Add some more extern C code.

build.rs

@@ -1,7 +1,5 @@
 fn main() {
     // Tell Cargo to rerun if the c file is changed
     println!("cargo:rerun-if-changed=src/test.c");
-    cc::Build::new()
-        .file("src/test.c")
-        .compile("test");
+    cc::Build::new().file("src/test.c").compile("test");
 }

src/main.rs

@@ -13,18 +13,28 @@ impl Greeter {
         Greeter { greeting }
     }
 
-    fn greet(&self) {
+    pub fn greet(&self) {
         println!("{}", self.greeting);
     }
 }
 
 extern "C" {
     fn print_num(num: i32);
+    fn print_a_string(s: *const u8, len: usize);
 }
 
 fn main() {
     Greeter::new("Hello, Jesse!").greet();
 
+    // Calling some C
+
+    let original_s = "Hello from C-Rust land!";
+    unsafe {
+        print_a_string(original_s.as_ptr(), original_s.len());
+    }
+
+    // Testing out stack
+
     let mut my_stack = Stack::new();
     my_stack.push(Greeter::new("Hello"));
     my_stack.push(Greeter::new("Beautiful"));
@@ -49,5 +59,7 @@ fn main() {
 
     // calling some C
     let find_result = bst.find(3).unwrap_or(-1);
-    unsafe { print_num(find_result); }
+    unsafe {
+        print_num(find_result);
+    }
 }

src/test.c

@@ -1,5 +1,12 @@
 #include <stdio.h>
 
-void print_num(int num) {
+void print_num(const int num) {
     printf("[from c]: num is %d\n", num);
 }
+
+void print_a_string(const char* s, const size_t length) {
+    for (int i = 0; i < length; i++) {
+        printf("%c", s[i]);
+    }
+    printf("\n");
+}