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// Simple example of how to use parity-wasm builder api.
// Builder api introduced as a method for fast generation of
// different small wasm modules.
extern crate parity_wasm;
use std::env;
use parity_wasm::builder;
use parity_wasm::elements;
fn main() {
// Example binary accepts one parameter which is the output file
// where generated wasm module will be written at the end of execution
let args = env::args().collect::<Vec<_>>();
if args.len() != 2 {
println!("Usage: {} output_file.wasm", args[0]);
return;
}
// Main entry for the builder api is the module function
// It returns empty module builder structure which can be further
// appended with various wasm artefacts
let module = builder::module()
// Here we append function to the builder
// function() function returns a function builder attached
// to the module builder.
.function()
// We describe signature for the function via signature()
// function. In our simple example it's just one input
// argument of type 'i32' without return value
.signature().with_param(elements::ValueType::I32).build()
// body() without any further arguments means that the body
// of the function will be empty
.body().build()
// This is the end of the function builder. When `build()` is
// invoked, function builder returns original module builder
// from which it was invoked
.build()
// And finally we finish our module builder to produce actual
// wasm module.
.build();
// Module structure can be serialzed to produce a valid wasm file
parity_wasm::serialize_to_file(&args[1], module).unwrap();
}
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