wabam

A crate for creating WebAssembly modules.

Example

let mut module = wabam::Module::default();

module.types = vec![
    wabam::func_type!((param) (result)),
    wabam::func_type!((param i32 i32 i32 i32) (result i32)),
];

// Import WASI's `fd_write`, to print to the terminal
let fd_write = wabam::interface::FuncImport {
    module: "wasi_snapshot_preview1".into(),
    name: "fd_write".into(),
    type_idx: 1, // types[1], see above
};
module.imports.functions.push(fd_write);

// Define memory
let memory = wabam::Limit {
    start: 1,
    end: None,
};
module.memories.push(memory);

let text = "Hello, wasm!";
let text_ptr = 12;

// Load the text into memory
let data = wabam::Data::Active {
    mem_index: 0,
    offset: wabam::instr!(i32.const { text_ptr }).into(),
    data: text.into(),
};
module.datas.push(data);

let body = wabam::instrs!(
    (i32.const 0) // Where the `(ptr, len)` pair is
    (i32.const { text_ptr })
    (i32.store) // Write ptr
    
    (i32.const 0) // Where the `(ptr, len)` pair is
    (i32.const { text.len() as i32 })
    (i32.store offset=4) // Write len

    (i32.const 1) // File descriptor, stdout is 1.
    (i32.const 0) // Where the `(ptr, len)` pair is
    (i32.const 1) // How many `(ptr, len)` pairs there are
    (i32.const 8) // Where to write the number of written bytes
    (call 0) // imported functions are at the start of the address space
    // this current function would be 1 (this is important later!)
    (drop) // Ignore the error, this is just an example after all!
);

let func = wabam::functions::Function {
    type_idx: 0, // types[0], see above
    locals: vec![], // no local variables
    body: body.into(),
};
module.functions.push(func);

// Export the start function
let func_export = wabam::interface::Export {
    name: "_start".into(),
    idx: 1, // this is where that's important
};

// Export memory
let mem_export = wabam::interface::Export {
    name: "memory".into(),
    idx: 0,
};
module.exports.functions.push(func_export);
module.exports.memories.push(mem_export);

let output = module.build();

std::fs::write("./hello.wasm", &output).unwrap();

Then run it:

$ wasmtime ./hello.wasm
Hello, wasm!

Licensing

This project is licensed under either Apache License Version 2.0 or MIT License at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.