support dynamic function calls in component model

crates/component-macro/Cargo.toml

@@ -17,6 +17,7 @@ proc-macro = true
 proc-macro2 = "1.0"
 quote = "1.0"
 syn = { version = "1.0", features = ["extra-traits"] }
+wasmtime-component-util = { path = "../component-util", version = "=0.40.0" }
 
 [badges]
 maintenance = { status = "actively-developed" }

crates/component-macro/src/lib.rs

@@ -5,6 +5,7 @@ use std::fmt;
 use syn::parse::{Parse, ParseStream};
 use syn::punctuated::Punctuated;
 use syn::{braced, parse_macro_input, parse_quote, Data, DeriveInput, Error, Result, Token};
+use wasmtime_component_util::{DiscriminantSize, FlagsSize};
 
 #[derive(Debug, Copy, Clone)]
 enum VariantStyle {
@@ -147,64 +148,6 @@ fn add_trait_bounds(generics: &syn::Generics, bound: syn::TypeParamBound) -> syn
     generics
 }
 
-#[derive(Debug, Copy, Clone)]
-enum DiscriminantSize {
-    Size1,
-    Size2,
-    Size4,
-}
-
-impl DiscriminantSize {
-    fn quote(self, discriminant: usize) -> TokenStream {
-        match self {
-            Self::Size1 => {
-                let discriminant = u8::try_from(discriminant).unwrap();
-                quote!(#discriminant)
-            }
-            Self::Size2 => {
-                let discriminant = u16::try_from(discriminant).unwrap();
-                quote!(#discriminant)
-            }
-            Self::Size4 => {
-                let discriminant = u32::try_from(discriminant).unwrap();
-                quote!(#discriminant)
-            }
-        }
-    }
-}
-
-impl From<DiscriminantSize> for u32 {
-    fn from(size: DiscriminantSize) -> u32 {
-        match size {
-            DiscriminantSize::Size1 => 1,
-            DiscriminantSize::Size2 => 2,
-            DiscriminantSize::Size4 => 4,
-        }
-    }
-}
-
-impl From<DiscriminantSize> for usize {
-    fn from(size: DiscriminantSize) -> usize {
-        match size {
-            DiscriminantSize::Size1 => 1,
-            DiscriminantSize::Size2 => 2,
-            DiscriminantSize::Size4 => 4,
-        }
-    }
-}
-
-fn discriminant_size(case_count: usize) -> Option<DiscriminantSize> {
-    if case_count <= 0xFF {
-        Some(DiscriminantSize::Size1)
-    } else if case_count <= 0xFFFF {
-        Some(DiscriminantSize::Size2)
-    } else if case_count <= 0xFFFF_FFFF {
-        Some(DiscriminantSize::Size4)
-    } else {
-        None
-    }
-}
-
 struct VariantCase<'a> {
     attrs: &'a [syn::Attribute],
     ident: &'a syn::Ident,
@@ -288,7 +231,7 @@ fn expand_variant(
         ));
     }
 
-    let discriminant_size = discriminant_size(body.variants.len()).ok_or_else(|| {
+    let discriminant_size = DiscriminantSize::from_count(body.variants.len()).ok_or_else(|| {
         Error::new(
             input.ident.span(),
             "`enum`s with more than 2^32 variants are not supported",
@@ -417,7 +360,7 @@ fn expand_record_for_component_type(
             const SIZE32: usize = {
                 let mut size = 0;
                 #sizes
-                size
+                #internal::align_to(size, Self::ALIGN32)
             };
 
             const ALIGN32: u32 = {
@@ -439,6 +382,23 @@ fn expand_record_for_component_type(
     Ok(quote!(const _: () = { #expanded };))
 }
 
+fn quote(size: DiscriminantSize, discriminant: usize) -> TokenStream {
+    match size {
+        DiscriminantSize::Size1 => {
+            let discriminant = u8::try_from(discriminant).unwrap();
+            quote!(#discriminant)
+        }
+        DiscriminantSize::Size2 => {
+            let discriminant = u16::try_from(discriminant).unwrap();
+            quote!(#discriminant)
+        }
+        DiscriminantSize::Size4 => {
+            let discriminant = u32::try_from(discriminant).unwrap();
+            quote!(#discriminant)
+        }
+    }
+}
+
 #[proc_macro_derive(Lift, attributes(component))]
 pub fn lift(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
     expand(&LiftExpander, &parse_macro_input!(input as DeriveInput))
@@ -523,7 +483,7 @@ impl Expander for LiftExpander {
         for (index, VariantCase { ident, ty, .. }) in cases.iter().enumerate() {
             let index_u32 = u32::try_from(index).unwrap();
 
-            let index_quoted = discriminant_size.quote(index);
+            let index_quoted = quote(discriminant_size, index);
 
             if let Some(ty) = ty {
                 lifts.extend(
@@ -666,7 +626,7 @@ impl Expander for LowerExpander {
         for (index, VariantCase { ident, ty, .. }) in cases.iter().enumerate() {
             let index_u32 = u32::try_from(index).unwrap();
 
