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/* * Copyright 2018, alex at staticlibs.net * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ //! Rust modules support for [Wilton JavaScript runtime](https://github.com/wilton-iot/wilton) //! //! Usage example: //! //! ``` //!// configure Cargo to build a shared library //![lib] //!crate-type = ["dylib"] //! //!// in lib.rs, import serde and wilton_rust //!#[macro_use] //!extern crate serde_derive; //!extern crate wilton_rust; //! ... //!// declare input/output structs //!#[derive(Deserialize)] //!struct MyIn { ... } //!#[derive(Serialize)] //!struct MyOut { ... } //! ... //!// write a function that does some work //!fn hello(obj: MyIn) -> MyOut { ... } //! ... //!// register that function inside the `wilton_module_init` function, //!// that will be called by Wilton during the Rust module load //!#[no_mangle] //!pub extern "C" fn wilton_module_init() -> *mut std::os::raw::c_char { //! // register a call, error checking omitted //! wilton_rust::register_wiltocall("hello", |obj: MyIn| { hello(obj) }); //! // return success status to Wilton //! wilton_rust::create_wilton_error(None) //!} //! //! ``` //! //! See an [example](https://github.com/wilton-iot/wilton_examples/blob/master/rust/test.js#L17) //! how to load and use Rust library from JavaScript. extern crate serde; extern crate serde_json; use std::os::raw::*; use std::ptr::null; use std::ptr::null_mut; // wilton C API import // https://github.com/wilton-iot/wilton_core/tree/master/include/wilton extern "system" { fn wilton_alloc( size_bytes: c_int ) -> *mut c_char; fn wilton_free( buffer: *mut c_char ) -> (); fn wiltoncall_register( call_name: *const c_char, call_name_len: c_int, call_ctx: *mut c_void, call_cb: extern "system" fn( call_ctx: *mut c_void, json_in: *const c_char, json_in_len: c_int, json_out: *mut *mut c_char, json_out_len: *mut c_int ) -> *mut c_char ) -> *mut c_char; } static EMPTY_JSON_INPUT: &'static str = "{}"; type WiltonCallback = Box<Fn(&[u8]) -> Result<String, String>>; // helper functions fn copy_to_wilton_bufer(data: &str) -> *mut c_char { unsafe { let res: *mut c_char = wilton_alloc((data.len() + 1) as c_int); std::ptr::copy_nonoverlapping(data.as_ptr() as *const c_char, res, data.len()); *res.offset(data.len() as isize) = '\0' as c_char; res } } fn convert_wilton_error(err: *mut c_char) -> String { unsafe { use std::ffi::CStr; if null::<c_char>() != err { let res = match CStr::from_ptr(err).to_str() { Ok(val) => String::from(val), // generally cannot happen Err(_) => String::from("Unknown error") }; wilton_free(err); res } else { // generally cannot happen String::from("No error") } } } // https://github.com/rustytools/errloc_macros/blob/79f5378e913293cb1b4a561fb7dc8d5cbcd09bc6/src/lib.rs#L44 fn panicmsg<'a>(e: &'a std::boxed::Box<std::any::Any + std::marker::Send + 'static>) -> &'a str { match e.downcast_ref::<&str>() { Some(st) => st, None => { match e.downcast_ref::<std::string::String>() { Some(stw) => stw.as_str(), None => "()", } }, } } // callback that is passed to wilton #[no_mangle] #[allow(private_no_mangle_fns)] extern "system" fn wilton_cb( call_ctx: *mut c_void, json_in: *const c_char, json_in_len: c_int, json_out: *mut *mut c_char, json_out_len: *mut c_int ) -> *mut c_char { unsafe { std::panic::catch_unwind(|| { let data: &[u8] = if (null::<c_char>() != json_in) && (json_in_len > 0) { std::slice::from_raw_parts(json_in as *const u8, json_in_len as usize) } else { EMPTY_JSON_INPUT.as_bytes() }; // https://stackoverflow.com/a/32270215/314015 let callback_boxed_ptr = std::mem::transmute::<*mut c_void, *mut WiltonCallback>(call_ctx); let callback_boxed_ref: &mut WiltonCallback = &mut *callback_boxed_ptr; let callback_ref: &mut Fn(&[u8]) -> Result<String, String> = &mut **callback_boxed_ref; match callback_ref(data) { Ok(res) => { *json_out = copy_to_wilton_bufer(&res); *json_out_len = res.len() as