Use StaticVec to avoid most allocations with function arguments.

src/any.rs

@@ -332,6 +332,12 @@ fn cast_box<X: Variant, T: Variant>(item: Box<X>) -> Result<Box<T>, Box<X>> {
 impl Dynamic {
     /// Create a `Dynamic` from any type.  A `Dynamic` value is simply returned as is.
     ///
+    /// # Safety
+    ///
+    /// This type uses some unsafe code, mainly for type casting.
+    ///
+    /// # Notes
+    ///
     /// Beware that you need to pass in an `Array` type for it to be recognized as an `Array`.
     /// A `Vec<T>` does not get automatically converted to an `Array`, but will be a generic
     /// restricted trait object instead, because `Vec<T>` is not a supported standard type.

src/api.rs

@@ -10,6 +10,7 @@ use crate::parser::{parse, parse_global_expr, AST};
 use crate::result::EvalAltResult;
 use crate::scope::Scope;
 use crate::token::{lex, Position};
+use crate::utils::StaticVec;
 
 #[cfg(not(feature = "no_object"))]
 use crate::engine::Map;
@@ -20,7 +21,6 @@ use crate::stdlib::{
     collections::HashMap,
     mem,
     string::{String, ToString},
-    vec::Vec,
 };
 #[cfg(not(feature = "no_std"))]
 use crate::stdlib::{fs::File, io::prelude::*, path::PathBuf};
@@ -994,7 +994,7 @@ impl Engine {
         args: A,
     ) -> Result<T, Box<EvalAltResult>> {
         let mut arg_values = args.into_vec();
-        let mut args: Vec<_> = arg_values.iter_mut().collect();
+        let mut args: StaticVec<_> = arg_values.iter_mut().collect();
         let fn_lib = ast.fn_lib();
         let pos = Position::none();
 
@@ -1004,7 +1004,7 @@ impl Engine {
 
         let state = State::new(fn_lib);
 
-        let result = self.call_script_fn(Some(scope), &state, fn_def, &mut args, pos, 0)?;
+        let result = self.call_script_fn(Some(scope), &state, fn_def, args.as_mut(), pos, 0)?;
 
         let return_type = self.map_type_name(result.type_name());
 

src/engine.rs

@@ -109,12 +109,12 @@ impl Target<'_> {
                         .as_char()
                         .map_err(|_| EvalAltResult::ErrorCharMismatch(pos))?;
 
-                    let mut chars: Vec<char> = s.chars().collect();
+                    let mut chars: StaticVec<char> = s.chars().collect();
-                    let ch = chars[x.1];
+                    let ch = *chars.get_ref(x.1);
 
                     // See if changed - if so, update the String
                     if ch != new_ch {
-                        chars[x.1] = new_ch;
+                        *chars.get_mut(x.1) = new_ch;
                         s.clear();
                         chars.iter().for_each(|&ch| s.push(ch));
                     }
@@ -194,7 +194,7 @@ pub struct FunctionsLib(HashMap<u64, ScriptedFunction>);
 
 impl FunctionsLib {
     /// Create a new `FunctionsLib` from a collection of `FnDef`.
-    pub fn from_vec(vec: Vec<FnDef>) -> Self {
+    pub fn from_iter(vec: impl IntoIterator<Item = FnDef>) -> Self {
         FunctionsLib(
             vec.into_iter()
                 .map(|fn_def| {
@@ -446,7 +446,7 @@ fn search_scope<'a>(
     #[cfg(not(feature = "no_module"))]
     {
         if let Some((modules, hash)) = modules {
-            let (id, root_pos) = modules.get(0);
+            let (id, root_pos) = modules.get_ref(0);
 
             let module = if let Some(index) = modules.index() {
                 scope
@@ -666,7 +666,7 @@ impl Engine {
     /// Function call arguments may be _consumed_ when the function requires them to be passed by value.
     /// All function arguments not in the first position are always passed by value and thus consumed.
     /// **DO NOT** reuse the argument values unless for the first `&mut` argument - all others are silently replaced by `()`!
-    pub(crate) fn call_script_fn(
+    pub(crate) fn call_script_fn<'a>(
         &self,
         scope: Option<&mut Scope>,
         state: &State,
@@ -892,7 +892,7 @@ impl Engine {
                 Expr::FnCall(x) if x.1.is_none() => {
                     let ((name, pos), _, hash, _, def_val) = x.as_ref();
 
