wrapper for xmlXPathCompile binding

src/xpath.rs

@@ -249,3 +249,14 @@ impl fmt::Display for Object {
     }
   }
 }
+
+/// Calls the binding to http://xmlsoft.org/html/libxml-xpath.html#xmlXPathCompile and return true if 
+/// a non-null pointer is returned. The idea is to use this to validate an xpath independent of context.
+/// Tests describing what this validates in tests/xpath_tests.rs
+pub fn xml_xpath_compiles(xpath: &str) -> bool {
+  let c_xpath = CString::new(xpath).unwrap();
+    let xml_xpath_comp_expr_ptr = unsafe { xmlXPathCompile(c_xpath.as_bytes().as_ptr()) };
+    let result = !xml_xpath_comp_expr_ptr.is_null();
+    unsafe { libc::free(xml_xpath_comp_expr_ptr as *mut c_void); }
+    result
+}

tests/xpath_tests.rs

@@ -192,3 +192,20 @@ fn cleanup_safely_unlinked_xpath_nodes() {
   drop(doc);
   assert!(true, "Drops went OK.");
 }
+
+/// Tests for the fn xml_xpath_compiles
+mod compile_tests {
+  use libxml::xpath::xml_xpath_compiles;
+
+  #[test]
+  fn can_compile_an_xpath() {
+      let compiles = xml_xpath_compiles("//a");
+      assert_eq!(compiles, true);
+  }
+
+  #[test]
+  fn invalid_xpath_does_not_compile() {
+      let compiles = xml_xpath_compiles("//a[but invalid]");
+      assert_eq!(compiles, false);
+  }
+}