c_int; null_mut::<c_char>() } Err(e) => copy_to_wilton_bufer(&e) } }).unwrap_or_else(|e| { copy_to_wilton_bufer(panicmsg(&e)) }) } } /// Registers a closure, that can be called from JavaScript /// /// This function takes a closure and registers it with Wilton, so /// it can be called from JavaScript using [wiltoncall](https://wilton-iot.github.io/wilton/docs/html/namespacewiltoncall.html) /// API. /// /// Closure must take a single argument - a struct that implements [serde::Deserialize](https://docs.serde.rs/serde/trait.Deserialize.html) /// and must return a struct that implements [serde::Serialize](https://docs.serde.rs/serde/trait.Serialize.html). /// Closure input argument is converted from JavaScript object to Rust struct object. /// Closure output is returned to JavaScript as a JSON (that can be immediately converted to JavaScript object). /// /// If closure panics, its panic message is converted into JavaScript `Error` message (that can be /// caugth and handled on JavaScript side). /// ///# Arguments /// ///* `name` - name this call, that should be used from JavaScript to invoke the closure ///* `callback` - closure, that will be called from JavaScript /// ///# Example /// /// ``` /// // declare input/output structs ///#[derive(Deserialize)] ///struct MyIn { ... } ///#[derive(Serialize)] ///struct MyOut { ... } /// ... /// // write a function that does some work ///fn hello(obj: MyIn) -> MyOut { ... } /// ... /// // register that function inside the `wilton_module_init` function, /// // that will be called by Wilton during the Rust module load ///#[no_mangle] ///pub extern "C" fn wilton_module_init() -> *mut std::os::raw::c_char { /// // register a call, error checking omitted /// wilton_rust::register_wiltocall("hello", |obj: MyIn| { hello(obj) }); /// // return success status to Wilton /// wilton_rust::create_wilton_error(None) ///} /// /// ``` pub fn register_wiltocall<I: serde::de::DeserializeOwned, O: serde::Serialize, F: 'static + Fn(I) -> O>( name: &str, callback: F ) -> Result<(), String> { unsafe { use std::error::Error; let name_bytes = name.as_bytes(); let callback_erased = move |json_in: &[u8]| -> Result<String, String> { match serde_json::from_slice(json_in) { Ok(obj_in) => { let obj_out = callback(obj_in); match serde_json::to_string_pretty(&obj_out) { Ok(json_out) => Ok(json_out), Err(e) => Err(String::from(e.description())) } }, Err(e) => Err(String::from(e.description())) } }; let callback_fatty: WiltonCallback = Box::new(callback_erased); let callback_slim: Box<WiltonCallback> = Box::new(callback_fatty); let callback_bare: *mut WiltonCallback = Box::into_raw(callback_slim); // unboxed callbacks are leaked here: 16 byte per callback // it seems not easy to make their destructors to run after main // https://stackoverflow.com/a/27826181/314015 // it may be easier to suppress wilton_module_inie leaks in valgrind // let callback_unleak = Box::from_raw(callback_bare); let err: *mut c_char = wiltoncall_register( name_bytes.as_ptr() as *const c_char, name_bytes.len() as c_int, callback_bare as *mut c_void, wilton_cb); if null_mut::<c_char>() != err { Err(convert_wilton_error(err)) } else { Ok(()) } } } /// Create an error message, that can be passed back to Wilton /// /// Helper function, that can be used with Rust `Result`s, returned /// from `wilton_rust::register_wiltoncall` function. /// ///# Arguments /// ///* `error_opt` - optional error message, that should be passed back to Wilton /// ///# Example /// ///``` /// // register a call ///let res = wilton_rust::register_wiltocall("hello", |obj: MyObj1| { hello(obj) }); /// /// // check for error ///if res.is_err() { /// // return error message to Wilton /// return wilton_rust::create_wilton_error(res.err()); ///} /// /// // return success status to Wilton ///wilton_rust::create_wilton_error(None) ///``` /// pub fn create_wilton_error(error_opt: Option<String>) -> *mut c_char { match error_opt { Some(msg) => copy_to_wilton_bufer(&msg), None => null_mut::<c_char>() } }