-                    let mut args: Vec<_> = once(obj)
+                    let mut args: StaticVec<_> = once(obj)
                         .chain(
                             idx_val
                                 .downcast_mut::<StaticVec<Dynamic>>()
@@ -902,7 +902,7 @@ impl Engine {
                         .collect();
                     // A function call is assumed to have side effects, so the value is changed
                     // TODO - Remove assumption of side effects by checking whether the first parameter is &mut
-                    self.exec_fn_call(state, name, *hash, &mut args, def_val.as_ref(), *pos, 0)
+                    self.exec_fn_call(state, name, *hash, args.as_mut(), def_val.as_ref(), *pos, 0)
                         .map(|v| (v, true))
                 }
                 // xxx.module::fn_name(...) - syntax error
@@ -1396,7 +1396,7 @@ impl Engine {
                     .map(|expr| self.eval_expr(scope, state, expr, level))
                     .collect::<Result<StaticVec<_>, _>>()?;
 
-                let mut args: Vec<_> = arg_values.iter_mut().collect();
+                let mut args: StaticVec<_> = arg_values.iter_mut().collect();
 
                 let hash_fn_spec =
                     calc_fn_hash(empty(), KEYWORD_EVAL, once(TypeId::of::<String>()));
@@ -1410,7 +1410,7 @@ impl Engine {
 
                     // Evaluate the text string as a script
                     let result =
-                        self.eval_script_expr(scope, state, args[0], args_expr[0].position());
+                        self.eval_script_expr(scope, state, args.pop(), args_expr[0].position());
 
                     if scope.len() != prev_len {
                         // IMPORTANT! If the eval defines new variables in the current scope,
@@ -1425,7 +1425,7 @@ impl Engine {
                         state,
                         name,
                         *hash_fn_def,
-                        &mut args,
+                        args.as_mut(),
                         def_val.as_ref(),
                         *pos,
                         level,
@@ -1444,9 +1444,9 @@ impl Engine {
                     .map(|expr| self.eval_expr(scope, state, expr, level))
                     .collect::<Result<StaticVec<_>, _>>()?;
 
-                let mut args: Vec<_> = arg_values.iter_mut().collect();
+                let mut args: StaticVec<_> = arg_values.iter_mut().collect();
 
-                let (id, root_pos) = modules.get(0); // First module
+                let (id, root_pos) = modules.get_ref(0); // First module
 
                 let module = if let Some(index) = modules.index() {
                     scope
@@ -1462,7 +1462,7 @@ impl Engine {
 
                 // First search in script-defined functions (can override built-in)
                 if let Some(fn_def) = module.get_qualified_scripted_fn(*hash_fn_def) {
-                    self.call_script_fn(None, state, fn_def, &mut args, *pos, level)
+                    self.call_script_fn(None, state, fn_def, args.as_mut(), *pos, level)
                 } else {
                     // Then search in Rust functions
 
@@ -1476,7 +1476,7 @@ impl Engine {
                     let hash = *hash_fn_def ^ hash_fn_args;
 
                     match module.get_qualified_fn(name, hash, *pos) {
-                        Ok(func) => func(&mut args, *pos),
+                        Ok(func) => func(args.as_mut(), *pos),
                         Err(_) if def_val.is_some() => Ok(def_val.clone().unwrap()),
                         Err(err) => Err(err),
                     }

src/optimize.rs

@@ -704,40 +704,29 @@ pub fn optimize_into_ast(
     const fn_lib: &[(&str, usize)] = &[];
 
