wasmi/examples/invoke.rs

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extern crate parity_wasm;
extern crate wasmi;
use std::env::args;
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use parity_wasm::elements::{External, FunctionType, Internal, Type, ValueType};
use wasmi::{ImportsBuilder, ModuleInstance, NopExternals, RuntimeValue};
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fn main() {
let args: Vec<_> = args().collect();
if args.len() < 3 {
println!("Usage: {} <wasm file> <exported func> [<arg>...]", args[0]);
return;
}
let func_name = &args[2];
let (_, program_args) = args.split_at(3);
let module = parity_wasm::deserialize_file(&args[1]).expect("File to be deserialized");
// Extracts call arguments from command-line arguments
let args = {
// Export section has an entry with a func_name with an index inside a module
let export_section = module.export_section().expect("No export section found");
// It's a section with function declarations (which are references to the type section entries)
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let function_section = module
.function_section()
.expect("No function section found");
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// Type section stores function types which are referenced by function_section entries
let type_section = module.type_section().expect("No type section found");
// Given function name used to find export section entry which contains
// an `internal` field which points to the index in the function index space
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let found_entry = export_section
.entries()
.iter()
.find(|entry| func_name == entry.field())
.expect(&format!("No export with name {} found", func_name));
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// Function index in the function index space (internally-defined + imported)
let function_index: usize = match found_entry.internal() {
&Internal::Function(index) => index as usize,
_ => panic!("Founded export is not a function"),
};
// We need to count import section entries (functions only!) to subtract it from function_index
// and obtain the index within the function section
let import_section_len: usize = match module.import_section() {
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Some(import) => import
.entries()
.iter()
.filter(|entry| match entry.external() {
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&External::Function(_) => true,
_ => false,
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})
.count(),
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None => 0,
};
// Calculates a function index within module's function section
let function_index_in_section = function_index - import_section_len;
// Getting a type reference from a function section entry
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let func_type_ref: usize =
function_section.entries()[function_index_in_section].type_ref() as usize;
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// Use the reference to get an actual function type
let function_type: &FunctionType = match &type_section.types()[func_type_ref] {
&Type::Function(ref func_type) => func_type,
};
// Parses arguments and constructs runtime values in correspondence of their types
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function_type
.params()
.iter()
.enumerate()
.map(|(i, value)| match value {
&ValueType::I32 => RuntimeValue::I32(
program_args[i]
.parse::<i32>()
.expect(&format!("Can't parse arg #{} as i32", program_args[i])),
),
&ValueType::I64 => RuntimeValue::I64(
program_args[i]
.parse::<i64>()
.expect(&format!("Can't parse arg #{} as i64", program_args[i])),
),
&ValueType::F32 => RuntimeValue::F32(
program_args[i]
.parse::<f32>()
.expect(&format!("Can't parse arg #{} as f32", program_args[i]))
.into(),
),
&ValueType::F64 => RuntimeValue::F64(
program_args[i]
.parse::<f64>()
.expect(&format!("Can't parse arg #{} as f64", program_args[i]))
.into(),
),
})
.collect::<Vec<RuntimeValue>>()
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};
let loaded_module = wasmi::Module::from_parity_wasm_module(module).expect("Module to be valid");
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// Intialize deserialized module. It adds module into It expects 3 parameters:
// - a name for the module
// - a module declaration
// - "main" module doesn't import native module(s) this is why we don't need to provide external native modules here
// This test shows how to implement native module https://github.com/NikVolf/parity-wasm/blob/master/src/interpreter/tests/basics.rs#L197
let main = ModuleInstance::new(&loaded_module, &ImportsBuilder::default())
.expect("Failed to instantiate module")
.run_start(&mut NopExternals)
.expect("Failed to run start function in module");
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println!(
"Result: {:?}",
main.invoke_export(func_name, &args, &mut NopExternals)
.expect("")
);
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}