Fix bind parameter address instability issue

The bind parameters rely on stable addresses in memory, however the Vec
used to hold them was being allowed to re-allocate and therefore change
the addresses refered to by the OCI execute function. Now the Vec is
reserved with the right number of elements to ensure that it does not get
increases automatically.

src/statement.rs

@@ -120,14 +120,18 @@ impl<'conn> Statement<'conn> {
     /// parameters, however this is not yet available through this crate.
     ///
     pub fn bind(&mut self, params: &[&ToSqlValue]) -> Result<(), OciError> {
+        // clear out previous bind parameters 
         self.values.clear();
+
+        // ensure that the vec is large enough to hold all the parameters
+        // otherwise the vec will re-size, re-allocated and the addresses will change
+        self.values.reserve(params.len());
 
         for (index, param) in params.iter().enumerate() {
             let sql_value = param.to_sql_value();
             self.values.push(sql_value);
             let binding: *mut OCIBind = ptr::null_mut();
             self.bindings.push(binding);
-
             let position = (index + 1) as c_uint;
             let null_mut_ptr = ptr::null_mut();
             let indp = null_mut_ptr;

src/types.rs

@@ -6,7 +6,7 @@ use oci_error::OciError;
 
 /// The types that support conversion from OCI to Rust types.
 ///
-#[derive(Debug, PartialEq)]
+#[derive(Debug, PartialEq, Clone)]
 pub enum SqlValue {
     /// Anything specified as `VARCHAR` or `VARCHAR2` will end up here.
     VarChar(String),