     #[cfg(not(feature = "no_function"))]
-    let lib = FunctionsLib::from_vec(
+    let lib = FunctionsLib::from_iter(functions.iter().cloned().map(|mut fn_def| {
-        functions
+        if !level.is_none() {
-            .iter()
+            let pos = fn_def.body.position();
-            .cloned()
-            .map(|mut fn_def| {
-                if !level.is_none() {
-                    let pos = fn_def.body.position();
 
-                    // Optimize the function body
+            // Optimize the function body
-                    let mut body =
+            let mut body = optimize(vec![fn_def.body], engine, &Scope::new(), &fn_lib, level);
-                        optimize(vec![fn_def.body], engine, &Scope::new(), &fn_lib, level);
 
-                    // {} -> Noop
+            // {} -> Noop
-                    fn_def.body = match body.pop().unwrap_or_else(|| Stmt::Noop(pos)) {
+            fn_def.body = match body.pop().unwrap_or_else(|| Stmt::Noop(pos)) {
-                        // { return val; } -> val
+                // { return val; } -> val
-                        Stmt::ReturnWithVal(x)
+                Stmt::ReturnWithVal(x) if x.1.is_some() && (x.0).0 == ReturnType::Return => {
-                            if x.1.is_some() && (x.0).0 == ReturnType::Return =>
+                    Stmt::Expr(Box::new(x.1.unwrap()))
-                        {
-                            Stmt::Expr(Box::new(x.1.unwrap()))
-                        }
-                        // { return; } -> ()
-                        Stmt::ReturnWithVal(x)
-                            if x.1.is_none() && (x.0).0 == ReturnType::Return =>
-                        {
-                            Stmt::Expr(Box::new(Expr::Unit((x.0).1)))
-                        }
-                        // All others
-                        stmt => stmt,
-                    };
                 }
-                fn_def
+                // { return; } -> ()
-            })
+                Stmt::ReturnWithVal(x) if x.1.is_none() && (x.0).0 == ReturnType::Return => {
-            .collect(),
+                    Stmt::Expr(Box::new(Expr::Unit((x.0).1)))
-    );
+                }
+                // All others
+                stmt => stmt,
+            };
+        }
+        fn_def
+    }));
 
     #[cfg(feature = "no_function")]
     let lib: FunctionsLib = Default::default();

src/parser.rs

@@ -724,7 +724,7 @@ fn parse_call_expr<'a>(
             #[cfg(not(feature = "no_module"))]
             let hash_fn_def = {
                 if let Some(modules) = modules.as_mut() {
-                    modules.set_index(stack.find_module(&modules.get(0).0));
+                    modules.set_index(stack.find_module(&modules.get_ref(0).0));
 
                     // Rust functions are indexed in two steps:
                     // 1) Calculate a hash in a similar manner to script-defined functions,
@@ -764,7 +764,7 @@ fn parse_call_expr<'a>(
                 #[cfg(not(feature = "no_module"))]
                 let hash_fn_def = {
                     if let Some(modules) = modules.as_mut() {
-                        modules.set_index(stack.find_module(&modules.get(0).0));
+                        modules.set_index(stack.find_module(&modules.get_ref(0).0));
 
                         // Rust functions are indexed in two steps:
                         // 1) Calculate a hash in a similar manner to script-defined functions,
@@ -1238,7 +1238,7 @@ fn parse_primary<'a>(
 
             // Qualifiers + variable name
             *hash = calc_fn_hash(modules.iter().map(|(v, _)| v.as_str()), name, empty());
-            modules.set_index(stack.find_module(&modules.get(0).0));
+            modules.set_index(stack.find_module(&modules.get_ref(0).0));
         }
         _ => (),
     }
@@ -1446,7 +1446,7 @@ fn make_dot_expr(
             #[cfg(feature = "no_module")]
             unreachable!();
             #[cfg(not(feature = "no_module"))]
-            return Err(PERR::PropertyExpected.into_err(x.1.unwrap().get(0).1));
+            return Err(PERR::PropertyExpected.into_err(x.1.unwrap().get_ref(0).1));
         }
         // lhs.dot_lhs.dot_rhs
         (lhs, Expr::Dot(x)) => {

src/scope.rs

@@ -7,7 +7,7 @@ use crate::token::Position;
 #[cfg(not(feature = "no_module"))]
 use crate::module::Module;
 