-            let index_quoted = discriminant_size.quote(index);
+            let index_quoted = quote(discriminant_size, index);
 
             let discriminant_size = usize::from(discriminant_size);
 
@@ -989,19 +949,6 @@ impl Parse for Flags {
     }
 }
 
-enum FlagsSize {
-    /// Flags can fit in a u8
-    Size1,
-    /// Flags can fit in a u16
-    Size2,
-    /// Flags can fit in a specified number of u32 fields
-    Size4Plus(usize),
-}
-
-fn ceiling_divide(n: usize, d: usize) -> usize {
-    (n + d - 1) / d
-}
-
 #[proc_macro]
 pub fn flags(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
     expand_flags(&parse_macro_input!(input as Flags))
@@ -1010,13 +957,7 @@ pub fn flags(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
 }
 
 fn expand_flags(flags: &Flags) -> Result<TokenStream> {
-    let size = if flags.flags.len() <= 8 {
-        FlagsSize::Size1
-    } else if flags.flags.len() <= 16 {
-        FlagsSize::Size2
-    } else {
-        FlagsSize::Size4Plus(ceiling_divide(flags.flags.len(), 32))
-    };
+    let size = FlagsSize::from_count(flags.flags.len());
 
     let ty;
     let eq;

crates/component-util/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "wasmtime-component-util"
+version = "0.40.0"
+authors = ["The Wasmtime Project Developers"]
+description = "Utility types and functions to support the component model in Wasmtime"
+license = "Apache-2.0 WITH LLVM-exception"
+repository = "https://github.com/bytecodealliance/wasmtime"
+documentation = "https://docs.rs/wasmtime-component-util/"
+categories = ["wasm"]
+keywords = ["webassembly", "wasm"]
+edition = "2021"

crates/component-util/src/lib.rs

@@ -0,0 +1,75 @@
+/// Represents the possible sizes in bytes of the discriminant of a variant type in the component model
+#[derive(Debug, Copy, Clone)]
+pub enum DiscriminantSize {
+    /// 8-bit discriminant
+    Size1,
+    /// 16-bit discriminant
+    Size2,
+    /// 32-bit discriminant
+    Size4,
+}
+
+impl DiscriminantSize {
+    /// Calculate the size of discriminant needed to represent a variant with the specified number of cases.
+    pub fn from_count(count: usize) -> Option<Self> {
+        if count <= 0xFF {
+            Some(Self::Size1)
+        } else if count <= 0xFFFF {
+            Some(Self::Size2)
+        } else if count <= 0xFFFF_FFFF {
+            Some(Self::Size4)
+        } else {
+            None
+        }
+    }
+}
+
+impl From<DiscriminantSize> for u32 {
+    /// Size of the discriminant as a `u32`
+    fn from(size: DiscriminantSize) -> u32 {
+        match size {
+            DiscriminantSize::Size1 => 1,
+            DiscriminantSize::Size2 => 2,
+            DiscriminantSize::Size4 => 4,
+        }
+    }
+}
+
+impl From<DiscriminantSize> for usize {
+    /// Size of the discriminant as a `usize`
+    fn from(size: DiscriminantSize) -> usize {
+        match size {
+            DiscriminantSize::Size1 => 1,
+            DiscriminantSize::Size2 => 2,
+            DiscriminantSize::Size4 => 4,
+        }
+    }
+}
+
+/// Represents the number of bytes required to store a flags value in the component model
+pub enum FlagsSize {
+    /// Flags can fit in a u8
+    Size1,
+    /// Flags can fit in a u16
+    Size2,
+    /// Flags can fit in a specified number of u32 fields
+    Size4Plus(usize),
+}
+
+impl FlagsSize {
+    /// Calculate the size needed to represent a value with the specified number of flags.
+    pub fn from_count(count: usize) -> FlagsSize {
+        if count <= 8 {
+            FlagsSize::Size1
+        } else if count <= 16 {
+            FlagsSize::Size2
+        } else {
+            FlagsSize::Size4Plus(ceiling_divide(count, 32))
+        }
+    }
+}
+
+/// Divide `n` by `d`, rounding up in the case of a non-zero remainder.
+fn ceiling_divide(n: usize, d: usize) -> usize {
+    (n + d - 1) / d
+}

crates/wasmtime/Cargo.toml

@@ -20,6 +20,7 @@ wasmtime-cache = { path = "../cache", version = "=0.40.0", optional = true }
 wasmtime-fiber = { path = "../fiber", version = "=0.40.0", optional = true }
 wasmtime-cranelift = { path = "../cranelift", version = "=0.40.0", optional = true }
 wasmtime-component-macro = { path = "../component-macro", version = "=0.40.0", optional = true }
+wasmtime-component-util = { path = "../component-util", version = "=0.40.0", optional = true }
 target-lexicon = { version = "0.12.0", default-features = false }
 wasmparser = "0.87.0"
 anyhow = "1.0.19"
@@ -115,4 +116,5 @@ component-model = [
   "wasmtime-cranelift?/component-model",
   "wasmtime-runtime/component-model",
   "dep:wasmtime-component-macro",
+  "dep:wasmtime-component-util",
 ]