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//! Module that defines the [`Scope`] type representing a function call-stack scope. use crate::dynamic::{AccessMode, Variant}; use crate::stdlib::{borrow::Cow, boxed::Box, iter, vec::Vec}; use crate::{Dynamic, Identifier, StaticVec}; /// Keep a number of entries inline (since [`Dynamic`] is usually small enough). const SCOPE_SIZE: usize = 16; /// Type containing information about the current scope. /// Useful for keeping state between [`Engine`][crate::Engine] evaluation runs. /// /// # Thread Safety /// /// Currently, [`Scope`] is neither [`Send`] nor [`Sync`]. /// Turn on the `sync` feature to make it [`Send`] `+` [`Sync`]. /// /// # Example /// /// ``` /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> { /// use rhai::{Engine, Scope}; /// /// let engine = Engine::new(); /// let mut my_scope = Scope::new(); /// /// my_scope.push("z", 40_i64); /// /// engine.eval_with_scope::<()>(&mut my_scope, "let x = z + 1; z = 0;")?; /// /// assert_eq!(engine.eval_with_scope::<i64>(&mut my_scope, "x + 1")?, 42); /// /// assert_eq!(my_scope.get_value::<i64>("x").unwrap(), 41); /// assert_eq!(my_scope.get_value::<i64>("z").unwrap(), 0); /// # Ok(()) /// # } /// ``` /// /// When searching for entries, newly-added entries are found before similarly-named but older entries, /// allowing for automatic _shadowing_. // // # Implementation Notes // // [`Scope`] is implemented as two [`Vec`]'s of exactly the same length. Variables data (name, type, etc.) // is manually split into two equal-length arrays. That's because variable names take up the most space, // with [`Cow<str>`][Cow] being four words long, but in the vast majority of cases the name is NOT used to // look up a variable. Variable lookup is usually via direct indexing, by-passing the name altogether. // // Since [`Dynamic`] is reasonably small, packing it tightly improves cache locality when variables are accessed. // // The alias is `Box`'ed because it occurs infrequently. #[derive(Debug, Clone, Hash)] pub struct Scope<'a> { /// Current value of the entry. values: smallvec::SmallVec<[Dynamic; SCOPE_SIZE]>, /// (Name, aliases) of the entry. names: Vec<(Cow<'a, str>, Option<Box<StaticVec<Identifier>>>)>, } impl Default for Scope<'_> { #[inline(always)] fn default() -> Self { Self { values: Default::default(), names: Vec::with_capacity(SCOPE_SIZE), } } } impl<'a> IntoIterator for Scope<'a> { type Item = (Cow<'a, str>, Dynamic); type IntoIter = Box<dyn Iterator<Item = Self::Item> + 'a>; #[inline(always)] fn into_iter(self) -> Self::IntoIter { Box::new( self.values .into_iter() .zip(self.names.into_iter()) .map(|(value, (name, _))| (name, value)), ) } } impl<'a> Scope<'a> { /// Create a new [`Scope`]. /// /// # Example /// /// ``` /// use rhai::Scope; /// /// let mut my_scope = Scope::new(); /// /// my_scope.push("x", 42_i64); /// assert_eq!(my_scope.get_value::<i64>("x").unwrap(), 42); /// ``` #[inline(always)] pub fn new() -> Self { Default::default() } /// Empty the [`Scope`]. /// /// # Example /// /// ``` /// use rhai::Scope; /// /// let mut my_scope = Scope::new(); /// /// my_scope.push("x", 42_i64); /// assert!(my_scope.contains("x")); /// assert_eq!(my_scope.len(), 1); /// assert!(!my_scope.is_empty()); /// /// my_scope.clear(); /// assert!(!my_scope.contains("x")); /// assert_eq!(my_scope.len(), 0); /// assert!(my_scope.is_empty()); /// ``` #[inline(always)] pub fn clear(&mut self) -> &mut Self { self.names.clear(); self.values.clear(); self } /// Get the number of entries inside the [`Scope`]. /// /// # Example /// /// ``` /// use rhai::Scope; /// /// let mut my_scope = Scope::new(); /// assert_eq!(my_scope.len(), 0); /// /// my_scope.push("x", 42_i64); /// assert_eq!(my_scope.len(), 1); /// ``` #[inline(always)] pub fn len(&self) -> usize { self.values.len() } /// Is the [`Scope`] empty? /// /// # Example /// /// ``` /// use rhai::Scope; /// /// let mut my_scope = Scope::new(); /// assert!(my_scope.is_empty()); /// /// my_scope.push("x", 42_i64); /// assert!(!my_scope.is_empty()); /// ``` #[inline(always)] pub fn is_empty(&self) -> bool { self.values.len() == 0 } /// Add (push) a new entry to the [`Scope`]. /// /// # Example /// /// ``` /// use rhai::Scope; /// /// let mut my_scope = Scope::new(); /// /// my_scope.push("x", 42_i64); /// assert_eq!