-use crate::stdlib::{borrow::Cow, boxed::Box, iter, vec::Vec};
+use crate::stdlib::{borrow::Cow, boxed::Box, iter, string::String, vec::Vec};
 
 /// Type of an entry in the Scope.
 #[derive(Debug, Eq, PartialEq, Hash, Copy, Clone)]

src/utils.rs

@@ -1,15 +1,18 @@
 //! Module containing various utility types and functions.
+//
+// TODO - remove unsafe code
 
 use crate::stdlib::{
     any::TypeId,
     fmt,
     hash::{Hash, Hasher},
+    iter::FromIterator,
     mem,
     vec::Vec,
 };
 
 #[cfg(not(feature = "no_std"))]
-use crate::stdlib::{collections::hash_map::DefaultHasher, iter::FromIterator};
+use crate::stdlib::collections::hash_map::DefaultHasher;
 
 #[cfg(feature = "no_std")]
 use ahash::AHasher;
@@ -23,7 +26,7 @@ pub fn EMPTY_TYPE_ID() -> TypeId {
 /// Module names are passed in via `&str` references from an iterator.
 /// Parameter types are passed in via `TypeId` values from an iterator.
 ///
-/// ### Note
+/// # Note
 ///
 /// The first module name is skipped.  Hashing starts from the _second_ module in the chain.
 pub fn calc_fn_spec<'a>(
@@ -47,8 +50,12 @@ pub fn calc_fn_spec<'a>(
 ///
 /// This is essentially a knock-off of the [`staticvec`](https://crates.io/crates/staticvec) crate.
 /// This simplified implementation here is to avoid pulling in another crate.
-#[derive(Clone, Hash, Default)]
+///
-pub struct StaticVec<T: Default> {
+/// # Safety
+///
+/// This type uses some unsafe code (mainly to zero out unused array slots) for efficiency.
+#[derive(Clone, Hash)]
+pub struct StaticVec<T> {
     /// Total number of values held.
     len: usize,
     /// Static storage. 4 slots should be enough for most cases - i.e. four levels of indirection.
@@ -57,7 +64,17 @@ pub struct StaticVec<T: Default> {
     more: Vec<T>,
 }
 
-impl<T: Default> FromIterator<T> for StaticVec<T> {
+impl<T> Default for StaticVec<T> {
+    fn default() -> Self {
+        Self {
+            len: 0,
+            list: unsafe { mem::MaybeUninit::zeroed().assume_init() },
+            more: Vec::new(),
+        }
+    }
+}
+
+impl<T> FromIterator<T> for StaticVec<T> {
     fn from_iter<X: IntoIterator<Item = T>>(iter: X) -> Self {
         let mut vec = StaticVec::new();
 
@@ -69,14 +86,22 @@ impl<T: Default> FromIterator<T> for StaticVec<T> {
     }
 }
 
-impl<T: Default> StaticVec<T> {
+impl<T> StaticVec<T> {
     /// Create a new `StaticVec`.
     pub fn new() -> Self {
         Default::default()
     }
     /// Push a new value to the end of this `StaticVec`.
     pub fn push<X: Into<T>>(&mut self, value: X) {
-        if self.len >= self.list.len() {
+        if self.len == self.list.len() {
+            // Move the fixed list to the Vec
+            for x in 0..self.list.len() {
+                let def_val: T = unsafe { mem::MaybeUninit::zeroed().assume_init() };
+                self.more
+                    .push(mem::replace(self.list.get_mut(x).unwrap(), def_val));
+            }
+            self.more.push(value.into());
+        } else if self.len > self.list.len() {
             self.more.push(value.into());
         } else {
             self.list[self.len] = value.into();
@@ -92,9 +117,19 @@ impl<T: Default> StaticVec<T> {
         let result = if self.len <= 0 {
             panic!("nothing to pop!")
         } else if self.len <= self.list.len() {
-            mem::take(self.list.get_mut(self.len - 1).unwrap())
+            let def_val: T = unsafe { mem::MaybeUninit::zeroed().assume_init() };
+            mem::replace(self.list.get_mut(self.len - 1).unwrap(), def_val)
         } else {
-            self.more.pop().unwrap()
+            let r = self.more.pop().unwrap();
+
+            // Move back to the fixed list
+            if self.more.len() == self.list.len() {
+                for x in 0..self.list.len() {
+                    self.list[self.list.len() - 1 - x] = self.more.pop().unwrap();
+                }
+            }
+
+            r
         };
 
