chore(cbindings): cbindings rust simple libwaku integration example

.gitignore

@@ -57,6 +57,8 @@ nimbus-build-system.paths
 *.sqlite3-wal
 
 /examples/nodejs/build/
+/examples/rust/target/
+
 
 # Coverage
 coverage_html_report/

examples/rust/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "waku-rust-simple-example"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[build-dependencies]
+cc = "1.0.52"

examples/rust/README.md

@@ -0,0 +1,6 @@
+
+This represents a very simple example on how to integrate the `libwaku` library in Rust, and then, only a few `libwaku` functions are being wrapped.
+
+In [waku-rust-bindings](https://github.com/waku-org/waku-rust-bindings) you will find a complete Waku integration in Rust.
+
+

examples/rust/build.rs

@@ -0,0 +1,5 @@
+
+fn main() {
+    println!("cargo:rustc-link-arg=-lwaku");
+    println!("cargo:rustc-link-arg=-L../../build/");
+}

examples/rust/src/main.rs

@@ -0,0 +1,114 @@
+
+use std::os::raw::{c_char, c_int, c_void};
+use std::{slice, thread, time};
+use std::cell::OnceCell;
+use std::ffi::CString;
+
+pub type WakuCallback =
+    unsafe extern "C" fn(
+        c_int,
+        *const c_char,
+        usize,
+        *const c_void,
+    );
+
+extern "C" {
+    pub fn waku_new(
+        config_json: *const u8,
+        cb: WakuCallback,
+        user_data: *const c_void,
+    ) -> *mut c_void;
+
+    pub fn waku_version(
+        ctx: *const c_void,
+        cb: WakuCallback,
+        user_data: *const c_void,
+    ) -> c_int;
+
+    pub fn waku_default_pubsub_topic(
+        ctx: *mut c_void,
+        cb: WakuCallback,
+        user_data: *const c_void,
+    ) -> *mut c_void;
+}
+
+pub unsafe extern "C" fn trampoline<C>(
+    return_val: c_int,
+    buffer: *const c_char,
+    buffer_len: usize,
+    data: *const c_void,
+) where
+    C: FnMut(i32, &str),
+{
+    let closure = &mut *(data as *mut C);
+
+    let buffer_utf8 =
+    String::from_utf8(slice::from_raw_parts(buffer as *mut u8, buffer_len)
+                    .to_vec())
+                    .expect("valid utf8");
+
+    closure(return_val, &buffer_utf8);
+}
+
+pub fn get_trampoline<C>(_closure: &C) -> WakuCallback
+where
+    C: FnMut(i32, &str),
+{
+    trampoline::<C>
+}
+
+fn main() {
+    let config_json = "\
+    { \
+        \"host\": \"127.0.0.1\",\
+        \"port\": 60000, \
+        \"key\": \"0d714a1fada214dead6dc9c7274581ec20ff292451866e7d6d677dc818e8ccd2\", \
+        \"relay\": true \
+    }";
+
+    unsafe {
+        // Create the waku node
+        let closure = |ret: i32, data: &str| {
+            println!("Ret {ret}. Error creating waku node {data}");
+        };
+        let cb = get_trampoline(&closure);
+        let config_json_str = CString::new(config_json).unwrap();
+        let ctx = waku_new(
+            config_json_str.as_ptr() as *const u8,
+            cb,
+            &closure as *const _ as *const c_void,
+        );
+
+        // Extracting the current waku version
+        let version: OnceCell<String> = OnceCell::new();
+        let closure = |ret: i32, data: &str| {
+            println!("version_closure. Ret: {ret}. Data: {data}");
+            let _ = version.set(data.to_string());
+        };
+        let cb = get_trampoline(&closure);
+        let _ret = waku_version(
+            &ctx as *const _ as *const c_void,
+            cb,
+            &closure as *const _ as *const c_void,
+        );
+
+        // Extracting the default pubsub topic
+        let default_pubsub_topic: OnceCell<String> = OnceCell::new();
+        let closure = |_ret: i32, data: &str| {
+            let _ = default_pubsub_topic.set(data.to_string());
+        };
+        let cb = get_trampoline(&closure);
+        let _ret = waku_default_pubsub_topic(
+            ctx,
+            cb,
+            &closure as *const _ as *const c_void,
+        );
+
+        println!("Version: {}", version.get_or_init(|| unreachable!()));
+        println!("Default pubsubTopic: {}", default_pubsub_topic.get_or_init(|| unreachable!()));
+    }
+
+    loop {
+        thread::sleep(time::Duration::from_millis(10000));
+    }
+}