rust: add static/shared library linking example

Author: jwatson0

runtime/rust/src/main.rs

@@ -24,16 +24,61 @@ mod bar {
 /// This struct is not [Bar]
 pub struct Foo1;
 
-fn main() {
-    println!("Hello, world!");
+//
+// external static C library example
+//
+use std::ffi::c_void;
+
+#[link(name = "uuid", kind = "static")]    // note: for shared lib, remove `kind = "static"`
+unsafe extern "C" {
+    // typedef unsigned char uuid_t[16];  // &[u128] or &[u8; 16]
+    fn uuid_generate_time(out: *mut u8) -> c_void;
+    fn uuid_generate_random(out: *mut u8) -> c_void;
+}
+
+fn example_external_C_static_lib() {
+    println!("\n\n+++ example_external_C_static_lib()");
+    // let uuid = 0u128;
+    let mut uuid = [0u8; 16];  // array of 16 unsigned byte zeroes
+    unsafe { uuid_generate_time(uuid.as_mut_ptr()) };
+    print_uuid(&uuid);
+    unsafe { uuid_generate_random(uuid.as_mut_ptr()) };
+    print_uuid(&uuid);
+}
+
+// print as xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+fn print_uuid(uuid: &[u8; 16]) {
+    print!("UUID: ");
+    for i in 0..uuid.len() {
+        print!("{:02x}", uuid[i]);
+        match i {
+            3 | 5 | 7 | 9 => print!("-"),
+            _ => ()
+        }
+    }
+    println!("");
+}
+
+//
+// Example usage of the regex crate
+//
+fn example_crate_usage() {
+    println!("\n\n+++ example_crate_usage()");
 
-    // Example usage of the regex crate
     let re = Regex::new(r"^Hello, (.+)!$").unwrap();
     let text = "Hello, world!";
     if let Some(caps) = re.captures(text) {
         println!("Greeting target: {}", &caps[1]);
     }
 
+}
+
+//
+// websockets client example
+//
+fn example_websocket_client() {
+    println!("\n\n+++ example_websocket_client()");
+
     let (mut socket, response) =
         connect("ws://corefx-net-http11.azurewebsites.net/WebSocket/EchoWebSocket.ashx")
             .expect("Can't connect");
@@ -54,6 +99,21 @@ fn main() {
     let _ = socket.close(None);
 }
 
+
+fn main() {
+    println!("Hello, world!");
+
+    example_external_C_static_lib();
+
+    example_crate_usage();
+
+    example_websocket_client();
+
+}
+
+//
+// tests
+//
 #[cfg(test)]
 mod tests {
     use super::*;