(my_scope.get_value::<i64>("x").unwrap(), 42); /// ``` #[inline(always)] pub fn push( &mut self, name: impl Into<Cow<'a, str>>, value: impl Variant + Clone, ) -> &mut Self { self.push_dynamic_value(name, AccessMode::ReadWrite, Dynamic::from(value)) } /// Add (push) a new [`Dynamic`] entry to the [`Scope`]. /// /// # Example /// /// ``` /// use rhai::{Dynamic, Scope}; /// /// let mut my_scope = Scope::new(); /// /// my_scope.push_dynamic("x", Dynamic::from(42_i64)); /// assert_eq!(my_scope.get_value::<i64>("x").unwrap(), 42); /// ``` #[inline(always)] pub fn push_dynamic(&mut self, name: impl Into<Cow<'a, str>>, value: Dynamic) -> &mut Self { self.push_dynamic_value(name, value.access_mode(), value) } /// Add (push) a new constant to the [`Scope`]. /// /// Constants are immutable and cannot be assigned to. Their values never change. /// Constants propagation is a technique used to optimize an [`AST`][crate::AST]. /// /// # Example /// /// ``` /// use rhai::Scope; /// /// let mut my_scope = Scope::new(); /// /// my_scope.push_constant("x", 42_i64); /// assert_eq!(my_scope.get_value::<i64>("x").unwrap(), 42); /// ``` #[inline(always)] pub fn push_constant( &mut self, name: impl Into<Cow<'a, str>>, value: impl Variant + Clone, ) -> &mut Self { self.push_dynamic_value(name, AccessMode::ReadOnly, Dynamic::from(value)) } /// Add (push) a new constant with a [`Dynamic`] value to the Scope. /// /// Constants are immutable and cannot be assigned to. Their values never change. /// Constants propagation is a technique used to optimize an [`AST`][crate::AST]. /// /// # Example /// /// ``` /// use rhai::{Dynamic, Scope}; /// /// let mut my_scope = Scope::new(); /// /// my_scope.push_constant_dynamic("x", Dynamic::from(42_i64)); /// assert_eq!(my_scope.get_value::<i64>("x").unwrap(), 42); /// ``` #[inline(always)] pub fn push_constant_dynamic( &mut self, name: impl Into<Cow<'a, str>>, value: Dynamic, ) -> &mut Self { self.push_dynamic_value(name, AccessMode::ReadOnly, value) } /// Add (push) a new entry with a [`Dynamic`] value to the [`Scope`]. #[inline(always)] pub(crate) fn push_dynamic_value( &mut self, name: impl Into<Cow<'a, str>>, access: AccessMode, mut value: Dynamic, ) -> &mut Self { self.names.push((name.into(), None)); value.set_access_mode(access); self.values.push(value.into()); self } /// Truncate (rewind) the [`Scope`] to a previous size. /// /// # Example /// /// ``` /// use rhai::Scope; /// /// let mut my_scope = Scope::new(); /// /// my_scope.push("x", 42_i64); /// my_scope.push("y", 123_i64); /// assert!(my_scope.contains("x")); /// assert!(my_scope.contains("y")); /// assert_eq!(my_scope.len(), 2); /// /// my_scope.rewind(1); /// assert!(my_scope.contains("x")); /// assert!(!my_scope.contains("y")); /// assert_eq!(my_scope.len(), 1); /// /// my_scope.rewind(0); /// assert!(!my_scope.contains("x")); /// assert!(!my_scope.contains("y")); /// assert_eq!(my_scope.len(), 0); /// assert!(my_scope.is_empty()); /// ``` #[inline(always)] pub fn rewind(&mut self, size: usize) -> &mut Self { self.names.truncate(size); self.values.truncate(size); self } /// Does the [`Scope`] contain the entry? /// /// # Example /// /// ``` /// use rhai::Scope; /// /// let mut my_scope = Scope::new(); /// /// my_scope.push("x", 42_i64); /// assert!(my_scope.contains("x")); /// assert!(!my_scope.contains("y")); /// ``` #[inline(always)] pub fn contains(&self, name: &str) -> bool { self.names .iter() .rev() // Always search a Scope in reverse order .any(|(key, _)| name == key.as_ref()) } /// Find an entry in the [`Scope`], starting from the last. #[inline(always)] pub(crate) fn get_index(&self, name: &str) -> Option<(usize, AccessMode)> { self.names .iter() .enumerate() .rev() // Always search a Scope in reverse order .find_map(|(index, (key, _))| { if name == key.as_ref() { Some((index, self.values[index].access_mode())) } else { None } }) } /// Get the value of an entry in the [`Scope`], starting from the last. /// /// # Example /// /// ``` /// use rhai::Scope; /// /// let mut my_scope = Scope::new(); /// /// my_scope.push("x", 42_i64); /// assert_eq!(my_scope.get_value::<i64>("x").unwrap(), 42); /// ``` #[inline(always)] pub fn get_value<T: Variant + Clone>(&self, name: &str) -> Option<T> { self.names .iter() .enumerate() .rev() .find(|(_, (key, _))| name == key.as_ref()) .and_then(|(index, _)| self.values[index].flatten_clone().try_cast()) } /// Update the value of the named entry in the [`Scope`]. /// /// Search starts backwards from the last, and only the first entry matching the specified name is updated. /// If no entry matching the specified name is found, a new one is added. /// /// # Panics /// /// Panics when trying to update the value of a constant. /// /// # Example /// /// ``` /// use rhai::Scope; /// /// let mut my_scope = Scope::new(); /// /// my_scope.push("x", 42_i64); /// assert_eq!