Rust: Add encoder/decoder tests

mojo/public/rust/tests/util/mod.rs

Index: mojo/public/rust/tests/util/mod.rs
diff --git a/mojo/public/rust/tests/util/mod.rs b/mojo/public/rust/tests/util/mod.rs
index 8464d5834789bef8062de85c5c9e5bfb0de98992..16fbaebba525946bc8e088c11584cd0f249715f2 100644
--- a/mojo/public/rust/tests/util/mod.rs
+++ b/mojo/public/rust/tests/util/mod.rs
@@ -4,6 +4,12 @@
 
 //! This module contains useful functions and macros for testing.
 
+pub mod mojom_validation;
+
+use std::ffi::CString;
+use std::os::raw::c_char;
+use std::ptr;
+
 /// This macro sets up tests by adding in Mojo embedder
 /// initialization.
 macro_rules! tests {
@@ -33,3 +39,41 @@ extern "C" {
     pub fn InitializeMojoEmbedder();
 }
 
+#[link(name = "validation_parser")]
+extern "C" {
+    #[allow(dead_code)]
+    fn ParseValidationTest(input: *const c_char,
+                           num_handles: *mut usize,
+                           data: *mut *mut u8,
+                           data_len: *mut usize)
+                           -> *mut c_char;
+}
+
+#[allow(dead_code)]
+pub fn parse_validation_test(input: &str) -> Result<(Vec<u8>, usize), String> {
+    let input_c = CString::new(input.to_string()).unwrap();
+    let mut num_handles: usize = 0;
+    let mut data: *mut u8 = ptr::null_mut();
+    let mut data_len: usize = 0;
+    let error = unsafe {
+        ParseValidationTest(input_c.as_ptr(),
+                            &mut num_handles as *mut usize,
+                            &mut data as *mut *mut u8,
+                            &mut data_len as *mut usize)
+    };
+    if error == ptr::null_mut() {
+        if data == ptr::null_mut() {
+            // We assume we were just given an empty file
+            Ok((Vec::new(), 0))
+        } else {
+            let buffer = unsafe {
+                Vec::from_raw_parts(data, data_len, data_len)
+            };
+            Ok((buffer, num_handles))
+        }
+    } else {
+        Err(unsafe {
+            CString::from_raw(error)
+        }.into_string().expect("Could not convert error message to UTF-8!"))
+    }
+}