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/// A WebAssembly guest function or host function
public struct Function: Equatable {
internal let address: FunctionAddress
/// Invokes a function of the given address with the given parameters.
public func invoke(_ arguments: [Value] = [], runtime: Runtime) throws -> [Value] {
try withExecution { execution in
try invoke(execution: &execution, with: arguments, runtime: runtime)
try execution.run(runtime: runtime)
return try Array(execution.stack.popTopValues())
}
}
private func invoke(execution: inout ExecutionState, with arguments: [Value], runtime: Runtime) throws {
switch try runtime.store.function(at: address) {
case let .host(function):
try check(functionType: function.type, parameters: arguments)
let parameters = execution.stack.popValues(count: function.type.parameters.count)
let moduleInstance = runtime.store.module(address: execution.stack.currentFrame.module)
let caller = Caller(runtime: runtime, instance: moduleInstance)
let results = try function.implementation(caller, Array(parameters))
try check(functionType: function.type, results: results)
execution.stack.push(values: results)
case let .wasm(function, _):
try check(functionType: function.type, parameters: arguments)
execution.stack.push(values: arguments)
try execution.invoke(functionAddress: address, runtime: runtime)
}
}
private func check(functionType: FunctionType, parameters: [Value]) throws {
let parameterTypes = parameters.map { $0.type }
guard parameterTypes == functionType.parameters else {
throw Trap._raw("parameters types don't match, expected \(functionType.parameters), got \(parameterTypes)")
}
}
private func check(functionType: FunctionType, results: [Value]) throws {
let resultTypes = results.map { $0.type }
guard resultTypes == functionType.results else {
throw Trap._raw("result types don't match, expected \(functionType.results), got \(resultTypes)")
}
}
}
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