1 files changed, 133 insertions, 0 deletions
diff --git a/third_party/rust/wasm-encoder/src/component/canonicals.rs b/third_party/rust/wasm-encoder/src/component/canonicals.rs
new file mode 100644
index 0000000000..e81819c44e
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/component/canonicals.rs
@@ -0,0 +1,133 @@
+use crate::{encode_section, ComponentSection, ComponentSectionId, Encode};
+
+/// Represents options for canonical function definitions.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum CanonicalOption {
+    /// The string types in the function signature are UTF-8 encoded.
+    UTF8,
+    /// The string types in the function signature are UTF-16 encoded.
+    UTF16,
+    /// The string types in the function signature are compact UTF-16 encoded.
+    CompactUTF16,
+    /// The memory to use if the lifting or lowering of a function requires memory access.
+    ///
+    /// The value is an index to a core memory.
+    Memory(u32),
+    /// The realloc function to use if the lifting or lowering of a function requires memory
+    /// allocation.
+    ///
+    /// The value is an index to a core function of type `(func (param i32 i32 i32 i32) (result i32))`.
+    Realloc(u32),
+    /// The post-return function to use if the lifting of a function requires
+    /// cleanup after the function returns.
+    PostReturn(u32),
+}
+
+impl Encode for CanonicalOption {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            Self::UTF8 => sink.push(0x00),
+            Self::UTF16 => sink.push(0x01),
+            Self::CompactUTF16 => sink.push(0x02),
+            Self::Memory(idx) => {
+                sink.push(0x03);
+                idx.encode(sink);
+            }
+            Self::Realloc(idx) => {
+                sink.push(0x04);
+                idx.encode(sink);
+            }
+            Self::PostReturn(idx) => {
+                sink.push(0x05);
+                idx.encode(sink);
+            }
+        }
+    }
+}
+
+/// An encoder for the canonical function section of WebAssembly components.
+///
+/// # Example
+///
+/// ```
+/// use wasm_encoder::{Component, CanonicalFunctionSection, CanonicalOption};
+///
+/// let mut functions = CanonicalFunctionSection::new();
+/// functions.lift(0, 0, [CanonicalOption::UTF8]);
+///
+/// let mut component = Component::new();
+/// component.section(&functions);
+///
+/// let bytes = component.finish();
+/// ```
+#[derive(Clone, Debug, Default)]
+pub struct CanonicalFunctionSection {
+    bytes: Vec<u8>,
+    num_added: u32,
+}
+
+impl CanonicalFunctionSection {
+    /// Construct a new component function section encoder.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// The number of functions in the section.
+    pub fn len(&self) -> u32 {
+        self.num_added
+    }
+
+    /// Determines if the section is empty.
+    pub fn is_empty(&self) -> bool {
+        self.num_added == 0
+    }
+
+    /// Define a function that will lift a core WebAssembly function to the canonical ABI.
+    pub fn lift<O>(&mut self, core_func_index: u32, type_index: u32, options: O) -> &mut Self
+    where
+        O: IntoIterator<Item = CanonicalOption>,
+        O::IntoIter: ExactSizeIterator,
+    {
+        let options = options.into_iter();
+        self.bytes.push(0x00);
+        self.bytes.push(0x00);
+        core_func_index.encode(&mut self.bytes);
+        options.len().encode(&mut self.bytes);
+        for option in options {
+            option.encode(&mut self.bytes);
+        }
+        type_index.encode(&mut self.bytes);
+        self.num_added += 1;
+        self
+    }
+
+    /// Define a function that will lower a canonical ABI function to a core WebAssembly function.
+    pub fn lower<O>(&mut self, func_index: u32, options: O) -> &mut Self
+    where
+        O: IntoIterator<Item = CanonicalOption>,
+        O::IntoIter: ExactSizeIterator,
+    {
+        let options = options.into_iter();
+        self.bytes.push(0x01);
+        self.bytes.push(0x00);
+        func_index.encode(&mut self.bytes);
+        options.len().encode(&mut self.bytes);
+        for option in options {
+            option.encode(&mut self.bytes);
+        }
+        self.num_added += 1;
+        self
+    }
+}
+
+impl Encode for CanonicalFunctionSection {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        encode_section(sink, self.num_added, &self.bytes);
+    }
+}
+
+impl ComponentSection for CanonicalFunctionSection {
+    fn id(&self) -> u8 {
+        ComponentSectionId::CanonicalFunction.into()
+    }
+}