execution(self)?;
return Ok(None);
}
VmHalt::Limited => return Ok(None),
halt => {
return Err(VmError::from(VmErrorKind::Halted {
halt: halt.into_info(),
}))
}
}
if len == 1 {
let value = vm.stack_mut().pop()?;
debug_assert!(vm.stack().is_empty(), "final vm stack not clean");
return Ok(Some(value));
}
self.pop_vm()?;
Ok(None)
}
/// Step the single execution for one step with support for async
/// instructions.
pub async fn async_step(&mut self) -> Result<Option<Value>, VmError> {
let len = self.vms.len();
let vm = self.vm_mut()?;
match budget::with(1, || Self::run(vm)).call()? {
VmHalt::Exited => (),
VmHalt::Awaited(awaited) => {
awaited.into_vm(vm).await?;
return Ok(None);
}
VmHalt::VmCall(vm_call) => {
vm_call.into_execution(self)?;
return Ok(None);
}
VmHalt::Limited => return Ok(None),
halt => {
return Err(VmError::from(VmErrorKind::Halted {
halt: halt.into_info(),
}))
}
}
if len == 1 {
let value = vm.stack_mut().pop()?;
debug_assert!(vm.stack().is_empty(), "final vm stack not clean");
return Ok(Some(value));
}
self.pop_vm()?;
Ok(None)
}
/// Push a virtual machine state onto the execution.
pub(crate) fn push_vm(&mut self, vm: Vm) {
self.vms.push(vm);
}
/// Pop a virtual machine state from the execution and transfer the top of
/// the stack from the popped machine.
fn pop_vm(&mut self) -> Result<(), VmError> {
let mut from = self.vms.pop().ok_or_else(|| VmErrorKind::NoRunningVm)?;
let stack = from.stack_mut();
let value = stack.pop()?;
debug_assert!(stack.is_empty(), "vm stack not clean");
let onto = self.vm_mut()?;
onto.stack_mut().push(value);
onto.advance();
Ok(())
}
#[inline]
fn run(vm: &mut Vm) -> Result<VmHalt, VmError> {
match vm.run() {
Ok(reason) => Ok(reason),
Err(error) => Err(error.into_unwinded(vm.unit(), vm.ip(), vm.call_frames().to_vec())),
}
}
}
/// A wrapper that makes [`VmExecution`] [`Send`].
///
/// This is accomplished by preventing any [`Value`] from escaping the [`Vm`].
/// As long as this is maintained, it is safe to send the execution across,
/// threads, and therefore schedule the future associated with the execution on
/// a thread pool like Tokio's through [tokio::spawn].
///
/// [tokio::spawn]: https://docs.rs/tokio/0/tokio/runtime/struct.Runtime.html#method.spawn
pub struct VmSendExecution(pub(crate) VmExecution);
// Safety: we wrap all APIs around the [VmExecution], preventing values from
// escaping from contained virtual machine.
unsafe impl Send for VmSendExecution {}
impl VmSendExecution {
/// Complete the current execution with support for async instructions.
///
/// This requires that the result of the Vm is converted into a
/// [crate::FromValue] that also implements [Send], which prevents non-Send
/// values from escaping from the virtual machine.
pub fn async_complete(
mut self,
) -> impl Future<Output = Result<Value, VmError>> + Send + 'static {
let future = async move {
let result = self.0.async_resume().await?;
match result {
GeneratorState::Complete(value) => Ok(value),
GeneratorState::Yielded(..) => Err(VmError::from(VmErrorKind::Halted {
halt: VmHaltInfo::Yielded,
})),
}
};
// Safety: we wrap all APIs around the [VmExecution], preventing values
// from escaping from contained virtual machine.
unsafe { internal::AssertSend::new(future) }
}
}