(my_scope.get_value::<i64>("x").unwrap(), 42); /// /// my_scope.set_value("x", 0_i64); /// assert_eq!(my_scope.get_value::<i64>("x").unwrap(), 0); /// ``` #[inline(always)] pub fn set_value(&mut self, name: &'a str, value: impl Variant + Clone) -> &mut Self { match self.get_index(name) { None => { self.push(name, value); } Some((_, AccessMode::ReadOnly)) => panic!("variable {} is constant", name), Some((index, AccessMode::ReadWrite)) => { *self.values.get_mut(index).unwrap() = Dynamic::from(value); } } self } /// Get a mutable reference to an entry in the [`Scope`]. /// /// If the entry by the specified name is not found, of if it is read-only, /// [`None`] is returned. /// /// # Example /// /// ``` /// use rhai::Scope; /// /// let mut my_scope = Scope::new(); /// /// my_scope.push("x", 42_i64); /// assert_eq!(my_scope.get_value::<i64>("x").unwrap(), 42); /// /// let ptr = my_scope.get_mut("x").unwrap(); /// *ptr = 123_i64.into(); /// /// assert_eq!(my_scope.get_value::<i64>("x").unwrap(), 123); /// ``` pub fn get_mut(&mut self, name: &str) -> Option<&mut Dynamic> { self.get_index(name) .and_then(move |(index, access)| match access { AccessMode::ReadWrite => Some(self.get_mut_by_index(index)), AccessMode::ReadOnly => None, }) } /// Get a mutable reference to an entry in the [`Scope`] based on the index. #[inline(always)] pub(crate) fn get_mut_by_index(&mut self, index: usize) -> &mut Dynamic { self.values.get_mut(index).expect("invalid index in Scope") } /// Update the access type of an entry in the [`Scope`]. #[cfg(not(feature = "no_module"))] #[inline(always)] pub(crate) fn add_entry_alias( &mut self, index: usize, alias: impl Into<Identifier> + PartialEq<Identifier>, ) -> &mut Self { let entry = self.names.get_mut(index).expect("invalid index in Scope"); if entry.1.is_none() { entry.1 = Some(Default::default()); } if !entry.1.as_ref().unwrap().iter().any(|a| &alias == a) { entry.1.as_mut().unwrap().push(alias.into()); } self } /// Clone the [`Scope`], keeping only the last instances of each variable name. /// Shadowed variables are omitted in the copy. #[inline(always)] pub(crate) fn clone_visible(&self) -> Self { let mut entries: Self = Default::default(); self.names .iter() .enumerate() .rev() .for_each(|(i, (name, alias))| { if !entries.names.iter().any(|(key, _)| key == name) { entries.names.push((name.clone(), alias.clone())); entries.values.push(self.values[i].clone()); } }); entries } /// Get an iterator to entries in the [`Scope`]. #[inline(always)] #[allow(dead_code)] pub(crate) fn into_iter( self, ) -> impl Iterator<Item = (Cow<'a, str>, Dynamic, Vec<Identifier>)> { self.names .into_iter() .zip(self.values.into_iter()) .map(|((name, alias), value)| { (name, value, alias.map(|a| a.to_vec()).unwrap_or_default()) }) } /// Get an iterator to entries in the [`Scope`]. /// Shared values are flatten-cloned. /// /// # Example /// /// ``` /// use rhai::{Dynamic, Scope}; /// /// let mut my_scope = Scope::new(); /// /// my_scope.push("x", 42_i64); /// my_scope.push_constant("foo", "hello"); /// /// let mut iter = my_scope.iter(); /// /// let (name, is_constant, value) = iter.next().unwrap(); /// assert_eq!(name, "x"); /// assert!(!is_constant); /// assert_eq!(value.cast::<i64>(), 42); /// /// let (name, is_constant, value) = iter.next().unwrap(); /// assert_eq!(name, "foo"); /// assert!(is_constant); /// assert_eq!(value.cast::<String>(), "hello"); /// ``` #[inline(always)] pub fn iter(&self) -> impl Iterator<Item = (&str, bool, Dynamic)> { self.iter_raw() .map(|(name, constant, value)| (name, constant, value.flatten_clone())) } /// Get an iterator to entries in the [`Scope`]. /// Shared values are not expanded. #[inline(always)] pub fn iter_raw(&self) -> impl Iterator<Item = (&str, bool, &Dynamic)> { self.names .iter() .zip(self.values.iter()) .map(|((name, _), value)| (name.as_ref(), value.is_read_only(), value)) } } impl<'a, K: Into<Cow<'a, str>>> iter::Extend<(K, Dynamic)> for Scope<'a> { #[inline(always)] fn extend<T: IntoIterator<Item = (K, Dynamic)>>(&mut self, iter: T) { iter.into_iter().for_each(|(name, value)| { self.names.push((name.into(), None)); self.values.push(value); }); } }