         self.len -= 1;
@@ -105,48 +140,99 @@ impl<T: Default> StaticVec<T> {
     pub fn len(&self) -> usize {
         self.len
     }
-    /// Get an item at a particular index.
+    /// Get a reference to the item at a particular index.
     ///
     /// # Panics
     ///
     /// Panics if the index is out of bounds.
-    pub fn get(&self, index: usize) -> &T {
+    pub fn get_ref(&self, index: usize) -> &T {
         if index >= self.len {
             panic!("index OOB in StaticVec");
         }
 
-        if index < self.list.len() {
+        if self.len < self.list.len() {
             self.list.get(index).unwrap()
         } else {
-            self.more.get(index - self.list.len()).unwrap()
+            self.more.get(index).unwrap()
+        }
+    }
+    /// Get a mutable reference to the item at a particular index.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the index is out of bounds.
+    pub fn get_mut(&mut self, index: usize) -> &mut T {
+        if index >= self.len {
+            panic!("index OOB in StaticVec");
+        }
+
+        if self.len < self.list.len() {
+            self.list.get_mut(index).unwrap()
+        } else {
+            self.more.get_mut(index).unwrap()
         }
     }
     /// Get an iterator to entries in the `StaticVec`.
     pub fn iter(&self) -> impl Iterator<Item = &T> {
-        let num = if self.len >= self.list.len() {
+        if self.len > self.list.len() {
-            self.list.len()
+            self.more.iter()
         } else {
-            self.len
+            self.list[..self.len].iter()
-        };
+        }
-
-        self.list[..num].iter().chain(self.more.iter())
     }
     /// Get a mutable iterator to entries in the `StaticVec`.
     pub fn iter_mut(&mut self) -> impl Iterator<Item = &mut T> {
-        let num = if self.len >= self.list.len() {
+        if self.len > self.list.len() {
-            self.list.len()
+            self.more.iter_mut()
         } else {
-            self.len
+            self.list[..self.len].iter_mut()
-        };
+        }
-
-        self.list[..num].iter_mut().chain(self.more.iter_mut())
     }
 }
 
-impl<T: Default + Clone + fmt::Debug> fmt::Debug for StaticVec<T> {
+impl<T: Copy> StaticVec<T> {
+    /// Get the item at a particular index.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the index is out of bounds.
+    pub fn get(&self, index: usize) -> T {
+        if index >= self.len {
+            panic!("index OOB in StaticVec");
+        }
+
+        if self.len < self.list.len() {
+            *self.list.get(index).unwrap()
+        } else {
+            *self.more.get(index).unwrap()
+        }
+    }
+}
+
+impl<T: fmt::Debug> fmt::Debug for StaticVec<T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "[ ")?;
         self.iter().try_for_each(|v| write!(f, "{:?}, ", v))?;
         write!(f, "]")
     }
 }
+
+impl<T> AsRef<[T]> for StaticVec<T> {
+    fn as_ref(&self) -> &[T] {
+        if self.len > self.list.len() {
+            &self.more[..]
+        } else {
+            &self.list[..self.len]
+        }
+    }
+}
+
+impl<T> AsMut<[T]> for StaticVec<T> {
+    fn as_mut(&mut self) -> &mut [T] {
+        if self.len > self.list.len() {
+            &mut self.more[..]
+        } else {
+            &mut self.list[..self.len]
+        }
+    }
+}