# `wasm-webidl-bindings`
**Read, write, and manipulate the Wasm WebIDL bindings custom section.**
[![](https://docs.rs/wasm-webidl-bindings/badge.svg)](https://docs.rs/wasm-webidl-bindings/)
[![](https://img.shields.io/crates/v/wasm-webidl-bindings.svg)](https://crates.io/crates/wasm-webidl-bindings)
[![](https://img.shields.io/crates/d/wasm-webidl-bindings.svg)](https://crates.io/crates/wasm-webidl-bindings)
[![Build Status](https://dev.azure.com/rustwasm/wasm-webidl-bindings/_apis/build/status/rustwasm.wasm-webidl-bindings?branchName=master)](https://dev.azure.com/rustwasm/wasm-webidl-bindings/_build/latest?definitionId=2&branchName=master)
### What's Inside
* A parser for the straw proposal text format. See `crates/text-parser/src/grammar.lalrpop`.
* A set of AST types for representing and manipulating WebIDL bindings. See
`src/ast.rs`.
* An encoder and decoder for the straw proposal binary format. See the
implementation at `src/binary/encode.rs` and details on the format at
`BINARY.md`.
### Example
#### Parsing the Text Format and Encoding it in the Binary Format
```rust
#[cfg(feature = "text")]
use wasm_webidl_bindings::{binary, text};
// Get the `walrus::Module` that this webidl-bindings section is for.
//
// The Wasm type and func that are being bound are:
//
// (type $EncodeIntoFuncWasm
// (param anyref anyref i32 i32)
// (result i64 i64))
//
// (func $encodeInto
// (import "TextEncoder" "encodeInto")
// (type $EncodeIntoFuncWasm))
let raw_wasm: Vec<u8> = get_wasm_buffer_from_somewhere();
let mut config = walrus::ModuleConfig::default();
// Register a function to run after the module is parsed, but with access to the
// mapping from indices in the original Wasm binary to their newly assigned
// walrus IDs.
//
// This is where we will parse the Web IDL bindings text.
config.on_parse(|module, indices_to_ids| {
let webidl_bindings = text::parse(module, indices_to_ids, r#"
type $TextEncoderEncodeIntoResult
(dict
(field "read" unsigned long long)
(field "written" unsigned long long))
type $EncodeIntoFuncWebIDL
(func (method any)
(param USVString Uint8Array)
(result $TextEncoderEncodeIntoResult))
func-binding $encodeIntoBinding import $EncodeIntoFuncWasm $EncodeIntoFuncWebIDL
(param
(as any 0)
(as any 1)
(view Int8Array 2 3))
(result
(as i64 (field 0 (get 0)))
(as i64 (field 1 (get 0))))
bind $encodeInto $encodeIntoBinding
"#)?;
println!("The parsed Web IDL bindings are {:#?}", webidl_bindings);
// Insert the `webidl_bindings` into the module as a custom section.
module.customs.add(webidl_bindings);
Ok(())
});
let mut module = config.parse(&raw_wasm)?;
// Reserialize the Wasm module along with its new Web IDL bindings
// section.
let new_raw_wasm = module.emit_wasm();
```