Parity as a library (#8412)

* Parity as a library

* Fix concerns

* Allow using a null on_client_restart_cb

* Fix more concerns

* Test the C library in test.sh

* Reduce CMake version to 3.5

* Move the clib test before cargo test

* Add println in test

parity-clib/src/lib.rs

@@ -0,0 +1,133 @@
+// Copyright 2018 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Note that all the structs and functions here are documented in `parity.h`, to avoid
+//! duplicating documentation.
+
+extern crate parity;
+
+use std::os::raw::{c_char, c_void, c_int};
+use std::panic;
+use std::ptr;
+use std::slice;
+
+#[repr(C)]
+pub struct ParityParams {
+	pub configuration: *mut c_void,
+	pub on_client_restart_cb: Option<extern "C" fn(*mut c_void, *const c_char, usize)>,
+	pub on_client_restart_cb_custom: *mut c_void,
+}
+
+#[no_mangle]
+pub extern fn parity_config_from_cli(args: *const *const c_char, args_lens: *const usize, len: usize, output: *mut *mut c_void) -> c_int {
+	unsafe {
+		panic::catch_unwind(|| {
+			*output = ptr::null_mut();
+
+			let args = {
+				let arg_ptrs = slice::from_raw_parts(args, len);
+				let arg_lens = slice::from_raw_parts(args_lens, len);
+
+				let mut args = Vec::with_capacity(len + 1);
+				args.push("parity".to_owned());
+
+				for (&arg, &len) in arg_ptrs.iter().zip(arg_lens.iter()) {
+					let string = slice::from_raw_parts(arg as *const u8, len);
+					match String::from_utf8(string.to_owned()) {
+						Ok(a) => args.push(a),
+						Err(_) => return 1,
+					};
+				}
+
+				args
+			};
+
+			match parity::Configuration::parse_cli(&args) {
+				Ok(mut cfg) => {
+					// Always disable the auto-updater when used as a library.
+					cfg.args.arg_auto_update = "none".to_owned();
+
+					let cfg = Box::into_raw(Box::new(cfg));
+					*output = cfg as *mut _;
+					0
+				},
+				Err(_) => {
+					1
+				},
+			}
+		}).unwrap_or(1)
+	}
+}
+
+#[no_mangle]
+pub extern fn parity_config_destroy(cfg: *mut c_void) {
+	unsafe {
+		let _ = panic::catch_unwind(|| {
+			let _cfg = Box::from_raw(cfg as *mut parity::Configuration);
+		});
+	}
+}
+
+#[no_mangle]
+pub extern fn parity_start(cfg: *const ParityParams, output: *mut *mut c_void) -> c_int {
+	unsafe {
+		panic::catch_unwind(|| {
+			*output = ptr::null_mut();
+			let cfg: &ParityParams = &*cfg;
+
+			let config = Box::from_raw(cfg.configuration as *mut parity::Configuration);
+
+			let on_client_restart_cb = {
+				struct Cb(Option<extern "C" fn(*mut c_void, *const c_char, usize)>, *mut c_void);
+				unsafe impl Send for Cb {}
+				unsafe impl Sync for Cb {}
+				impl Cb {
+					fn call(&self, new_chain: String) {
+						if let Some(ref cb) = self.0 {
+							cb(self.1, new_chain.as_bytes().as_ptr() as *const _, new_chain.len())
+						}
+					}
+				}
+				let cb = Cb(cfg.on_client_restart_cb, cfg.on_client_restart_cb_custom);
+				move |new_chain: String| { cb.call(new_chain); }
+			};
+
+			let action = match parity::start(*config, on_client_restart_cb, || {}) {
+				Ok(action) => action,
+				Err(_) => return 1,
+			};
+
+			match action {
+				parity::ExecutionAction::Instant(Some(s)) => { println!("{}", s); 0 },
+				parity::ExecutionAction::Instant(None) => 0,
+				parity::ExecutionAction::Running(client) => {
+					*output = Box::into_raw(Box::<parity::RunningClient>::new(client)) as *mut c_void;
+					0
+				}
+			}
+		}).unwrap_or(1)
+	}
+}
+
+#[no_mangle]
+pub extern fn parity_destroy(client: *mut c_void) {
+	unsafe {
+		let _ = panic::catch_unwind(|| {
+			let client = Box::from_raw(client as *mut parity::RunningClient);
+			client.shutdown();
+		});
+	}
+}