1 files changed, 188 insertions, 0 deletions
diff --git a/third_party/rust/wasm-encoder/src/lib.rs b/third_party/rust/wasm-encoder/src/lib.rs
new file mode 100644
index 0000000000..3f36562508
--- /dev/null
+++ b/third_party/rust/wasm-encoder/src/lib.rs
@@ -0,0 +1,188 @@
+//! A WebAssembly encoder.
+//!
+//! The main builder is the [`Module`]. You can build a section with a
+//! section-specific builder, like [`TypeSection`] or [`ImportSection`], and
+//! then add it to the module with [`Module::section`]. When you are finished
+//! building the module, call either [`Module::as_slice`] or [`Module::finish`]
+//! to get the encoded bytes. The former gives a shared reference to the
+//! underlying bytes as a slice, while the latter gives you ownership of them as
+//! a vector.
+//!
+//! # Example
+//!
+//! If we wanted to build this module:
+//!
+//! ```wasm
+//! (module
+//!   (type (func (param i32 i32) (result i32)))
+//!   (func (type 0)
+//!     local.get 0
+//!     local.get 1
+//!     i32.add)
+//!   (export "f" (func 0)))
+//! ```
+//!
+//! then we would do this:
+//!
+//! ```
+//! use wasm_encoder::{
+//!     CodeSection, ExportKind, ExportSection, Function, FunctionSection, Instruction,
+//!     Module, TypeSection, ValType,
+//! };
+//!
+//! let mut module = Module::new();
+//!
+//! // Encode the type section.
+//! let mut types = TypeSection::new();
+//! let params = vec![ValType::I32, ValType::I32];
+//! let results = vec![ValType::I32];
+//! types.function(params, results);
+//! module.section(&types);
+//!
+//! // Encode the function section.
+//! let mut functions = FunctionSection::new();
+//! let type_index = 0;
+//! functions.function(type_index);
+//! module.section(&functions);
+//!
+//! // Encode the export section.
+//! let mut exports = ExportSection::new();
+//! exports.export("f", ExportKind::Func, 0);
+//! module.section(&exports);
+//!
+//! // Encode the code section.
+//! let mut codes = CodeSection::new();
+//! let locals = vec![];
+//! let mut f = Function::new(locals);
+//! f.instruction(&Instruction::LocalGet(0));
+//! f.instruction(&Instruction::LocalGet(1));
+//! f.instruction(&Instruction::I32Add);
+//! f.instruction(&Instruction::End);
+//! codes.function(&f);
+//! module.section(&codes);
+//!
+//! // Extract the encoded Wasm bytes for this module.
+//! let wasm_bytes = module.finish();
+//!
+//! // We generated a valid Wasm module!
+//! assert!(wasmparser::validate(&wasm_bytes).is_ok());
+//! ```
+
+#![deny(missing_docs, missing_debug_implementations)]
+
+mod component;
+mod core;
+mod raw;
+
+pub use self::component::*;
+pub use self::core::*;
+pub use self::raw::*;
+
+/// Implemented by types that can be encoded into a byte sink.
+pub trait Encode {
+    /// Encode the type into the given byte sink.
+    fn encode(&self, sink: &mut Vec<u8>);
+}
+
+impl<T: Encode + ?Sized> Encode for &'_ T {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        T::encode(self, sink)
+    }
+}
+
+impl<T: Encode> Encode for [T] {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.len().encode(sink);
+        for item in self {
+            item.encode(sink);
+        }
+    }
+}
+
+impl Encode for [u8] {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.len().encode(sink);
+        sink.extend(self);
+    }
+}
+
+impl Encode for str {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        self.len().encode(sink);
+        sink.extend_from_slice(self.as_bytes());
+    }
+}
+
+impl Encode for usize {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        assert!(*self <= u32::max_value() as usize);
+        (*self as u32).encode(sink)
+    }
+}
+
+impl Encode for u32 {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        leb128::write::unsigned(sink, (*self).into()).unwrap();
+    }
+}
+
+impl Encode for i32 {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        leb128::write::signed(sink, (*self).into()).unwrap();
+    }
+}
+
+impl Encode for u64 {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        leb128::write::unsigned(sink, *self).unwrap();
+    }
+}
+
+impl Encode for i64 {
+    fn encode(&self, sink: &mut Vec<u8>) {
+        leb128::write::signed(sink, *self).unwrap();
+    }
+}
+
+impl<T> Encode for Option<T>
+where
+    T: Encode,
+{
+    fn encode(&self, sink: &mut Vec<u8>) {
+        match self {
+            Some(v) => {
+                sink.push(0x01);
+                v.encode(sink);
+            }
+            None => sink.push(0x00),
+        }
+    }
+}
+
+fn encoding_size(n: u32) -> usize {
+    let mut buf = [0u8; 5];
+    leb128::write::unsigned(&mut &mut buf[..], n.into()).unwrap()
+}
+
+fn encode_section(sink: &mut Vec<u8>, count: u32, bytes: &[u8]) {
+    (encoding_size(count) + bytes.len()).encode(sink);
+    count.encode(sink);
+    sink.extend(bytes);
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn it_encodes_an_empty_module() {
+        let bytes = Module::new().finish();
+        assert_eq!(bytes, [0x00, b'a', b's', b'm', 0x01, 0x00, 0x00, 0x00]);
+    }
+
+    #[test]
+    fn it_encodes_an_empty_component() {
+        let bytes = Component::new().finish();
+        assert_eq!(bytes, [0x00, b'a', b's', b'm', 0x0c, 0x00, 0x01, 0x00]);
+    }
+}